Patent Description:
The use of one or more 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 pivotal ly 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, either directly or via a pedestal, and the air spring is in turn connected to a respective one of the main members. The air spring cushions the ride of the axle/suspension system during operation and, in some cases, provides damping characteristics. In those cases where the air spring does not provide damping, one or more shock absorbers are employed to provide damping. 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 is also included on the vehicle axle/suspension system. 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 effect of these forces on the vehicle and/or its cargo 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 due to operation of the vehicle and/or road conditions, and side-load and torsional forces associated with transverse vehicle movement, such as turning of the vehicle and lane-change manoeuvers. 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 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 in order to reduce wheel and/or suspension bounce, which in turn can potentially harm the wheels and the components of the axle/suspension system, thereby reducing optimal ride characteristics of the axle/suspension system and the life of the components of the axle/suspension system. A key component of the axle/suspension system that cushions the ride of the vehicle from vertical impacts is the air spring or other spring mechanism, such as a coil spring or a leaf spring, while a shock absorber typically provides damping to the axle/suspension system. In some instances, the air spring can also provide 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. Usually, 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. In any event, 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. Most prior art air springs of the non-damping variety utilize a "molded-in" end closure that is attached to the top plate of the piston by a fastener. In this design, the bottom end of the bellows is integrally molded with a metal end closure, so that the end closure is typically not removable from the bellows. These types of air springs make up a majority of the non-damping air spring market and typically do not exhibit the disadvantages of the "take-apart" design described below.

Prior art air springs such as the one described above, while providing cushioning to the vehicle cargo and occupant(s) during operation of the vehicle, provide little if any damping characteristics to the axle/suspension system. Such damping characteristics are instead typically provided by a pair of hydraulic shock absorbers, although a single shock absorber has also been utilized and is generally well known in the art. Each one of the shock absorbers is mounted on and extends between the beam of a respective one of the suspension assemblies of the axle/suspension system and the hanger mounted on a respective one of the main members of the vehicle. These shock absorbers add complexity and weight to the axle/suspension system. Moreover, because the shock absorbers are a service item of the axle/suspension system that will require maintenance and/or replacement from time to time, they also add additional maintenance and/or replacement costs to the axle/suspension system.

The amount of cargo that a vehicle may carry is governed by local, state, and/or national road and bridge laws. The basic principle behind most road and bridge laws is to limit the maximum load that a vehicle may carry, as well as to limit the maximum load that can be supported by individual axles. As a result, the weight of the shock absorbers undesirably reduces the amount of cargo that can be carried by the heavy-duty vehicle. Depending on the shock absorbers employed, they also add varying degrees of complexity to the axle/suspension system, which is also undesirable.

Because of the undesirable increased weight to the axle/suspension system attributed to the shock absorbers, prior art air springs with damping characteristics were developed. Prior art air springs with damping characteristics enabled removal of the shock absorbers while maintaining desirable soft ride characteristics. More specifically, prior art air springs with damping characteristics typically included openings between the bellows and the piston in order to allow fluid communication between the volume of the bellows chamber and the volume of the piston chamber. This fluid communication between the bellows chamber volume and the piston chamber volume provided damping characteristics to the air spring while maintaining a soft ride to the vehicle during operation. Prior art air springs with damping characteristics are typically of the "take-apart" design variety, meaning that the bottom end of the bellows of the air spring is operatively connected to a protrusion that extends upwardly from the piston top plate that is formed with a barb. In these types of air springs, the bellows can be taken apart from the piston. However, air springs having the "take-apart" design are limited during rebound travel and jounce travel and can experience fold in issues in "low pressure" or "no air" situations. Known air springs for vehicle suspension assemblies are described in <CIT> and <CIT>.

Although prior art air springs with damping characteristics provide a softer ride during vehicle operation, they typically require a custom designed air spring piston for each specific application. More specifically, each anticipated use of the axle/suspension system requires certain damping characteristics, which, in turn, requires a different air spring configuration. As a result, each prior art air spring with damping characteristics requires a different custom design and manufacturing process. This leads to undesirable increases in both design and manufacturing costs and an undesirable increase in production time for the air spring. Moreover, the "take-apart" design of the air springs with damping characteristics potentially limits rebound travel and jounce travel and potentially exacerbates fold in issues in "low pressure" or "no air" situations. The air spring for heavy-duty vehicles of the present invention overcomes the problems associated with prior art non-damping air springs by removing the prior art shock absorber and converting the non-damping air spring with a "molded-in" end closure into an air spring that provides damping characteristics. It also allows for the use of different piston/pedestal combinations to be used in the air spring so that the volume of the piston can be varied along with the opening size between the piston chamber and the bellows chamber to optimize the damping characteristics of the air spring. Additionally, the air spring for heavy- duty vehicles of the present invention provides an air spring with damping characteristics that may be optimized for different uses without requiring custom design and manufacturing of the air springs for each specific use, as is typically required by prior art air springs with damping characteristics.

Objectives of the present invention include providing an air spring with damping characteristics for heavy-duty vehicles that enables removal of shock absorbers while maintaining desirable soft ride and damping characteristics.

Another objective of the present invention is to provide an air spring with damping characteristics for heavy-duty vehicles that in certain applications is free of the "take-apart" design so that the air spring does not experience fold in issues in "lower pressure" or "no air" situations.

