between the support plates 120 121 for angular movement about its own axis extending parallel to the shaft 34 the shaft 123 is located remotely from the electrostatic recording head 21 with the shaft 34 interposed therebetween a pair of cams 84 85 are secured to the shaft 123 at its end portions respectively for contact with lower surfaces of the bearings 80 81 respectively an attachment wheel 86 is mounted on one end of the shaft 123 outside of the support plate 121 and has an eccentric pin 87 projecting parallel to the axis of the shaft 123 to the eccentric pin 87 there is pivotably attached an actuator bar 88 coupled to a plunger 90 of a solenoid operated plunger unit 89 the actuator bar 88 is connected at a distal end thereof to a tension spring 91 for normally biasing the actuator bar 88 in a direction away from the solenoid operated plunger unit 89 when a solenoid 92 of the solenoid operated plunger unit 89 is energized the plunger 90 and hence the actuator bar 88 are axially displaced against the biasing force of the tension spring 91 to the right as illustrated in fig6 and 9 then the cams 84 85 are angularly moved into engagement with the bearings 80 81 respectively to displace the latter toward the electrostatic recording head 21 when the solenoid 92 is de energized the plunger 90 and the actuator bar 88 are forced by the tension spring 91 to return to the left fig6 and 9 thereby turning the cams 84 85 out of engagement with the bearings 80 81 which are then allowed to descend by gravity along the slots 82 83 respectively the shaft 34 and hence the roller 22 are now lowered.