In a second, more limited aspect, the invention relates to a link device intended for permanently connect- ing two rail-mounted vehicle units of the type that com- prises two link members connected via a common hinge, one of which is divided into two parts translationally movable in relation to each other, namely a front link head connected to the hinge and a rear carrier fixedly connectable to a vehicle unit, between said parts an energy-extincting or energy-absorbing element of deformable character serving as collision protection being arranged.

Already now it should be pointed out that the colli- sion protection henceforth treated constitutes a protection in the sense that the same has the purpose of protecting the rail-mounted vehicles in question against plastic deformation upon moderate collisions, the energy that is absorbed in the collision protection included in the cou- pling only constituting a part of all energy that is absorbed by the total collision protection equipment of the rail-mounted vehicle (comprising, for instance, deformation zones in the vehicles) upon larger collisions.

Description of the Prior Art A collision protection and a link device of the above generally mentioned kind is previously known by EP 1312527.

In this case, the energy-extincting element consists of a plastically deformable tube, which at a rear end is fixedly united to the rear carrier of the individual link member and which at a front end co-operates with a mandrel-like male element (in the form of a more robust tube) that proj- ects rearward from the link head connected to the hinge.

More precisely, said deformation tube is at the front end thereof formed with a conical collar widening forwards, in which a partially conically shaped ring on the rear end of the male element is inserted. More precisely, the conical surface on said ring is pressed in close contact with or free from play against the collar of the deformation tube <BR> <BR> already in the starting position of the device, i. e. , with- out collision having occurred. When an axial force in excess of a predetermined limit value is applied to the individual link member, the male element is allowed to penetrate axially into the deformation tube during radial expansion of the same, the material in the tube being deformed plastically under simultaneous heat release; all with the purpose of transforming kinetic energy to heat energy and thereby abate or reducing the effect of axial impulsive forces between two connected rail-mounted vehicle units.

However, in practice, this type of collision protec- tion is associated with a plurality of disadvantages. One disadvantage is caused by the deformation work and the transformation of energy taking place by radial expansion of the deformation tube so far that this requires a certain available space around the tube. In such a way, the possi- bilities of the designer to attain desired compactness of the link device in its entirety are limited. Furthermore, the fact that the deformation takes place by radial expan- sion entails a latent risk that the material in the defor- mation tube breaks before the male element has had time to run the entire length of stroke thereof. In such a way, the energy transformation process may cease prematurely, whereby the effect of the collision protection of the tube is lost too fast. In addition, the general energy-absorbing capacity of the construction is fairly limited also in the case the tube does not break.

Objects and Features of the Invention In the broadest aspect thereof, the present invention aims at obviating the disadvantages of previously known collision protections in general and at providing an improved collision protection. Thus, a primary object of the invention is to provide a collision protection, which can be realized in a compact embodiment by not requiring any particular space of receipt of radially expanding com- ponents. An additional object is to provide a collision protection, the energy-extinction elements of which do not risk breaking and which, therefore, do not risk prematurely losing the energy-converting and shock-absorbing capacity thereof.

According to the invention, at least the primary object is attained by the features that are defined in the characterizing clause of claim 1. Preferred embodiments of the collision protection according to the invention are furthermore defined in the dependent claims 2-15.

In a second, more limited aspect, the invention also relates to a link device of the type initially mentioned.

The features of this link device is seen in the character- izing clause of claim 16.

Summary of the Invention The invention is based on the idea of using one or more tubes or sleeves as energy-extinction elements, which tubes or sleeves are plastically deformable by radial com- pression such as a consequence of they having a first, tapering end portion inserted into a thinner bore in one of the two parts of a coupling element and an opposite, free end distanced from the second part in order to, upon dis- placement of the two parts in the direction of each other- in connection with a collision accident-be pressed axi- ally into the bore. This means that the deformable element never can become enlarged radially and occupy space in the surroundings outside the same. Neither it is risked that the element breaks prematurely because of material break.

