WO2009101457A1

WO2009101457A1 - Arrangement for clamping rails to railway sleepers and a clamping spring for the same

Info

Publication number: WO2009101457A1
Application number: PCT/HU2009/000015
Authority: WO
Inventors: Róbert CSÉPKE
Original assignee: Csepke Robert
Priority date: 2008-02-12
Filing date: 2009-02-11
Publication date: 2009-08-20
Also published as: HUP0800082A2; HU0800082D0

Abstract

A clamping spring (1) for the elastic clamping of iron rails (3) to sleepers (6), formed from a wire of circular cross section by bending, the ends of which are adapted for clamping them to the rail flange of the iron rail (3), and comprising parallel linear sections (Ic) and a U-shaped part including the parallel linear sections and an arcuate part connecting the linear parts to each other, as well as arcuate arms (Ia) showing outwards relative to the U-shape and connected to the parallel sections via arcuate transition parts (Ic). In the assembled state, the ends of the arms adapted for contacting the rail (3) to the rail flange (2) are situated at the end of these arms (Ia). A clamping structure using such a clamping spring (1) comprises a holder piece (5) fitted to a corresponding element (6a) formed in the upper surface of the sleeper (6), in the upper surface (5f ) of the holder piece (5) a U-shaped groove (5e) for receiving the clamping spring (1), and a fastening element (4) in the holder piece (5) between the two side parts of the U-shape connected to the sleeper (6) through a through- hole (5g).

Description

Arrangement for clamping rails to railway sleepers and a clamping spring for the same

Different rail fastenings are generally used in adhesion railways, where these clamping structures are destined for producing a firm, durable and multidirectionally elastic coupling between the rail and the supporting structure: sleeper, stringer of wood or concrete.

Before the development of today's up-to-date floor structures, the rails were fastened to the sleepers or stringers made preferably of hardwood by various kinds of rail spikes. On tracks with higher load steel plates were used between the rail and the sleeper for distributing the weight, against a seizure of the rail.

At the appearance of sleepers made of concrete it has been recognised that the concrete of high strength doe's not need any load distribution, by applying an elastic (usually made of some plastic) pad, the steel plate can be omissed, thereby the rail fastening is made simpler. Considering the increasing steel prices, this is justified also economically. This was, how the first rail fastening structures without steel plates were born. The development of transport on rails goes together with a rapid increase in speed and axial pressure, which means a larger dynamic stress for the rails and the vehicles; periods without trains used for maintenance become shorter and shorter. It became obvious that the future belonged to rail fastenings of small relaxation, being elastic, and consisting of a few components in order to make them easy and quick to assemble.

Such are e.g. the solutions of the German firm Vossloh of types W14, SkI 300, DFF

14 and DFF 300. Clamping or shackle springs of the form of epsilon, omega or W are widely used at the German railway and in other European countries following the German example. The material demand of this clamping spring is low, it is very elastic in both, horizontal and vertical direction, and it can be assembled very simply, even mechanically. Its drawbacks are that in small curves it does not provide sufficient support, does not give appropriate safety against the swing out of the rail, and in such situations it tends to loosening, due to an insufficient spring lead at mechanical mounting, the mounting position is often incorrect during its push in. The clamping strength depends on the tightening of the screw fastening the shackle spring, therefore the tightness should be checked regularly. In addition to the solution mentioned above, numerous solutions exist many of which are functioning well, but in case of certain track conditions they do not provide satisfactory results.

A general expectation concerning coupling structures is a large spring force, elasticity, spring power, and that the spring system could be applied in the building and maintaining process of the given railway. Thus, there is demand for a cheaper, more economic and preferably better and more reliable solution.

By considering the results and experience of experiments and research performed recently, a solution satisfying at least one of the requirements could be elaborated. As the first aspect in the development of the spring, the generally acknowledged most important requirement was taken into account, namely that the spring force should be generated preferably by torsional stress originating from the spring. The task to be solved was that the torsion stress should be present possibly uniformly in a length as long as possible. This task can be solved practically by using a screw spring or a torsion spring. In this invention a torsion-type spring is used. The aim to achieve was that the section of the spring subjected to the torsion load should be as long as possible. Thereby increase of the elastic path and decrease of the fatigue phenomenon can be achieved.

