Abstract: This invention relates to a vibrator which for example can be used to vibrate a tray for the purpose of conveying articles or material along the tray or alternatively can be used for vibrating articles or material where there is no requirement for conveyance in a pre-determined direction. A vibrator according to the invention has an actuator assembly which includes an actuator shaft which can rotate relative to said assembly but which is prevented from longitudinal movement relative to the assembly.