Patent Publication Number: US-2016244919-A1

Title: Intermediate Element and System for Fixing a Rail for a Rail Vehicle Onto a Foundation

Description:
The invention relates to an intermediate element for a system for fixing a rail for a rail vehicle onto a foundation. The intermediate element is provided to be arranged between an end section of a spring element and a rail for rail vehicles such that the spring element exerts a retaining force on the rail by means of the intermediate element during use. The intermediate element has a supporting surface for this purpose on which the end section of the spring element rests during use, and a contact surface that sits on the rail during use. 
     The invention also concerns a system having such an intermediate element for fixing a rail for a rail vehicle onto a foundation. 
     An intermediate element and a system of this kind are known from DE 20 2007 018 500 UI, for example. In this known system, a so-called ‘tensioning clamp’ is used as the spring element, which is configured in the shape of a ‘W’ having a middle bend and two spring arms extending away therefrom. The free end sections of the spring arms of the spring element each rest inside a retainer which is moulded into the supporting surface of the intermediate element. The intermediate element made of a non-conductive synthetic material rests on the upper side of the rail foot of the rail fixed using the system. In this manner, the intermediate element electrically separates the rail from the spring element and at the same time guarantees extensive exertion of the retaining force on the rail foot. 
     When a rail vehicle travels over rail fixing points set up using systems of the type in question, low-frequency movements, which are triggered by weight-loading, caused by the weight of the respective rail vehicle or train comprising several rail vehicles, medium-frequency movements, which are triggered by the distribution and dead weight of the axles or bogeys of the train, or high-frequency rail movements may occur, which are triggered by geometric deviations of the wheels of the respective rail vehicle travelling over said rail fixing points or damage on the running surface of the respective fixed rail. Each of these types of movement can lead to highly dynamic stresses on the spring element used to retain the rail. They can even be such that the spring element starts to resonate. The spring element is excited to its natural frequency in the process and as a result may be exposed to extremely high dynamic stress in spite of only minimal rail movements. Stresses of this kind may lead to premature material fatigue or such extensive wear and tear that early replacement is necessary. 
     In the light of the prior art described above, the purpose of the invention consists in providing means to minimise the risk of a shortening of the service life of a spring element, which is used in a system for fixing a rail to a foundation to hold down the rail, occurring following intermittent movements. 
     A system for fixing a rail should also be mentioned wherein simple means are used to prevent premature wear and tear of the spring element used in such a system to hold the rail down on the respective foundation. 
     To perform the task referred to above with respect to the means, the invention provides an intermediate element having the features indicated in claim  1 . 
     In order to perform the task referred to above with regard to the rail fixing system, the invention stipulates the use of an intermediate element configured according to the invention. 
     Advantageous embodiments of the invention are indicated in the dependent claims and are explained in detail below along with the inventive concept. 
     The intermediate element according to the invention for a system for fixing a rail for a rail vehicle onto a foundation is provided accordingly to be arranged between an end section of a spring element and the rail to be fixed such that the spring element exerts a retaining force on the rail by means of the intermediate element. The intermediate element has a supporting surface on which the end section of the spring element rests during use, and a contact surface that sits on the rail during use. According to the invention, the intermediate element is now designed to be resiliently compliant in an active direction from the supporting surface to the contact surface. 
     A system according to the invention for fixing a rail for a rail vehicle onto a foundation in which the rail has a rail foot, which supports it on the foundation, comprises accordingly
         a spring element braced against the foundation by means of a tensioning element, which has at least one spring arm with an end section configured on the free end thereof, and   an intermediate element configured according to the invention, the contact surface of which rests on the foot of the rail and the end section of the spring arm of the spring element rests on its supporting surface.       

