The present invention relates to an automatic patting mechanism, which includes a support frame, a driving device, and a patting device, wherein the support frame is used to support the weight of the user, the driving device has a motor and a cam connected with the motor, and the patting device has a rod pivoted to the support frame, a patting member connected with the rod, a roller connected with the rod and abutting the cam, and an elastic member connected with the support frame and the rod. As such, the cam will push the rod to a pre-pressing position through the roller when the cam is driven by the motor to rotate then when the cam continues to rotate, it will relieve the push force on the rod so that the rod will swing to a patting position by the pulling force of the elastic member and swings back and forth repeatedly between these two positions to achieve the effects of soothing back muscles or helping to cough out sputum.本發明有關於一種自動拍打機構,包含有一支撐架、一驅動裝置,以及一拍打裝置,其中的支撐架用來支撐使用者的重量,驅動裝置具有一馬達及一連接馬達之凸輪,拍打裝置具有一樞設於支撐架之桿件、一連接桿件之拍打件、一連接桿件且抵接凸輪之滾輪,以及一連接支撐架及桿件之彈性件,藉此,當凸輪受到馬達之驅動而開始轉動時,凸輪會透過滾輪來將桿件推動至一預壓位置,接著當凸輪繼續轉動時會解除對桿件之推力,此時的桿件會受到彈性件之拉力而偏擺至一拍擊位置,如此在兩個位置之間重複作動,即可有效達到舒緩背部肌肉或拍痰的效果。10‧‧‧自動拍打機構20‧‧‧支撐架21‧‧‧椅架22‧‧‧坐墊23‧‧‧背墊24‧‧‧底板25‧‧‧背板32‧‧‧電源供應器42‧‧‧拍打件44‧‧‧桿件