Another feature characteristic of the invention is that the front, free end of the deformation tube or tubes is dis- tanced from one part of the coupling element via a certain gap. In such a way, it is guaranteed that the deformation tube never can be influenced by the normal, moderate stresses that occur in the link device. Not until such con- siderable impulsive forces that occur in connection with collisions or the like have detached the translationally movable part, this will contact the deformation tube and trigger the collision protection function.

Brief Description of the Appended drawings In the drawings: Fig. 1 is a side view of a link device intended for perma- nent coupling and in which a collision protection according to the invention is included, Fig. 2 is a planar view from above of the link device according to fig. 1, Fig. 3 is a longitudinal section through the same link device, Fig. 4 is a perspective exploded view of two link members included in the link device, Fig. 5 is a perspective exploded view of only one of the link members, Fig. 6 is an enlarged longitudinal section through a car- rier included in the link member, Fig. 7 is a first longitudinal section through a back piece included in the carrier, Fig. 8 is a second longitudinal section through the same back piece, Fig. 9 is a side view of first type of deformation tube included in the collision protection, Fig. 10 is a longitudinal section through the same tube, Fig. 11 is a side view of another type of deformation tube, Fig. 12 is a longitudinal section through the tube accord- ing to fig. 11, and Fig. 13 is a simplified, perspective exploded view showing the link device adjacent to two rail-mounted vehi- cle units in the form of chassis or car bodies, as well as a Jakobs bogie co-operating with the same.

Detailed Description of a Preferred Embodiment of the Invention Below, the invention will be described, reference being made to a particular form of coupling for rail- mounted vehicles, namely a link device or link coupling, which in practice is used for permanently connecting two <BR> <BR> rail-mounted vehicle units, e. g. , two wheel-carried chassis or car bodies, which together form a railroad car, which can be inserted into arbitrary train units by being con- nected with other cars or locomotives, usually via auto- matic couplers or the like. However, it should already now be pointed out that the invention is not limited to a link device of the type that is shown in the drawings, but rather may also be applied to arbitrary coupling elements in order to interconnect rail-mounted vehicles, e. g. , auto- matic couplers, other permanent couplers or the like.

The link device selected as embodiment example and illustrated in figs. 1-4 includes two components, namely a first, complete link member 1 and a part designated 2, which is included in a second link member. More precisely, the part 2 is insertable into a box-like frame 2', shown in fig. 13, which forms a second link part that is fastenable on another vehicle unit or car body than the link member 1.

The two link members are mutually articulately connected via a hinge in its entirety designated 3. In a conventional way, this hinge includes a vertical pin 4, which enables the link members 1,2 to turn in relation to each other in the horizontal plane, as is outlined by means of the angle range a in fig. 2, as well as a spherical bearing box 5, which allows that the link members turn in the vertical plane in relation to each other, as is outlined by means of the angle range ffi in fig. 3. Each link member 1, 2 is fas- tenable on a rail-mounted vehicle unit or a chassis, as is outlined in fig. 13. In the example, only one of the link members, namely the link member 1, is formed with a collision protection according to the invention, and therefore the second link member 2,2'will not be described closer.

As is best seen in fig. 4 in combination with figs.

1-3, the link member 1 includes a front link head 6 and a rear carrier, fixedly connectable to a co-operating vehicle unit, which carrier in its entirety is designated 7. In the example, said carrier is composed of two assembled compo- nents, namely a box-like frame 8, as well as a back piece 9 located in the area of the rear end thereof. The frame 8 includes a bottom plate 10, as well as a vertical front plate 11 from which two vertical side pieces 12 extend, which are stiffly united to the front plate as well as the bottom plate, e. g. , by being welded against the same. The side pieces are oriented perpendicularly to the front plate 11 and spaced-apart mutually, at the same time as they separately are located at a certain distance inside the opposite side edges of the bottom plate 10. In practice, the frame 8 is made from a strong steel plate (thickness within the range of 25-50 mm). The back piece 9 is even more robust, which advantageously can be made in the form of a solid cast steel body, which is connected to the side pieces 12 of the frame 8 via a plurality of strong connect- <BR> <BR> ing elements 13, e. g. , large screws or pins. Connection of the carrier 7 to the appurtenant rail-mounted vehicle unit takes place via the bottom and front plates 10,11 of the frame 8, more precisely via connecting elements, not shown, that are applied in holes 14 in the respective plates.

