Patent Description:
The use of air-ride trailing and leading arm rigid beam-type axle/suspension systems has been popular in the heavy-duty truck and tractor-trailer industry for many years. Although such axle/suspension systems can be found in widely varying structural forms, in general their structure is similar in that each system typically includes a pair of suspension assemblies. In some heavy-duty vehicles, the suspension assemblies are connected directly to the primary frame of the vehicle. In other heavy-duty vehicles, the primary frame of the vehicle supports a subframe, and the suspension assemblies connect directly to the subframe. For those heavy-duty vehicles that support a subframe, the subframe can be non-movable or movable, the latter being commonly referred to as a slider box, slider subframe, slider undercarriage, or secondary slider frame. For the purpose of convenience and clarity, reference herein will be made to main members, with the understanding that such reference is by way of example, and that the present invention applies to heavy-duty vehicle axle/suspension systems suspended from main members of: primary frames, movable subframes and non-movable subframes.

Specifically, each suspension assembly of an axle/suspension system includes a longitudinally extending elongated beam. Each beam typically is located adjacent to and below a respective one of a pair of spaced-apart longitudinally extending main members and one or more cross members, which form the frame of the vehicle. More specifically, each beam is pivotally connected at one of its ends to a hanger, which in turn is attached to and depends from a respective one of the main members of the vehicle. An axle extends transversely between and typically is connected by some means to the beams of the pair of suspension assemblies at a selected location from about the mid-point of each beam to the end of the beam opposite from its pivotal connection end. The opposite end of each beam also is connected to an air spring, or its equivalent, which in turn is connected to a respective one of the main members. A height control valve is mounted on the hanger or other support structure and is operatively connected to the beam and to the air spring in order to maintain the ride height of the vehicle. A brake system and one or more shock absorbers for providing additional damping to the vehicle axle/suspension system are also included. The beam may extend rearwardly or frontwardly from the pivotal connection relative to the front of the vehicle, thus defining what are typically referred to as trailing arm or leading arm axle/suspension systems, respectively. However, for purposes of the description contained herein, it is understood that the term "trailing arm" will encompass beams, which extend either rearwardly or frontwardly with respect to the front end of the vehicle.

The axle/suspension systems of the heavy-duty vehicle act to cushion the ride, dampen vibrations and stabilize the vehicle. More particularly, as the vehicle is traveling over the road, its wheels encounter road conditions that impart various forces, loads, and/or stresses, collectively referred to herein as forces, to the respective axle on which the wheels are mounted, and in turn, to the suspension assemblies that are connected to and support the axle. In order to minimize the detrimental affect of these forces on the vehicle as it is operating, the axle/suspension system is designed to react and/or absorb at least some of them.

These forces include vertical forces caused by vertical movement of the wheels as they encounter certain road conditions, fore-aft forces caused by acceleration and deceleration of the vehicle, and side-load and torsional forces associated with transverse vehicle movement, such as turning of the vehicle and lane-change maneuvers. In order to address such disparate forces, axle/suspension systems have differing structural requirements. More particularly, it is desirable for an axle/suspension system to be fairly stiff in order to minimize the amount of sway experienced by the vehicle and thus provide what is known in the art as roll stability. However, it is also desirable for an axle/suspension system to be relatively flexible to assist in cushioning the vehicle from vertical impacts, and to provide compliance so that the components of the axle/suspension system resist failure, thereby increasing durability of the axle/suspension system. It is also desirable to dampen the vibrations or oscillations that result from such forces. A key component of the axle/suspension system that cushions the ride of the vehicle from vertical impacts is the air spring, while a shock absorber typically provides additional damping to the axle/suspension system.

