EP0370234B2 - Radiator filling neck with a closure cap - Google Patents

Description

The invention relates to a radiator neck with a closure cap according to the preamble of claim 1, which corresponds to an unpublished, internal prior art of the applicant.

Coolant and / or steam escapes through a radial outlet opening of the connecting piece between the two sealing rings when the pressure relief valve is open. If one attaches the complete pressure relief valve, that is to say its closure member and its valve seat, to the closure cover, as far as the functionality of this closure cover is concerned, the attachment of a valve seat to the radiator neck is not necessary. The same applies to the vacuum valve. As a result, both the pressure relief valve and the vacuum valve can be completely assembled, checked and adjusted as necessary at the factory. So that the cooling liquid or vapor formed from it cannot escape past the sealing cap between the latter and the radiator socket when the sealing cap is in place, the sealing cap must be sealed at a suitable point with respect to the radiator socket. On the other hand, when the pressure relief valve is open, a hydraulic connection to the outside is necessary so that the coolant under pressure can escape from the connection piece. For this reason, the inner seal with respect to the free radiator nozzle end must be arranged in such a way that the coolant under pressure can in principle only flow out through the pressure relief valve. On the other hand, however, one must ensure that the cooling medium flowing out under excess pressure can only emerge from the radiator nozzle via the outlet opening of the radiator nozzle and not in any other way. This makes it necessary to attach a second sealing ring, the outlet opening of the radiator neck for the cooling medium flowing out under excess pressure being between these two seals. The second seal can, for example, rest against the free end of the radiator neck, wherein it is assigned to the inner surface of a closure cap of the closure cover. In this case it is a flat gasket. In such a construction, the inner seal is an O-ring held on the closure cover. Instead of the flat gasket mentioned, a second O-ring can be attached to the cover. Theoretically, it is even conceivable that in addition to these two O-rings, the flat gasket mentioned is also provided. At least in the normal case, the latter is of no importance with regard to a perfect seal. It only becomes effective when the middle of these three seals fails.

The closure cap according to this internal prior art is held on the radiator neck by means of a threaded connection, it having a cylindrical projection provided with a bolt thread, while the radiator neck is equipped with a corresponding nut thread. The O-ring or the O-rings are located further inside in the socket with regard to this thread.

From US-A-3 216 608 it is also already known to hold a sealing cap on a radiator neck by means of a bayonet thread, which has a counter-stroke curve and a pre-locking position. There is no complete pressure relief valve on the cover, but only the valve plate of the latter. The associated valve seat is attached to the metal radiator neck, preferably molded on. An exact presetting of the pressure relief valve is practically not possible here, because the sealing cap is normally supplied separately from the radiator neck and therefore it is not certain from the outset which radiator neck will be used with a particular cap. This construction can lead to an unfortunate meeting of the tolerances.

Furthermore, the radial outlet opening is not provided on the radiator neck, but on the cover.

In modern automotive engines, higher pressures and temperatures of the cooling medium are used. This makes a closer tolerance for the response pressures necessary. This close tolerance can only be guaranteed if the pressure and vacuum valve is completely on the cover. On the other hand, however, there is as yet no possibility of holding such a cover on the radiator neck by means of a bayonet lock.

The object of the invention is therefore to develop a radiator neck with a cap of the type described in such a way that the cap is attached to the neck despite maintaining an integrated overpressure and vacuum valve and thereby a screw connection of the radiator neck and the cap can be dispensed with.

To achieve this object, it is proposed according to the invention that the radiator neck with a closure cover is designed according to the preamble of claim 1 in accordance with the characterizing part of this claim. As already explained, of the two or even three sealing rings, at least the inner one is an O-ring. This bears against the assigned radiator nozzle wall with radial pressure, which is particularly strong when the radiator system is under pressure. As a result, this cap can only with overpressure and even after releasing the overpressure a corresponding effort or be removed from the radiator neck. In the known threaded connection, this axial force is applied when the closure cover is unscrewed. A corresponding axial force does not occur with a conventional bayonet lock. Rather, it must be applied by pulling the closure lid accordingly. This can be associated with a corresponding tilt and lead to damage to the O-ring.