     According to the invention, an intermediate element is inserted between the respective rail to be fixed and the end of the respective spring element acting on the rail. Compared with insulating intermediate elements used in known rail fixing systems, said intermediate element has significantly greater elastic resilience and correspondingly less rigidity thereby creating a cushioning effect. The intermediate element according to the invention thus offers significantly better shock-absorbing characteristics than is the case with insulating elements arranged in conventional systems for fixing rails for the purpose of electrical insulation between the respective spring element and the rail. 
     In this manner, the intermediate element according to the invention equipped with specific elastic resilience during use allows isolation of the spring element exerting the retaining force from the movements made by the rail. On account of the arrangement of the elastic intermediate element between the ends of the spring element and the rail, the vibrations of the spring arms are minimised and the cushioning effect achieved in this manner results in a reduction of the fading time for a natural vibration of the spring element. The spring element is thus protected against excessive stress and its service life is increased significantly. 
     The default elasticity according to the invention and cushioning effect of the intermediate element can be guaranteed through a suitable design or the selection of a suitable material. Thus it is possible, for example, to manufacture the intermediate element from a solid material, but to shape it in the manner of a spring such that it has elastic resilience that is adequate for the purposes according to the invention. 
     The intermediate element as a whole can also be made from an elastic or cushioning material, which has the required elasticity or attenuating characteristics, and at the same time is so wear-resistant that it can withstand the abrasive stresses that it is exposed to during use. Such materials are used in rail systems for intermediate plates, for example, which are placed in a rail fixing point between the respective foundation and the rail resting on it, in order to guarantee a defined resilience of the rail in the direction of gravity. 
     In order that the intermediate element transmits retaining forces, which are exerted by the respective spring element during use, to the rail in a permanently safe manner, it may be appropriate for the intermediate element to have a dimensionally stable section, on the upper side of which the supporting surface is configured, upon which the spring element acts using the respective end section of its spring arm. In this case, the elastic element is arranged on the underside of the dimensionally stable section assigned to the rail. In this manner the retaining forces applied by the spring element during use will be distributed over a large area of the elastic element and will prevent the elastic element from being damaged by the potentially sharp-edged end section of the spring element acting upon it or, on account of too small a contact surface between spring element and elastic element, from being placed under such heavy local strain that premature wear and tear occurs. 
     Alternatively or additionally, the intermediate element can also have a dimensionally stable section on the underside of which the contact surface is configured and on the upper side of which facing away from the contact surface, the elastic element rests accordingly. The dimensionally stable section thus arranged between the elastic element and the rail during use protects the elastic element, in particular against abrasive wear and tear, which may otherwise occur in the event of contact between the elastic element and the generally comparably rough surface of the rail. 
     An intermediate element according to the invention has optimum effect and durability if the elastic element is arranged between two dimensionally stable sections, i.e. is shielded both on its upper side assigned to the respective end section of the spring element and on its underside assigned to the rail by a dimensionally stable section of the type explained above. 
     The embodiments of the intermediate element according to the invention explained above and requiring at least one dimensionally stable section prove particularly practical if the elastic element is a layer made of an elastic, more particularly visco-elastic material, which is covered by the respective dimensionally stable section. However, the elastic element can also be configured as a separately pre-assembled spring which is connected to the respective dimensionally stable section. 
     In practice, the dimensionally stable sections can each consist of a wear-resistant, hard material with a rigidity that is sufficient to absorb the strains occurring during use and to guarantee adequate dimensional stability of the respective section. 
     Thus, the dimensionally stable sections can be made of metal, for example. However, it is advantageous with regard to their wear behaviour and the costs of their manufacture if the dimensionally stable sections are made from a synthetic material. Synthetic materials, which come into consideration here, are known per se from the manufacture of insulating intermediate elements of the type referred to at the beginning. They offer not only sufficient resistance to wear and tear and stability, but are also not electrically conductive. 
     In a case advantageous for practical use where the intermediate element is formed from at least one wear-resistant hard component acting as a vibration or electrical voltage insulator, which establishes contact with the rail or tensioning clamp, and an elastic soft component acting as an attenuator, the soft component can be applied to the hard component, i.e. the respectively available dimensionally stable section, in the manufacturing process such that a firmly bonded connection is established. This can be done through injection moulding or casting. However, it is also possible to pre-fabricate the respective dimensionally stable section and the elastic component separately and assemble them with the intermediate element subsequently. The elastic element can be firmly bonded to the respective dimensionally stable element, for example, more particularly glued or moulded, or connected in another manner, for example, through a form-fit connection. 
     It may be advisable from a manufacturing perspective, if the elastic element is intended to be arranged as an intermediate layer between two dimensionally stable sections, to connect the dimensionally stable sections together by means of a material support, which is less elastic than the elastic element, and consequently the dimensionally stable sections and the support define a retainer on the upper side, underside and long side thereof, in which the elastic element sits. This embodiment has the advantage that the dimensionally stable sections connected to each other by means of the support can be manufactured as a single piece in one operation, for example from a suitable, hard synthetic material. The support can be easily designed through a corresponding reduction in its wall thickness such that it does not prevent the necessary elastic resilience of the elastic element sitting between the dimensionally stable sections. 
     A particularly suitable embodiment of an intermediate element according to the invention, in particular for use in rail fixing systems, in which a W-shaped tensioning clamp is used as a spring element, is characterised in that it is configured in the shape of an elongated rectangle. In this manner, the end sections of the spring arms of such a tensioning clamp spring element can act upon the rail together by means of a single intermediate element. However, an individual intermediate element can of course also be assigned to each of the spring arms. 
     In order to ensure particularly secure bracing of the respectively assigned end section on the supporting surface of an intermediate element according to the invention, moulded elements can be configured on the supporting surface thereof against which the assigned end section of the spring element is braced during use. 
    
