TECHNICAL FIELD OF THE INVENTION

The invention concerns a draft gear for rail vehicles comprising a coupler head, which in a rear end is mountable on a drawbar to extend in the longitudinal direction of the same to a front end, which carries a front plate. The coupler head houses components of a mechanical coupling effective for automatic coupling to the corresponding coupling components of a connecting draft gear. More precisely, the invention relates to a draft gear of this type that is arranged to resist buckling in the event of a deforming compressive force being applied to the draft gear in the longitudinal direction thereof.

BACKGROUND AND PRIOR ART

The understandings of the ability to reduce the risk of derailment and in particular the danger of cars climbing up on each other, if the cars of a train remain in the coupled state after a collision, form the basis of the invention.

For the absorption of energy in a draft gear between rail vehicles, different solutions are previously known. These solutions comprise, for example, shock-absorbing elastic damping devices introduced in the coupler, but also devices that are arranged to be plastically deformed in the event of a collision, in the conversion of at least a portion of the generated force into kinetic energy and heat. To these latter devices, expanding or compressible deformation tubes typically belong, which may be included in the fixing of the coupler to a car chassis or be integrated parts of the drawbar. As an example of the latter, EP 1 312 527 Al or EP 1 663 755 B l could be pointed out.

The coupler head of an automatic coupler, which in a surrounding housing accommodates the mechanical coupling components necessary for coupling for automatic engagement with a meeting coupler, is usually made of castings and lacks typically shock-absorbing measures. A coupler head housing made of weldable forged steel for a central buffer coupling is, however, previously known from DE 1 124 535. This coupler head housing is dimensioned to resist occurring normal traction and thrust forces, but lacks measures for a predetermined shock- absorbing deformation. Notwithstanding conventional and known measures to mitigate the effects of a deforming force, in known draft gears, the problem remains that the draft gear can be bent and buckled in the course of deformation, with the result that the coupling between the rail vehicles is released.

SUMMARY OF THE INVENTION

The invention aims generally at providing a draft gear having a sufficient bending or buckling stiffness in order to, in spite of a shock-absorbing, deforming collision, remain in the coupled state.

The invention aims in addition at providing a draft gear having the ability to absorb energy and thereby providing an increased protection against deformation of the car chassis and the draft gear. Therefore, an object of the invention is to provide a draft gear for the automatic coupling of rail vehicles, which draft gear is arranged to be deformed in a predetermined way while absorbing energy.

In order to meet the object set forth, according to the invention, there is provided a draft gear of the type described by way of introduction, in which the automatic coupling is supported in a beam that traverses the coupler head and extends from the front plate in an axially overlapping relationship with the drawbar.

The solution guarantees retained functionality of the coupling, which by being supported in a beam connecting to the front plate keeps its relative position in relation to the front plate and to the coupling mechanism of the connecting draft gear.

For the purpose, the beam is, against overcoming of a predetermined force, displaceably supported at the drawbar in the common longitudinal direction. As a result of this, the beam is decoupled from the force initiated in the draft gear, which instead can be transmitted to shock-absorbing means that are arranged detached from the beam, while the relative relationship and integrity of the front plate, coupling and beam remain essentially unaffected by the force. Simultaneously, extension of the overlapping area is achieved in a meritorious way, which contributes to guaranteeing and increasing the buckling stiffness of the draft gear. In a preferred embodiment, the beam is displaceably supported at the drawbar against the force of a controlled deformation of a coupler head housing surrounding the beam. The embodiment provides increased capability of the draft gear of absorbing energy besides other occurring shock-absorbing devices, such as deformation tubes or dampers arranged in the drawbar or the chassis.