Our further aim was to elaborate a full clamping structure for fastening iron rails to sleepers, which structure contains such a clamping spring. According to this invention, the clamping structure comprises a holder fitted to the appropriate configuration formed in the upper surface of the sleeper, a clamping spring to be placed into a U-shaped groove formed in the upper surface of the holder, and a fastening element provided with a lower pressing surface as related to the sleeper and passeded through an opening between the two side parts of the U-shape. The clamping spring has an arcuate arms protruding sidewards relative to the side parts of the U-profile, the ending of which is supported in its mounted position by the rail flange of the rail. The pressing surface of the fastening element bears up against the top surface of the holder at the material part remaining between the side parts of the U-shaped groove.

In pre-assembled position, the fastening element realized as a screw is loosened so that the clamping spring could be elevated above the level of the upper surface of the holder. In order to hinder the rotation of the clamping spring, at the bend of the U-shape, i.e. at the meeting point of the side parts of the U-shape, a stop protruding from the upper surface of the plate is provided, which, together with the fastening element, guides the clamping spring so that it cannot be rotated. In order to inhibit an excessive backward displacement and disengagement of the clamping spring from the head of the fastening element, extensions combined with grooves are formed on the upper surface of the plate, thereby the side parts of the U-shaped part of the clamping spring are guided by the grooves of the extensions in order to inhibit the lifting out of the clamping spring. The position of these hooked extensions is determined so that in the case of a removal of the fastening element, the clamping spring could be clamped between the stop protruding from the top surface of the holder and the extensions containing the grooves due to elastic deformation of the material. After inserting the fastening element, i.e. in the pre-assembled position, the clamping spring cannot be removed even by tugging, cannot be turned, thus a mounting in th incorrect position is structurally excluded.

In order to ensure that the clamping spring could be fixed also temporarily in the pre- assembled position sloped guide surfaces are formed at the sides of the holder, and they represent receiving seats for the arcuate arms of the clamping spring in its drawn back position. In the drawn back position, the endings of the arcuate arms of the clamping spring are supported by these sloped guide surfaces and by a slight tightening of the fastening element the clamping spring remains in a temporarily fixed position. During assembly, by a weak loosening of the fastening element in the sleeper, the clamping spring can be slided onto the rail flange, and by contacting it to the stop, the U-shaped part of the clamping spring fits into the corresponding U-shaped groove on the plate, then it can be fixed in this position by tightening the fastening element.

In the following the invention will be described in more detail with reference to the drawings showing examplary embodiments. In the drawings: Figure 1 shows top view of the structure according to the invention in its assembled position;

Figure 2 shows the situation of Fig. 1 in a section perpendicular to the rail,

Figure 3 shows the structure according to the invention in its pre-assembled conditon,

Figure 4 is the view of the structure according to the invention,

Figure 5 is the view of the clamping spring according to the invention, - A -

Figure 6 is the view of a second embodiment of the structure according to the invention,

Figure 7 is a partialf the side view of the clamping structure shown in Fig. 6.

In Figures 1 and 2, the structure according to the invention is shown in assembled condition and comprises a holder piece 5 fitted to a profiled conformation 6a formed on the upper surface of a sleeper 6 which serves for holding a rail 3 , and on the top surface 5f of holder piece 5 a U-shaped groove is formed, into which a U-shaped part of a clamping spring 1 is fitted. Arcuate arms Ia are connected via transition parts Id having relatively small radius to both side parts of the U-shaped part of the clamping spring 1. Endings Ib of arcuate arms Ia press against the flange 2 of rail 3 and are formed correspondingly with a flat surface. Between the side parts of the U-shaped groove 5e of the holder piece 5, a through-hole is formed, through which a fastening element 4 realized as a screw is driven into the insert 7 made preferably of plastic and being in an appropriate position in sleeper 6.

In Figure 2 it can be seen that in tightened condition the lower pressing surface 4a of the head of fastening element 4 is supported by the upper surface 5f of holder piece 5, i.e. fastening element 4 is not clamping the U-shaped part of clamping spring 1 , it only retains it in the U-shaped groove 5e. Of course, the ends Ib of the arcuate arms Ia of the clamping spring 1 are pressing the rail flange 2 , and as a result the upper surface of the U-shaped part of clamping spring 1 is pressed to the pressing surface 4a of the head of fastening element 4, whereas the lower surface of clamping spring 1 touches with the bottom of groove 5e only at the connecting part Ie of the side parts of the U-shaped part, whereas at other sites they may not touch at all. At the ends Ib of arms Ia of spring 1, the clamping force arising while tightening the fastening element 4 falls outside of the axis defined by the side parts of the U-shaped part of spring 1, thus it exerts a torque to the side parts. Due to this torque the side parts of the U-shaped twist elastically.