Reference is now made to figs. 5 and 6, which more in detail illustrate the nature of the link member 1. In fig.

5, it is seen that the link head 6 at a rear end has a cross piece 15, which extends perpendicularly to the geo- metrical longitudinal axis of the link head. More pre- cisely, the cross piece 15 is of a rectangular basic shape, grooves 16 being recessed in the opposite short side edges thereof. In mounted state, the link head 6 projects through a central opening 17 in the front plate 11 of the frame 8, the cross piece 15 abutting against the back side of the front plate 11. In the cross piece 15, four threaded holes 18 are formed for receipt of equally many screws or bolts 19 (see fig. 6), which have the purpose of holding the link head in place. In the area between the male thread and head 20 of the individual screw, the shank of the screw is some- what weakened via a waist 21, the diameter of which decides the strength of the screw. By endowing the waist 21 a suit- able diameter, it may be predetermined at which stress the screw should break. If the link device would be exposed to extreme, axial impulsive forces of the type that arise in connection with collisions and the like, accordingly the link head 6 can be detached from the frame 8 by the fact that the screws 19 break, and then be set in an axial, translational motion in relation to the frame.

On the inside of the individual side piece 12, an axially oriented guide bar 22 is arranged, which engages a co-operating groove 16 in the cross piece 15 of the link head. Thus, upon translational move of the link head in relation to the frame, the link head is guided by the guide bars 22.

With the back piece 9, three tubes or sleeves serving as collision protection are connected, namely a central tube 23 of a first type, and two co-lateral tubes 24 of another type. The nature of these tubes, which in practice are denominated deformation tubes, will be described closer below, reference being made to figs. 9-12. The most con- spicuous difference between the two types of tubes is that they have different diameters. More precisely, the interme- diate tube 23 has a larger diameter than the two side tubes 24. The tubes co-operate with through bores 25,26 in the back piece 9.

Reference is now made to figs. 7 and 8, which illus- trate the nature of the above-mentioned bores 25,26 of the deformation tubes 23,24. Although the intermediate bore 25 of the central deformation tube 23 and the co-lateral bores 26 of the tubes 24 have different diameters, they are formed in principally the same way. Thus, the individual bore is of a cylindrical basic shape and is formed with a funnel-like mouth 27, which widens in the forward direction towards the front surface 28 of the back piece 9. In the example, each bore is divided into three different sections having different diameters, namely a front section 29, which has a smallest diameter and is located in close vicinity of the mouth 27, an intermediate section 30 having a somewhat larger diameter, and a rear section 31, which has a larger diameter than the intermediate section 30.

Between the two last-mentioned sections, a ring-shaped shoulder surface 32 is formed. In this case, the shape of the mouth 27 is genuinely conical, i. e. , the surface defining the mouth is rotationally symmetrical and generated by a rectilinear generatrix. In this connection, it should, however, be pointed out that the shape of the funnel mouth 27 tapering in the backward direction also may be defined by other surfaces than a genuinely conical one, e. g. , a convexly curved surface (= the generatrix being arched).

In fig. 6, a particular insert ring 33 is shown, which is not shown in figs. 7 and 8, but which after manu- facture of the body forming the back piece 9, is mounted in the ring-shaped space adjacent to the bore. Said insert ring 33 consists of another material than the material in the rest of the back piece. For instance, the ring 33 may be composed of a high-strength and heat-resistant steel, while the body 9, for instance, consists of cast steel.