In an advantageous design of the draft gear, the coupler head housing has at least one notch for a predetermined deformation of the coupler head housing. In particular, it is envisaged that notches for the folding of the coupler head housing are made at least in the sides of the coupler head housing, preferably also in the upper part and bottom thereof. Hereby, the deformation may, at least up to a certain magnitude, be limited to areas of the coupler head housing that are not essential for retained functionality of the coupling. By a beam having a requisite axial stiffness to act force-transmittingly between the front plate and the drawbar, energy can be carried along rearward through the drawbar and, at least up to a certain magnitude, be quenched in rear impact- absorbing members. In that connection, it is preferred that the beam and the drawbar are coupled in a telescopic relationship. In this embodiment, the beam and the drawbar may be arranged mutually displaceable against the force of a radial deformation of the beam and/ or of the drawbar in the overlapping area. This preferred embodiment may be realised by a tubular end portion of the beam being formed with a circumferential wedge-shaped shoulder that rests against a corresponding wedge-shaped stopper formed in the mouth area of an opposite tubular end of the drawbar, or of a connecting tube coupleable to the drawbar, in which the end portion of the beam is insertable. The beam and the

drawbar/ connecting tube, respectively, are preferably cylindrically tubular in the mutually overlapping area, but may alternatively have the shape of a tube having four or more sides in this area.

It will be appreciated that the beam, by the above measures, is in a thrust force- transmitting relationship to the drawbar.

The beam is in addition coupled in a traction force-transmitting relationship to the drawbar. This may be realised by means of a nut that is screwable into the tubular end portion of the beam and in the screwed-in position rests against a radial shoulder formed internally in the drawbar. In this way, the coupler head housing is relieved from traction forces found in normal operation. In a preferred embodiment, the beam extends fork- shaped on both sides of the coupling from the front plate toward the drawbar. More precisely, an upper branch of the beam runs above the central plate of the coupling, while a lower branch of the beam runs under the central plate. The embodiment results in a symmetrical distribution and transmission of the transmitted force and guarantees that the main shaft of the coupling, which is supported in mutually aligned seats arranged in the branches of the beam, retains a vertical orientation after a deforming collision.

In order to distribute the forces in the front plate and reduce the risk of the beam penetrating the same, the beam may in its front end carry a thrust plate in abutting contact with the back side of the front plate. The beam may alternatively also be integrated with the front plate and formed in one and the same piece with the same.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated below by embodiment examples and reference being made to the accompanying schematic drawings, of which

Fig. 1 shows a coupler head included in a draft gear in perspective view; Fig. 2 shows a partially broken-away longitudinal cross-section through the coupler head in Fig. 1;

Fig. 3 shows a beam traversing the coupler head in side view, and Fig. 4 shows the beam in a longitudinal cross-section along the line IV-IV in Fig. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT EXAMPLES

It should be emphasized that the drawing figures are schematic and only suited to elucidate the general idea of the invention such as the same is seen in the written description and in the connecting claims. Therefore, the invention should not be considered limited to shown dimensions, geometries or to the detailed embodiment of construction elements in the embodiment examples, because these have to be considered by a person skilled in the art in each individual application of the invention. In particular, it should be noted that material thicknesses and other dimensions may be over dimensioned and that the constructive design of details simplified, for reasons of drawing technique. The drawing figures schematically show a draft gear comprising a tubular drawbar 1 , which in its rear end is coupleable to a car chassis and in its front end is arranged for the mounting of a coupler head 2. Here, it should be pointed out that the part of the drawbar 1 shown in the described embodiment also may be regarded as a connecting tube arranged to, by means of a flange coupling, be coupled to a front end of an interconnected rod, which in a conventional way per se may be arranged to, in its rear end, be coupled to the vehicle chassis, typically via a swivel joint carried on the chassis.

The coupler head 2 comprises a coupler head housing 3 that in its rear end is attachable to the drawbar 1, or indirectly via an interconnected connecting tube, and that in its front end is arranged to carry a front plate 4, typically comprising a guide cone 5 (see Fig. 2) for the alignment of the draft gears upon coupling.

Components included in a mechanical coupling 6, such as a central plate 7 and a coupling link 8, are housed in the coupler head housing and rotatably carried on a pivot or shaft 9, which in turn is mounted in bearings 10 arranged in the coupler head. Devices for the locking/ unlocking of the coupling mechanism may be arranged in a known way in the coupler head housing, as well as devices for the connection of electricity and pneumatics /hydraulics, which usually are carried on the outside of the coupler head.

