Nilfisk-Advance Advance SC750 Service Manual

Also see for Advance SC750 ST: Instructions for use How-to

Contents

Nilfisk-Advance Advance SC750 Service Manual Manual pdf 77 page image

Service Manual: SC750, SC800, SC 750 ST, SC800 STForm Number 56043150 Page 77Scrub System – CylindricalFunctional DescriptionThe scrub system moves the scrub head up and down and turns the scrub motors on and off at the operator’s request, toprovide floor scrubbing action. The brushes spin toward one another at the bottom. The head is moved up and down byan electric actuator motor that has integrated position switches. The weight of the scrub head provides the downwardpressure for scrubbing. The actuator linkage is slotted to allow the brush head to “float” when going over low and highspots on the floor. A spring is used to lift just a bit of weight in order to obtain optimal scrub pressure weight. Note: Thecylindrical scrub system does not have an “extreme pressure” mode.• The Main Machine Controller energizes the brush solenoid to turn on the brush motors when the followinginputs have been met:o Key switch ono Operator requesto Machine moving signal (FOR/REV)is received from the Drive Motor Controller (A2 PG Drives Speed Con-troller) Approximately 24 volts received from the main controller (J3 Pin 6) is switched to battery nega-tive by the Drive Motor Controller, dropping the voltage to 0 volts.Here is how the circuit works for the scrub motors: The Main Machine Controller turns on the scrub motors indirectlyby energizing the Brush Contactor. The brush contactor coil is fed battery positive voltage through the key switch. Thevoltage goes through the coil and on to the controller. Inside the controller, it switches the circuit to battery negative toenergize the relay. When the relay energizes, positive battery voltage is applied through its contacts to the brush motors.Since the other side of the motors is connected to battery negative, they turn on.The Main Machine Controller also monitors the amount of electrical current (Amps) that is flowing through the brushmotor ground circuit. If it is higher or lower than expected a fault code will be set. It monitors the amperage indirectlyon a “sense” wire by measuring the difference in voltage (Voltage Drop) between a point near the motors and the mainbattery negative terminal. As actual current increases, the voltage drop measured increases. The controller then convertsthe voltage value to “Amps”. The monitoring circuit relies on a calibrated ground wire that is a specific gauge and length.An electric actuator is used to move the scrub head up and down. The actuator has a DC permanent magnet electric mo-tor which is driven by the Main Machine Controller. The motor turns a threaded shaft. When the threaded shaft turns, itmoves a threaded rod up and down. Since the rod is attached to the deck, it moves the deck up and down.Inside the actuator housing, there are also three position switches which are monitored by the Main Machine Controller.One for the “retracted” position, one for the “middle” position (Normal scrub pressure) and one for the “Extended” posi-tion (Extreme scrub pressure). Each switch is normally closed. The threaded rod has a collar on it that opens each switchas it passes by it. When the Main Machine Controller sees the middle position switch open, it knows that the deck is inthe normal scrub position. If that was its goal position, the controller turns off the motor to stop the deck in that posi-tion.