A further objective of the present invention is to provide an air spring with damping characteristics for heavy-duty vehicles that enables one to convert a non-damping air spring with a "molded-in" or "take-apart" end closure into an air spring providing damping characteristics.

Yet another objective of the present invention is to provide an air spring with damping characteristics for heavy-duty vehicles that allows for the use of different piston/pedestal combinations to be used in the air spring, so that the volume of the piston can be varied along with the opening size between the piston chamber and the bellows chamber to optimize the damping characteristics of the air spring.

Still another objective of the present invention is to provide an air spring with damping characteristics for heavy-duty vehicles that may be optimized for different uses without requiring custom design and manufacturing of the air springs for each specific use.

These objectives and advantages are obtained by the air spring with damping characteristics for heavy-duty vehicles of the present invention which includes a bellows for attachment to a main member of a heavy-duty vehicle and a piston for mounting on a said suspension assembly of the heavy-duty vehicle. The bellows includes a bellows chamber and is attached to the piston. The piston having an open bottom, a top plate and a retaining plate for the bellows mounted on the top plate, and a disc attached to the open bottom of said piston to close it sealingly whereby the piston and the disc define a piston chamber. The bellows chamber and the piston chamber are in fluid communication with each other via at least one opening including aligned openings formed in said retaining plate and piston top plate, said at least one opening including a cross-sectional area of from <NUM><NUM> to <NUM><NUM> (<NUM> in. <NUM> to <NUM> in. <NUM>), wherein airflow between the bellows chamber and the piston chamber provides damping to the suspension assembly of the heavy-duty vehicle. Other aspects of the invention are defined by the claims.

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

In order to better understand the environment in which the air spring with damping characteristics for a heavy-duty vehicle of the present invention is utilized, a trailing arm overslung beam-type air-ride axle/suspension system that incorporates a prior art air spring <NUM>, is indicated generally at <NUM>, is shown in <FIG> and <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 <NUM> (<FIG>, only one 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>.

With continued reference to <FIG> and <FIG> and with additional reference to <FIG>, suspension assembly <NUM> also includes air spring <NUM>, mounted on and extending between beam rear end <NUM> and main member <NUM> (<FIG>). Air spring <NUM> includes a bellows <NUM> and a piston <NUM>. The top portion of bellows <NUM> is sealingly engaged with a bellows top plate <NUM>. An air spring mounting plate <NUM> (<FIG> and <FIG>) is mounted on bellows top plate <NUM> by fasteners <NUM> which are also used to mount the top portion of air spring <NUM> to the vehicle main member <NUM>. Piston <NUM> is generally cylindrical-shaped and includes a sidewall <NUM>, a generally flat bottom plate <NUM>, and a top plate <NUM>. The bottom portion of bellows <NUM> is sealingly engaged with piston top plate <NUM> in a manner well known in the art utilizing a "molded-in" end closure or retaining plate <NUM>.

As shown in <FIG> and <FIG>, prior art non-damping air spring <NUM> includes a bumper <NUM> that is mounted on piston top plate <NUM> by a nut <NUM> which is threaded onto a fastener <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 during operation of the vehicle during "low pressure" or "no air" events.

With particular reference to <FIG>, piston <NUM> of prior art air spring <NUM> is formed with a central hub <NUM> attached to sidewall <NUM> in a well-known manner. A plurality of ribs <NUM> extend radially between hub <NUM> and sidewall <NUM> to provide structural support to prior art air spring <NUM>.

A first configuration for mounting piston bottom plate <NUM> directly to beam top plate <NUM> at beam rear end <NUM> is shown generally in <FIG>. In this configuration bottom plate <NUM> of piston <NUM> is attached directly to beam rear end <NUM> via fasteners (not shown). A second configuration for mounting prior art air spring <NUM> to beam <NUM> will be discussed below in connection with <FIG> and <FIG>.

As shown in <FIG>, prior art air spring <NUM> may alternatively be mounted on beam <NUM> via a beam mounting pedestal <NUM>. With particular reference to <FIG>, more specifically, 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> further includes an upwardly extending column <NUM>, which is formed with an opening <NUM>. Fastener <NUM> is disposed through opening <NUM> and a nut <NUM> is threaded onto the fastener to attach piston <NUM> to beam mounting pedestal <NUM> as known in the art. A pair of strengthening webs <NUM> (<FIG>) extend outwardly from column <NUM> on flat base <NUM>. A pair of openings (not shown) are formed in flat base <NUM>. Each opening (not shown) receives a fastener (not shown) for attaching beam mounting pedestal <NUM> to beam top plate <NUM> at beam rear end <NUM>. It should be understood that other types of beam mounting attachments having different structures are also known in the art and are used to mount the air spring to the beam.

With continued reference to <FIG>, prior art air spring <NUM> includes bellows top plate <NUM>, piston top plate <NUM>, and bellows <NUM> defining a bellows chamber <NUM>. Because the bottom of piston <NUM> is open and the piston does not communicate with bellows chamber <NUM>, the piston does not generally contribute any appreciable volume to air spring <NUM>.

Referring now to <FIG> and <FIG>, the top end of a shock absorber <NUM> (<FIG>) is 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.

