Description of Prior Art Automatic couplers for rail mounted vehicles or rail- way vehicles are used in order to couple together vehicles mechanically without the need of manual manipulation of the couplers. The individual coupler-which is mounted on one end of, e. g. , a carriage or wagon or a locomotive-may depending on the purchaser's wishes be composed of a quan- tity of different components, such as shock absorber, crash absorption, etc, but includes, however, always a so-called head, which can be coupled together with a compatible head on another coupler. Said coupler head consists of a hous- ing-like construction, which in front has a robust front plate that is formed with a male-like projection, as well as a female-like seat beside the same. In the'seat, a ratchet mechanism is arranged, which is activated when the male projection of a co-operating coupler head is inserted into the same, at the same time as the male projection activates the corresponding ratchet mechanism in the other coupler head. In order to resist the stresses that the cou- pler head is exposed to, not only the housing construction, but also the front plate are made from a powerful material.

Thus, the front plate may be manufactured from a 15-40 mm thick steel plate.

As need arises, the automatic couplers may also be formed so that the pneumatic system of the vehicles auto- matically is coupled together in connection with the

mechanical coupling being executed. In such a way, com- pressed air may be transferred between, for instance, the locomotive and different wagons in a train unit. Pneumatic coupling is carried out by means of one or more valves mounted in the coupler head, more precisely in the immedi- ate vicinity of the front plate thereof. Each such valve co-operates with an elastic, cylindrical sealing sleeve, as well as a front gasket exposed forwards, which is comprised in a holder in the form of a ring. The front gasket usually consists of rubber and the ring of metal. The front gasket together with the ring has the possibility of resiliently moving inwards in the front of the coupler head in order to give a suitably adapted contact force between the two gas- kets that meet each other upon the mechanical coupling of the couplers. When two front gaskets meet, they seal against each other, and the sleeve usually consisting of rubber being behind, guaranteeing the requisite seal between the holding ring of the front gasket and the real valve, which is in the form of a housing placed at a cer- tain distance behind the front plate. In said housing, a conventional valve cone is included, which on one hand, holds the way of communication through the valve closed as long as the coupler is uncoupled, but which opens the way of communication when coupling takes place and compressed air activates the cone.

Since in particular the front gasket consisting of rubber is a component which is worn and broken down, e. g. by sunlight, environmental influence and mechanical influ- ence, it is important to fast and easy be able to exchange the gasket without the valve in its entirety needing to be dismounted. In other words, the front gasket should be able to be dismounted and mounted from the front side of the front plate. For this reason, the holding ring of the front gasket is mounted by means of a bayonet coupling, which usually includes two diametrically opposed shoulders on the outside of the holding ring, as well as two sockets in the form of two diametrically opposed recesses, which are formed in a comparatively narrow, ring-shaped flange in the through hole in the front plate in which the front gasket

is accommodated. By means of a special key, the holding ring may be pressed into the hole in the front plate, the shoulders passing axially through the recesses in said flange, more precisely against the action of the spring force in the above-mentioned sealing sleeve as well as a screw compression spring arranged between the holding ring and the valve housing. When the shoulders have passed through the recesses, the holding ring is turned, e. g. 90°, the shoulders resiliently being pressed against the back side of the flange. Unintentional turning of the holding ring together with the front gasket, e. g. as a consequence of vibrations or relative motions between two meeting front gaskets, may however lead to not only the front gasket and the appurtenant holding ring, but also the sealing sleeve being behind and the screw spring falling out of the cou- pler. This may have catastrophic consequences. Therefore, in order to secure the front gasket, two small locking screws have previously been used which are screwed in threaded holes on each side of one of the two shoulders of the holding ring. Although this construction, per se, obvi- ates the risk of unintentional turning of the holding ring, the same is associated with a plurality of disadvantages, which above all are based on the fact that the holding ring is secured by means of locking screws, which for their mounting require particular machining of the front plate of the coupler head. Thus, the flange behind which the shoul- ders of the holding ring are clamped have to be formed by particular machining of the appurtenant hole in the front plate at the same time as two threaded holes have to be formed with great exactness so far that the same on one hand should have full diameter through the flange, and on the other hand proceed in a cup-shaped flute in which the tightened screw projects from the inside of the hole for locking the shoulder on the holding ring. Furthermore, the construction requires that the proper valve housing is mounted from the back side of the coupler. This means that the complete valve cannot be mounted together completely and be function tested until all parts have been mounted in the coupler. In other words, loose parts have to be handled

