CA1327054C - Plunger piston system - Google Patents

Abstract

Abstract The present invention relates to a plunger piston system used, for example, to support and guide the pneumatic spring bellows (24) of an air suspension axle of a commercial vehicle or the like, with a plunger piston (1) that has a cylindrical plunger piston skirt (9) with a bottom foot area (5) for the connection with an air spring bearing arm and an upper plunger piston edge (6) that adjoins the plunger piston skirt (9) and which becomes, radially in an inward direction, a trough section that has, preferably, a trough base (8) that incorporates an opening (20) for the passage of a bolt (22) for a force-fit connection with a base (23) of the air spring bellows (24), which forms a trough (26) to accommodate the convex base (23) of the air spring bellows (24), there being a supporting body (11) in the inner space (27) that is surrounded by the plunger piston, the lower foot area (12) of said supporting body resting on the lower foot area (5) of the plunger piston (1). In order to create a light but nevertheless rugged construction, the present invention proposes that the plunger piston (1) and the supporting body (11) be of plastic: that the plunger piston (1) be configured so as to be pot-shaped with an essentially cylindrical casing (9); that the supporting body (11) be configured as a separate part of essentially truncated conical shape with a diameter (D) that grows smaller from the lower foot area (5) to the trough base (8) of the plunger piston (1); and that the supporting body ( 11) rest with a upper base plate (18) on the underside (28) of the trough base (8) of the plunger piston (1).

Figure 2b

Description

The present invention relates to a plunger piston system used, for example, to support and guide the pneumatic spring bellows of an air suspension axle of a commercial vehicle or the like, with a plunger piston that has a cylindrical plunger piston skirt with a bottom foot region for a connection with an air spring bearing arm and an upper plunger piston edge that adjoins the plunger piston skirt and which becomes, radially in an inward direction, a trough section that has a trough base that incorporates an opening for the passage of a bolt for a force-fit connection with a base of the air spring bellows, which forms a trough to accommodate the convex base of the air spring bellows, there being a supporting body in the inner space that is surrounded by the plunger piston casing, the lower foot area of said supporting body resting on the lower ~oot area of the plunger piston.
More and more frequently, commercial vehicles are being equipped with air spring systems to increase the level of comfort provided by the springs, to take advantage of the ride height adjustment and height control, in order to ensure optimal distribution of axle loads by means o~ compensation lines in multi-axle units~ and to protect the surface of the road. Axles with air springing within multi-axle aggregates can be raised in a simple manner by auxiliary systems in order to protect the tires.
Pneumatic springs can transfer only vertical forces. Other chassis elements are required in order to absorb all the other !