Clamping spring 1 is made of spring steel with a circular cross section. The clamping spring according to the invention is a specially formed torsion spring transmitting the clamping force to sleeper 2 by the two arcuate arms Ia having a bend radius of R , the plane formed by the two bends is parallel with the vertical axis of rail 3 , and its BJd ratio lies in the range 1.8-2.8, where d is the diameter of the cross section of clamping spring 1, and R is the radius of the centerline of the arcuate arm Ia. If this ratio decreases, the stiffness increases, what is unfavourable from the viewpoint of clamping the rail down. In the opposite case stiffness decreases and elasticity increases, and even effecting a significant displacement only a smaller clamping force can be ensured what is also disadvantageous. The endings Ib of the arms are flat surfaces perpendicular to their longitudinal centerline, and in their clamped position, realize force transmission while pressing the rail flange. In a not tightened position the ends of arms Ib are lower by about 15 mm than the horizontal sections Ic in their assembled position, and while tightening fastening element 4 the angular displacement due to this tightening creates a clamping force. This embodiment ensures that in the material of clamping spring 1 practically only a normal forces develop at a minimum bending force. These two arms Ia, though they comprise essential parts of clamping spring 1, may be considered as auxiliary structures for transmitting the torsion force of the clamping spring 1.

The material of clamping spring 1 should be at least of 38 Si 7 quality, and it should be homogeneous in its full length in order to ensure economic production.

The arcuate arms Ia are connected to the linear section Ic serving as a torsion spring through a small arcuate transition part Id having a bending radius r at its centerlin. Thus the longitudinal centerline of this transition part Id covers an arc of 90 degrees of a circle having the radius r, thus it creates an orthogonal connection between the arcuate side parts Ia and the horizontal linear section Ic subjected to torsion, where the ratio r/d should be in the range of 0.9-1.8. If it is larger, then in that small, arcuate part of the transition element Id the stress due to bending increases significantly, what is unfavourable. If the value of r/d is smaller than 0.9, the material of the clamping spring 1 can be deteriorated significantly, and an undesirable internal stress may remain in the spring after bending. Fastening element 4, as a clamping screw clamps the linear section Ic to the rail 3 at the nearest possible position so that it should not disturb the lifting of rail 3 in and out during assembly. The near position of the screw to rail flange 2 involves that clamping spring 1 is clamped next to rail flange 2, and as a result in tightened position the torsional stress in the linear part Ic of horizontal position will be of crucial importance and originates from the torque produced by the perpendicular movement of arcuate arm Ia, which influences favourably the loosening tendency of clamping. The reason for this is that the permanent deformation originating from the torsion stress is very small, and the displacements caused by bending and the permanent deformation are negligible. Linear section Ic is positioned so that its horizontal axis is perpendicular to the vertical middle plane of rail 3. The length of the linear section is most favourable if the ratio L/d is in the range of 3.9-5.5, where d is the diameter of the spring and L is its length. If this ratio decreases, stiffness increases which is disadvantageous from the viewpoint of clamping. In the opposite case, stiffness decreases, elasticity increases, and even at a significant displacement only a small clamping force is generated, what is also undesirable.

The last section of clamping spring 1 , i.e. connecting arc Ie bear up against said plastic holder piece 5.

A further structural benefit is that clamping arms Ia parallel to the edge of rail flange 2, even at a rotation of rail flange 2, transmit further on a force nearly perpendicular to rail flange 2, the vertical vector of which hardly changes, thus in the torsional horizontal linear section Ic the torsion stress accumulates owing to the vertical movement, thus the clamping force increases. The two sides of clamping spring 1 are formed identically, they are the axial mirror picture of each other. The distance of the two horizontal, linear sections is so that the fastening element 4 and eventually its complementary appliances can find room between them, thus they should be able to take up the horizontal displacements originating from rail movements which would draw near the two linear sections Ic to each other. Considering conventional rail screws of normal size, this distance may be 26 mm.

A further advantage of the clamping is the capability of exerting a relatively high clamping force, and using material sparing solutions its production is economically also favourable, because it shows fast refunfd even at small numbers of pieces (10000- 15000 pieces).