in order to provide a complete valve. It is also necessary to secure the proper locking screws by means of glue or glue-like locking liquid. This means in practice that dis- mounting of a worn out front gasket becomes intricate and many times difficult to carry out. The requisite machining of the front plate of the coupler housing is furthermore complicated and expensive.

Objects and Features of the Invention The present invention aims at obviating the above- mentioned disadvantages of previously known coupler heads and at providing an improved coupler head of the type that includes one or more pneumatic valves. Therefore, a primary object of the invention is to provide a coupler head in which a complete, function tested pneumatic valve may be mounted without the front plate needing to be machined in order to be able to co-operate with the valve. Another object is to provide a coupler head having a valve, the front gasket of which can be secured in a mounted position in an easy and fast way without the need of particular locking screws. It is also an object to provide a coupler head, the valve'function of which should be entirely com- patible with the valve function of older, existing coupler heads.

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 coupler head according to the invention are furthermore defined in the dependent claims.

Brief Description of the Appended drawings In the drawings: Fig 1 is an perspective exploded view of two separated automatic couplers, the front one of which is shown obliquely from behind and the rear one obliquely from the front, Fig 2 is a likewise perspective exploded view showing solely the rear coupler head and with parts of a pneumatic valve separated from the coupler head,

Fig 3 is a perspective exploded view of the different parts which are included in said pneumatic valve, Fig 4 is a longitudinal section through the front part of a sleeve included in the valve, Fig 5 is a front view of the valve, Fig 6 is an enlarged cross-section illustrating a bayonet coupling for the front gasket of the valve, the hold- ing ring of the front gasket being shown in a locked, active position, and Fig 7 is a cross-section corresponding to fig 6 showing the holding ring of the front gasket twisted to a posi- tion in which it may be dismounted.

Detailed Description of a Preferred Embodiment of the Invention In fig 2 individual heads 1 to two automatic couplers are shown, which in addition to the heads include a number of additional components, not shown, (shock absorbers, crash absorptions, etc) and which are mounted on each vehi- cle, e. g. wagons and/or locomotive. The individual coupler head includes a housing-like body 2, as well as a front plate 3, which in practice may consist of strong steel plate. The front plate 3 includes on one hand a male-like projection 4, and on the other hand a female-like seat 5 in which a ratchet mechanism, not shown, is mountable. When the projection 4 on one of the couplers is brought to engagement with the seat 5 in the second coupler, the same mechanisms lock the couplers in relation to each other.

Furthermore, a pneumatic valve which in fig 3 gener- ally is designated 7 is included in the. coupler head and which includes among other things a valve housing 8, which is placed behind the front plate 3 to the individual cou- pler head. As is seen in figs 1 and 2, each coupler head includes two'such valves, which mouth in through holes 9 in the front plate. The valve housing 8 is kept in place by means of fixing screws 10 which in a conventional way are accessed from the front side of the front plate. To the valve housing, a compressed-air tube is connected, which is outlined at 11.

Now reference is also made to figs 3-7, in which is seen that the valve 7 in addition to the proper valve hous- ing 8 includes an elastic sealing sleeve 12 as well as a front gasket 13, which is comprised in a holder in the form of a ring 14 of metal. The sleeve 12 has a cylindrical basic shape and may advantageously be manufactured from rubber. Also the front gasket 13 is of an elastic character and may advantageously be manufactured from rubber. Behind the holding ring 14, a screw compression spring 15 is fur- thermore arranged which in combination with the sleeve 12 aims to press the holding ring together with the front gas- ket in the direction outwards. On the outside of the hold- ing ring 14, a pair of opposite shoulders 16 are arranged (in fig 4 the shoulders are rotated 90° in relation to the position according to fig 3). The same shoulders form part of a bayonet coupling, which in other respects includes two sockets or recesses 17, through which the shoulders may pass.