.~ 5' 1 327054 forces and moments. The known air suspension systems comprise primarily an air spring bellows that frequently incorporate a rubber buffer as a stop, a plunger piston, and a bearing arm that is, in its turn, mounted on or under the vehicle. The air spring bellows are in the form o~ a rotationally symmetrical rubber sack that can be filled with air and that is connected to the vehicle frame by means of a steel plate that is fastened at the top as a force transfer element. A round steel base that can support the rubber buffer inside the air spring is clamped or vulcanized to the bottom. The convex underside of the base is a form fit in a correspondingly concave upper trough of the plunger piston and is securely bolted to said piston.
In the usual steel version, the plunger piston is a rotationally symmetrical deep-drawn or extruded part, the surface o~ which is provided with corrosion protection. Its skirt, which is essentially cylindrical, is shaped so as to be slightly conical to the outside and then flanged inward in a semi-circle.
Holes in the flanged edge facilitate connection to the plate-shaped end of the air spring bearing arm. In the upper section, the plunger piston skirt maXes the transformation through an essent~ally semi-circular edge into a truncated conical trough with a level bottom, this serving to accommodate the convex trough of the air spring bellows. The base of the trough incorporates at least one drilled hole through which a screw bolt can be passed to form a friction fit connection between the plunger piston and the air spring bellows. ~hen under 4 ~ ~ 327054 compression, the base of the air filled spring bellows is a friction fit in the trough of the plunger piston, whereas the side wall of the essentially cylindrical air spring bellows is slipped over the upper edge of the plunger piston and the essentially cylindrical plunger piston skirt. The plunger piston can move so deep into the air spring bellows that the rubber buffer in the air spring bellows is clamped between the upper steel plate and the plunger piston of the air spring bellows, foxming a stop by so doing. In such cases, shock loads exert a significant amount of stress directly on the surface of the trough base.
Because they are made of metal, such plunger pistons are relatively heavy and costly. Furthermore, metal plunger pistons can corrode in their rolling region after prolonged periods o use, and this can lead to increased wear of the rubber sack. For this reason, attempts have been made to develop a plunger piston of glass-fibre reinforced plastic, so as to reduce weight and production costs, as well as to increase the useful life of the entire air spring bellows, as a result of the smooth and non-corrosion-free surface of the plunger piston. In this regard, the outer shape of the plunger piston is similar to that of the embodiment that is of steel. However, the edge near the foot is not flanged, but its cross-s~ction is approximately trapezoidal so as to ensure improved seating on the bearing arm plate.
Perpendicular to the foot edge at most four rîbs that are offset by 90- relative to each other extend along the inner surface Or ' the skirt up to the upper edge of the plunger piston. In their lower section, the rein~orcing ribs incorporate threaded holes or threaded inserts of metal, these being used for the bolted connection to the bearing arm plate.
In a ~urther emhodiment of a plunger piston of glass-fibre reinforced plastic, it has been proposed to incorporate a plurality of reinforcing ribs internally in the area of the upper rounded transition from the plunger piston sXirt to the truncated conical troughO In the event o~ shock stresses, however, at the upper s~op, breaks still occur at the transition from the plunger piston sXirt to the truncated conical trough. On the other hand, it has also been seen that the base of the trough has been torn out on rebound, because the efective tensile force is transferred through the screw head and, optionally, a washer, from the air spring bellows directly to the trough base of the plunger piston. Besides these functional disadvantages, because of the numerous ribs, this embodiment of the plunger piston is almost as heavy as the steel version. Furthermore, the tool costs associated with the production oP such embodiments of :
plunger pistons are extremely high.
~ In still another embodiment of a plunger piston of glass '! fibre reinforced plastic, a pipe stub is moulded into the interior of the piston, starting concentrically from the trough ~ base; this pipe stub extends downward to the supporting arm plate s and rests on said plate when subjected to a load. The object of thin pipe stub was to transfer the shocks from the baee of the :`
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trough to the ~earing arm plate and to remove the load ~rom the edge area of the plunger piston. However, the disadvantage vf this embodiment is that in the production process that is used, the reinforcing glass fibres do not get into the lower third of the pipe stub, so that it fails under elevated shock stresses.
In addition, the dimensions of the pipe stub make it difficult to install the supporting arm plate on a parabolic link, which is necessary under some circumstances, if it should be n~cessary for structural reasons to install it in this way instead of on the supporting arm. For this reason, an area on the bottom edge of the short pipe has been subsequently notched, which of course further reduces the supporting effect.
GB-PS 1 231 766 describes a damped pneumatic spring with a main and an secondary chamber, these being connected by an opening in the partition wall that separates them. The main chamber is formed by an air spring ~ellows, the base of which is connected with the base plate o~ the plunger piston that forms the second chamber that is closed up to the connection with the ~irst chamber. The upper base plate of the plunger piston welded to the lower cover plate through a pipe-like member. The plunger pi~ton wall is formed in part from a wall section that i5 sharply curved and adjacent to the upper base plate, and in part from a flange area that slopes upwards from the lower cover plate. If this plunger piston system is to be used for supportiny and guiding an air spring bellows incorporated in an air-sprung axle of a commercial vehicle or the like, the plunger piston and the 7 ~ 1 32705~
pipe-like element must have extraordinarily thick walls in order to b~ able to withstand the stresses to which they are subjected.
Because of its construction, this known plunger piston arrangement is very heavy and entails very high production costs.
Proceeding from this, it is the task of the present invention to develop a plunger piston system of the a~orementioned kind, of glass ~igure reinforced plastic or similar composite ~aterial, which even in extreme cases can absorb all the compressive and tensile forces that occur during the compression and rebound of the air suspension axles of a commercial vehicle without incurring any damage, which can provide for the smooth sliding of the air spring bellows when describing the spring excursion, without the air spring bellows becoming pinched, which also permits installation on a parabolic link, and which can be manufactured in a cost-effective manner.
According to the present invention, this problem has been solved essentially in that the plunger piston and the supporting body are o~ plastic, preferably glass fibre reinforoed plastic or composite material; in that the plunger piston is pot-shaped with an essentially cylindrical casing; that the supporting body is formed as a separate part of essentially truncated conical shape :
with a diameter that grows smaller from the lower foot area to the base of the trough of the plunger piston; and in that the upper base plate of the supporting body lies against the under id~ o~ the trough base of the plungQr piston.