The use of a bayonet lock is now possible in that, according to the invention, there is also a stroke counter-curve which, in cooperation with the counter-cam, forms a respective lifting device for the cover, which presses the cover so far outwards during the opening-rotary movement the inner O-ring has come free of its wall or, in the case of a conical wall, the pressure on it has been overcome. On the other hand, however, a bayonet lock has the advantage over a rotary lock that the closed rotary end position can be found safely due to the existing rotary stops, which is not guaranteed with a screw-on cover. In particular, users with slightly less force or anxious users who do not want to damage the closure cap, or also somewhat carefree users who do not take care that the closure cap is fully unscrewed, attach the screw closure cap, at least occasionally, not firmly enough, and This then leads to a seal between the radiator nozzle and the sealing cap at the free nozzle end by means of a flat gasket, which means that insufficient pressure is generated in the radiator system. In addition, the cooling water can then escape undesirably at this point.

In the radiator neck according to the invention with a closure cover, this cannot happen because the bayonet, as said, clearly signals the user that the end of rotation position has been found. Otherwise, this design has the advantage that you are not bound to certain materials for the radiator neck and sealing cap. Of course, this does not apply to the strength, corrosion resistance and temperature compatibility.

When and to what extent when opening the bayonet lock the stroke counter curve becomes effective in the sense of a stroke effect of the cover depends on the shape of the stroke counter curve, i.e. their respective inclination with respect to a plane perpendicular to the radiator nozzle axis.

If you follow the bayonet cam with the counter cam, starting from the rotary stop the bayonet curve rises at least in this area, the bayonet cams can move axially from the bayonet curve by the amount of the bayonet curve incline and the corresponding Remove the angle of rotation somewhat. However, the counter cam and the bayonet cam, and thus the entire cover in the stroke opening direction, are finally raised via the inner stroke section of the stroke counter curve. The inner stroke section is now dimensioned such that it lifts the closure lid until the first inner O-ring comes free from its wall. As a result, the overpressure in the cooler system can be reduced to the outside in the form of a bypass past the sealing cover. This corresponds to the known pre-locking position.

After a further rotary movement, the counter cam finally reaches the outer stroke section of the stroke counter curve. At the latest at its outer end, an optional second O-ring is then at least released from the cylinder wall to such an extent that the cover can be removed without any particular effort.

An embodiment of the invention is characterized in accordance with claim 2, characterized in that each bayonet curve and each associated stroke-counter curve form an outer groove running in the circumferential direction of the nozzle, which is open to the outside in the radial direction of the nozzle and opens axially at the free nozzle end, whereby the width of this mouth, seen in the circumferential direction, corresponds at least to the length of bayonet cams and counter cams. About this mouth, the bayonet cam with the lifting counter-cam is pushed into the outer groove when the closure cover is placed, with this axial movement then being followed by the rotary movement when the closure cover is to be attached to the connecting piece. The weight loss takes place in the opposite direction. For the rest, the bayonet cam encompasses the nozzle part which has the bayonet curve in exactly the same way as is known from the conventional radiator cap made of sheet metal, from above and from the outside inwards in relation to the mentioned external groove of the radiator nozzle.

Another variant of the invention is characterized by the features of claim 3.

Further important refinements and advantages of the invention result from the claims and the following description of exemplary embodiments.

Fig. 1

Das freie Ende eines Kühlerstutzens mit einem im Abstand davon befindlichen und damit verbindbaren Verschlußdeckel in der Seitenansicht,

Fig. 2

in vergrößerter Darstellung einen Vertikalschnitt einer anderen Ausführungsform des Verschlußdeckels,

Fig. 3

in einer halbschnittartigen Darstellung, wobei die linke Hälfte zur besseren Darstellung der Erfindung in die Bildebene hineingedreht ist, wiederum in vergrößertem Maßstab, einen an einem Behälter angeformten Kühlerstutzen mit aufgesetztem Verschlußdeckel in der Schließ-Endstellung,

Fig. 4

in vergleichbarer Darstellung dieselbe Ausführung in der sogenannten Vorraststellung,

Fig. 5

eine der Fig. 3 entsprechende Darstellung einer weiteren Variante der Erfindung,

Fig. 6

eine der Fig. 4 entsprechende Darstellung der Fig. 7,

Fig. 7

eine Abwicklung eines Teils des Kühlerstutzens im Bereich der Außennut bei einer weiteren Variante der Erfindung,

Fig. 8

einen Ausschnitt eines zur Fig. 7 gehörenden Verschlußdeckels im Bereich seines Bajonettnockens.