The typical air spring of the type utilized in heavy-duty air-ride axle/suspension systems includes three main components, a flexible bellows, a bellows top plate and a piston. The bellows is typically formed from rubber or other flexible material, and is sealingly engaged with the bellows top plate and also to the top portion of the piston. The volume of pressurized air, or "air volume", that is contained within the air spring is a major factor in determining the spring rate of the air spring. More specifically, this air volume is contained within the bellows and, in some cases, the piston of the air spring. The larger the air volume of the air spring, the lower the spring rate of the air spring. A lower spring rate is generally more desirable in the heavy-duty vehicle industry because it allows for softer ride characteristics for the vehicle. Typically, the piston either contains a hollow cavity, which is in communication with the bellows and which adds to the air volume of the air spring by allowing unrestricted communication of air between the piston and the bellows volumes, or the piston has a generally hollow cylindrical-shape and does not communicate with the bellows volume, whereby the piston does not contribute to the air volume of the air spring. The air volume of the air spring is in fluid communication with an air source, such as an air supply tank, and also is in fluid communication with the height control valve of the vehicle. The height control valve, by directing air flow into and out of the air spring of the axle/suspension system, helps maintain the desired ride height of the vehicle.

The prior art air spring piston is generally cylindrically shaped and includes a continuous generally stepped sidewall attached to a generally flat bottom plate. A top plate is formed at the top of the piston. The bottom plate is formed with an upwardly extending central hub. The central hub includes a bottom plate formed with one or more central openings. A fastener is disposed through the openings in the central hub bottom plate in order to attach the piston to the beam of the suspension assembly at its rear end. The top plate, sidewall and bottom plate of the piston define a piston chamber having an interior volume. The top plate of the piston is formed with a circular upwardly extending protrusion having a lip or barb around its circumference. The barb cooperates with the lowermost end of the air spring bellows to form an airtight seal between the bellows and the piston. A bumper is attached to a bumper mounting plate, which is in turn mounted on the piston top plate by a fastener. The bumper extends upwardly from the top surface of the bumper mounting plate and serves as a cushion between the piston top plate and the bellows top plate in order to cushion contact between the two plates during operation of the vehicle. The piston is typically formed from steel, aluminum, fiber reinforced plastic or other rigid material.

Because the prior art air spring piston typically has a relatively complex integral one-piece structural design, manufacture of the piston from composite materials can be complicated. More particularly, because the lip or barb is integrally formed in one piece on the upwardly extending protrusion, which in turn is integrally formed in one piece with the top plate of the piston, manufacture of the piston from composite materials can be quite complex and therefore inefficient, as is well known to those of ordinary skill in the art. In addition, because the bottom plates of the piston and the central hub, respectively, are generally flat, the volume contained in the piston is generally limited because of spatial limitations between the beam of the suspension assembly and the main member of the vehicle.

An alternative method for manipulating the ride characteristics of an air spring is shown in <CIT> where a modular piston is used which can have a number of attachable plates at the end of the piston to increase the piston length. This allows the air spring to be adapted to provide the desired spring travel without the need of removing the piston from the bellows.

<CIT> describes a pedestal-mounted air spring piston made from a main shell and a bottom end plate, both of plastics materials. The shell has integral inner and outer annular walls forming an outer annular sub-chamber around a central upwardly-open sub-chamber, without a top plate. Air passageways connect the sub-chambers. The flat bottom of the main shell projects centrally downward as a central base which fixes to a support.

The air spring piston for heavy-duty vehicles of the present invention, overcomes the problems associated with prior art air spring piston designs by providing an air spring piston upper portion formed in two parts that are assembled. Moreover, the air spring piston for heavy-duty vehicles of the present invention includes a downwardly extending piston bottom plate that allows for an increased piston volume while still utilizing the same mount configuration and hardware existing in prior art designs. This downwardly extending piston bottom plate allows for an increased piston volume without the need for redesigned or additional mounting brackets and without changing the spatial measurements between the beam and the main member. Therefore, the spring piston for heavy-duty vehicles of the present invention provides for more efficient and simple manufacture that reduces manufacturing costs and provides for an increased piston chamber volume using existing piston-to-beam mounting hardware, whereby the increased piston chamber volume provides a reduced spring rate and/or better damping characteristics to the air spring.

Objectives of the present invention include providing a piston for an air spring of a heavy-duty vehicle that is more efficient and simple to manufacture and that reduces manufacturing costs. A further objective of the present invention is to provide a piston for an air spring of a heavy-duty vehicle that provides increased piston chamber volume using existing piston-to-beam mounting hardware.