Prior art air spring <NUM> has very limited or no damping capabilities because its structure, as described above, does not provide for the same. Instead, prior art air spring <NUM> relies on shock absorbers <NUM> to provide damping to axle/suspension system <NUM>. Because each shock absorber <NUM> is relatively heavy, this adds weight to axle/suspension system <NUM> and therefore reduces the amount of cargo that can be carried by the heavy-duty vehicle. Shock absorbers <NUM> also add complexity to axle/suspension system <NUM>. Moreover, because shock absorbers <NUM> are a service item of axle/suspension system <NUM> that will require maintenance and/or replacement from time to time, they also add additional maintenance and/or replacement costs to the axle/suspension system.

Turning now to <FIG>, a prior art air spring <NUM> with damping characteristics is shown, which is typically used without shock absorbers. Prior art air spring <NUM> is typically incorporated into an axle/suspension system such as axle/suspension system <NUM> (<FIG>), or other similar air-ride axle/suspension systems. 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 (not shown) is typically mounted on the top surface of bellows 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. 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 sidewall <NUM> attached to a generally flat bottom plate <NUM>. Piston <NUM> also includes 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> and is utilized to attach piston <NUM> directly to the beam (not shown), similar to the mount of prior art air spring <NUM> shown in <FIG>.

Piston top plate <NUM>, sidewall <NUM>, and bottom plates <NUM> and <NUM> of piston <NUM> define a piston chamber <NUM>. Sidewall <NUM> of piston <NUM> includes 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 and is known as a "take-apart" design. Additionally, bellows <NUM>, bellows top plate <NUM>, and piston top plate <NUM> define a bellows chamber <NUM>.

A bumper <NUM> extends into bellows chamber <NUM> and 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> is formed from rubber, plastic or other compliant material and extends upwardly from the top surface of bumper mounting plate <NUM>. Additionally, 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. Piston top plate <NUM> is formed with a pair of openings <NUM>, which allow a volume V<NUM> of the piston chamber <NUM> and a volume V<NUM> of the bellows chamber <NUM> to communicate with one another. More specifically, openings <NUM> allow fluid or air to pass between piston chamber <NUM> and bellows chamber <NUM> during operation of the vehicle. Openings <NUM>, piston chamber <NUM> and bellows chamber <NUM> require custom design and manufacture for different applications to achieve optimal damping. As a result, prior art piston <NUM> is expensive to design and manufacture for each specific axle/suspension system application.

Although prior art air spring <NUM> does provide sufficient damping characteristics, the manufacturing process of the prior art spring with damping characteristics requires a custom designed piston <NUM> thus undesirably increasing design and manufacturing costs. Moreover, the "take-apart" design of prior art air spring <NUM> with damping characteristics, may potentially limit rebound travel and jounce travel and may potentially exacerbate fold in issues in "low pressure" or "no air" situations. The air spring of the present invention overcomes the problems associated with prior art air springs <NUM>, <NUM>, by providing a method for converting an existing non-damping air spring having a "molded-in" or "take-apart" end closure into an air spring with damping features, thus minimizing both design and manufacturing costs as well as production costs. The air spring of the present invention will now be described in detail below.

Turning to <FIG>, a first exemplary embodiment air spring <NUM> of the present invention is shown mounted on a prior art axle/suspension system <NUM>, described in detail above. First exemplary embodiment air spring <NUM> is similar to prior art air spring <NUM> with respect to its structure, but with some differences that include modification to provide damping characteristics by including a circular disc <NUM>, an opening <NUM> (<FIG>), and an opening <NUM> (<FIG>), as will be described in detail below.

With additional reference to <FIG> and <FIG>, first exemplary embodiment air spring <NUM> generally includes a bellows <NUM>, a bellows top plate <NUM>, and a piston <NUM>. Bellows top plate <NUM> includes a pair of fasteners <NUM>, each formed with an opening <NUM>. Fasteners <NUM> are utilized to mount air spring <NUM> to an air spring plate (not shown), that in turn is mounted to main member <NUM> (<FIG>). Piston <NUM> is generally cylindrical-shaped and includes a sidewall <NUM>, a flared portion <NUM>, and a top plate <NUM>.

With particular reference to <FIG>, a bumper <NUM> is disposed on a top surface of a retaining plate <NUM> (<FIG>). Retaining plate <NUM>, bumper <NUM> and piston top plate <NUM> are each formed with an aligned opening <NUM>, <NUM>, and <NUM>, respectively. A fastener <NUM> is disposed through piston top plate opening <NUM>, retaining plate opening <NUM>, and bumper opening <NUM>. A washer <NUM> and a nut <NUM> are disposed on fastener <NUM> to mount bumper <NUM> and retaining plate <NUM> on the top surface of piston top plate <NUM>. Retaining plate <NUM> includes a flared end <NUM> that is molded into the lower end of bellows <NUM>, which holds the bellows in place on piston <NUM> and forms an airtight seal between the bellows and the piston. Thus, first exemplary embodiment air spring <NUM> is known as a "molded-in" air spring design. It should be understood that flared end <NUM> of retaining plate <NUM> could also be separate from the lower end of bellows <NUM>, whereby the flared end would capture and hold the lower end of the bellows in place on piston <NUM> to form an airtight seal between the bellows and the piston, without changing the overall concept or operation of the of the present invention. Bellows <NUM>, retaining plate <NUM>, and bellows top plate <NUM> generally define a bellows chamber <NUM> having an interior volume V<NUM> at standard ride height. Bellows chamber <NUM> preferably has a volume of from about <NUM><NUM> (<NUM> in. <NUM>) to about <NUM><NUM> (<NUM> in. More preferably, bellows chamber <NUM> has a volume of about <NUM><NUM> (<NUM> in. Bumper <NUM> is formed from rubber, plastic or other compliant material and extends generally upwardly from retaining plate <NUM> mounted on piston top 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 during operation of the vehicle.