The invention is explained in more detail with reference to the drawing. The drawing shows different ones Embodiments of the invention. Here represent:

Fig. 1

The free end of a radiator socket with a sealing cover located at a distance from it and thus connectable in a side view,

Fig. 2

an enlarged view a vertical section of another embodiment of the closure cover,

Fig. 3

in a half-sectional view, the left half being rotated into the image plane for a better illustration of the invention, again on an enlarged scale, a radiator neck molded onto a container with a closure cap attached in the closed end position,

Fig. 4

in a comparable representation the same version in the so-called pre-locking position,

Fig. 5

3 shows a representation of a further variant of the invention,

Fig. 6

1 corresponding representation of FIG. 7,

Fig. 7

a development of part of the radiator neck in the area of the outer groove in a further variant of the invention,

Fig. 8

a section of a closure lid belonging to FIG. 7 in the region of its bayonet cam.

The cover 1 and the radiator neck 2 are connected to each other by means of a bayonet lock. The cover 1 is placed on the radiator neck 2 in the mounting direction 3 until the bayonet cams 4 lie below the start edge of the respectively assigned bayonet curve 5, so that subsequently turning in the direction of the arrow 6, that is to say in the closing direction of rotation, is possible. Each bayonet cam 4 then slides in a known manner along the bayonet curve 5, which descends downwards, which leads to a lowering movement of the closure cover 1 superimposed on the rotary movement. In the exemplary embodiment according to FIG. 1, the latter bears a sealing ring 7 designed as an O-ring 7 at its front end in the direction of attachment 3. As shown in FIG. 5, for example, it rests on a cylindrical inner surface 8, at least when the bayonet is completely closed, and seals thus at this point the gap 9 between the sealing cap 1 and the radiator neck 2.

According to, for example, FIG. 1, each of the two bayonet curves 5 of the exemplary embodiments initially runs approximately in a plane perpendicular to the geometric axis 10 of the radiator connector 2 or at most when the closure cover is screwed in slightly inclined to this. This is then followed by the inclined or steeper section, which causes the closure cover 1 to be pulled in in the direction of the arrow 3. The so-called pre-locking position is reached at the transition between these two curve sections (FIG. 4). The inner sealing ring, which in the case of two O-rings forms a first inner O-ring 7, is not yet in contact with the cylinder inner surface 8. As a result, a flow connection between the inside of the cooler and the outside atmosphere or a drain pipe 11 via a radial outlet opening 12 of the cooler neck 2 is still open. The cooler neck inner wall is reduced conically or in the manner of a shoulder in the area of the sealing cover 1 (FIG. 4). The transition takes place e.g. B. via an intermediate cone 13. The diameter of the further bore part 14 is selected so that the first, inner O-ring 7 can not rest on it. Starting from the closed position of the closure cover 1 (for example FIG. 3), after a partial rotation into the pre-locking position (FIG. 4) the excess pressure inside the cooler system can be reduced via the radial outlet opening 12. After the pressure has been released, the sealing cover is opened completely in the opposite direction to arrow 6 and then raised in the opposite direction to arrow 3 from the radiator neck 2. Otherwise, the turning in the direction of arrow 6 takes place until the front edge 15 of the bayonet cam 4 in the closing direction of rotation bears against the assigned rotary end stop 16 of the radiator connector 2. In the exemplary embodiment according to FIGS. 5 and 6, in addition to the first O-ring 7, a second O-ring 17 is also provided. It is already in place when the closure cap 1 is plugged onto the upper end of the radiator connector 2 against the additional bore part 14 of the radiator connector 2 with a diameter. As a result, in the pre-locking position (FIG. 6), the steam cannot flow out via the opening of the radiator connector 2 in the direction of the arrow 18. Otherwise, in the embodiment according to FIGS. 5 and 6, a third sealing ring 19 is provided, which is designed in a known manner as a flat sealing ring and rests on the bead-like opening of the radiator connector 2 when the bayonets are completely closed or is pressed thereon in a sealing manner. In the pre-locking position, this seal is of course relieved or lifted from the mouth opening. At this point it is pointed out that instead of the step-like widened bore of the radiator connector 2, a conically tapering from the outside in can also be provided, the cone then having to be selected such that in the case of two O-rings the second O-ring 17 also bears sealingly against the radiator socket wall 2 in the pre-locking position. The O-ring grooves are designated 21 and 22.