Yet another objective of the present invention is to provide a piston for an air spring of a heavy-duty vehicle that provides a reduced spring rate and/or provides improved damping characteristics to the air spring.

These objectives and advantages are obtained by the piston for an air spring of a heavy-duty vehicle of the present invention as specified in claim <NUM>.

These objectives and advantages are also obtained by an air spring as set forth in claim <NUM>, and a suspension assembly as set forth in claim <NUM>.

The preferred embodiment of the present invention, illustrative of the best mode in which applicants have contemplated applying the principles, is set forth in the following description and is shown in the drawings, and is particularly and distinctly pointed out and set forth in the appended claims.

In order to better understand the environment in which the air spring piston for heavy-duty vehicles of the present invention is utilized, a trailing arm overslung beam-type air-ride axle/suspension system that incorporates a prior art heavy-duty vehicle trailer air spring <NUM>, is indicated generally at <NUM>, is shown in <FIG>, and now will be described in detail below.

It should be noted that axle/suspension system <NUM> is typically mounted on a pair of longitudinally-extending spaced-apart main members (not shown) of a heavy-duty vehicle, which is generally representative of various types of frames used for heavy-duty vehicles, including primary frames that do not support a subframe and primary frames and/or floor structures that do support a subframe. For primary frames and/or floor structures that do support a subframe, the subframe can be non-movable or movable, the latter being commonly referred to as a slider box. Because axle/suspension system <NUM> generally includes an identical pair of suspension assemblies <NUM>, for sake of clarity only one of the suspension assemblies will be described below.

Suspension assembly <NUM> is pivotally connected to a hanger <NUM> via a trailing arm overslung beam <NUM>. More specifically, beam <NUM> is formed having a generally upside-down integrally formed U-shape with a pair of sidewalls <NUM> and a top plate <NUM>, with the open portion of the beam facing generally downwardly. A bottom plate <NUM>(<FIG>) extends between and is attached to the lowermost ends of sidewalls <NUM> by any suitable means such as welding to complete the structure of beam <NUM>. Trailing arm overslung beam <NUM> includes a front end <NUM> having a bushing assembly <NUM>, which includes a bushing, pivot bolts and washers as are well known in the art, to facilitate pivotal connection of the beam to hanger <NUM>. Beam <NUM> also includes a rear end <NUM>, which is welded or otherwise rigidly attached to a transversely-extending axle <NUM>.

Suspension assembly <NUM> also includes the top end of a shock absorber <NUM> mounted on an inboardly extending wing <NUM> of hanger <NUM> via a mounting bracket <NUM> and a fastener <NUM>, in a manner well known in the art. The bottom end of shock absorber <NUM> is mounted to beam <NUM> (the mount not shown) in a manner well known to those having skill in the art. For the sake of relative completeness, a brake system <NUM> including a brake chamber <NUM> is shown mounted on prior art suspension assembly <NUM>.

As mentioned above, axle/suspension system <NUM> is designed to absorb forces that act on the vehicle as it is operating. More particularly, it is desirable for axle/suspension system <NUM> to be rigid or stiff in order to resist roll forces and thus provide roll stability for the vehicle. This is typically accomplished by using beam <NUM>, which is rigid, and also is rigidly attached to axle <NUM>. It is also desirable, however, for axle/suspension system <NUM> to be flexible to assist in cushioning the vehicle (not shown) from vertical impacts and to provide compliance so that the axle/suspension system resists failure. Such flexibility typically is achieved through the pivotal connection of beam <NUM> to hanger <NUM> with bushing assembly <NUM>. Air spring <NUM> and shock absorber <NUM> also assist in cushioning the ride for cargo and passengers.