First exemplary embodiment air spring <NUM> is formed with an upwardly extending central hub <NUM> attached to sidewall <NUM> in a well-known manner. Central hub <NUM> is formed with an opening <NUM> that is continuous with piston top plate opening <NUM>. A plurality of ribs <NUM> (<FIG>) extend radially between central hub <NUM> and sidewall <NUM> to provide structural support to air spring <NUM> of the present invention.

In accordance with one of the primary features of the present invention, as more clearly shown in <FIG> and <FIG>, generally circular disc <NUM> is attached or mated to the bottom of piston <NUM> of first exemplary embodiment air spring <NUM> of the present invention. Circular disc <NUM> is formed with an opening <NUM> that aligns with opening <NUM> of piston central hub <NUM>. Fastener <NUM> extends downwardly through piston central hub opening <NUM>, through disc opening <NUM>, through an opening (not shown) formed in beam mounting pedestal <NUM>, and through an opening (not shown) formed in beam rear end top plate <NUM>. A nut (not shown) is threaded onto the bottom end of fastener <NUM> to sealingly attach circular disc <NUM> to first exemplary embodiment air spring <NUM>, and also attaches piston <NUM> of air spring <NUM> to beam <NUM>. Once attached, a top surface <NUM> of circular disc <NUM> is mated to a lower surface <NUM> of sidewall <NUM> of piston <NUM> of first exemplary embodiment air spring <NUM> to provide an airtight seal between circular disc <NUM> and piston <NUM>. Circular disc <NUM> is formed with a continuous raised lip <NUM> on its top surface along the periphery of the disc, with the lip being disposed generally between flared portion <NUM> and sidewall <NUM> of piston <NUM> when circular disc <NUM> is mated to the piston. Optionally, the attachment of circular disc <NUM> to piston <NUM> may be supplemented by additional attachment means such as welding, soldering, crimping, friction welding, an O-ring, a gasket, adhesive or the like. Alternatively, the attachment of circular disc <NUM> to piston <NUM> may be accomplished via means other than fastener <NUM>, such as other types of fasteners, welding, soldering, crimping, friction welding, adhesives and the like, without changing the overall concept or operation of the present invention. Circular disc <NUM> may be composed of metal, plastic, and/or composite material, or other materials known to those skilled in the art, without changing the overall concept or operation of the present invention. Circular disc <NUM> may optionally include a groove (not shown) formed in top surface <NUM> disposed circumferentially around the disc, and configured to mate with a downwardly extending hub of the piston in order to reinforce the connection of the disc to the bottom of piston <NUM>. An O-ring or gasket material could optionally be disposed in the groove to ensure an airtight fit of circular disc <NUM> to piston <NUM>.

With continued reference to <FIG>, once circular disc <NUM> is attached to piston <NUM>, top plate <NUM>, sidewall <NUM>, and the disc, define a piston chamber <NUM> having an interior volume V<NUM>. Piston chamber <NUM> is generally able to withstand the required burst pressure of the axle/suspension system <NUM> during vehicle operation. Piston chamber <NUM> preferably has a volume of from about <NUM><NUM> (<NUM> in. <NUM>) to about <NUM><NUM> (<NUM> in. More preferably, piston chamber <NUM> has a volume of about <NUM><NUM> (<NUM> in.

In accordance with another of the primary features of the present invention, opening <NUM> is formed in retaining plate <NUM> and aligned opening <NUM> is formed in top plate <NUM> of piston <NUM>. More particularly, aligned openings <NUM>, <NUM> are disposed generally adjacent to bumper <NUM>. Openings <NUM>, <NUM> are generally cylindrical-shaped but may include other shapes including oval, elliptical or other shapes without changing the overall concept or operation of the present invention. Aligned openings <NUM>,<NUM> together form a continuous opening <NUM> that allows piston chamber <NUM> to fluidly communicate with bellows chamber <NUM>. Alternatively, openings <NUM>, <NUM> may include a spring pin (not shown), or a self-tapping screw with an integral opening, or other similar conduit that provides communication of fluid or air between piston chamber <NUM> and bellows chamber <NUM> during operation of the vehicle. In this manner, damping characteristics are provided to first exemplary embodiment air spring <NUM> of the present invention. Opening <NUM> has a cross sectional area of from about <NUM><NUM> to <NUM><NUM> (<NUM> in. <NUM> to about <NUM> in. More preferably, opening <NUM> has a cross sectional area of about <NUM><NUM> (<NUM> in.

It is contemplated that the ratio of the cross-sectional area of opening <NUM> measured in cm<NUM> (in. <NUM>)to the volume of piston chamber <NUM> measured in cm<NUM> (in. <NUM>) to the volume of bellows chamber <NUM> measured in cm<NUM> (in. <NUM>) is in the range of ratios of from about <NUM>:<NUM>:<NUM>,<NUM> to about <NUM>:<NUM>,<NUM>:<NUM>,<NUM>. This is an inclusive range that could be alternatively expressed as <NUM>:<NUM>-<NUM>,<NUM>:<NUM>,<NUM>-<NUM>,<NUM>, including any combination of ratios in between, and, for example, would necessarily include the following ratios <NUM>:<NUM>:<NUM>,<NUM> and <NUM>:<NUM> ,<NUM>:<NUM>,<NUM>.