The special feature of the combination of the closure cover 1 and the radiator connector 2 according to the invention is that there is a counter stroke curve 23 opposite each bayonet curve 5. Due to their axial spacing, the two together form an outer groove 24 running in the circumferential direction of the connecting piece. The bottom of the groove can be seen in FIG. 1. In addition, each outer groove opens at the free radiator nozzle end, the groove opening being designated by 25 in FIG. 1. Its length measured in the circumferential direction corresponds to the length of the bayonet cam 4.

Each bayonet cam 4 is connected to a counter cam 26, in particular directly, or is produced in one piece in the case of plastic production. The counter cam 26 is then formed by the surface or edge of the associated bayonet cam 4 pointing in the mounting direction 3 of the closure cover 1. Seen in the closed direction of rotation 6, this counter cam 26 drops towards the rear, as shown in FIG. 1 of the drawing. This creates at this point a sliding bevel 27 which is of importance when the closure cover 1 is opened in the manner explained below. The height of the bayonet cams 4 and counter-cams 26 together is measured in the axial direction so that both are not greater than the width of the outer groove 24 measured in the axial direction at the narrowest point, although the bayonet engagement at the start of the closing rotary movement is not taken into account is left.

For example, from FIG. 1 it can be seen that, starting from the common rotary end stop 16 of the bayonet curve 5 and the stroke counter-curve 23, the latter initially begins with an approximately flat section 28. This is followed by an inner lifting section 29, which can merge into a second flat section 30. Seen in the opening direction of rotation, the last section is followed by an outer lifting section 31. The latter can also extend directly to the inner lifting section 29 with a decreasing inclination.

After the closure cap 1 has been placed on the radiator connector 2, each bayonet of the bayonet closure is closed in a known manner, the bayonet cam 4 interacting with its associated bayonet curve 5. Due to the strong friction between the one or more O-rings and the associated wall of the radiator connector 2, the closure cover 1 would remain in its lowest position when viewed in the axial direction when the bayonets were opened. The bayonet surfaces and cam surfaces that are effective when plugged in are not able to exert a pulling action against the arrow 3 on the closure cover 1. This is also the reason why there is no closure cover knows, which is held by means of a bayonet lock on a radiator neck and sealed against the radiator neck by means of O-rings.

It is only through the creation of a special lifting device for such a closure cover that is designed in accordance with the invention that a bayonet closure can also be used with closure covers sealed by O-rings, which offers the advantage of finding a safe rotary end position. During a first rotational opening position, each counter cam 26 is first moved along the flat or approximately flat section 28 of the stroke counter curve 23. As seen in the axial direction, the bayonet cam 4 then continuously moves away from the part of the inner bayonet curve that drops in the rotational closing direction. As a result, the closure cover 1 does not yet perform any stroke-opening movement, or at least not completely. It is only in the interaction of the sliding bevel 27 with the inner lifting section 29 of the bayonet counter-curve 23 that the closure cover 1 is raised a first time. It is chosen such that it does not go beyond the known pre-locking position. After the overpressure has been released, the closure cap 1 is turned further in the opposite direction of the arrow 6, the sliding bevel 27 then interacting with the outer lifting section 31 and thereby lifting the closure cap 1 so high that it can be removed from the radiator neck 2 without, at least without any significant force .

