RO135521A2 - Hydraulic lifting unit with hydraulic cylinder and potential energy recovery upon load lowering at controlled speed, without throttling - Google Patents

Abstract

The invention relates to a hydraulic lifting unit with hydraulic cylinder and with recovery of potential energy upon lowering the load with controlled speed, without throttling, such as: hoists, freight or passenger elevators, lifting platforms, which use hydraulic cylinders to lift a load, and upon lowering, accumulate the potential load energy as pressure energy of working fluid in a pneumatic-hydraulic accumulator (4) and control the speed without throttling the working fluid discharged from the cylinder. According to the invention, the unit recovers the potential energy of the load upon lowering it, for this purpose switching an electrovalve (6) on a field (b), allowing the pressurized oil discharged from a cylinder (1) under the pressure created by the load to enter a hydraulic motor (2) it drives, the motor (2) driving a pump (3) which pumps the oil partially or integrally sucked from the motor (2) into a pneumatic-hydraulic accumulator (4) where the lowering speed of a load (vS) is proportional to a rotary speed (n) of the common motor (2) - pump (3) shaft, the lowering speed being controlled by a PLC (7) which reads the rotary speed (n), compares it with the preset one and controls the change of a capacity ( α ) of the pump (3) so that the actual rotary speed is equal to the preset one according to the desired speed (vS) for lowering the load, the PLC also managing the overall operation of the hydraulic lifting unit, while for lifting the load by using the recovered potential energy converted into hydraulic pressure energy and stored in the pneumatic-hydraulic accumulator (4), the electrovalve (6) is switched to the field (b).

Description

HYDRAULIC LIFTING INSTALLATION WITH HYDRAULIC CYLINDER AND POTENTIAL ENERGY RECOVERY FOR DOWNLOADING SPEED WITH LOAD CONTROL WITHOUT DROSELING

The invention relates to a hydraulic lifting system used in S 5 lifting machines>

type: lift, freight or passenger elevator, lifting platform, etc., which use hydraulic cylinder to lift the load, and when descending accumulates the potential load energy in the form of working fluid pressure energy in a pneumatic-hydraulic accumulator and controls the speed without dredge the working fluid discharged from the cylinder.

Hydraulic lifting cylinders are known in which the working fluid coming out of the cylinder pushed by the piston under the action of the load is drossed to prevent the uncontrolled increase of the lowering speed due to gravitational acceleration.

The disadvantages of these installations are:

• low energy efficiency due to the dredging of the working fluid when the load drops;

• heating of the working fluid due to the transformation of the pressure energy of the working fluid into heat, by drossing;

• additional energy consumption with working fluid cooling.

The hydraulic lifting system according to the invention is characterized in that, when the load is lowered, it accumulates the potential load energy in the form of working fluid pressure energy in a pneumatic-hydraulic accumulator and controls the lowering speed without dredging the working fluid.

The hydraulic lifting installation according to the invention has the following advantages:

• high energy efficiency due to the accumulation of potential load energy in the form of hydraulic energy;

• minimal energy losses due to the fact that the working fluid is not drossed when the load is lowered;

• lower prices for both the construction and operation of the hydraulic lifting system because it is no longer necessary to cool the oil.

The following is an embodiment of the invention in connection with:

FIG. 1: Hydraulic lifting installation with energy recovery and speed controlled on descent - Hydraulic diagram.

Description and operation of the hydraulic lifting installation

a) Description

Hydraulic cylinder 1 lifts the load with the help of the supplied hydraulic energy or the pneumatic-hydraulic accumulator 4. EU ^.

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The hydraulic motor 2 receives the hydraulic energy from cylinder 1 as the load drops and converts it into mechanical energy which it transmits to the variable capacity pump 3.

The shaft of motor 2 is integral with the shaft of pump 3. Pump 3 converts the mechanical energy received from motor 2 into hydraulic pressure energy with which it charges the battery 4.

Solenoid valve 6 closes / opens the connection between the lifting cylinder 1 and the hydraulic motor 2. Solenoid valve 5 closes / opens the connection between the pneumatic-hydraulic accumulator 4 and the lifting cylinder 1. Distributor 9 directs the flow of the electric pump 8 to the lifting cylinder 1 or to the basin 13. Safety valve 10 protects the electric pump circuit from overpressure 8. Pressure gauge 12 indicates pressure to the pump circuit. in the basin 13 is the working fluid of the installation. The one - way valve 11 allows the working fluid to flow only from the pump 3 to the battery 4.

b) Operation

When the battery 4 is discharged, the load is lifted with the electric pump 8 by means of the distributor 9 whose electromagnet He is electrically supplied.

The recovery of the potential energy of the load is done when the load is lowered. For this, the electromagnet E2 is supplied and the solenoid valve 6 allows the working fluid from cylinder 1 to enter with pressure into the hydraulic motor 2 with a constant capacity Vm which it drives.

In order to prevent the load from descending rapidly due to gravity, the shaft of the hydraulic motor 2 must be braked. in the battery 4.

The speed of lowering the load v _s is proportional to the speed of the motor shaft 2 - pump 3. In order for the load to descend with a constant speed v _s , the speed n must remain constant. PLC 7 does this by changing the capacity of pump 2 so that the speed of the motor shaft 2 - pump 3 is equal to that prescribed.

The PLC 7 receives information on the pressure p _a in the battery 4, the pressure p _c required by the load and calculates the power and energy required to lift the load and which is available in the battery to manage the lifting of the load with hydraulic energy fully supplied by the battery 4, partly from the battery 4 and in addition from the electric pump 8 or partly from the electric pump 8.

For the forced lowering of the load in case of failure, the distributor 9 is switched to field b which droselizes the circulation of the hydraulic oil on the route from A to T.

Claims (3)

demand 1. Hydraulic lifting system with hydraulic cylinder characterized in that during the lowering of the load it recovers its potential energy transforming it into pressure energy of the hydraulic oil with the help of the hydraulic motor 2 - see fig. 1 - which is supplied with oil pressurized by the piston of cylinder 1 under the action of the load and of the pump 3 which is driven by the engine 2 and charges the battery 4 with oil under pressure. 2. Hydraulic cylinder lifting system, characterized in that it controls the speed of lowering the load by means of the PLC 7 - see fig. 1 - which reads the speed of the common motor shaft 2 - pump 3 compares it with the set one and commands the modification of the capacity of the pump 3 so that the achieved speed is equal to the predetermined speed according to the desired speed v _s for lowering the load. 3. Hydraulic cylinder lifting system characterized in that it is driven by PLC 7 - see fig. 1 - which controls the recovery of potential load energy, controls the speed of the load lowering and manages the overall operation of the hydraulic system.