More specifically, when axle <NUM> of axle/suspension system <NUM> experiences a jounce event, such as when the vehicle wheels encounter a curb or a raised bump in the road, the axle moves vertically upwardly toward the vehicle chassis. In such a jounce event, bellows chamber <NUM> is compressed by axle/suspension system <NUM> as the wheels of the vehicle travel over the curb or the raised bump in the road. The compression of air spring bellows chamber <NUM> causes the internal pressure of the bellows chamber to increase. Therefore, a pressure differential is created between bellows chamber <NUM> and piston chamber <NUM>. This pressure differential causes air to flow from bellows chamber <NUM>, through continuous opening <NUM> and into piston chamber <NUM>. The flow of air between bellows chamber <NUM> into piston chamber <NUM> through opening <NUM> causes damping to occur. As an additional result of the airflow through continuous opening <NUM>, the pressure differential between bellows chamber <NUM> and piston chamber <NUM> is reduced. Air continues to flow through opening <NUM> until the pressures of piston chamber <NUM> and bellows chamber <NUM> have equalized.

Conversely, when axle <NUM> of axle/suspension system <NUM> experiences a rebound event, such as when the vehicle wheels encounter a large hole or depression in the road, the axle moves vertically downwardly away from the vehicle chassis. In such a rebound event, bellows chamber <NUM> is expanded by axle/suspension system <NUM> as the wheels of the vehicle travel into the hole or depression in the road. The expansion of air spring bellows chamber <NUM> causes the internal pressure of the bellows chamber to decrease. As a result, a pressure differential is created between bellows chamber <NUM> and piston chamber <NUM>. This pressure differential causes air to flow from piston chamber <NUM>, through continuous opening <NUM> and into bellows chamber <NUM>. The flow of air through opening <NUM> causes damping to occur. As an additional result of the airflow through opening <NUM>, the pressure differential between bellows chamber <NUM> and piston chamber <NUM> is reduced. Air will continue to flow through continuous opening <NUM> until the pressures of piston chamber <NUM> and bellows chamber <NUM> have equalized. When little or no suspension movement has occurred over a period of several seconds, the pressure of bellows chamber <NUM> and piston chamber <NUM> can be considered equal.

As a result of attaching circular disc <NUM> to piston <NUM>, and providing opening <NUM> in retaining plate <NUM> and opening <NUM> in top plate <NUM> of the piston, collectively, continuous opening <NUM>, a non-damping air spring, such as prior art air spring <NUM> (<FIG>), may be converted to an air spring that provides damping characteristics such as first exemplary embodiment air spring <NUM> of the present invention. In this manner, axle/suspension system <NUM> does not require a shock absorber to provide damping to the axle/suspension system, thus reducing the weight of the axle/suspension system. Further, first exemplary embodiment air spring <NUM> of the present invention provides damping characteristics without requiring a custom design and manufacturing process, as an existing designed and manufactured piston <NUM> is utilized, resulting in a desirable decrease in design and manufacturing costs when compared to the prior art air spring with damping characteristics, such as prior art air spring <NUM> (<FIG>). As a result, air spring <NUM> of the present invention converts non-damping air springs, such as prior art air spring <NUM>, to an air spring with damping characteristics, in an economical manner without an undesirable increase in manufacturing and design costs, and also avoiding the potential deficiencies of the "take-apart" air spring design.

It should be understood that first exemplary embodiment air spring <NUM> could also be utilized in conjunction with a "take-apart" air spring design having an open bottom, without changing the overall concept or operation of the present invention. In such an application, continuous opening <NUM> is formed through the piston top plate, as the "take-apart" air spring design typically does not include a retaining plate. Disc <NUM> is attached to the open bottom of the piston of the "take-apart" air spring design, and as a result, allows a non-damping "take- apart" air spring design to be converted to a damping "take-apart" air spring design that includes damping characteristics similar to the "molded-in" air spring design described above.

Turning to <FIG>, a second exemplary embodiment air spring <NUM> of the present invention, is shown mounted on prior art axle/suspension system <NUM>, described in detail above.

Second exemplary embodiment air spring <NUM> is similar to prior art air spring <NUM> with respect to its structure, but with some differences that include modification to provide integration of the beam mounting pedestal and damping characteristics by including a disc <NUM>, an opening <NUM> and an opening <NUM>, as will be described below. Second exemplary embodiment air spring <NUM> generally includes a bellows <NUM>, a bellows top plate <NUM>, and a piston <NUM>. Top plate <NUM> includes a pair of fasteners <NUM>, each formed with an opening <NUM>. Fasteners <NUM> are utilized to mount air spring <NUM> to an air spring plate (not shown) that in turn is mounted to main member <NUM> (<FIG>). Piston <NUM> is generally cylindrical-shaped and includes a sidewall <NUM>, a flared portion <NUM>, and a top plate <NUM>.

