What Is a Hydraulic Elevator?

The hydraulic elevator refers to an elevator that presses oil into a cylinder to make a plunger move linearly through a hydraulic power source and directly or indirectly through a wire rope to move a car. Hydraulic elevator is an integrated product of machinery, electricity, electronics and hydraulics. It consists of the following relatively independent but interrelated systems: pump station system, hydraulic system, guidance system, car, door system, electrical control system, safety protection System, etc. ^[1]

Hydraulic drive is an early form of elevator drive. The transmission medium of the early hydraulic elevator was water. The incompressible nature of water was used to increase the pressure of the water by pressurizing it. The water with a certain pressure was inserted into the cylinder, and the plunger inside the cylinder lifted the car, so that The car runs upwards; the drain is opened by the relief valve, and the car descends under its own weight. However, it is difficult to solve the problem that the water pressure contains air bubbles and the cylinder rust, and then the oil is used to drive the plunger to perform linear motion. Because the hydraulic elevator has a large lifting force, can provide high mechanical efficiency and low energy consumption, the advantages are particularly obvious for short strokes and heavy loads. In addition, because the hydraulic elevator does not need to have a machine room on the roof, the vertical size of the hoistway is reduced, and the building space is effectively used, the application prospect of the hydraulic elevator is broad. Hydraulic elevators are now widely used in parking lots, factories and low-rise buildings. For occasions with large loads, slow speeds and short strokes, the use of hydraulic elevators is more economical and suitable than traction elevators. ^[2]

Hydraulic elevator operation is divided into up and down. When the elevator descends, open the valve group and use the weight of the car [the weight of the passenger (cargo)]

Hydraulic elevator is a high-tech system with mechanical, electrical and hydraulic integration. It can be divided into multiple relatively independent but coordinated sub-systems.

(I) Pumping station system

Pumping station system consists of

(I) Characteristics of hydraulic elevator building structure

(1) There is no need to set up a machine room with high requirements and cost above the shaft, and the roof can be flush with the roof.

(2) The equipment room is flexible. The hydraulic transmission system relies on oil pipes to transmit power, so the location of the machine room can be set within 20 m from the shaft, and the area occupied by the machine room is only 4 to 5 m².

(3) High shaft utilization. Generally, the hydraulic elevator is not provided with a counterweight device, so the utilization rate of the hoistway area can be improved.

(4) The structural strength of the hoistway is low. Because the vertical load of the hydraulic elevator car such as its own weight and load are all applied to the foundation of the hoistway through hydraulic cylinders, the building performance requirements for the walls and top of the hoistway are low.

(Two) characteristics of technical performance of hydraulic elevator

(1) Smooth running and comfortable ride. The hydraulic system transmits power uniformly and smoothly, and can realize stepless speed regulation, and the elevator's running speed curve changes gently, so the comfort is better than that of speed regulating elevator.

(2) Good safety, high reliability and easy maintenance. Hydraulic elevators are not only equipped with the safety devices of universal traction elevators, but also with the following devices:

1) Overflow valve. Prevents excessive system pressure during upward movement.

2) Emergency manual valve. When a power failure occurs, the car can be lowered to the nearest floor position to open the hall and car door automatically to ensure that passengers can safely exit the car.

3) Manual pump. When the system fails, the manual pump can be operated to release high pressure oil to make the car rise to the nearest floor position.

4) Pipe rupture valve. When the hydraulic system pipeline is broken and the car stall is reduced, the oil circuit can be cut off automatically.

5) Oil tank oil temperature protection. When the oil temperature in the fuel tank exceeds a certain value, the oil temperature protection device sends a signal to suspend the use of the elevator. When the oil temperature drops, the elevator can be started.

(3) Heavy load. The hydraulic system has a large power-to-weight ratio, so an elevator of the same specification can carry a large weight.

(4) The noise is small. The hydraulic system can use low-noise screw pumps. At the same time, the pump and motor can be designed as submersible structure, forming a whole pumping station, which can greatly reduce the impact of noise.

(5) Good explosion-proof performance. The hydraulic elevator uses low-condensing flame-retardant hydraulic oil, the fuel tank is integrally sealed, and the motor and hydraulic pump are immersed in the hydraulic oil, which can effectively prevent the combustion of combustible gas and liquid. ^[3]

According to the connection between the car and the hydraulic cylinder, the hydraulic elevator can be divided into two types: straight top and side top:

1) Straight type is to directly apply the plunger to the car or car frame. The connection between the car and the plunger must be flexible. Straight-top hydraulic elevator can be provided without emergency safety braking device and speed limiter, so the car structure is simple and the hoistway space is small. No steel wire rope is required at the top of the building, and the total load of the car is added to the bottom of the pit. Therefore, a deeper vertical pit must be made for the hydraulic cylinder.

2) The side top type connects the plunger to the car frame through a suspension device (rope, chain). Generally, the displacement ratio of the plunger and the car is 1: 2, and 1: 4 and 1: 6 are also used. Side top hydraulic elevators do not require vertical pits. Because wire ropes or chains are used, speed limiters and safety gear devices are required. Because the lifting hydraulic cylinder is on the side of the car, the required hoistway space is larger than that of the straight top. ^[4]