Transmission device capable of changing speed with stored energy

A transmission device for driving a carriage to move back and forth between a first position and a second position, the transmission device comprising:

• a base;
• a motor mounted on the base;
• a variable speed transmission mechanism mounted on the base and driven by the motor, wherein the variable speed transmission mechanism has a first state for moving the carriage with a first speed and a second state for moving the carriage with a second speed, and the first state and the first speed are respectively different from the second state and the second speed;
• a first energy storage mechanism, which is mounted on the variable speed transmission mechanism and has a first energy-storing state and a first energy-releasing state, wherein the first energy storage mechanism stores first energy to become the first energy-storing state under an action of an object approaching the base;
• a first latch mechanism, which is mounted on the base and has a first latch state and a first loose state for respectively latching and loosing the variable speed transmission mechanism such that the variable speed transmission mechanism is respectively in the first state and the second state, wherein the first latch state of the first latch mechanism enables the variable speed transmission mechanism to be in the first state, and the first loose state of the first latch mechanism enables the variable speed transmission mechanism to be in the second state;
• a second energy storage mechanism, which is mounted on the variable speed transmission mechanism and has a second energy-storing state corresponding to the first energy-releasing state and a second energy-releasing state corresponding to the first energy-storing state, wherein the second energy storage mechanism stores energy in the second state and releases energy in the first state;
• and
• a second latch mechanism, which is mounted on the base and has a second latch state and a second loose state for respectively latching and loosing the variable speed transmission mechanism such that the variable speed transmission mechanism is in the second state and the first state, respectively, wherein the second latch state of the second latch mechanism enables the variable speed transmission mechanism to be in the second state, and the second loose state of the second latch mechanism enables the variable speed transmission mechanism to be in the first state.