More specifically, prior art air spring <NUM> shown in <FIG> now will be described in detail. Air spring <NUM> is typically incorporated into an axle/suspension system such as axle/suspension system <NUM>, or other similar air-ride axle/suspension system. Air spring <NUM> includes a bellows <NUM>, a bellows top plate <NUM> and a piston <NUM>. The top end of bellows <NUM> is sealingly engaged with bellows top plate <NUM> in a manner well known in the art. An air spring mounting plate <NUM> (<FIG>) is typically mounted on the top surface of top plate <NUM> by fasteners <NUM> which are also used to mount the top portion of air spring <NUM> to a respective one of the main members (not shown) of the vehicle. Alternatively, bellows top plate <NUM> could also be mounted directly on a respective one of the main members (not shown) of the vehicle. Piston <NUM> is generally cylindrical-shaped and includes a continuous generally stepped sidewall <NUM> attached to a generally flat bottom plate <NUM> and integrally formed in one piece with a top plate <NUM>. Bottom plate <NUM> is formed with an upwardly-extending central hub <NUM> and is attached to sidewall <NUM> in a well known manner. Central hub <NUM> includes a bottom plate <NUM> formed with a central opening <NUM>. A fastener <NUM> is disposed through opening <NUM> in order to attach piston <NUM> to a beam mounting pedestal <NUM> (<FIG>), of a type that is well known in the beam-air spring mounting art.

With additional reference to <FIG>, beam mounting pedestal <NUM> includes a generally flat base <NUM> for contacting and seating on beam top plate <NUM> at beam rear end <NUM>. Beam mounting pedestal <NUM> also includes an upwardly extending column <NUM>, which contacts central hub bottom plate <NUM> of piston <NUM> of air spring <NUM>. Column <NUM> is formed with a central generally vertically-extending opening <NUM>, through which fastener <NUM> is disposed. A lock nut (not shown) is threaded onto a threaded end of fastener <NUM> in order to attach piston <NUM> to beam mounting pedestal <NUM>. A pair of strengthening webs <NUM> are located on column <NUM> and extend outwardly from the column on flat base <NUM>. An opening <NUM> is formed in pedestal base <NUM>. Opening <NUM> receives a fastener (not shown) for attaching pedestal <NUM> to beam top plate <NUM> at beam rear end <NUM>. Beam mounting pedestal <NUM> is typically formed from a rigid material such as steel, aluminum or composite material, as is well known in the art, and may or may not include strengthening webs <NUM>.

With continued reference to <FIG>, top plate <NUM>, sidewall <NUM> and bottom plate <NUM> of piston <NUM> define a piston chamber <NUM>. Top plate <NUM> of piston <NUM> is formed with a circular upwardly extending protrusion <NUM> having a lip or barb <NUM> around its circumference. Barb <NUM> cooperates with the bottom terminal end of bellows <NUM> to form an airtight seal between the bellows and the barb around the circumference of protrusion <NUM> of piston <NUM>, as is well known to those of ordinary skill in the art. Bellows <NUM>, top plate <NUM> and piston top plate <NUM> define a bellows chamber <NUM>. A bumper <NUM> is rigidly attached to a bumper mounting plate <NUM> by means generally well known in the art. Bumper mounting plate <NUM> is in turn mounted on piston top plate <NUM> by a fastener <NUM>. Bumper <NUM> extends upwardly from the top surface of bumper mounting plate <NUM>. Bumper <NUM> serves as a cushion between piston top plate <NUM> and the underside of bellows top plate <NUM> in order to prevent the plates from damaging one another in the event that the piston top plate and the underside of the bellows top plate contact one another during operation of the vehicle. Manufacture of piston <NUM> from composite materials can be quite complicated and therefore inefficient, as is well known to those of ordinary skill in the art.

Piston top plate <NUM> is formed with a pair of openings <NUM>, which allow the volume of piston chamber <NUM> and the volume of bellows chamber <NUM> to communicate with one another. More particularly, openings <NUM> allow fluid or air to pass between piston chamber <NUM> and bellows chamber <NUM> during operation of the vehicle.

