RU2547946C2 - Method of two-stage amortisation of machine support structures - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building. Method means formation of the system of two-stage supporting of the vibration object on the base via the shock-absorbers and intermediate support frame. Liquid with elements in form of balls is injected inside cavities of the frame. The balls are made out of heavy material, for example lead, and are located inside the ball-like plastic containers, that partially compensate in liquid their gravity.

EFFECT: improved efficiency of the vibration isolation in wide range of frequencies of forcing external loads.

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Description

The proposed method relates to mechanical engineering and, in particular, to shipbuilding, and in particular to methods of reducing vibration levels of ship machinery, mechanisms and equipment.

Known methods of vibration isolation using shock absorbers and shock absorbing supports (Patent No. 2313704, class F16F 9/10 of 06/09/2006) [1] and (Patent No. 2307267 of 03/28/2006) [2], which consist in the use of a fluid overflowing which from one cavity to another provides a hydrodynamic vibration damping (dissipative) shock absorber effect. However, this method does not use the mass properties of the liquid.

Closest to the proposed method is a method of creating a shock-absorbing system by attaching vibrating objects (machines, mechanisms, equipment) to the hull structures of the vessel through the supporting shock-absorbing elements (shock absorbers) of various designs. The specified method is proposed in a number of inventions (AC SU 1388618 A1, F16F 15/00 from 15.04.88, Bull.14 [3] and AC SU 1719743 A1, F16F 15/00 from 15.03.92, Bull. No. 10 [4]) . As practice shows, the two-stage depreciation system demonstrates the greatest efficiency on ships. In the case of its use, the depreciable object (engine, mechanism, equipment) is attached to the intermediate support frame using the supporting shock absorbers of the first stage, which, in turn, through the shock absorbers of the second stage to the deck, platform or bottom of the vessel. However, this method does not provide effective damping of oscillations in a wide range of frequencies. In addition, the spectrum of natural frequencies, formed in a similar way to the oscillatory system, is extremely dense. Therefore, the resonance phenomenon becomes a serious aspect of the problem of reducing the vibrational activity of an object with a depreciation device. In this regard, additional intermediate structural elements included in the two-stage shock absorbing system can worsen the vibration situation, since they can become critical vibroactive (resonating) elements when the frequency of disturbing loads changes. The problem can be solved by creating a two-stage vibration isolation with variable characteristics, capable of significantly reducing the vibration levels of the support system in a wide frequency range.

The main objective of the proposed method is to increase the efficiency of two-stage vibration isolation of the object in a wide frequency range of forcing external loads.

This goal is achieved by the fact that in the intermediate supporting frame, which is part of a two-stage depreciation system, an internal cavity is created, which is filled with liquid with elements that increase its density. Essentially, we are talking about the inclusion of a sealed metal (or composite) container filled with liquid instead of an intermediate support frame. As an option, it is proposed to manufacture a volumetric welded frame, for example, of channels (or thick plates), sealed with plates on the top and bottom to form internal voids (volumes) filled with liquid.

The effect of the modernization of the support frame in the depreciation system is associated with the peculiarities of the physicomechanical properties of the fluid, which has incommensurable magnitude moduli of bulk elasticity and shear. A liquid as a specific continuous medium weakly resists shear deformations (rotations), as a result of which its influence on the structure always manifests itself in resonance and in antiphase with respect to external load. The result is a significant damping effect, increasing with increasing volume and density (mass) of the liquid. The liquid used to dampen the vibration of the system, due to its inertial and specific elastic properties, can have a significant effect on the entire frequency spectrum, as well as on the vibration levels of the structure as a whole.

The enhancement of the vibration damping effect can be achieved by placing elements in the liquid that increase its bulk density. As such elements can be used, for example, heavy metal shot. The latter is enclosed in a spherical shell - a container made of lightweight durable material, such as plastic. The buoyant force acting in a liquid on a container with a fraction reduces (compensates) its gravity (but not mass). The most appropriate use of a liquid with a high specific gravity, for example glycerol, etc.

The use of containers also serves as a means of reducing the overall dimensions of the intermediate support frame if it is necessary to maintain its optimal weight.

The two-layer structure of the container shell improves its performance. The outer (slippery) thin layer is made of noise-absorbing wear-resistant material (for example, rubber or plastic). The inner layer should be made of a sufficiently strong material in order to prevent the destruction of the shell by a shot (for example, porous plastic can serve as a filler material). To reduce the noise level resulting from the friction of the containers inside the support frame, its internal surfaces are covered with a layer of noise-absorbing waterproof material (for example, rubber, plastic).

The method is as follows.

To reduce the level of vibration transmitted to the ship’s hull from the side of a vibroactive object (a working machine, equipment, mechanism), carried out by means of a two-stage depreciation system, fluid is pumped into the internal cavities of the intermediate support frame. To enhance the effect in the internal cavities of the frame in the required amount previously (at the manufacturing stage) are placed heavy elements. The latter are balls made of heavy material, such as lead. Elements are placed inside spherical plastic containers, partially compensating gravity in the liquid. After placing these elements, the frame is finally sealed with overhead sheets. Subsequent pumping (pumping) of the liquid is carried out through special nozzles using a hydraulic pump. After injection, the nozzles are sealed with plugs. The proposed method can be implemented using a two-stage depreciation of the support connections, the elements of which are shown in figures 1, 2, 3, where:

figure 1 shows the appearance of the design of two-stage depreciation;

figure 2 shows a cross section of a modernized intermediate support frame;

figure 3 shows a cross section of a container with a heavy element.

A two-stage depreciation device includes: a vibrating object (machine, mechanism, equipment) 1, mounted on the deck (platform, bottom) of the ship's hull 2 through two cascades of shock-absorbing elements (shock absorbers) 3, an intermediate supporting frame 4 with internal cavities formed by the upper 5 and lower 6 overhead sheets for pumping fluid 7 and placing heavy elements 8. For pumping (pumping) fluid inside the support frame, special inlet 9 and outlet 10 nozzles and openings 14 for fluid flow from one no cavity in another. Each heavy element (container) has an outer 11 and an inner shell 12, inside which a fraction 13 is placed.

Thus, the proposed method, the use of which will allow for effective vibration isolation of the supporting structures of ship machinery, mechanisms and equipment at various modes of their operation, as well as to improve the reliability of the structure, improve living conditions in the adjacent premises of the vessel. The proposed method can be applied to reduce the vibration activity of other ship structures, for example hydrofoils (wing stabilizers of movement).

The ability to effectively reduce vibration using the proposed method will expand the range of permissible parameters and structural materials analyzed in the process of design optimization of structures. This will make it possible to make new design decisions for which vibration is the main constraint.

Information sources

1. Patent No. 2313704, cl. F16F 9/10 dated 06/09/2006.

2. Patent No. 2307267 of 03/28/2006.

3. A.c. SU 1388618 A1, F16F 15/00 dated 04/15/88, Bull. 14.

4. A.c. SU 1719743 A1, F16F 15/00 dated 03/15/92, Bull. No. 10.

Claims (1)

The method of two-stage depreciation of the supporting structures of machines, mechanisms and equipment at various modes of their operation, including the formation of a system of two-stage support of the vibrating object on the base through shock absorbers and an intermediate support frame, characterized in that the frame is made hollow; liquid was pumped into the cavities with elements made in the form of balls made of heavy material, such as lead, and placed inside spherical plastic containers, partially compensating for their gravity in the liquid.

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