So there is an interaction of a bayonet lock with a rotary lock that only acts in the direction of the opening, whereby the bayonet lock provides the sealing via the O-ring or rings, while the lifting rotary lock makes this seal ineffective again in two stages. The straight and the oblique curve parts of the bayonet curve and the counter stroke curve are dimensioned and assigned to one another such that when a slope becomes effective, the opposite curve cannot hinder the resulting stroke movement in the direction of arrow 3 or in the opposite direction.

The closure cover is provided with a centering pin 32 which carries the first inner O-ring 7 in the region of its free end and which at the same time forms the housing for a pressure relief valve. It is preferably made of plastic, as is the lid upper part 33 with the molded-on bayonet cams 4 and counter cams 26. Both are, as shown for example in FIG. 4, connected to one another via a centering and firmly held together in a known manner. Each O-ring groove is molded on. The same preferably also applies to the valve seat 34 of the pressure relief valve 35 and at least one radial outlet opening 36 on the outflow side of the valve housing wall, via which when the pressure relief valve is open, the medium can pass into the gap 37 between the centering pin 32 or valve housing and the radiator nozzle. From there, it arrives in the manner described, even when the radiator cap 1 is firmly closed, via the radial outlet opening 12 of the radiator connector 2.

The closure member of the pressure relief valve 35 is designated 38 (FIG. 4) and is designed in a known manner. It is spring-loaded by means of a helical compression spring 39. The vacuum valve 40 is arranged centrally for this purpose. In the exemplary embodiment (FIG. 4), its closure member 42, which is loaded by the spring 41, bears against the common sealing ring 43, which at the same time forms the valve seat of the vacuum valve 40. In the event of overpressure, the closure member 38 of the pressure relief valve 35 is lifted upward, while in the event of negative pressure, the closure member 42 of the vacuum relief valve 40 is shifted downward, in each case against the resistance of the loading spring 39 or 41.

In a particularly preferred embodiment of the invention, the part 44 of the radiator connector 2 which has the stroke countercurves 23 is located on a compensating tank 45, but at least on an upper part of such a compensating tank. In a modern cooler system, in a known manner, in addition to the cooler, there is a so-called expansion tank, which carries the sealing cover and into which both the cooling water and cooling water additives are poured.

As shown in FIG. 3, it is not only possible to produce this part 44 with the stroke counter-curves 23, but also the entire radiator neck 2 in one piece with the expansion tank 45 or an expansion tank upper part. In contrast, the radiator neck can also be formed in two parts and while the inner part of the radiator neck forms the radiator neck part 44 with the stroke opposing curves 23, the bayonet curves 5 are located on a separately produced outer radiator neck part 46 or 47.

In all of the above-described embodiments of the radiator connector, there is a molded valve seat 53 on its inner end (FIG. 3). This is normally of no importance. However, should the cap 1 get lost or fail, you can attach any conventional, easy-to-obtain cap that has a complete vacuum valve to the bayonet of the radiator neck 2 in such an emergency. He must be equipped with a spring-loaded valve plate, which corresponds to the closure member 38 (Fig. 6). A known pressure relief valve is then created together with the valve seat 53. This allows this radiator neck 2 can be used in the same way as a conventional radiator neck despite its special training. It is also expressly pointed out once again that the inner part 44 of the radiator neck does not necessarily have to be connected to an expansion tank or be part of the same, but that it can also be the tubular attachment of a radiator upper part or radiator water box. For manufacturing and cost reasons, it is advantageous, if not essential, that the inner part 44 of the connector 2 is made of plastic, as well as the plastic production of the entire closure cover 1 (with the exception of the springs) is preferred. Polypropylene is preferably used for the expansion tank, while the lid is expediently made from polyamide, a highly heat-resistant variant having to be used and glass fiber reinforcement or the like also being able to be provided.