Turning now to <FIG>, a prior art air spring for a truck axle/suspension system is shown generally at <NUM>. Air spring <NUM> generally includes a bellows <NUM>, a bellows chamber <NUM>, a bellows top plate <NUM>, a piston chamber <NUM> and a piston <NUM>. Piston <NUM> is formed with a generally flat bottom plate <NUM> and an open top plate <NUM> having an upwardly-extending protrusion <NUM> formed with a lip or barb <NUM>. Piston <NUM> includes a hollow piston chamber <NUM>, which is in fluid communication with bellows <NUM> and allows unrestricted communication of air between the piston cavity and the bellows. Because prior art air spring piston <NUM> has an integral one-piece structural design, manufacture of the piston from composite materials can be complicated. More particularly, because lip <NUM> is integrally formed in one-piece on upwardly-extending protrusion <NUM>, manufacture of the piston from composite materials can be quite complicated and therefore inefficient, as is well known to those of ordinary skill in the art.

Turning now to <FIG>, another example of a prior art air spring for an axle/suspension system is shown generally at <NUM>. Air spring <NUM> generally includes a bellows <NUM>, a bellows top plate <NUM> and a piston <NUM>. Piston <NUM> is mounted on suspension assembly beam <NUM> by fastener <NUM> disposed through conventional beam mounting pedestal <NUM>, described in detail above. Air spring <NUM> is representative of an air spring configuration different from prior art air springs <NUM> and <NUM>, whereby piston <NUM> does not contribute to the air volume of the air spring and which still utilizes conventional beam mounting pedestal <NUM> in the field, i.e. no piston chamber, only a bellows chamber <NUM>.

As set forth above, because prior art air spring pistons <NUM>,<NUM> have a relatively complex integral one-piece structural design, manufacture of the pistons from a composite material can be complicated. More particularly, because lip or barb <NUM>,<NUM> is integrally formed on upwardly extending protrusion <NUM>,<NUM>, respectively, which in turn is integrally formed with top plate <NUM> of piston <NUM> and top plate <NUM> of piston <NUM>, respectively, manufacture of the piston from composite materials can be quite complex and therefore inefficient as is known to those of ordinary skill in the art. The air spring piston of the present invention overcomes the problems associated with prior art air spring pistons <NUM>,<NUM>, and will now be described in detail below.

A preferred embodiment air spring piston of the present invention is shown generally at <NUM> in <FIG>, with <FIG> showing the air spring piston of the present invention incorporated into an air spring <NUM> of an axle/suspension system (not shown), and now will be described in detail below. In accordance with one of the primary features of the present invention, air spring <NUM> includes a bellows <NUM>, a bellows top plate <NUM> and preferred embodiment air spring piston <NUM> of the present invention. The top end of bellows <NUM> is sealingly engaged with bellows top plate <NUM> in a manner well known in the art. An air spring mounting plate (not shown) is mounted on the top surface of top plate <NUM> by fasteners (not shown) which are also used to mount the top portion of air spring <NUM> to a respective one of the main members (not shown) of the vehicle frame. Alternatively, bellows top plate <NUM> could also be mounted directly on a respective one of the main members (not shown) of the vehicle.

