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Testing device for hydraulic rope system tensile force equalizing unit

Hrabovský Leopold, Frydrýšek Karel

Mechanics and Mechanical Engineering

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2021

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Vol. 25, nr 1

22--31

EN

Rope elevators, also referred to as traction elevators, have a cabin suspended from a system of ropes. The system of ropes consists of at least two load-bearing steel ropes with six strands or, from the point of view of easier bending, and currently more widespread, ropes with eight strands. Lifting or lowering of the car, run between the guides, is ensured by the frictional force of the steel ropes in the grooves of the traction disk of the elevator machinery. As the load-bearing capacity of the elevator increases, the required number of load-bearing ropes also increases, especially in the case where small diameter ropes are used in traction elevators. The actual weight of the car and the weight of the load must be evenly distributed among all supporting ropes that are used in the given layout of the elevator. Currently, several principles are known by which it is possible to detect and also change the values of the instantaneous magnitudes of the tensile forces acting in a system of ropes. The paper describes the principle of operation of hydraulic balancing of tensile forces in the system of supporting ropes, which uses the laws of hydromechanics and knowledge of pressure transfer to any place in the fluid, known as Pascal’s law. Balancing of differently set values of tensile forces in three supporting ropes, to values of the same size, can be simulated on a test device. This presents the correct operation of the hydraulic system and the possibility of balancing tensile forces in the system of supporting ropes described by the principle of hydraulic device.

2

Tensile Forces in Lift Carrier Ropes Exerted by the Fluid Pressure

Hrabovský Leopold

Advances in Science and Technology. Research Journal

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2019

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Vol. 13, no 3

31--37

EN

This paper describes the methodology by which it is possible to compare different tensile forces that are caused by the uneven distribution of loads in carrier ropes of lifts. In order to compare the applied tensile forces in a certain number of carrier ropes, it is possible to use the device called “rope hydraulic tension compensator”, when, for example, building new elevators, changing carrier ropes during renovations or servicing existing lifts. The comparison of tensile forces in lift carrier ropes by the described device is based on the method of liquid pressure diffusion in a closed vessel. The rope hydraulic tension compensator consists of a number of structural parts, the main of which are double-acting hydraulic cylinders. The number of these cylinders is equal to the number of carrier ropes of the given lift. The pressure of the hydraulic fluid, which is supplied to the inner shell of individual hydraulic cylinders, controls the length of extension of individual piston rods of the hydraulic cylinders. The position of the piston in each of the hydraulic cylinders is directly proportional to the length of the extended piston rod, which corresponds to compression of the cylindrical coiled spring, above which the respective hydraulic cylinder is located. Different compressions of individual cylindrical springs exert different magnitude of tensile forces in suspension eye-bolts, into whose longitudinal axes the total load size is distributed unevenly. The paper also describes the description and hydraulic circuit diagram of a hydraulic power unit, which is used to control the piston positions of two-way hydraulic cylinders.

3

Properties of homogeneous flow of hydraulic fluid retaining gap

Ułanowicz L.

Journal of KONBiN

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2011

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No. 1 (17)

283--296

EN

This paper presents the laminar flow of homogeneous liquids in crevices of smooth hydraulic resistance. The paper presents a theoretical model for the distribution of pressure in the gap and the flow rate through the slot hydraulic. The presented theoretical models for the distribution of pressure and flow in the gap on conventional hydraulic resistance of hydraulic joints, whose shape is related to the errors of their execution. In deriving the theoretical models, by introducing a variable height of the gap in the initial episode, was founded stream velocity profile variability in the hydraulic fluid retaining gap and zero values of local losses at the entrance to the slot. An analysis of the validity of the simplifications adopted in the given formulas for the distribution of pressure and flow in the hydraulic gap and on the basis provides guidelines for estimating the energy losses that occur cracks in the hydraulic resistance.

PL

W artykule przedstawiono zagadnienia przepływu laminarnych cieczy jednorodnych w gładkich hydraulicznych szczelinach oporowych. Przedstawiono wzory teoretyczne na rozkład ciśnień w obszarze szczeliny oraz natężenia przepływu przez szczelinę hydrauliczną. Przedstawione wzory teoretyczne na rozkład ciśnień i natężenia przepływu w szczelinie hydraulicznej dotyczą typowych hydraulicznych szczelin oporowych, których kształt związany jest z błędami ich wykonania. Przy wyprowadzaniu wzorów teoretycznych, przez wprowadzenie zmiennej wysokości szczeliny we wstępnym jej odcinku, założono zmienność profilu prędkości strugi cieczy w hydraulicznej szczelinie oporowej oraz zerowe wartości strat lokalnych na wejściu do szczeliny. Dokonano analizy zasadności przyjętych uproszczeń w podanych wzorach na rozkład ciśnień i natężenia przepływu w szczelinie hydraulicznej i na jej podstawie przedstawiono wytyczne dotyczące szacowania strat energetycznych jakie mają miejsce w hydraulicznych szczelinach oporowych.