link supporting device 20d a lower end of a link member 14d is pivotally connected to a link support axis member 38 which extends in a direction perpendicular to a base plate 11 a base axis member 39 is pivotally supported by the base plate 11 such that the base axis member 39 extends horizontally frontward parallel to the link support axis member 38 a connection link 40 which includes in an intermediate portion thereof a u shaped leaf spring 41 as an elastic member elastically connects between the two axis members 38 39 when rotation of a drive motor 12 is stopped the link member 14d vibrates and the link support axis member 38 pivotally connected to the link member 14d also vibrates with elastic deformation of the leaf spring 41 of the connection link 40 elastically connected to the base axis member 39 thus the vibration of the link member 14d is effectively attenuated by the elastic deformation of the leaf spring 41 the link supporting device 20d enjoys a simple construction the connection link 40 may include in an intermediate portion thereof an elastic member different from the leaf spring 41 such as a plate like rubber member fig1 shows a sixth embodiment of the present invention in which the link supporting device 20 shown in fig1 is partly modified to a link supporting device 20e a lower end of a link member 14e is pivotally connected to a link support axis member 43 which extends in a direction perpendicular to a base plate 11 a base axis member 44 is pivotally supported by the base plate 11 such that the base axis member 44 extends horizontally through a thickness of the base plate 11 parallel to the link support axis member 43 a connection.