with reference to the drawings and in particular to fig1 and 5 , a massage mechanism 5 in accordance with the present invention is received in a backrest 3 of a massage chair 1 . the massage mechanism 5 includes a kneading motor 9 installed on a frame 4 . the kneading motor 9 connects with a first belt pulley 8 to which a first belt 6 is connected . the first belt 6 is connected to a second belt pulley 7 which is connected with a worm rod 29 . the worm rod 29 connected to a main part 30 is engaged with a worm wheel assembly 32 connected to the main part 30 . the massage mechanism 5 further includes a tapping motor 12 installed on the frame 4 and the tapping motor 12 connects with a third belt pulley 14 to which a second belt 13 is connected . an eccentric shaft 31 is connected to the main part 30 and connected with a fourth belt pulley 15 to which the second belt 13 is connected . the eccentric shaft 31 has a cam 11 to which a connecting rod 10 is engaged . referring to fig1 and 4 , the worm wheel assembly 32 and the connecting rod 10 are connected to a swing arm seat 16 which is fixed on a roller frame 28 . the roller frame 28 has two rollers 27 , a vibration generator 26 and a shoulder detection device 22 connected thereto . the roller frame 28 faces a support surface 2 of the backrest 3 of the massage chair 1 . the shoulder detection device 22 includes an emitting device 25 and a sensing device 24 . the emitting device 25 includes a magnet 20 and a fixing plate 21 fixed on the roller frame 28 . the sensing device 24 includes a pcb board 17 and a hall sensor 18 fixed on the swing arm seat 16 . as shown in fig6 , the vibration generator 26 includes a cover 33 , a vibration motor 34 , an eccentric member 35 and a base 36 , wherein the base 36 has a slot 37 and is connected to an underside of the cover 33 , the vibration motor 34 is mounted inside the cover 33 , and the eccentric member 35 is connected to an output shaft of the vibration motor 34 . as shown in fig1 - 6 , when the rollers 27 are not applied by the load of a user &# 39 ; s body through the support surface 2 , the hall sensor 18 of the shoulder detection device 22 is in an off status . when the massage chair is activated , the massage mechanism 5 moves to the user &# 39 ; s shoulders and the rollers 27 bring the magnet 20 on the emitting device 25 of the shoulder detection device 22 on the roller frame 28 to move to generate a shift relative to the hall sensor 18 on the sensing device 24 of the shoulder detection device 22 on the swing arm seat 16 . in other words , the hall sensor 18 senses the change of magnetic field of the magnet 20 . when the change reaches a certain level , the hall sensor 18 is activated , thereby obtaining a precise positioning on the user &# 39 ; s shoulders . as shown in fig1 - 3 , in the operation of kneading , the kneading motor 9 drives the first belt pulley 8 , the first belt 6 , the second belt pulley 7 , and the worm rod 29 one after the other . then , the worm wheel assembly 32 engaged with the worm rod 29 drives the swing arm seat 16 and the roller frame 28 to move back and forth , so that the rollers 27 fixed on the roller frame 28 produce kneading actions to the user . in the operation of tapping , the tapping motor 12 drives the third belt pulley 14 , the second belt 13 , the fourth belt pulley 15 , and the eccentric shaft 31 one after the other . the connecting rod 10 connected to the eccentric shaft 31 drives the swing arm seat 16 and the roller frame 28 so that the rollers 27 fixed on the roller frame 28 move front and rear to tap the user &# 39 ; s body . as shown in fig3 - 6 , in the operation of vibration , the vibration motor 34 drives the eccentric member 35 to eccentrically rotate to cause vibration of the roller frame 28 , so that the rollers 27 vibrate at a high frequency . the shoulder detection device 22 allows the massage mechanism 5 to precisely massage the user &# 39 ; s shoulders . the magnet 20 and the hall sensor 18 are not in contact with each other directly and this ensures that the emitting device 25 and the sensing device 24 do not fail . the vibration generator 26 is located beneath the rollers 27 so that the rollers 27 can move toward the user &# 39 ; s body and the vibration generator 26 can be operated together with the massage mechanism 5 . by this arrangement , when the rollers 27 move , the user feels a high frequency of vibration and continuous tapping . this can effectively massage the user and provide with complete relaxation . the cover 33 is made of elastic material so that the vibration motor 34 can be avoided from being damaged . the base 36 is made of steel board that secures the vibration motor 34 in position , so that the vibration motor 34 cannot move both in longitudinal and lateral directions . the vibration generator 26 is connected to the roller frame 28 that is made of elastic material so that the vibration generated by the vibration generator 26 can be effectively transferred . although the present invention has been described with reference to the preferred embodiment thereof , it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims .
a massage mechanism for a massage chair includes a roller frame which includes a roller , a vibration generator and a shoulder detection device . the massage mechanism detects the precise position of a user &# 39 ; s shoulder so that the roller and the vibration generator are moved to precise positions to massage the desired parts of the user .