We install hydraulic elevators by a variety of manufacturers.
Commercial hydraulic elevators fall into two basic categories; conventional (or
in-ground) and holeless.
All hydraulic elevators are driven by a pump and motor combination. The actual lifting
is done by a piston mounted within a casing or cylinder (jack assembly). Car speed,
acceleration, deceleration and relief pressure are regulated by a control valve mounted
between the pump and the cylinder. When the motor turns the pump, the pump creates
pressure which drives the piston and elevator up. To come down, a valve is opened
which allows the oil previously pumped into the casing to flow back into the reservoir,
allowing the car and piston to come down .
In-ground elevators are so called because the cylinder goes down into the ground as far
as the elevator travels up. This type of installation requires the drilling of a hole
below the elevator. Typical installations today utilize a PVC liner to protect the steel
cylinder from electrolytic action and other chemical reactions. RMR does not
install this type of elevator. Due to the inability to observe and maintain the
jack assembly after it is placed into the ground, we have determined that there
is no need to expose our customer or our firm to the liability associated with
an underground hydraulic oil leak.
Holeless elevators are
called so because they do not
use a conventional piston/casing arrangement. Holeless elevators come
in many different
styles. The two predominant types are direct-acting and roped. Holeless
equipment is typically more expensive than in-ground equipment;
however, the additional
expense is offset by the high cost of drilling a jack hole. Thye
other benefit to hole less equipment is that there is no possibility of
an environmental contamination.
Direct acting holeless elevators employ a piston that is connected directly to the
steel that supports the elevator cab. Typically this requires either a cantilevered
platform support or a second jack assembly. Also included in this category are telescopic
jacks that have multiple pistons within a single jack assembly. Direct acting hydraulic
elevators are only practical for a limited amount of travel.
Roped hydraulic elevators are more complicated as they employ an
indirect attachment to
the car. Roped hydraulic elevators utilize the same steel cables
that support high rise elevators but in a 1:2 arrangement. (See Illustration} In this manner the cab will move two inches for
every inch the piston travels. Roped hydraulic elevators are well suited to existing
buildings, applications where drilling a hole for the jack assembly is impractical or in
an application where travel is more than is practical for a direct acting hydraulic