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In this manner, the previous one-piece plunger piston, which was a costly design, has been replaced by a two-part version, both parts of which perform specific tasks, such that the outer plunger piston essentially manages the usual guiding o~ the air spring bellows during compres~ion and rebound, whereas a truncated-conical one that is bolted with the outer plunger piston to the lower convex air spring bellows plate essentially absorbs the compressive and tensile forces that can be especially damaging at the upper stop or during total rebound. Because of the fact that the upper base plate of the supporting body is adjacent to the under side of the plunger piston base plate, both plates are strong enough, because of their sandwich construction, with regard to the tensile stresses that result from sudden and total rebound. The outer lower edge of the supporting body that is positioned in the inside space of the plunger piston lies in the foot area of the plunger piston skirt so as to provide radial and axial to stabilize this edge area.
Despite its simple rotationally symmetrical shape and the very simple construction method used as compared to the prior art, the solution according to the present invention exhibits ~ar greater serviceability than embodiments known from the prior art. The supporting function is particularly effective because the foot area of the supporting body is braced upward or outwards, respectively, on the lower foot araa of the plunger piston.
Ef~ective savings of materials and effective absorption of the compressive and tensile forces is achieved, in particular, in ~U 1 327054 that the supporting body is of ~ssentially truncated c~nical shape, with a diameter that grows smaller from the lower foot area to the base o~ the trough of the plunger piston.
It is preferred that khe supporting body be so configured as to be rotationally symmetrical and are axranged to be coaxial with the plunger piston, so that the forces involved are absorbed uniformly around the perimeter One specific embodiment of the present invention provides that the plunger piston incorporates reinforcing ribs that are oriented radially inwards and are distributed uniformly about the periphery of the plunger piston, there being depressions in the face ends of these to accommodated bolts for connection to the air spring bearer; and that in its foot area the supporting body is form-fitted at the foot region of the reinforcing ribs.
According to another feature of the present invention, the supporting body and one preferably circular stop rib that is incorporated at its bottom edge can be snapped in the manner of a snap lock into at least a plurality of detent recesses that are distributed around the periphery of the foot area of the plunger pis~on skirt. Thus, the separate components, i.e., plunger piston and supporting member, form a structural and functional unit.
The notched recesses can preferably be incorporated in the foot region of the reinforcing ribs.

