Hill-Rom CareAssist P1170, Service Manual

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Electrical System
Chapter 3: Theory of Operation
CareAssist™ Bed Service Manual (man330) Page 3 - 9
3
The two hilow columns also have upper and lower internal EOT devices. For
safety reasons, they are both backed up at each end. If one of these safety
devices is activated, the column cannot be used; however the other functions
remain operational.
Complementing these EOT devices, the overload limiting function of the
power supply unit provides protection in the event of mechanical failures,
obstacles, or overload.
Detection of Bed Not in Low Position
This type of detection is obtained by taking into account the state of the low
EOT of the hilow columns. The power supply unit controls the corresponding
indicator of the control unit as soon as one of the two EOTs is released.
Automatic Contour
The power supply, when it received a command from the control unit, controls
the automatic contour (head section and thigh section) operation of the bed.
This function is carried out through an intermediate switch of the thigh section
actuator. When the Head Up function is activated from the horizontal position,
the head section and knee section rise until the intermediate internal
microswitch of the knee section actuator cuts its power at approximately 20°.
The head section actuator continues to operate until its upper EOT is reached
or the control is released. When the Head Down function is activated and the
head section reaches the low position, the knee section actuator continues
operating until its lower EOT is reached or the control is released.
Dining Chair™ Position
The Dining Chair™ Position function combines the movements of the bed
frame sections and uses the intermediate internal microswitches of the knee
section and foot section motors to control the interaction between these two
sections.
Detection of Bed Connected to AC Power but Brakes Not Set
The detection system operates by a normal on switch, mounted on the foot end
crossbar and is activated by the brake/steer bar. The power supply unit controls
an audible alarm if the following two elements occur together: AC power is
present and the switch not activated. The audible alarm stops when the brake is
applied or when the bed is unplugged from the power source.