A common feature of the two types of tubes 23,24 (see figs. 9-12) is that the same have a first, rear end portion 34, which tapers in the backward direction from the long, front portion 35 of the tube. In the example, the portion 35, which extends along the major part of the length L of the tube, has a genuinely cylindrical shape, i. e. , the envelope surface 36 thereof is cylindrical and generated by a conceived rectilinear generatrix that is parallel to the centre axis C (see figs. 11,12). The tapering shape of the end portion 34 is determined by an external envelope surface 37, which in the example is genu- inely conical, i. e. , generated by a conceived generatrix that is rectilinear. In the example, the conical end por- tion 34 has the same thickness T as the cylindrical portion 35, more precisely as a consequence of the internal surface 38 of the end portion 34 having the same conicity as the external surface 37. The same conicity, which is determined by angle y, is of great importance for the serviceability of the deformation tube. In the example, the angle y amounts to 15°. Although the conicity may vary upward as well as downward from this value, the cone angle in ques- tion should, however, amount to at least 5° and at most 20°, and suitably be within the range of 10-16°. Tests that form the basis of the invention have been most successful when the cone angles have varied within the range of 11- 15°. In this connection, it should be emphasized that it is the cone angle of the external envelope surface 37 that is most critical. Accordingly, adaptation and variation of the energy-absorbing capacity of the deformation tube to desired characteristics may be effected by varying the wall thickness in the end portion 34. Thus, by decreasing the cone angle of the internal surface 38, the end portion 34 may successively become thinner in the backward direction towards the smallest opening of the tube.

The wall thickness of the cylindrical tube portion 35 is defined as D1-D2/2, where D1 is the outer diameter and D2 the inner diameter. In the example, the tube 24 of the thinner type has an outer diameter D1 of 60 mm and an inner diameter D2 of 42 mm, i. e. , the wall thickness amounts to 9,0 mm. Simultaneously, the total length L is 249 mm. In this connection, it should be pointed out that the front end of the tube 24 is constituted by a ring-shaped, planar surface 39, which extends perpendicularly to the centre axis C.

At the rear end thereof, the tube 24 has a seating in which a washer 40 having a nut 41 is welded.

The differences between the embodiment described above and shown in figs. 8 and 9 and the thicker tube 23 shown in figs. 10 and 11 are few. However, the outer diame- ter D1 of the tube 23 is larger and amounts in the example to 134 mm, at the same time as the inner diameter D2 amounts to 120,2 mm, i. e. , in this case the wall thickness of the tube amounts to 6,9 mm (to compare with the thick- ness of 9,0 mm of the thinner tube 24). When a plurality of tubes having different diameters are used in combination with each other, it has turned out that the wall thickness of the sleeves should be in inverse proportion to the diameter so far that a thicker tube should have a smaller wall thickness than any thinner tube and vice versa.

The total length L of the thick tube 23 amounts to 266 mm. In other words, the tube 23 is somewhat longer than the tube 24.

In other respects, the tube 23 resembles the tube 24 so far that it includes a welded washer 40 and a nut 41, and the conical end portion 34 having the same wall thick- ness 1 as the cylindrical portion 35.

Now reference is made again to figs. 7 and 8, which- in the concrete embodiment example-illustrate the dimen- sions of the bores 25,26 that co-operate with the deforma- tion tubes 23,24. For the thick bore 25, it applies that the inner diameter D3 of the section 29 amounts to 120 mm.

This dimension agrees with the smallest inner diameter of the insert ring 33 (see fig. 6) at the rear end of the ring. As has been pointed out above, the deformation tube 23 has an outer diameter D1 of 134 mm. This means that the diameter of the hole section 29 amounts to only approx.

90 % of the outer diameter of the tube and that the outer diameter of the tube will be reduced by 14 mm when the tube is pressed into the bore.

As to the rest, the diameter D4 of the intermediate section 30 is 122 mm, while the rear section 31 has a diameter D5 of 127 mm. The axial length Li of the back piece amounts to 160 mm. As to the rest, the length dimen- sions are L2 95 mm, L3 45 mm and L4 26 mm. The largest outer diameter D6 of the mouth 27 amounts to 146 mm.

The cone angle A agrees with the cone angle y accord- ing to fig. 12 (the complementary mounted insert ring 33 is of uniform thickness and has, therefore, the same cone angle as the seating of the mouth).