During simple assembly, this snap-in function is achieved in that the detent recesses are undercut, as viewed from below, i.e., from the side from which the supporting member is introduced into the interior space o~ the piston.
In addition, the notched recesses can incorporate a lead-in slope so as to facilitate assembly.
Furthermore, if the notched recesses form an upper stop edge for the preferably circular stop rib of the supporting member, there i8 a greater likelihood o~ the supporting member being supported on the plunger piston.
For the sake of simplicity during the joint assembly of the supporting body and the plunger piston, the base plate of the supporting body can incorporate an opening that is coaxial with the opening within the trough base of the plunger piston, so as to a~low passage of a bolt for the common force-fit connection with the base of the air spring bellows.
Another feature of the invention is that the base plate of the supporting body incorporates central reinforcement, optionally with radial ribs and a circular ridge. This enhances the absorption of the tensile for~es that, during rebound, act through the central bolted connection between the air spring bellows and the plunqer system or the supporting body, respectively, on the base plate of the plunger piston or the base plate o~ the supporting body, respectively.
Good conditions for the transfer of ~orces can be provided if the upper side of the base plate is supported by an annular area that surrounds ieS opening on the underside of the trough 11 rr ~ 327054 base of the plunger piston that is, in any case, level in this annular area.
It is particularly advantageous if a shallow hollow space so that encloses the opening is left free between the underside oE
the trough base and the upper side of the base plate, the base plate being configured in the area of this hollow space that it aompresses under the action o~ the bolt. This can be aahieved, for example, in that the base plate of the supporting body is sllghtly curved downward relative to the essentially flat base o~
the trough of the plunger piston. If the plunger piston and the supporting body are connected to each other and to a rubber stop by means of a bolt that passes through the openings provided at this location, and a rubber buffer, for example, then the base plate can be easily compressed. Kowever, if the bolt is screwed firmly home to the stop, the base plate will remain flexible in the area of the space. Although the parts are clamped together by this, the air spring bellows with the hole pattern for attachment in the upper steel plate and the air connection can be rotated radially ralative to the plunger piston. This results in considerable simplification of construction and assembly because it becomes easier to adapt to the specific characteristi¢s of a particular vehicle without any need to loosen and then tighten all the parts involved.
An additional guarantee against the base plate of the supporting body b~ing torn out when under tension is achieved if the under sida of the base plate of the supporting body is transformed throuyh an arc with a large radius to the inner surface of the conical casing of the supporting body.
The ~nnular cross-sectional sur~ace of the casing of the supporting body is preferably equal at every level of the truncated cone, so that the greatest possible transfer of compressive and tensile forces is achieved for very low material costs.
Essentially, this can be accomplished in that the inside surface of the casing of the supporking member is more sharply inclined relative to the vertical than the outer surface of the supporting body casing.
In addition, the present invention proposes that for reasons of production technology, the skirt of the plunger piston is inclined less relative to the vertical for a considerable part of its length and widens out conically in a wide-radius arc in its lower foot area. This widening of the lower area of th~ plunger piston increases the e~fective area of the air spring bellows if the plunger piston plunges in by a corresponding amount. This avoids violent impact against the rubber buffer (as can happen during total deflectton).
In addition to the reinforcing ribs~ the plunger piston can also incorporate inwardly oriented stif~ening ribs tha.
preferably extend to the complete height of the plunger piston skirt, the inside contour of these being matched to the contour of the outer surface of the supporting body casing. This makes it possible to achieve not only an additional enhancement of the ~ 1 32705~