    
     
       The invention is explained in more detail below using a drawing that represents an example embodiment. A schematic view is shown in each case: 
         FIG. 1  a cross-section of a fixing point for a rail at right angles to the long side of the rail. 
         FIG. 2  a perspective view of an intermediate element for a system for fixing the rail. 
     
    
    
     The fixing point B shown in  FIG. 1  comprises two identically constructed systems  1 ,  1 ′ for fixing the conventionally configured rail S onto a fixed foundation U formed, for example, by a concrete sleeper or a concrete slab. A system  1 ,  1 ′ is arranged on each of the long sides of the rail S. The rail S is part of a track for rail vehicles (the rest of which is not shown) and has a rail foot F, a support resting on the top thereof as well as a rail head borne by the support on the free upper side of which the running surface for the wheels of the rail vehicle is configured. 
     The systems  1 ,  1 ′ each comprise a guide plate  2 ,  2 ′. A spring element  3 ,  3 ′ configured as a conventional W-shaped tensioning clamp sits on each of said guide plates. Each spring element  3 ,  3 ′ is braced against the foundation U by means of a tensioning element  4 ,  4 ′ configured as a conventional sleeper screw, which is screwed into a hole running through the respective guide plate  2 ,  2 ′ from the upper to the underside thereof and into a plastic pin  5 ,  5 ′ embedded in the foundation U. 
     The guide plate  2 ,  2 ′ is configured in the manner of a conventional angled guide plate. Said guide plate has a heel on its underside assigned to the foundation U with which it sits in a bonded manner in a correspondingly configured narrow channel  6 ,  6 ′ moulded into the foundation and extending along the rail S. The supporting surface of the respective guide plate  2 ,  2 ′ facing the foot F of the rail S abuts the long side of the respective rail foot F assigned thereto. In this manner, the rail S is braced laterally by the guide plates  2 ,  2 ′ on the respectively assigned long side. The guide plates  2 ,  2 ′ divert the shearing forces Q, which occur when a rail vehicle travels over the fixing point B, to the foundation. 
     In order to give the rail S a defined resilience in direction of gravity K at fixing point B, an intermediate layer Z commonly used for this purpose made of an elastically resilient material, is placed between the rail foot F and the foundation U. 
     The respective spring element  3 ,  3 ′ in system  1 ,  2  exerts a retaining force N, N′ on the foot F of the rail S by means of the end sections  7 ,  8  of its respective elastically resilient spring arms  10 ,  11  extending from its middle bend  9 , with which the rail S is held pressed against the foundation U. 
     An intermediate element  12 ,  12 ′ sits between the respective end sections  7 ,  8  of the spring elements  3 ,  3 ′ and the foot F of the rail S. 
     The elongated rectangular and identically configured intermediate elements  12 ,  12 ′ each have a first, dimensionally stable, plate-shaped section  13  extending over their length LZ and width BZ, on the upper side of which a supporting surface  14  is configured for the respectively assigned end sections  7 ,  8  of the spring elements  3 ,  3 ′. Moulded parts  17 ,  18  are moulded onto the end sections of the supporting surface  14  adjacent to the front sides  15 ,  16  of the intermediate elements  12 ,  12 ′ which each define a cavity-like retainer  19 ,  20  extending in the longitudinal direction L of the intermediate element  12 ,  12 ′. The respectively assigned straight end section  7 ,  8  of the spring elements  3 ,  3 ′ sits in said retainers  19 ,  20  during use. In this manner, the end sections  7 ,  8  are guided on their long sides such that their position remains secure on the respective intermediate element  12 ,  12 ′ even in the event of stronger relative movements between spring element  3 ,  3 ′ and rail S. 
     The intermediate elements  12 ,  12 ′ also comprise a second, plate-shaped, dimensionally stable section  21 , which is arranged in a direction normally aligned towards to the supporting surface  14  at a distance from the first section  13 , and also extends along the length LZ and width BZ of the respective intermediate element  12 ,  12 ′. A flat contact surface  22  is configured on the underside of the second dimensionally stable section  21  assigned to the rail foot F with which the respective intermediate element  12 ,  12 ′ rests on the upper surface of the rail foot assigned thereto during use. 
     The dimensionally stable sections  13 ,  21  are connected by means of a support  23 , which extends along one long side  24  of the intermediate elements  12 ,  12 ′. Looking at a cross sectional view of the long side L of the intermediate elements  12 ,  12 ′, the dimensionally stable sections  13 ,  21  and the support  23  encompass a ‘C’ shaped slot-like retainer  25 , which is open in the direction of the respective spring element  3 ,  3 ′ in the position of use and extends along the length of the intermediate element  12 ,  12 ′. 
     The dimensionally stable sections  13 ,  21  and the support  23  for the intermediate elements  12 ,  12 ′ are formed in a single-piece from a solid, dimensionally stable synthetic material, such as polyamide, for example, which optionally may be fibre or particle-reinforced. 
     An elastic element  26  consisting of a viscoelastically resilient synthetic material, such as a mixed or closed-cell material, for example polyurethane or ethylene propylene diene rubber, sits in the retainer  25  of the intermediate elements  12 ,  12 ′. 
     A circular recess  27  extending above the height H of the intermediate element  12 ,  12 ′ is formed in a central section of the intermediate element  12 ,  12 ′, starting from the long side, which is assigned to the respective spring element  3 ,  3 ′ during use, with which the arc of the U-shaped middle bend  9  of the respective spring element  3 ,  3 ′ engages in ready-assembled systems  1 ,  1 ′. 
     During the manufacture of the intermediate elements  12 ,  12 ′ the material of the elastic element  26  is injected into the retainer  25  such that a firm, inseparable bond is created between the dimensionally stable sections  13 ,  21  and the support  23  on the one hand and the elastic element  26  on the other. 
     The arrangement of the elastic element  26  in the retainer  25 , firstly guarantees adequate dimensional stability and secondly, a defined elastic resilience of the intermediate elements  12 ,  12 ′ in an active direction W corresponding to the active direction of the retaining force N, which is directed from the supporting surface  14  towards the contact surface  22 . 
     As a result of the viscoelastic properties of the respective intermediate element  12 ,  12 ′ effected by the elastic element  26 , in particular high and medium frequency movements of the rail S, which occur when a rail vehicle travels over the fixing point B, will be dampened if need be and transmitted to the respective spring element  3 ,  3 ′. This minimises the risk that the respective spring element  3 ,  3 ′ will resonate and wear prematurely. 
     On account of the design according to the invention as described, in addition to high elasticity and the associated attenuation effect in active direction W, the intermediate elements  12 ,  12 ′ are extremely rigid in a transverse direction to the active direction W. This ensures a higher creep resistance as a result of which a relative movement between the respective intermediate element  12 ,  12 ′ and the assigned spring element  3 ,  3 ′ is guaranteed. 
     According to an embodiment not shown here, the second dimensionally stable section  21  can even be dispensed with. In this case, in an assembled position, the elastic element  26  rests directly on the upper surface of the rail foot F assigned thereto. If a suitable material is available, the elastic element  26  could itself be used as an intermediate element or positioned sandwich-style between two dimensionally stable layers, which ensures even distribution of the loads acting on the elastic element. The elastic element can also be enclosed in a robust material, wherein in this case, said enclosure must be configured such that use can be made of the attenuation effect of the elastic element as before. 
     REFERENCE NUMERALS 
     