Clamping spring 1 is situated far away from the ridge of rail 3, near to the sides of rail flange 2, it has no penetrating component near to the ridge, thus there is no need for applying other clamping structure at an eventual building in of rail insulators in contrast to other clamping springs.

The seating and positioning of clamping spring 1 is made by the plastic holder piece 5, which performs several functions in the clamping of rails. .

It provides an elastic , electrically insulating support in the horizontal direction to rail 3, ensuring the track distance, and at the same time it transmits the horizontal load to the concrete sleeper 6 or to the concrete plate. Clamping spring 1 in the pre-assembled position 1 ' shown in Fig. 3 (during transport and laying) keeps it reliably in position until the start of assembly, pushed or clamped in between two hooked extensions 5a formed on its upper part farther from rail 3. In the pre- assembled state, holder piece 5 keeps the two arms Ia of clamping spring 1 in the nest 5b formed on the side of holder piece 5, which serves also for retaining the stability of pre- assembled state r.

Assembly occurs so that first the fastening element 4 is driven out to such an extent that arms 1 a can find room below it during push- in. After that, clamping spring 1 has to be pushed towards rail 3 in a manual or mechanical way, while clamping spring 1 is guided by holder piece 5 so that it provides guiding surfaces to the clamping spring 1 at two sites. First, the two linear sections Ic are led by the upper hooked extensions 5a so that the linear sections Ic are situated between the two hooked extensions 5a, and they slide farther in, while the hooked extensions 5a hinder also the swing of linear sections Ic. After that, the groove 5c starting from nests 5b formed at the sides of holder piece 5 and ascending towards the sloped guide surface forms a sliding track and guides the two arcuate arms Ia of clamping spring 1 during push-in onto the rail flange 2, which system makes both manual and automated push-in, i.e. assembly possible. An excessive pushing of clamping spring 1 is made impossible by the stop 5d situated between the two linear sections Ic of spring 1 being part of the holder piece 5. This is the end position of clamping spring 1. Here - by moving vertically downwards along stop 5d - the rear transition arc Ie of clamping spring 1 reaches its end position , it sank into groove 5e formed for holding clamping spring 1 where the stop 5d between the two linear sections Ic hinders the excess movement of clamping spring 1 towards rail 3 by supporting transition arc Ie from the inside. Then, only tightening of fastening element 4 is to be done, while the linear sections Ic find their place in holder piece 5 ensuring thereby the support of clamping spring 1 even in cases of rail movements or twists. A faulty assembly can be excluded due to the multiple leading - namely that of hooked extensions 5a, grooves 5e, the stable spring nest formed by the limiting surfaces of grooves 5e- in case of using the above procedure.

Fastening element 4 is to be tightened until the pressing surface of screw-head 4a reaches the plane of the upper surface 5f of the plastic holder piece, but only a momentum of 200 Nm can be applied by using a momentum-limiting screwing machine. The introduction of the fastening element 4 occurs through the throgh hole 5g on holder piece 5 to the corrugated plastic insert 7 situated in sleeper 6 or in the concrete slab.

On the basis of the results of investigating experimental flat wheels tested in several institutes, generally the placing of an elastic pad 8 of 7-10 mm thickness is justified between rail 3 and sleeper 6, for decreasing the destruction or breaking of sleeper 6 caused by the non-circulatity of wheels. In the embodiment according to the invention a pad 8 made of perforated or ribbed rubber plate with a stiffness of lOOkN/mm is inserted between the rail 3 and sleeper 6. Depending on the embodiment and the curvature relations of the track to be built, the technical characteristics of clamping spring 1 , elastic holder piece 5 and pad 8 should be harmonised, eventually the increase or decrease in the stiffness and/or thickness of the pad 8 is feasible. This should be determined individually in the function of loading on the track, the strength of the other appliances, and on the basis of such experimental results the final dimensions and materials can be determined.

Figure 6 shows another embodiment of the clamping structure according to the invention, in which on the lower surface of holder piece 5 a shoulder 5h is formed, which is situated transversally to side parts 5e of the U-shaped grove of the holder piece 5 and at a position being farther away from the rail 3 to be fixed than hole 5g. The profiled element 6a formed on the upper surface of sleeper 6 in this case comprises a step 6h, which step in the embodiment shown runs along transversally on the upper surface of sleeper 6. Its length should be at least so that it could receive shoulder 6h of the holder piece 5, however, this is not necessary by all means.