resistance moment of the plunger piston skirt, but also of its support on the supporting body. The stif~ening ribs can be arranged as a continuation of the reinforcing ribs or can be arranged between the reinforcing ribs, preferably symmetrically, around the periphery. If, for all practical purposes, they extend to the total height of the plunger piston skirt, the width of the stiffening ribs also fills the interior space between the plunger piston skirt and the trough section as far as the trough base, so that the upper, rounded edge of the plunger piston is also relieved. Of course, it is also possible that, instead of or in addition to this, the supporting body has stiffening ribs that are oriented radially outwards, and these can extend as far as the skirt of the plunger piston.
In a further embodiment of the presant invention the supporting body can incorporate reinforcing ribs that project radially outward and are distributed around the periphery o~ the supportin~-body casing, there being depressions in the faces of these to accommodate bolts for the csnnection with the air spring bearer, the foot area of the plunger piston being a shape-locking fit on the foot area of the reinforcing ribs. The stiffening ribs do not have to extend to the full height of the supporting body, o t~at it is possible to achieve a further effective saving of materials, particularly in the case of larga plunger pistons.
As another alternative, it can also be arranged that the base plate of the supporting body is configured so as to be ' 14 ~ 1 327054 concave and rest with a middle, flat annular area that immediately surrounds its opening on the underside of the base of the trough of the plunger piston. This results in a favourable flow of forces when the plunger piston is under tensile stresses, particularly in the case of large plunger pistons.
Additional objectives, features, advantages and application possibilities for the present invention are ~et out in the following descrip~ion of embodiments shown in the drawings appended hereto. All of the feature described and or shown, either singly or in any combination, con~titute the object o~ the present invention, regardless of tha wording of the claims or references thereto. The drawings show the following:
Figure 1: A vertical cross~section of a complete air spring bellows with a plunger piston formed as a deep-drawn sheet me~al body as in the prior art.
Figure 2a: A section as seen ~rom the direction A in Figure 2b of a plunger piston system according to the present invention.
Figure 2~: A vertical cross-section on the section line BB in figure 2a.
Figure 2c: A detail enlargement as in section C in figure 2b.
Figur2s 3a to 4b: Diagrams as in fiyures 2a and 2b for two other embodiments of the present invention.
The air spring shown in figure 1 incorporates an air spring bellows 24 in the form of an air-filled, rotationally symmetrical 15' 1 32705~
rubber sack, which is to be connected through an upper flanged steel plate 17, as a force transfer element, to a vehicle frame (not shown herein). A convex, circular steel base is vulcanized onto the underside of the air spring bellows24, and this supports a rubber buffer as a stop inside the air spring bellows 24. The underside of the base 23 is convex and is a form fit in a correspondingly convex shaped upper trough base of a plunger piston 1 and is bolted to this to form a force fit by means of a bolt 22. Th~ plunger piston 1 is a pot-shaped rotationally symmetrical deep-drawn part that is of steel. The essentially cylindrical plunger piston skirt 9 is shaped so as to be slightly conical to the outside and is then flanged in a semicircular shape to the inside. Drilled hol~s in the flanged edge enable connection to the plate-shaped end of an air spring bearing arm (not shown herein).
The plunger piston system according to the present invention and ~hown in figures 2a to 2c is intended for use with an air spring bellows system 17, 23 ~24, 25 that is configured in essentially the same way. The outer, pot-shaped plunger piston 1 incorporates four reinforcing ribs 2 that are displaced by 90 relative to each other, that are oriented inwards, and extend to the whole height of the plunger piston skirt 9. In the foot area 3 of the reinforcing ribs 2 there are reces~es 4 to accommodate threaded bolts (not shown harein) for connection with a bearer arm plate (no~ shown herein~. At the top, the essentially cylindrical plunger piston skirt 9 makes a transition to becom- a 16 ~ l 327054 rounded plunger piston edge 6 that is essentially semicircular in cross-section, to which inclined inwards an essentially truncated conical trough section 7 is connected to an essentially flat trough base 8 to form an essentially truncated conical trough 27 in which the convex base 23 can be accommodated by a form fit.
The plunger piston skirt 9 has a smaller inclination (e.g., approximately 1) relative to the perpendicular S and widens out in its lower foot area S outwards in the shape of a cone in an arc 10 of a greater radius (e.g., approximately lO0 mm).
A hollow, truncated conical suppoxting body 11 is positioned within the plunger piston 1. Its annular foot region 12 has on its outer side a stop rib 13 that is, for example, circular and can engage in corresponding detent recesses 14 on tha inner side of the foot areas 3 of the four reinforcing ribs 2. To this end, as viewed from below, the detent recesses 14 incorporate a lead-in slope 29 that makes the transition to become a undercut 34 to which in turn a stop edge 30 for the upper side of the stop rib 13 is adjacent at the top. Because of this detent and snap connaction 13, 14, the two parts, i.e., the plunger piston and the supporting body ll can be connected ri~idly but releasably by a shape fit and support each other upwards and to the outside in the foot areas 3, 12.
The slop~ of the inner surface 15 of the supporting body ca~ing 33 is greater than the slope of the outer surface 16 to the point that the annular cross-~ectional area F of tha ' 1 32705~