It should also be pointed out that the holding ring 14 is formed with two front seats 18 in which a key (not shown) for turning the ring may engage.

As far as the shown valve has been described hith- erto, the same is in all essentials previously known. How- ever, in previously known coupler heads, the holding ring 14 of the front gasket 13 has been applied against a thin flange formed in the front part of the through hole 9 in the front plate 3. In doing so, the sockets 17 for the stop shoulders 16 were formed in the flange integrated with the front plate. This meant, among other things, that all com- ponents in the valve could be assembled together and func- tion tested first when the valve housing 8 had been mounted in place in the area behind the front plate.

In contrast to prior art, the holding ring 14 in the construction according to the invention co-operates with a flange 19 which is joined to the valve housing rather than the front plate, more precisely with a pipe section 20 pro- jecting from the valve housing. The two sockets or the recesses 17 for the shoulders 16 are formed in the inwardly turned flange 19, wherein the shoulders may freely pass in

the axial direction through the recesses if the ring is adjusted in a matching rotation angle position. As soon as the ring is turned in relation to said position, however, the shoulders are locked against the rear shoulder surface on the flange 19. On the inside thereof, the pipe section 20 is formed with an inner bore 21 for the sealing sleeve 12 and an outer bore 22 for housing the screw compression spring 15. When the holding ring 14 is pressed into the interior of the pipe, the sleeve 12 as well as the screw compression spring 15 are compressed, and then said ele- ments by considerable spring force press the stop shoulders 16 against the flange 19.

In order to secure the holding ring 14 together with the appurtenant front gasket 13 against unintentional turn- ing, a spring element 23-instead of small locking screws in the front plate 3-is arranged, which in the example consists of a generally U-shaped spring band that may enclose the pipe section 20. More precisely, the spring band 23 is formed with two side pieces 24, which in fig 3 are shown having planar shape, but which in figs 6 and 7 are shown having convexly inwards bent shape. Said side pieces are arranged to engage two diametrically opposed recesses 25 in the pipe section 20. More precisely, said recesses 25 are formed in a comparatively thin-walled, front neck portion 26 the envelope surface of which is somewhat countersunk in relation to other parts of the pipe section 20. In such a way, a groove 27 is formed in which the spring band 23 may be snapped-in and held in place.

Furthermore, it should be pointed out that the shoul- ders 16 are wedge-shaped, more precisely in such a way that they taper in the backward direction towards the valve housing 8. Thanks to the same wedge-shape, the shoulders will, at the entry thereof in the recesses 25, which are located in the axial extension of the sockets 17, press out the two side pieces of the spring band When the holding ring 14 then is turned (e. g. 45° or 90°), the side pieces 24 again spring into the recesses 25, more precisely to the position shown in fig 6. In this position, the side pieces 24 form stops for the shoulders 16, whereby unintentional

turning of the holding ring 14 is prevented. Only if a con- siderable, intentional turning force is applied to the ring 14 by means of the above-mentioned key, the spring force in the spring band 23 is overcome, whereby the ring may be turned to the rotation angle position shown in fig 7 in which the shoulders may be led out through the sockets 17.

A substantial advantage of the invention is that the machining of the front plate to the coupler head is sub- stantially facilitated and cheapened. Another advantage is that the valve may be assembled to a unit independent of the front plate which can be function tested before the valve in its entirety is mounted on the coupler head. Fur- thermore, every need for safety screws is obviated which on one hand are difficult to handle in connection with mount- ing and dismounting, and on the other hand easy to lose. In such a way, the requisite exchanges of worn out front gas- kets are to a large extent facilitated because the same can be dismounted as well as reassembled by means of one single simple key recess.

Feasible Modifications of the Invention The invention is not limited only to the embodiment described above and shown in the drawings. Thus, the hold- ing ring of the front gasket needs not necessarily include two shoulders, although this number is preferred. Further- more, the spring element for securing the holding ring may be formed in another way than in the shape of a U-bolt.