If, in the case of two O-rings, the two O-rings 7 and 17 (e.g. FIG. 5) lie tightly against the radiator socket wall and you want to open the closure cap 1, this means that the two O-rings are under a heavy load Friction seen in the circumferential direction of rotation. In order to protect the two O-rings, the part of the sealing cap 1, which carries the two O-rings 7 and 17, can be rotatably supported on the remaining part of the sealing cap 1, in particular on the upper part carrying the bayonet cams 4, in a manner not shown .

The medium flowing out under pressure enters the pressure relief valve (35) via at least one opening (44) at the free inner end of the radiator connector (2).

Each bayonet cam and its associated counter cam form a movable element along the outer groove of the radiator neck, which is why this outer groove, measured in the axial direction, must be at least as high at every point that the movement of this element is not hindered when the closure cap is attached and when it is released. On the other hand, however, the height of the individual sections is quite different, which results from their special shape and the mutual assignment. The bayonet curve also has the otherwise usual task here, namely when closing the closure cover to pull it against the neck opening (arrow direction 3 in FIG. 1) in such a way that a seal which may be located between the neck opening and a lid edge is pressed. Even when using O-rings for sealing, an at least partially inclined bayonet curve is necessary in order to achieve the desired sealing between the sealing cap and the radiator neck.

As can be seen from the above description of the drawing and, for example, FIG. 1, the bayonet curve does not have to extend inclined over its entire length to the neck opening or a plane perpendicular to the longitudinal axis of the neck, rather it is sufficient if only a part of it has such an inclination. In Fig. 1, this is the last section which extends in each case up to the rotary end stop 16. The section of the bayonet curve first reached by the slot mouth 25 runs approximately parallel to the mouth plane in FIG. 1. The start of this section is opposite to the second flat section 30 of the stroke counter-curve 23, which merges smoothly into the outer stroke section 31. To the left of the second flat section 30 there is the inner lifting section 29, to which the first flat section of the counter stroke curve 23 is connected up to the rotary end stop 16. As a result, the two flat sections 28 and 30 of this embodiment are at different levels in the axial direction of the nozzle.

Comparing this embodiment with that of FIG. 7, for example, it is found that in the latter the second flat section 30 has been displaced towards the lower nozzle end and that it is preferably at approximately the same height level as the first flat section 28. As a result, the inner lifting section 29 does not merge directly into the second flat section 30, but rather a flank 55 falling to the right is interposed. Together with the inner lifting section 29, this forms a cam-like lifting element 56.

The second flat section 30 of the stroke counter-curve 23 is axially opposite an auxiliary cam 57 pointing into the socket interior. Such an auxiliary cam 57 is provided on each bayonet curve 5. It is particularly important when opening the closure lid. When the closure cap 1, which is usually under high overpressure, is opened, the inner lifting section 29 releases the first O-ring 27 and thus connects the interior of the socket or the cooler to the outside atmosphere. The overpressure can be released in this way. This process can take a certain amount of time, especially in the case of very high overpressure and a small overflow cross section. If you were to turn the partially raised cap very quickly towards the open position, this could lead to the fact that the excess pressure in the cooler has not yet been reduced, but on the other hand the cover can already be removed or possibly blown off by the excess pressure. That would be one There is a risk of accidents, for example from scalding or from the cover itself flying away.

In order to ensure good security even in such a case, the auxiliary cam 57 mentioned is present in the exemplary embodiment according to FIG. 7. After reaching the pre-locking position with overpressure reduction, the counter-cam 26 abuts the auxiliary cam 57, which prevents rapid further rotation in the direction of arrow 58. In order to bring this cover into a rotational position suitable for removal, the auxiliary cams 57 must be overcome. This means that the sealing cover must again make a lowering movement towards the cooler. This is not possible, or at least not readily possible, in the case of excess pressure in the radiator neck. The user is thus prevented from "turning" the closure lid quickly in the opening direction 58 and the inattentive user is made aware by the auxiliary cams 57 that he does not continue to turn the lid too quickly, but first waits for the excess pressure to be released. In order to enable the lowering movement of the counter cam 26 which is necessary when overcoming the auxiliary cam 57, in the exemplary embodiment according to FIG. 7 the second flat section 30 of the stroke counter curve 23 is lowered in the manner described. This sliding edge of the auxiliary cam 57 is designated 59 and the falling edge 60. In addition, the oblique edge 61 in FIG. 7 has turned out to be relatively short, in relation to the exemplary embodiment according to FIG. 1, for example. Similar to FIG. 1, the oblique edge 61 of the bayonet curve 5 is followed by an approximately flat section 62, which extends to the auxiliary cam 57, the latter then merging into the groove opening 25.