supporting body 11 remains constant at every level of the truncated conical supporting body 11.
The upper base plate 18 which the supporting body aasing 33 becomes, abuts by its upper side 35, which i8 ~lat in an annular area, against a similarly flat annular area of the underside 28 of the trough base 8 of the plunger piston 1. The base plate 18 incorporates an opening 19 that is coaxial to the opening 20 in the trough base 8; a boIt 22 (not shown herein) that i5 used to connect the two parts 1, 11 of the two-part plunger piston system with the base 23 of the air spring bellows 24 can be passed through this opening. The base plate 18 is configured so as to be concave and resilient in the area of the opening 19, so that a shallow space 36 remains free in the direction of the trough base 8: this space decreases somewhat when the bolt 22 is tightened in the rubber buffer 25 as far as the base~ Because o~ the flat annular contact between the outer plunger piston 1 and the supporting body 11 that is arranged within this inside space 27, the trouqh 26 that is enclosed by the trough section 7 form a sort of double cone in the upper area of the outer plunger piston 1 and the supporting body 11.
In order to enhance the absorption of tensile forces that act during rebound on the plunger piston system through the above-described central bolt attachment between the air spring bellows 24 and the plunger piston 1 or the supporting body 11, respectively, on the trough base 8 or the base plate 18, respectively, the latter has a reinforcement 31 in its central 18 132705~
area. The underside 32 of the bas-e plate 18 makes a transition ,f~ in an arc 2~ of relatively large radius to become the inner sur~ace 15 of the truncated conical supporting body casing 33.
The ensures the highest degree o~ protection against the base plate 18 tearing out when subjected to tensile loads.
Figures 3a and 3b show another embodiment of a ~lunger piston 1, in this case without the supporting body 2, as viewed from the direction A in figure 3b or on the section line B-B in figure 3a, respectively. In this case, the plunger piston 1 incorporates additional stiffening ribs 37 that are distributed symmetrically to the reinforcing ribs 2 around the periphery, there sti~fening ribs are oriented radially inwards, and each of them ~ills, to its whole width, the space between the plunger piston skirt 9 and the trough section 7, and contribute to increasing the moment of resistance of the plunger piston 1. The inner shape 38 of the stiffening ribs 37 is matched to the shape of the outer contour of the outer surface 16 of the supporting body 33 so that the plunger piston 1 can rest on the outer periphery of the supporting body 11 through the stiffening ribs 37. In this case, the depressions 4 are not threaded, as is the case in the embodiment shown in figure 2 a to c. In this case, self-tapping screws are used to produce the connection to the bearer arm plate.
In the embodiment o~ the plunger piston system shown in figures 4a and 4b, in place of the plunger piston 1 the supporting body ll incorporate~ reinforcing ribs 39 thàt are 19 ~ 1 327054 distributed about the periphery of the supporting body casing 33 and which project radially outwards, and in which there are face end depressions 40 to accommodate bolts to produce the connection with the air spring bearer. The foot area 5 of the plunger piston 1 abuts to form a shape-locking fit on the foot area 41 of the reinfor~ing ribs. Seating thereon i~ enhanced by the external pressure that is exerted by the air spring bellows 24 when it rolls over [bei dessen Ueberollen ~sic)--Tr.)~ The plunger piston 1 and the supporting body 11 are only connected to each other in the area of the trough base 8 and of the base plate 17, so as to be releasable, during assembly on the base ~3 of the air spring bellows 24. In this case, the base plate 18 of the supporting body 11 is configurPd so as to be slightly concave so that it rests with a centre annular area that surrounds its opening on the underside 28 of the trough base 8 of tha plunger piston 1. The supporting body casing 33 is widened and extended beyond the base plate 18 to form a supporting ring 41. This supporting ring 41 lies with its face surface in an outer annul~r area on the underside 28 of the trough base 8. Of course, here, too, it is possible that the plunger piston skirt ~, like the embodiment shown in figures 3a and 3b, be provided with stiffening ribs 37 that are oriented radially inwards.