This shoulder 5h has the advantage that the mass of the holder piece 5 is reduced, and the material which can be spared here, can be replaced by the cheaper concrete material of sleeper 6. Its function is to hinder the rotation of holder piece 5.

Figure 7 shows the structure in the state of its use, namely spring 1 is supported by the upper surface of the rail flange 3 to be fixed, and it is clamped to the upper surface of sleeper 6 by the mediation of plate 8. Spring 1 is placed into holder piece 5, and the fastening element 4 realized as a screw to be driven in from the upper side clamps and keeps it on its place. In the embodiment shown in Figs 6 and 7, it is obvious that the distance between the central line of the hole 5g formed in holder piece 5 and shoulder 5h should be identical with that between shoulder 6h and fastening element 4 (in this case a screw ), where the connection site 4b is the central line of insert 7 fixed into sleeper 6. Naturally, the fastening element is not necessarily such a screw, it can be substituted by other solutions known by the professionals, e.g. by a screw , threaded spindle fixed into sleeper 6 or led through a through-hole made into it, e.g. by a T-bolt and a nut screwed on it. Both this through-hole and the through-hole 5g can be made in elliptical form, in which case the head of a T-bolt can be led through it, and in addition, it makes a certain adjustment possible, and on the other hand, it ensures manufacturing tolerances. In these cases the connection site 4b is the central line of the screw standing out of sleeper 6.

Claims

1. Clamping spring for elastically clamping of a railway rail (3) to sleepers (6), said spring beimg formed from a wire of circular cross section by bending, and having endinds to be clamped to the flange of the rail (3), characterized in that it comprises a U-shaped part having parallel rectilinear sections (Ic) and a curved connecting section (Ie) for connecting the linear sections (Ic) together, as well as arcuate arms (Ia) projecting sideward relative to said U-shaped part and connected to the linear sections (Ic) through arcuate transition elements (Id) and provided with said endings (5b) adapted to be contacted to the flange (2) of the rail (3)in assembled state.

2. Clamping structure for clamping railway rails 1 to sleepers (6) by clamping springs according to claim l,said sleepers comprise corresponding conformations (6a) on the upper surface of the sleeper (6), said structure comprises a holder piece (5) fitting to the conformation (6a), the holder piece (5) has a groove (5e) for receiving a clamping spring (1) on its upper surface (5f), and comprises a fastening element (4) having a lower pressing surface (4a) for pressing the clamping spring (1) towards the sleeper (6) and extending through a through-hole (5g) formed in the holder piece (5), characterized in that the groove (5e) for receiving the clamping spring (1) is U-shaped, and in assembled state the lower pressing surface (4a) of the fastening element (4) is pressing between side parts of the U- shaped groove (5e) against the upper surface (5f) of the holder piece (5), and it closes the U- shaped groove (5e) around the through-hole (5g) from above.

3. Structure according to claim 3 characterized by a stop (5d) protruding from the upper surface (5f) of the holder piece (5) and formed between the arcuate part connecting the side parts of the U-shaped groove and the through-hole (5g), and by two elastic hooked extensions (5a) situated adjacent the arcuate part of the groove (5e) opposite to the stop (5d) for cooperation with the stop (5d) to retain the clamping spring pressed into the groove (5e) and to hinder unwanted removal.

4. Structure according to any of claims 2 or 3 characterized in that at the sides of the holder piece (5) nests are situated perpendicular to the rail (3) and aligned with the ends (Ib) of the arms (Ia), the bottom of which have the form of a sloped guide surface (5c) ascending towards the rail (3), and in a pre-assembled state of the structure removed from the rail flange (2), the lower pressing surface (4a) of the fastening element (4) is pressing from above the linear section (Ic) of the clamping spring (1), whereas the endings (Ib) of the clamping spring (1) are leaning against the sloped guide surface (5c).

5. Structure according to claim 2 characterized by a shoulder (5h) provided at a prescribed distance from the through-hole (5g) on the lower surface of holder piece (5) and extending transversally relative to the side parts (5e) of the U-shaped groove, and the conformations (6a) formed on the upper surface of the sleeper (6) comprise a transversal step (6h) spaced by said prescribed distance from the connecting site (4b) established for the fastening element (4).