In order to enable the sliding movement of the bayonet cams 4 and the counter-cams 26 in the outer grooves formed in this way, the element of the closure cover 1 formed from these two cams must also be given a corresponding shape. Of particular importance here is a rear bevel 63, which is located at the rear end of the counter cam 26 or this element in the opening direction 58. It preferably runs approximately parallel to the sliding counter bevel 27 of the counter cam 26 (FIG. 8).

Claims (10)

1. Radiator neck (2) with a closure cap (1) in which a pressure-relief valve (35) and a suction-relief valve (40) are disposed and which is sealed with respect to the radiator neck by means of at least two sealing rings (19; 7, 17), of which at least the inner ring, viewed from the interior of the radiator, is a first O-ring (7) which is disposed around a centering plug (32) of the closure cap (1) and, at least when the closure cap (1) is fully closed, abuts a cylindrical internal surface (8) of the radiator neck (2) in a leaktight manner, the pressure-relief valve (35) and the suction-relief valve (40) being disposed in the centering plug (32), the centering plug (32) comprising at least one radial through-hole (36) and the radiator neck (2) comprising at least one radial outlet opening (12) which is disposed between the two sealing rings when the closure cap is fully closed, characterized in that the closure cap (1) and the radiator neck (2) are connected to each other by means of a bayonet fixing (4, 5) wherein, opposite each bayonet cam profile (5) of the neck (2) and axially spaced therefrom, there is a reverse lifting cam profile (23) which, at least during the opening of the closure cap (1), cooperates with the surface or edge of the associated bayonet cam-follower (4) which points in the direction (3) in which the closure cap (1) is mounted and which forms a reverse cam-follower (26), in a manner such that, during the opening of the closure cap (1), an axial force is exerted and helps to overcome the frictional force caused by the O-ring or by the O-rings when they abut the cylindrical internal surface (8) in a leaktight manner, viewed in the closure sense (6) each bayonet cam profile (5) and each associated reverse lifting cam profile (23) finishing at a common rotation stop (16) in that the bayonet cam profile (5) is formed, at least along part of its length, by a sloping edge inclined towards the plane of the mouth of the neck, and each reverse lifting cam profile (23) consists of two level portions (28, 30) and two lifting portions (29, 31) which rise towards the free end (20) of the neck, the outer lifting portion (31) extending as far as the free end (20) of the neck and the first level portion (28) being disposed between the limit stop (16) for the closure rotation and the inner lifting portion (29), and in that the axial distance between the bayonet cam profile (5) and the reverse lifting cam profile (23) corresponds at least to the axial distance between the bayonet cam-follower (4) and the reverse cam-follower (26), in that the internal wall of the radiator neck (2) is widened slightly towards the exterior by means of a taper or shoulder in the region of the inner O-ring or of the O-rings (7, 17), the step (13), in the case of a shoulder, being disposed between the first, inner O-ring (7) and the outer sealing ring (19; 17) when the cap (1) is closed, and in that, when the surface or edge of the reverse cam-follower (26) is sliding along the inner lifting portion (29) of the reverse lifting cam profile (23), the radial outlet opening (12) of the radiator neck (2) gets in communication with the interior of the radiator, since the inner O-ring no longer abuts the cylindrical inner surface which adjoins the tapered or shoulder-like widening.
2. Radiator neck with a closure cap according to Claim 1, characterised in that each bayonet cam profile (5) and each associated reverse lifting cam profile (23) form an external groove (24) which extends around the periphery of the neck (2), which is open to the exterior radially of the neck (2), and which opens to the exterior axially at the free end (20) of the neck, the width of this opening (25), viewed along the periphery of the neck corresponding at least to the length of the bayonet cam-follower (4) and the reverse cam-follower (26).