Claims (16)

1. A plunger piston system used to support and guide an air spring bellows of an air suspension vehicle axle, with a plunger piston that has a cylindrical plunger piston skirt with a lower foot area for connection with an air spring bearing arm and an upper plunger piston edge that adjoins the plunger piston skirt and which becomes, radially in an inward direction, a trough section that has, preferably, a trough base that incorporates an opening for the passage of a bolt for a force-fit connection with a base of the air spring bellows, which forms a trough to accommodate the convex base of the air spring bellows, there being a supporting body in the inner space that is surrounded by the plunger piston, the lower foot area of said supporting body resting on the lower foot area of the plunger piston, characterized in that the plunger piston and the supporting body are of plastic, glass fibre reinforced plastic or the like composite materials; in that the plunger piston is pot shaped with an essentially cylindrical casing; in that the supporting body is configured as a separate part of essentially truncated conical shape with a diameter D that grows smaller from the lower foot area to the trough base of the plunger piston; and in that the supporting body is adjacent with an upper base plate to the underside of the trough base of the plunger piston.

2. A plunger piston system as defined in claim 1, wherein the supporting body is essentially rotationally symmetrical and arranged coaxially with the plunger piston.

3. A plunger piston system as defined in claim 1, wherein the plunger piston incorporates reinforcing ribs that are distributed around the periphery of the plunger piston skirt, these being oriented radially inwards and incorporating face-side depressions to accommodate bolts used to produce the connection with the air spring bearer; and wherein the supporting body rests with its foot area to form a shape-locking fit with the foot area of the reinforcing ribs.

4. A plunger piston system as defined in claim 1, 2 or 3, wherein the supporting body can engage with a stop rib that is part of its lower foot area and which is preferably circular, at least in a plurality of notched recesses that are distributed around the periphery of the foot area of the plunger piston skirt in the manner of a snap lock.

5. A plunger piston system as defined in claim 4, wherein the notched recesses are incorporated in the foot area of the reinforcing ribs.

6. A plunger piston system as defined in claim 4, wherein the notched recesses are undercut, as viewed from below, and optionally incorporate a lead-in slope and optionally an upper stop edge for the stop rib that is preferably circular.

7. A plunger piston system as defined in any one of claims 1 to 3, 5 or 6, wherein the base plate of the supporting body incorporates an opening coaxially with the opening in the trough base of the plunger piston for passage of a bolt used to produce a common force-fit connection with the base of the air spring bellows.

8. A plunger piston system as defined in any one of claims 1 to 3, 5, or 6, wherein the upper base plate of the supporting body has a middle reinforcement, optionally configured with radial ribs and a circular ridge.

9. A plunger piston system as defined in any one of claims 1 to 3, 5 or 6, wherein the upper side of the base plate rests with a flat annular area that surrounds the opening on the underside of the trough base of the plunger piston that is flat in this annular area.

10. A plunger piston system as defined in any one of claims 1 to 3, 5 or 6, wherein between the underside of the trough base and the upper side of the base plate a circular, shallow space that surrounds the opening is left free, in the area of which the base plate has been configured to be elastic under the action of the bolt.

11. A plunger piston system as defined in any one of claims 1 to 3, 5 or 6, wherein the underside of the base plate of the supporting body merges into the inner surface of the conical supporting body casing through a large radius arc.

12. A plunger piston system as defined in any one of claims 1 to 3, 5 or 6, wherein the cross-section area of the supporting body casing is the same at every level of the truncated conical supporting body.

13. A plunger piston system as defined in claim 12, wherein the inside surface of the supporting body casing is more sharply inclined relative to the vertical than the outer surface of the supporting body casing.

14. A plunger piston system as defined in any one of claims 1 to 3, 5, 6 or 13, wherein the plunger piston incorporates stiffening ribs that are oriented radially inward and preferably extend to the whole height of the plunger piston skirt, the inner contour of these being matched to the contour of the outer surface of the supporting body casing.

15. A plunger piston system a defined in any one of claims 1 to 3, S, 6 or 13, wherein the supporting body incorporates reinforcing ribs that are distributed about the periphery of the supporting body casing and oriented so as to project radially outwards, in which there are face-end depressions to accommodate bolts used to produce the connection with the air spring bearer;
and wherein the plunger piston 13 adjacent with its lower foot area to form a form fit on the foot area of the reinforcing ribs.

16. A plunger piston system as defined in any one of claims 1 to 3, 5, 6 or 13, wherein the upper base plate of the supporting body is so configured to be concave and rests with a middle flat annular area that surrounds its opening on the underside of the trough base of the plunger piston.