With additional reference to <FIG>, a bumper <NUM> is disposed on a top surface of a retaining plate <NUM>. Retaining plate <NUM>, bumper <NUM>, and piston top plate <NUM> are each formed with aligned openings <NUM>, <NUM>, and <NUM>, respectively. A fastener <NUM> is disposed through piston top plate opening <NUM>, retaining plate opening <NUM>, and bumper opening <NUM>. A washer (not shown) and a nut (not shown) are threadably disposed on fastener <NUM> to mount bumper <NUM> and retaining plate <NUM> on the top surface of piston top plate <NUM>. Retaining plate <NUM> includes a flared end <NUM> that is molded into the lower end of bellows <NUM>, which holds the bellows in place on piston <NUM> and forms an airtight seal between the bellows and the piston. Thus, second exemplary embodiment air spring <NUM> is known as a "molded-in" air spring design. It should be understood that flared end <NUM> of retaining plate <NUM> could also be separate from the lower end of the bellows <NUM>, whereby the flared end would capture and hold the lower end of the bellows in place on piston <NUM> to form an airtight seal between the bellows and the piston, without changing the overall concept or operation of the present invention. Bellows <NUM>, retaining plate <NUM>, and the bellows top plate (not shown) generally define a bellows chamber <NUM> having an interior volume V<NUM> at standard ride height. Bellows chamber <NUM> preferably has a volume of from about <NUM><NUM> (<NUM> in. <NUM>) to about <NUM><NUM> (<NUM> in. More preferably, bellows chamber <NUM> has a volume of about <NUM><NUM> (<NUM> in. Bumper <NUM> is formed from rubber, plastic or other compliant material and extends generally upwardly from retaining plate <NUM> mounted on piston top plate <NUM>. Bumper <NUM> serves as a cushion between piston top plate <NUM> and the underside of the bellows top plate <NUM> in order to prevent the plates from damaging one another during operation of the vehicle.

Second exemplary embodiment air spring <NUM> is formed with an upwardly extending central hub <NUM> attached to sidewall <NUM> in a well-known manner. Central hub <NUM> is formed with an opening <NUM> that is continuous with top plate opening <NUM>. A plurality of ribs <NUM> extend radially between central hub <NUM> and sidewalls <NUM> to provide structural support to second exemplary embodiment air spring <NUM> of the present invention.

In accordance with one of the primary features of the present invention, generally cup-shaped disc <NUM> is attached to the bottom of piston <NUM> of second exemplary embodiment air spring <NUM> of the present invention. Cup-shaped disc <NUM> includes a disc base <NUM> and a vertical sidewall <NUM>. Vertical sidewall <NUM> extends upwardly from disc base <NUM> to facilitate a sealing attachment to piston <NUM>, as will be described below.

More specifically, disc base <NUM> is formed with an opening <NUM> that aligns with opening <NUM> of piston central hub <NUM>. Fastener <NUM> extends downwardly through piston hub central opening <NUM>, through disc opening <NUM>, and through an opening <NUM> formed in beam rear end <NUM>. A washer <NUM> and a nut <NUM> are threadably engaged with the bottom end of fastener <NUM> to sealingly attach cup-shaped disc <NUM> to first exemplary embodiment air spring <NUM>, and attach the piston of the air spring to the beam. Therefore, cup-shaped disc <NUM> is attached to beam <NUM> without the use of a beam mounting pedestal, such as beam mounting pedestal <NUM> (<FIG>), because cup-shaped disc <NUM> integrates the beam mounting pedestal into its structure. Once attached, an upper surface <NUM> of an interior vertical wall <NUM> of disc base <NUM> of cup-shaped disc <NUM> mates with a lower surface <NUM> of sidewall <NUM>, and a top edge <NUM> of disc vertical sidewall <NUM> mates with a lower surface <NUM> of flared portion <NUM> of piston <NUM> to provide an airtight sealing engagement with the piston. Additionally, an upper surface <NUM> of a central portion <NUM> of cup-shaped disc <NUM> mates with a lower surface <NUM> of central hub <NUM> to provide a sealing engagement with piston <NUM>. In this manner, cup-shaped disc <NUM>, piston top plate <NUM>, and piston sidewall <NUM> define a piston chamber <NUM> having an interior volume V<NUM>. Piston chamber <NUM> generally is able to withstand the required burst pressure of the axle/suspension system <NUM> (<FIG>) during vehicle operation. Piston chamber <NUM> preferably has a volume of from about <NUM><NUM> (<NUM> in. <NUM>) to about <NUM><NUM> (<NUM> in. More preferably, piston chamber <NUM> has a volume of about <NUM><NUM> (<NUM> in. It is important to note that cup-shaped disc <NUM> may be attached at different locations on piston <NUM> to vary the volume V<NUM> based on the specific application of the heavy- duty vehicle (not shown) to facilitate optimization of damping characteristics of air spring <NUM> of the present invention. Optionally, the attachment of cup-shaped disc <NUM> to piston <NUM> may be supplemented by additional attachment means such as welding, soldering, crimping, friction welding, an O-ring, a gasket, adhesive or the like. Alternatively, the attachment of cup-shaped disc <NUM> to piston <NUM> may be accomplished via means other than fastener <NUM>, such as other types of fasteners, welding, soldering, crimping, friction welding, adhesives and the like, without changing the overall concept or operation of the present invention. In addition, cup-shaped disc <NUM> may be composed of metal, plastic, and/or composite material, or other materials known to those skilled in the art, without changing the overall concept or operation of the present invention.