3. Radiator neck with a closure cap according to Claim 1, characterised in that, when there are two bayonet cam profiles (5), viewed in the closure sense (6), the inner end of one bayonet cam profile (5) extends as far as the start of the reverse lifting cam profile (23) associated with the other bayonet cam profile (5), and in that the reverse cam follower (26), at least at its front end, when viewed in the opening sense, has a reverse sliding slope (27), which preferably has the same inclination as the rising, lifting portions (29, 31) of the reverse lifting cam profile (23), and which adjoins a level portion facing inwardly of the neck.
4. Radiator neck with a closure cap according to at least one of the preceding claims, characterized in that the centering plug (32) of the closure cap is made of plastics material and comprises a first peripheral groove (21) in the region of its free end for housing the first, inner O-ring (7), and in that there is a second peripheral groove (22) for housing a second, outer O-ring (17), axially spaced from the first groove (21) towards the exterior of the radiator, the radial through-hole or holes being disposed between the two grooves.
5. Radiator neck with a closure cap according to Claim 4, characterised in that the tapered or shoulder-like widening of the internal wall of the radiator neck is disposed between the first, inner O-ring (7) and the second, outer O-ring (17) when the closure cap is closed.
6. Radiator neck with a closure cap according to at least one of the preceding claims, characterized in that the radiator neck (2), at least in the region of the reverse cam-follower (26) and, in particular, also the upper portion (33) of the closure cap with the bayonet cam-follower (4) are made of plastics material, and in that the portion of the radiator neck (2) which comprises the reverse lifting cam profile (23) is disposed on an expansion tank (45) of a cooling system, particularly made of plastics material, or at least on an upper portion of an expansion tank, the inner portion (44) of the radiator neck (2) preferably being formed integrally with the plastics expansion tank (45) or with the upper portion of the expansion tank.
7. Radiator neck with a closure cap according to Claim 6, characterised in that an outer portion of the radiator neck (2) which comprises the bayonet cam profile (5) is formed separately from the inner portion (44) and is connected thereto in a leaktight manner, the outer portion (47) of the radiator neck (2) either being made of plastics material and connected in a leaktight manner to the inner portion (44) and/or to the expansion tank (45), that is, of the radiator neck (2) or being made of metal or connected in a leaktight manner to the inner portion (44) and/or to the expansion tank (45), that is, the upper portion thereof, in particular, fixed thereto by beading.
8. Radiator neck with a closure cap according to at least one of the preceding claims, characterized by a valve seat (53) mounted on, particularly formed on, the radiator neck (2) for the valve disc of a spare closure cap, the valve disc and the valve seat forming the pressure-relief valve (35).
9. Radiator neck with a closure cap according to one of Claims 1 and 3 to 8, characterized in that the central plug (32) which serves as a valve housing of the closure cap (1) is mounted for rotating about the geometrical axis on the upper portion of the cap which has the bayonet cam-follower (4) and the reverse cam-follower (26), and in that an auxiliary cam (57) pointing inwardly of the neck is mounted on each bayonet cam profile (5) axially opposite the second, outer, level portion (30) of the reverse lifting cam profile (23), the first inner, level portion (28) of the reverse lifting cam profile (23) forming one side of a cam-like lifting element (56) which points towards the free end (20) of the neck, and the other side (55) of which is inclined downwards towards the second, outer, level portion (30).
10. Radiator neck with a closure cap according to Claim 9, characterised in that the first, inner level portion and the second, outer, level portion (28, 30) of the reverse lifting cam profile (23) lie in the same plane and the bayonet cam profile (5) comprises a level portion (62) which is disposed opposite the cam-like lifting element (56) of the reverse lifting cam profile (23) and which extends from its auxiliary cam (57) to its inclined edge (61), the reverse cam-follower (26) merging, at its rear end in the opening direction (58), with a rearward slope (63) which extends parallel to its reverse sliding slope (27).

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