|
The usual approach is to retain the dc motors and install a system that includes "silicon-controlled rectifier" (SCR) drive system and digital logic. It will have a "floor locator", an electromechanical system that tells the controller just where the elevator is in the hoistway, with sufficient accuracy to achieve leveling at each floor within about 0.2 inch. The controller contains all of the "smarts" needed to receive input signals from the call buttons in the car and on the floors served, start the car in motion with minimal jerk, accelerate it smoothly to "cruising speed", then slow and stop it very close to the landing. It has all of the information for firefighters' service, accepting input signals from the fire alarm and key switches.
If you have an alternating-current machine, the new technology of variable frequency drives will provide a great improvement in the quality of the ride. Though devices such as reduced-voltage starters and two-speed motors were used to smooth things a bit, the basic mode is "on-off", resulting in pronounced jerks when the car starts and stops. Adding one of the new VF drives will provide smooth acceleration and deceleration comparable to a modern dc elevator.
Most controllers have built-in logic to handle "duplex operation," simple dispatching for two cars. More sophisticated "group operation" for two or more cars requires a separate dispatcher module.
Hydraulic Elevator Drives: The hydraulic elevator uses a motor-driven pump to supply high-pressure hydraulic fluid to move the car, and the key component is a very complex multiport valve that accepts signals from the controller and controls the flow of the oil from pump to the "jack" -- the hydraulic cylinder -- to raise the car, and from the jack back to the oil reservoir to lower it. The controller operates the valve in response to signals it receives from the call buttons in the car and on the floors, and from the floor locator system.
Modernizing a hydraulic elevator can involve only the controls and locator system, or it can include a new motor, pump, and valve as well. The choices are highly dependent upon the condition of the existing equipment and the maintenance arrangements.
Both elevator types can benefit from door improvements, including new operators ( the motor and drive gears) and other mechanisms. Sometimes new rollers and tracks are warranted as well. If hall buttons need to be relocated for ADA compliance, usually a surface-mounted fixture is best. The good ones operate well and, with the "fire warning" sign embossed into
|
|
the upper part, they look good, too. In the car, new operating panels and new handrails are the norm for ADA compliance. A hint: the old-style flat handrail that you remove makes an effective bumper when mounted eight inches or so above the floor, and the price is right.
b) Mechanical and Electrical and Fire Protection Connections
Improving machine room cooling is required in about 90% of elevator renovations; few elevators from the '60s and '70s had adequate cooling even for the relay controllers. Today's solid-state equipment is more sensitive to heat than the relay equipment, and additional cooling is a must. West of the Cascades, we usually cool with ventilation only, moving lots of outside air through the machine room with an air intake on one side and an exhaust fan on the other. East of the Cascades, mechanical cooling is a must.
For many years, the UBC required a smoke vent at the top of the hoistway, with the option of covering it with a moveable damper controlled by the fire alarm. We
|