In accordance with another of the primary features of the present invention, opening <NUM> is formed in retaining plate <NUM> and aligned opening <NUM> is formed in top plate <NUM> of piston <NUM>. More particularly, aligned openings <NUM>,<NUM> are adjacent to bumper <NUM>. Openings <NUM>,<NUM> are generally cylindrical-shaped but may include other shapes including oval, elliptical or other shapes without changing the overall concept or operation of the present art. Aligned openings <NUM>,<NUM> together form a continuous opening <NUM> that allows piston chamber <NUM> to fluidly communicate with bellows chamber <NUM>. Alternatively, openings <NUM>,<NUM> may include a spring pin (not shown), or a self-tapping screw with an integral opening, or other similar conduit that provides communication of fluid or air between piston chamber <NUM> and bellows chamber <NUM> during operation of the vehicle. In this manner, damping characteristics are provided to second exemplary embodiment air spring <NUM> of the present invention. Continuous opening <NUM> has a cross sectional area of from about <NUM><NUM> to <NUM><NUM> (<NUM> in. <NUM> to about <NUM> in. More preferably, continuous opening <NUM> has a cross sectional area of about <NUM><NUM> (<NUM> in.

It is contemplated that the ratio of the cross-sectional area of opening <NUM> measured in cm<NUM> (in. <NUM>) to the volume of piston chamber <NUM> measured in cm<NUM> (in. <NUM>) to the volume of bellows chamber <NUM> measured in cm<NUM> (in. <NUM>) is in the range of ratios of from about <NUM>:<NUM>:<NUM>,<NUM> to about <NUM>:<NUM> ,<NUM>:<NUM>,<NUM>. This is an inclusive range that could be alternatively expressed as <NUM>:<NUM>-<NUM>,<NUM>:<NUM>,<NUM>-<NUM>,<NUM>, including any combination of ratios in between, and, for example, would necessarily include the following ratios <NUM> :<NUM>:<NUM>,<NUM> and <NUM> :<NUM> ,<NUM><NUM> :<NUM>,<NUM>.

As shown in <FIG>, with the attachment of cup-shaped disc <NUM> to piston <NUM>, and the disc to beam <NUM>, a damping feature is provided to second exemplary embodiment air spring <NUM> of the present invention, which doubles as a mount for the air spring to the beam. More specifically, when axle <NUM> of axle/suspension system <NUM> experiences a jounce event, such as when the vehicle wheels encounter a curb or a raised bump in the road, the axle moves vertically upwardly toward the vehicle chassis. In such a jounce event, bellows chamber <NUM> is compressed by axle/suspension system <NUM> as the wheels of the vehicle travel over the curb or the raised bump in the road. The compression of air spring bellows chamber <NUM> causes the internal pressure of the bellows chamber to increase. Therefore, a pressure differential is created between bellows chamber <NUM> and piston chamber <NUM>. This pressure differential causes air to flow from bellows chamber <NUM>, through continuous opening <NUM> and into piston chamber <NUM>. The flow of air between bellows chamber <NUM> into piston chamber <NUM> through continuous opening <NUM> causes damping to occur. As an additional result of the airflow through continuous opening <NUM>, the pressure differential between bellows chamber <NUM> and piston chamber <NUM> is reduced. Air continues to flow through continuous opening <NUM> until the pressures of piston chamber <NUM> and bellows chamber <NUM> have equalized.

Conversely, when axle <NUM> of axle/suspension system <NUM> experiences a rebound event, such as when the vehicle wheels encounter a large hole or depression in the road, the axle moves vertically downwardly away from the vehicle chassis. In such a rebound event, bellows chamber <NUM> is expanded by axle/suspension system <NUM> as the wheels of the vehicle travel into the hole or depression in the road. The expansion of air spring bellows chamber <NUM> causes the internal pressure of the bellows chamber to decrease. As a result, a pressure differential is created between bellows chamber <NUM> and piston chamber <NUM>. This pressure differential causes air to flow from piston chamber <NUM>, through continuous opening <NUM> and into bellows chamber <NUM>. The flow of air through continuous opening <NUM> causes damping to occur. As an additional result of the airflow through continuous opening <NUM>, the pressure differential between bellows chamber <NUM> and piston chamber <NUM> is reduced. Air will continue to flow through continuous opening <NUM> until the pressures of piston chamber <NUM> and bellows chamber <NUM> have equalized. When little or no suspension movement has occurred over a period of several seconds the pressure of bellows chamber <NUM> and piston chamber <NUM> can be considered equal.

As a result of attaching circular disc <NUM> to piston <NUM>, and providing opening <NUM> in retaining plate <NUM> and opening <NUM> in top plate <NUM> of the piston, collectively, continuous opening <NUM>, a non-damping air spring, such as prior art air spring <NUM> (<FIG>), may be converted to an air spring that provides damping characteristics such as second exemplary embodiment air spring <NUM> of the present invention. In this manner, axle/suspension system <NUM> does not require shock absorber <NUM> (<FIG>) to provide damping to the axle/suspension system, thus reducing the weight of the axle/suspension system. Further, second exemplary embodiment air spring <NUM> of the present invention provides damping characteristics without requiring a custom design and manufacturing process, as an existing designed and manufactured piston <NUM> is utilized, resulting in a desirable decrease in design and manufacturing costs when compared to prior art air springs with damping characteristics such as prior art air spring <NUM> (<FIG>). Moreover, second exemplary embodiment air spring <NUM> with cup-shaped disc <NUM> does not require a discrete beam mounting pedestal, thus desirably reducing weight and desirably reducing the amount of time needed to install the air spring of the present invention. As a result, air spring <NUM> of the present invention converts non-damping air springs, such as prior art air spring <NUM>, to an air spring with damping characteristics, in an economical manner without an undesirable increase in manufacturing and design costs, and also avoiding the potential deficiencies of the "take-apart" air spring design.