The coupler head housing 3 extends between the front plate 4 and the drawbar 1. The coupler head housing has a box-shaped structure and consists of an upper part 11, a bottom 12, and two opposite sides 13 and 14, respectively. The upper part and the bottom, as well as the two sides, may suitably be mutually identically shaped with the exception of externally or internally arranged attachments and seats for the mounting of additional equipment. The parts of the coupler head housing are preferably manufactured from steel and are suitably assembled by welding and/ or screw fitting. As is seen in Fig. 1 the coupler head housing is generally shaped as a funnel the sides of which suitably are bent in such a way that a predetermined deformation commences upon axial compression of the coupler head housing. For this purpose, the coupler head housing is preferably formed with deformation notches 15 along which the coupler head housing is folded in a predetermined way upon a shock- absorbing deformation. In order to assist a controllable and essentially straight axial compression of the coupler head housing, slots 16 may be arranged in the transition between the sides and the bottom and upper part, respectively, by which a uniform bulging of the deformable areas is promoted.

From the front plate 4, a beam 17 extends rearward through the coupler head in an axially overlapping relationship (see Fig. 2) with the drawbar 1. In overcoming of a predetermined force, the beam 17 is displaceably supported at the drawbar 1 and carried along by the front plate in a displacement motion in the longitudinal direction of the drawbar in the event of a collision. The beam 17 is preferably supported at the drawbar 1 in a telescopic relationship, and may be supported outside the drawbar, or internally in the same in ways shown in the embodiment example. In this way, the beam 17 retains a bending- or buckling- resistant connection between the drawbar and the front plate also after a collision that causes a deformation and compression of the coupler head housing.

The beam 17 is made with the requisite axial stiffness to transmit, with a maintained integrity and without being bent, compressive forces up to a certain magnitude from the front plate to the drawbar.

In the shown embodiment example, in its rear end, the beam 17 comprises a tubular, preferably cylindrical insertion portion 18 the diameter of which is adapted to the inner diameter of the drawbar so as to allow insertion of the beam into the drawbar in a telescopic relationship. A circumferential, wedge-shaped shoulder 19 in the outside of the beam rests in the mounted state against a corresponding wedge-shaped mouth area 20 in the front end of the drawbar. The shoulder 19 forms transition to a beam section of a greater diameter, and forces a radial compression of the insertion portion of the beam, and/ or a radial expansion of the drawbar, upon the insertion of the beam into the drawbar. In other words, in the described embodiment, the beam 17 is displaceable in the longitudinal direction of the drawbar against the force of a radial deformation of the beam and/ or of the drawbar. The beam 17 is in addition coupled in a traction force- transmitting relationship to the drawbar 1. For the purpose, a nut 21 screwable into the end portion of the beam is arranged with a flange that in the screwed-in position rests against a radial shoulder 22 formed internally in the drawbar. In this way, the coupler head housing 3 is relieved from normal traction forces that, via the beam 17, are transmitted from the front plate 4 to the drawbar 1.

From the front plate 4, the beam 17 extends split in the form of a fork rearward toward the drawbar 1. More precisely, said front part of the beam comprises an upper branch 23 and a lower branch 24. The upper branch 23 runs above the coupling mechanism supported between the branches, while the lower branch 24 runs underneath the same. In other words, the main shaft 9 of the coupling mechanism is vertically supported in mutually aligned seats 25 arranged in the upper and lower branches 23 and 24.

The front end of the beam 17 is preferably connected with the front plate 4.

Alternatively, the front end of the beam may be formed to extend parallel to the front plate 4 in a contact abutting against the back side of the front plate.

Alternatively, the beam 17 is, or at least parts thereof, such as the fork-shaped part 23-24 thereof, integrated with the front plate 4 and formed integrally with the same in the way schematically shown in Fig. 2.