91Service Manual – SC600034 - Scrub System, DiscFunctional DescriptionThe disc deck is available in a 36-inch and 40-inch size The deck uses two, gear-reduced, drivemotors to drive the two brush or pad holder discsThe scrub deck is raised and lowered using aleadscrew actuatorThe deck also includes two removable sidesqueegees that help keep the scrub watercontained within the path of the scrub deck, andsubsequently within the rear squeegee pathDeck Lift ActuatorThe deck lift actuator controls the raising andlowering of the deck, as well as the amount ofpressure the scrub disks apply to the floor.To extend or retract the actuator, the powermodule reverses polarity to the actuator Theactuator determines how long it should run to reachfull extension or retraction It accomplishes this witha pair of cams, limit switches, and diodesAs each cam rotates, it opens the normally closedcircuit and stops the motor’s rotation However eachcam is functional only for its intended direction ofrotation This is accomplished with the diodes, whicheffectively short circuit the switch for one direction(polarity), but not the otherIn the diagram below, the clockwise cam/limitswitch is effectively short circuited by its diode whenthe electrical polarity is driving the motor in thecounterclockwise direction (and vice versa for theCCW) But the counterclockwise cam is not shortcircuited, so it will open the motor circuit when thecam lobe reaches the limit switchThe down-limit cam isn’t adjustable, but by adjustingthe position of the up-limit cam, the actuator cancontrol its length of travel for the leadnut along the leadscrewMCW CCWDiodes LimitSwitchesUp LimitCamDown LimitCam