For the thinner bore 26 according to fig. 8, the following vital dimensions apply: D3 = 52 mm, D4 = 54 mm, L2 = 105 mm, L3 = 45 mm, L4 = 18 mm and D6 = 72 mm. Also in this case, the cone angle X agrees with the cone angle y of the tube 24.

From the above, it is seen that the inner diameter D3 (52 mm) of the hole section 29 amounts to approx. 87 % of the outer diameter D1 (60 mm) of the tube 24. Thus, in this case, the diameter of the tube 24 is reduced by 8 mm upon deformation. Generally, the degree of reduction should be within the range of 80-95 %, suitably 85-90 %.

Now reference is made again to fig. 6, which illus- trates how a deformation tube 24 is mounted in the back piece 9. More precisely, the mounting is carried out by means of a bolt 42 provided with a head 42', the male thread of which bolt is screwed into the female thread of the nut 41. The head 42'is tightened against a stopping element in the form of a washer 43, which is pressed against the aforementioned shoulder 32. Between the washers 40,43 serving as stopping elements, a spacer member 44 extends, the length of which decides the tightening force by which the conical end portion of the tube 24 is fastened in the mouth or the seating 27 in the back piece 9.

Reference is now made to fig. 2, in which is seen that the tubes 23,24 protrude differently far in the for- ward direction from the back piece 9. More precisely, the thick, central tube 23 protrudes somewhat longer than the two thinner, co-lateral tubes 24. Between the tube 23 and the cross piece 15 of the link head 6, a gap 45 is accord- ingly formed, which is somewhat smaller or founder than the gaps 46 between the front end surfaces 39 of the side tubes 24 and said cross piece 15. In practice, the gap 45 may have an axial length within the range of 5-15 mm and the gaps 46 a length within the range of 10-20 mm. This means that one of the tubes, namely the central tube 23 will be impinged by the cross piece 15 somewhat before the same cross piece impinges on the other tubes in connection with a possible triggering of the collision protection.

The choice of material in the deformation tubes 23, 24 is of vital importance. Generally, the tubes should be made from steel, more precisely carbon steel. After a plu- rality of tests, it has turned out that a commercially available steel of the type OVAKO 280 has particularly suitable properties. This steel is characterized by the following principal analysis: C: 0,17-0, 20 %, Si: 0,30- 0,45 %, Mn: 1,45-1, 60 %, P: max 0,030 %, S: 0,020-0, 035 %, Cr: 0,202-0, 30 %, Ni: max 0,30 %, Mo: max 0,10 %, Cu: max 0,30 %, V: 0,08-0, 12 %, Ca: max 15 ppm, Ti: max 30 ppm, 0 : max 15 ppm and N: 70-150 ppm.

The Function and Advantages of the Invention During normal circumstances, i. e. , when the cars or the vehicle units in a train unit are exposed to usual ten- sile, compressive and torsion stresses, the collision pro- tection formed by the three deformation tubes is inactive so far that the screws 19 hold the link head 6 fixed in the position shown in the drawings in which the cross piece 15 is kept pressed in close contact against the back side of the front plate 11. In this state, the cross piece has no contact at all with the deformation tubes 23,24 because of the presence of the gaps 45,46. However, if a collision would occur and the cars or the vehicle units are applied extreme impulsive forces, which aim to propagate through a train unit, the collision protection is activated. This takes place by the screws 19 breaking, whereby the link head 6 is detached so that the same and the back piece may move towards each other. In doing so, the cross piece 15 first impinges on the central tube 23 and shortly after- wards the two thinner side tubes 24, wherein all tubes will be pressed into the appurtenant bore in the back piece up to a point where the cross piece 15 is stopped against the front surface 28 of the back piece 9. When the individual tube is pressed into the appurtenant bore, the same will be deformed successively by being compressed or pressed together in the radial direction while the outer diameter of the tube is reduced to the same inner diameter as the front section 29 in the bore (= the smallest inner diameter of the insert ring). During this deformation, which in all essentials takes place in the area of the conical insert ring 33, the kinetic energy in the detached link head is converted into heat in the deformation tubes as well as the back piece 9. This means that a substantial part of the kinetic energy is extincted before it is transferred from one of the cars or vehicle units to the other.