In accordance with another important feature of the present invention, air spring <NUM> includes air spring piston <NUM>, which is generally cylindrical-shaped and includes a continuous generally stepped sidewall <NUM> and a central hub <NUM>, each attached to a generally downwardly extending flat bottom plate <NUM> and a discrete top plate <NUM>. More particularly, the lower end of sidewall <NUM> is formed with a groove <NUM>, which receives a correspondingly shaped outer tongue <NUM> formed on bottom plate <NUM>. The lower end of central hub <NUM> also is formed with a groove <NUM>, which receives a correspondingly shaped inner tongue <NUM> formed on bottom plate <NUM>. In this manner, grooves <NUM>,<NUM> and inner and outer tongues <NUM>, <NUM>, respectively, allow bottom plate <NUM> to be friction welded to piston central hub <NUM> and piston sidewall <NUM>. Central hub <NUM> includes an integrally formed generally flat recessed bottom plate <NUM> formed with a central opening <NUM>, and which is recessed relative to bottom plate <NUM>. A fastener <NUM> is disposed through opening <NUM> in order to attach piston <NUM> to prior art beam mounting pedestal <NUM> described above. Beam mounting pedestal <NUM> includes generally flat base <NUM> for contacting the beam top plate of its respective suspension assembly. Beam mounting pedestal <NUM> also includes upwardly extending column <NUM>, which contacts central hub bottom plate <NUM> (<FIG>). Column <NUM> is formed with central opening <NUM>, through which fastener <NUM> is disposed. Lock nut <NUM> is threaded onto a threaded end of fastener <NUM> in order to attach piston <NUM> to beam mounting pedestal <NUM>. Strengthening webs <NUM> (not shown in <FIG>) are located on column <NUM> and extend outwardly from the column on flat base <NUM>. Opening <NUM> (not shown in <FIG>) is formed in pedestal base <NUM>. Base opening <NUM> receives fastener (not shown in <FIG>)for attaching pedestal <NUM> to beam top plate <NUM> at beam rear end <NUM>. Beam mounting pedestal <NUM> is typically formed from a rigid material such as steel, aluminum or composite material, as is well known in the art, and may or may not include strengthening webs <NUM>. Top plate <NUM> is formed with a plurality of openings <NUM>. Openings <NUM> (<FIG> and <FIG>) align with openings (not shown) formed in the top portion of piston central hub <NUM>. A fastener (not shown) is disposed through openings <NUM> and aligned openings (not shown) in the top portion of central hub <NUM> in order to attach top plate <NUM> to the piston central hub and piston sidewall <NUM>. Top plate <NUM>, sidewall <NUM>, central hub bottom plate <NUM>, and piston bottom plate <NUM> define a piston chamber <NUM>. Because piston bottom plate <NUM> is generally downwardly extending, piston chamber <NUM> volume is greater than prior art piston chamber <NUM> volume, shown and described above. Moreover, because piston bottom plate <NUM> is generally downwardly extending, a recess <NUM> is formed in piston <NUM> by a portion of central hub recessed bottom plate <NUM> and a portion of bottom plate <NUM>. Top plate <NUM> also is formed with a circular upwardly extending protrusion <NUM> formed with a lip or barb <NUM> around its circumference. Barb <NUM> cooperates with the bottom terminal end of bellows <NUM> to form an airtight seal between the bellows and the barb, as is well known to those of ordinary skill in the art. It should be understood that top plate <NUM> could be formed having a larger diameter than central hub <NUM> such that the outer edge of the top plate would form barb or lip <NUM>, without changing the overall concept or operation of the present invention.

Bellows <NUM>, top plate <NUM> and top plate <NUM> define a bellows chamber <NUM>. A bumper <NUM> is rigidly attached to top plate <NUM> by adhesive or other means generally well known in the art, Bumper <NUM> extends upwardly from the top surface of top plate <NUM>. Bumper <NUM> serves as a cushion between top plate <NUM> and bellows top plate <NUM> in order to keep the plates from damaging one another in the event that the piston top plate and the bellows top plate contact one another during operation of the vehicle. A plurality of strengthening webs <NUM> extend between piston sidewall <NUM> and piston central hub <NUM> and between the walls of the central hub itself in order to strengthen piston <NUM>.

Top plate <NUM> also is formed with a pair of openings <NUM>, which allow the volume of piston chamber <NUM> and the volume of bellows chamber <NUM> to communicate with one another. More particularly, openings <NUM> allow fluid or air to pass between piston chamber <NUM> and bellows chamber <NUM> during operation of the vehicle. This communication between piston chamber <NUM> and bellows chamber <NUM> through openings <NUM> provides viscous damping to air spring <NUM> as described and shown in <CIT>, owned by the assignee of the present application.

