According to international classification of patents, the invention may be designated with symbol B61F5/00, referring to construction elements of railway vehicles bogies, or more specifically to B61F5/08 that comprises rubber springs bogie reinforcements.

It may also be designated with symbol B60G13/00 describing elastic suspensions, especially with symbol F16F15/OS defining vibration elimination by rubber springs.

Technical problem The invention solves problem of reducing of spring breakdowns caused by influence of shock stresses on suspension system. The solution is based on design of rubber elastic element that disburdens spring and damps shock stresses imposed on spring.

Present state In order to reduce strikes caused by transition of wheels over rail contacts and other rail unevennesses, total car weight is transferred to rails over some elastic parts, i. e. different kinds of springs, bumpers, dampers and shock absorbers.

Depending on number of elastic elements set, the damping between body and wheel sets is divided into single, double and multiple damping.

Recently, special rubber dampers of various shape and construction, some of them with reinforcements, are used for balancing of load distribution over axle stubs and damping of all shock stresses caused by wheel transition over rail contacts and crossings, in order to protect both rail and wheel.

In this sense, laminated springs are also used.

YU patent nr. P-0175193 named"Railway wagon running stock"where running stock with cradle is hanged on chassis by two binding bridges; cradle is bound on lower part of bridges by hinges; bridges are bound to chassis on their upper part also by hinges. Cradle is in the same time also bound to chassis with two hydraulic dampers with twofold action : by vertical, and by lateral movement of cradle.

This solution is applicable also on tramcars.

YU patent nr. 47913 of German company ABB HENSCHEL WAGGON GmbH from Berlin shows solution of coupling of driving mechanism to railway car bridge utilizing spring that tenses both parts in opposite directions, being itself tensed in direction opposite to those of laminated springs of driving set.

The same company patented in Yugoslavia solution with nr. 47915 named"High-speed railway vehicle bogie"where a dangling damper is put between laminated-spring outer levers of each double laminated-spring joining lever; the damper dampens horizontal displacements between axle bearing and bogie frame.

The same company presents in German patent nr. 4313129 named"Running gear for railway vehicles"where frame is set over primary springs on wheels, or running axle stocks ; on the other side chassis cradle or railway vehicle chassis are leaning over secondary spring also on wheels, or running axle stocks and in the same time it is joined to bogie frame by shock absorbers that are dampening vertical displacements and lateral dangling.

Yugoslav patent nr. 48803 describes"Valve for prevention of airbags puncturing in bus suspension system"where valve body is at one end joined to airbag by wind and pipe, and at the other end is joined by wind and pipe to pressurized air reservoir in bus. This solution is just mentioned as illustration of wider area of dampening solutions, and not as solution that is similar to invention presented in this paper.

At last, a solution of screw spring with trapezoid-circular cross-section of spring wire for Y25 bogie, resulted from UIC investigations of empty wagon noise reduction. This spring, due to its specific construction, has characteristics similar to those of pair of standard springs (inner and outer) of Y25 bogie, and therefore can replace them. This solution is protected by patent of LANGEN & SONDERMANN GmbH.

And finally, there exists a steel element with main role to limit amplitudes of load. The main disadvantage of such solution is that it does not dampens shock stresses, but only limits displacement-amplitudes. With such a solution, shock stresses on suspension are reduced, but large percent of spring damages is still present.

The essence of the invention Rubber elastic element consists of elastic delimiter and its holder.

Elastic delimiter consists of three parallel metal plates with two rubber inserts between them. Through process of rubber vulcanization, the elastic element becomes single unit.

Elastic delimiter is placed within its holder thus making set-rubber elastic element.

Positioning of elastic element relative to its holder is accomplished by nails through appropriate holes that prevent sliding of delimiter from holder.

Holder of elastic element is welded to longitudinal wagon bearer and is aimed for rubber elastic element binding.

The main idea of invention is that rubber elastic element is activated as bearer of part of dynamic load when some selected wagon load is exceeded. In this manner rubber elastic element changes characteristic of suspension system.

Rubber elastic element leans over lower metal plate indirectly, and over elastic delimiter directly on spring belt during shock stroke.

Introduction of rubber elastic element reduces static load in amount of 15% and dynamic load in amount of 30%. Simultaneously, in case of main spring leaf breaking axle bearing remains loaded over rubber elastic element, reducing in this manner possibility of derailment.

It is also important that breakdown dynamics is not influenced by difference of springs on the same axle.

Short description of outline The invention is described in details in implementation example presented at the following drawings: Drawing 1 : presents top view of elastic delimiter; Drawing 2: presents side view of elastic delimiter (outline) with partial section over holes on metal plates; Drawing 3: presents side view of elastic delimiter (profile) with partial section over holes on metal plates ; Drawing 4: representing set of elastic element and holder (without nails) with partial section over holes on metal plates; Detailed description of invention The drawings present rubber elastic element, that is attached by splits (not shown) to holder bear through holes (7). Holder bear is welded for longitudinal chassis bearer.

Rubber elastic element consists of elastic delimiter (6) placed within holder (3) presenting together integral part.

Elastic delimiter (6) consists of top metal plate (1) with several holes (7), bottom metal plate (2), middle metal plate (5) positioned symmetric relative to top metal plate (1) and bottom plate (2). Between top metal plate (1) and middle metal plate (5), as well as between middle metal plate (5) and bottom metal plate (2) there are rubber inserts (4). Through process of vulcanization elastic delimiter (6) becomes single unit.

Join between holder (3) and elastic delimiter (6) is accomplished by nails (not shown) through holes (8), therefore disabling sliding of elastic delimiter (6) from its holder (3).

Main idea of invention is that at selected wagon load rubber elastic element (in fact, its elastic delimiter (6) ) is activated, taking part of load together with springs, changing in this manner characteristic of whole spring system in comparison with case when rubber elastic element is not built in.

In order to achieve the main idea, the invention is designed so that rubber elastic element leans on spring belt over bottom metal plate (2) and to wagon chassis over holder (3) of elastic delimiter (6).

Characteristic (dependence of force F on displacement f) of suspension depends on characteristic of spring and characteristic of rubber elastic element, and it may be considered as two-stepped: in first step, before crossing displacement is reached, only spring is activated, and in the second step, both spring and rubber elastic element are activated.

The choice of rubber elastic element, i. e. the choice of rubber insert (4) is performed in such a manner that both spring and rubber elastic element can carry suspended weight of vehicle, both in lower part of loads (empty and partially loaded vehicle) and in upper part of load (partially and fully loaded vehicle). The effect of the construction is that by empty and partially loaded vehicle only spring is active, so the characteristic has mild slope. By larger loads, rubber elastic element is also activated, carries part of the load, increasing in this manner rigidity of suspension.