The above-mentioned screws 19 extend axially, i. e., parallel to the length extension of the link member or par- allel to the direction of the relative motion between the link head 6 and the frame 7. Therefore, rupture takes place by the material in the screws, more precisely the waists of the screws, attaining the ultimate tensile strength. In this connection, the screws serve as triggering members, which-by suitable choice of the diameter of the screws or the waists-can be dimensioned so that they activate the collision protection at a very exact, predetermined limit value of the impulsive forces that the link coupling should carry. In addition to this, the screws also contribute in the shock-absorbing and kinetic energy-extincting work so far that the material in the same is deformed under strain and heat release up to the point where the ultimate tensile strength is attained. In this connection, it should also be mentioned that the strain of the screws is possible as a consequence of the presence of the gaps 45,46 between the cross piece 15 of the link head and the free ends of the deformation tubes 23,24, i. e. , as a consequence of the deformation tubes not being clamped at the opposite ends thereof. The fact that the screws are stretched and exten- ded a distance before they break also means that the cross piece 15 of the link head is in the immediate vicinity of the ends of the deformation tubes (the gap 45 between the deformation tube 23 and the cross piece 15 is reduced to some or a few millimetres) when the screws break and trig- ger the proper collision protection. Furthermore, the prestress of the screws 19 gives a joint free of play and fatigue resistant to normal vertical, lateral and longitu- dinal operational loads. Furthermore, in this connection, it should be pointed out that the link head and the cross piece thereof are guided axially without being angularly displaced thanks to the guide bars 22 engaging in the guid- ing grooves 16.

Although it would be feasible to use only one defor- mation tube that can be pressed together radially, it is preferred to use two or more differently long tubes in which the deformation work is initiated differently far after the link head having been released from the locked position thereof. In such a way, a more even energy-extinc- tion course is obtained. Furthermore, the use of a plural- ity of tubes having limited diameter instead of one single tube having a large diameter means an improved utilization of the available height space in the link device or the coupling. In other words, for a given specification of requirements, a collision protection from a plurality of co-lateral deformation tubes occupies a considerably smaller space in the vertical direction than a single tube for the same specification of requirements.

By modifying the deformation forces of the triggering screws 19 and of the tubes 23,24 and combine these in a suitable way, a progressive course of forces can be achieved during the entire impact upon a collision.

Feasible Modifications of the Invention The invention is not solely limited to the embodiment described and shown in the drawings. As already previously has been pointed out, the general inventive idea may accordingly be applied in any couplings for rail-going <BR> <BR> vehicles, e. g. , in automatic couplers or permanent couplers of a type that does not form link devices of the permanent type described above. Entering into details, the collision protection may be modified in various ways, in particular regarding the geometry of the deformation tubes and the receiving bores. Thus, the tapering portion on the deforma- tion tube does not necessarily need to have a genuinely conical shape, neither the receiving, tapering mouth.

List of Reference Designations 1 = link member 2 = link part 2'= link part 3 = hinge 4 = pivot pin 5 = bearing box 6 = link head 7 = carrier 8 = frame 9 = back piece 10 = bottom plate 11 = front plate 12 = side pieces 13 = connecting elements 14 = hole 15 = cross piece 16 = guiding grooves 17 = opening 18 = hole 19 = screws 20 = screw head 21 = waist 22 = guide bar 23 = intermediate deformation tube 24 = co-lateral deformation tubes 25 = bore 26 = bore 27 = bore mouth 28 = front surface 29 = front bore section 30 = intermediate bore section 31 = rear bore section 32 = shoulder surface 33 = insert ring 34 = conical tube end portion 35 = main tube portion 36 = tube envelope surface 38 = internal cone surface 39 = planar tube end surface 40 = washer 41 = nut 42 = bolt 43 = washer 44 = spacer member 45 = gap 46 = gap 37 = conical envelope surface