Improved air spring piston <NUM> for heavy-duty vehicles of the present invention overcomes the problems associated with prior art air spring pistons <NUM>,<NUM> by providing an air spring piston upper portion, which is formed in two separate parts that are assembled. This two-part assembly provides a top plate <NUM> that is easier to manufacture than prior art piston top plates that are formed integrally with the rest of the piston. Moreover, air spring piston <NUM> for heavy-duty vehicles of the present invention includes downwardly extending piston bottom plate <NUM> that allows for an increased piston chamber <NUM> volume while still utilizing the same air spring-to-beam mount configuration existing in prior art designs. More particularly, downwardly extending piston bottom plate <NUM> and recessed central hub bottom plate <NUM> allow for an increased piston volume while utilizing prior art pedestal <NUM>, without the need for new or additional mounting brackets and without changing the spatial measurements between beam <NUM> of the axle/suspension system <NUM> and the main member of the vehicle. Therefore, preferred embodiment air spring piston <NUM> for heavy-duty vehicles of the present invention provides for more efficient and simple manufacture that reduces manufacturing costs and provides for greater piston chamber <NUM> volume using existing piston-to-beam mounting hardware, whereby the increased piston volume provides a reduced spring rate and/or better damping characteristics to the air spring.

It is contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized on trucks or tractor-trailers having one or more than one axle without changing the overall concept or operation of the present invention. It is further contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized on vehicles having frames or subframes which are moveable or non-movable without changing the overall concept of the present invention. It is yet even further contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized on all types of air-ride leading and/or trailing arm beam-type axle/suspension system designs known to those skilled in the art without changing the overall concept or operation of the present invention. For example, the present invention finds application with beams or arms that are made of materials other than steel, such as aluminum, other metals, metal alloys, composites, and/or combinations thereof. It is also contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized on axle/suspension systems having either an overslung/top-mount configuration or an underslung/bottom-mount configuration, without changing the overall concept or operation of the present invention. The present invention also finds application in beams or arms with different designs and/or configurations than that shown above, such as solid beams, shell-type beams, truss structures, intersecting plates, spring beams and parallel plates. The present invention also finds application in intermediary structures such as spring seats. It is also contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized in conjunction with other types of air-ride rigid beam-type axle/suspension systems such as those using U-bolts, U-bolt brackets/axle seats and the like, without changing the overall concept or operation of the present invention. It is also contemplated that preferred embodiment air spring piston <NUM> of the present invention could be formed from various materials, including but not limited to composites, metal and the like, without changing the overall concept or operation of the present invention. It is yet even further contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized with fewer than two or more than two openings <NUM> such as three, four or even five or more openings without changing the overall concept for operation of the present invention. It is also contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized with any viscous fluid, such as air or hydraulic fluid, without changing the overall concept of the present invention. It is further contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized in combination with prior art shock absorbers and other similar devices and the like, without changing the overall concept of the present invention. It is contemplated that top plate <NUM> of air spring piston <NUM> of the present invention could be utilized either with or without bumper <NUM>, without changing the overall concept or operation of the present invention. It is also contemplated that top plate <NUM> of air spring <NUM> of the present invention could be utilized either with or without openings <NUM>, without changing the overall concept or operation of the present invention. It is even further contemplated that preferred embodiment air spring piston <NUM> of the present invention could be utilized in conjunction with prior art pedestal <NUM> or other similar pedestals or beam mounting structures, without changing the overall concept or operation of the present invention. It is yet even further contemplated that bottom plate <NUM> of air spring piston <NUM> could be adhesively bonded to, mechanically fastened to, attached via other means well known in the art to, or even formed as a part of, the air spring piston, without changing the overall concept or operation of the present invention. It is also understood that preferred embodiment air spring piston <NUM> of the present invention could be utilized with all types of air springs without changing the overall concept or operation of the present invention.

Claim 1:
A piston for an air spring of a heavy duty vehicle, said piston comprising a sidewall (<NUM>) and a central hub (<NUM>), and a discrete top plate (<NUM>) attached to a top portion of said sidewall (<NUM>) and a top portion of said central hub (<NUM>), and wherein:
a) said sidewall (<NUM>) and said central hub (<NUM>) are attached to a first bottom plate (<NUM>);
b), said top plate (<NUM>) includes a barb (<NUM>) around its circumference; and
c) a bottom portion of said central hub (<NUM>) includes a second bottom plate (<NUM>);
characterised in that:
the second bottom plate is for attachment to a piston mounting pedestal; and
the second bottom plate (<NUM>) is recessed relative to said first bottom plate (<NUM>).