         
           1 ,  1 ′ Systems for fixing the rail S 
           2 ,  2 ′ Guide plates 
           3 ,  3 ′ Spring elements 
           4 ,  4 ′ Clamping screws 
           5 ,  5 ′ Plastic pin 
           6 ,  6 ′ Narrow channel 
           7 ,  8  End sections of the spring elements  3 ,  3 ′ 
           9  Middle bend of the spring elements  3 ,  3 ′ 
           10 ,  11  Spring arms 
           12 ,  12 ′ Intermediate element 
           13  First dimensionally stable section of the intermediate elements  12 ,  12 ′ 
           14  Supporting surface of the intermediate elements  12 ,  12 ′  15 ,  16  Front sides of the intermediate elements  12 ,  12 ′  17 ,  18  Moulded parts 
           19 ,  20  Retainers on the supporting surface  14   
           21  Second dimensionally stable section of the intermediate elements  12 ,  12 ′ 
           22  Contact surface of the intermediate elements  12 ,  12 ′ 
           23  Support for intermediate elements  12 ,  12 ′ 
           24  A long side of the intermediate elements  12 ,  12 ′ 
           25  Slot-shaped retainer for the intermediate elements  12 ,  12 ′ 
           26  Elastic element of the intermediate elements  12 ,  12 ′ 
           27  Recess for intermediate elements  12 ,  12 ′ 
         B Fixing point 
         BZ Width of the intermediate elements  12 ,  12 ′ 
         F Rail foot 
         H Height of the intermediate elements  12 ,  12 ′ 
         K Direction of gravity 
         L Longitudinal direction of the intermediate elements  12 ,  12 ′ 
         LZ Length of the intermediate elements  12 ,  12 ′ 
         N, N′ Retaining force 
         Q Shearing forces 
         S Rail 
         U Foundation (sleeper or concrete slab) 
         W Active direction of elastic resilience of the elastic element  25   
         Z Intermediate layer