Raised and lowered by means of movable rod (plunger) rigidly fixed to the bottom of the elevator car.
More inexpensive than Traction = No cables, drums, traction motors, elaborate controllers, safety devices or penthouse equipment required
Seed & rise = low speed - 200 fpm & low-rise - up to 65 ft
Hydraulic oil used, powered by an oil pump.
No overhead machine room required (a big plus)
Additional advantages over traction units:
Load is carried by ground rather than structure at top of shaft
Smaller hoistway due to absence of counterweight and its guide rails
cars lower manually by operation of oil valves (good if control equip. or power fails)
No limit to load that can be lifted
Inherent disadvantages
- operating expense
- not counterweight creates necessity of large motor to drive oil pump and all energy is lost in heat.
- limited to low rise, low speed applications, four story max.
- ride quality inferior to traction
- temp of pump and oil storage tank must be controlled to keep oil viscosity at acceptable levels
- high inrush of current taken by pump each time ti travels up requires a "stiff" power supply to avoid line voltage fluctuations.
- Pump, motor and piping can be noisy, mitigation by locating pump mechanism up to fifty feet from the elevator shaft
Plunger type have been used less due to oil seepage into the ground, Hole-less and roped Hydraulics have come into more common use in response.
No comments:
Post a Comment