It should be understood that second exemplary embodiment air spring <NUM> could also be utilized in conjunction with a "take-apart" air spring design having an open bottom, without changing the overall concept or operation of the present invention. In such an application, continuous opening <NUM> is formed only through the piston top plate, as the "take-apart" air spring design typically does not include a retaining plate. Disc <NUM> is attached to the open bottom of the piston of the "take-apart" air spring design, and as a result, allows a non-damping "take-apart" air spring design to be converted to a damping "take-apart" air spring design that has damping characteristics similar to the "molded-in" air spring design described above.

Turning to <FIG>, a third exemplary embodiment air spring <NUM> of the present invention is shown. Third exemplary embodiment <NUM> is utilized on prior art axle/suspension system <NUM>, described in detail above. Third exemplary embodiment air spring <NUM> is similar to prior art air spring <NUM> with respect to its structure, but with some differences that include modification to provide damping characteristics by including a disc <NUM> and a threaded rod <NUM> formed with an opening <NUM>, as will be described below. Third exemplary embodiment air spring <NUM> generally includes a bellows <NUM>, a bellows top plate <NUM>, and a piston <NUM>. Bellows top plate <NUM> is formed with a pair of openings <NUM> through which a pair of fasteners <NUM> are disposed. Fasteners <NUM> are utilized to mount air spring <NUM> to an air spring plate (not shown), that in turn is mounted to the main member (not shown) of the axle/suspension system (not shown). Piston <NUM> is generally cylindrical-shaped and includes a sidewall <NUM>, a flared portion <NUM>, and a top plate <NUM>, as will be described below.

A bumper <NUM> is disposed on a top surface of a retaining plate <NUM>. Retaining plate <NUM>, bumper <NUM>, and piston top plate <NUM> are each formed with an aligned opening <NUM>, <NUM>, and <NUM>. Threaded rod <NUM> extends upwardly through piston top plate opening <NUM>, retaining plate opening <NUM>, and bumper opening <NUM>. A washer <NUM> and a nut <NUM> are disposed on threaded rod <NUM> to mount bumper <NUM> and retaining plate <NUM> on the top surface of piston top plate <NUM>. Retaining plate <NUM> includes a flared end <NUM> that captures and holds the lower end of bellows <NUM> in place on piston <NUM> to form an airtight seal between the bellows and the piston. Thus, third exemplary embodiment air spring <NUM> is known as a "molded-in" air spring design. It should be understood that retaining plate <NUM> could also be integrally molded into the lower end of bellows <NUM>, without changing the overall concept or operation of the present invention. Bellows <NUM>, retaining plate <NUM>, and bellows top plate <NUM> generally define a bellows chamber <NUM> having an interior volume V<NUM> at standard ride height. Bellows chamber <NUM> preferably has a volume of from about <NUM><NUM> (<NUM> in. <NUM>) to about <NUM><NUM> (<NUM> in. More preferably, bellows chamber <NUM> has a volume of about <NUM><NUM> (<NUM> in. Bumper <NUM> is formed from rubber, plastic or other compliant material and extends generally upwardly from retaining plate <NUM> mounted on piston top plate <NUM>. Bumper <NUM> serves as a cushion between piston top plate <NUM> and the underside of bellows top plate <NUM> to prevent the plates from damaging one another during operation of the vehicle.

Third exemplary embodiment air spring <NUM> is formed with an upwardly extending central hub <NUM> attached to sidewall <NUM> in a well-known manner. Central hub <NUM> includes an opening <NUM> that is continuous with top plate opening <NUM> and through which threaded rod <NUM> is disposed, as will be described below. A plurality of ribs <NUM> extend radially between central hub <NUM> and sidewall <NUM> to provide structural support to third exemplary embodiment air spring <NUM>.

With continued reference to <FIG>, and in accordance with one of the primary features of the present invention, generally circular disc <NUM> is attached to the bottom of piston <NUM> of third exemplary embodiment air spring <NUM> of the present invention. More specifically, circular disc <NUM> includes a base <NUM> and a vertical sidewall <NUM> that extends vertically upwardly from the base. Base <NUM> is formed with a central opening <NUM> that aligns with opening <NUM> of piston central hub <NUM>. Base <NUM> is also formed with a second opening <NUM> that is radially spaced from first opening <NUM>. It should be understood that second opening <NUM> could be formed in base <NUM> at any accessible location without changing the overall concept or operation of the present invention. Threaded rod <NUM> extends downwardly through piston central hub opening <NUM>, through disc opening <NUM>, through an opening (not shown) formed in the beam mounting pedestal (not shown), and through an opening formed in the top wall of beam rear end (not shown). A nut (not shown) is threaded onto the bottom end of the threaded rod to sealingly attach circular disc <NUM> to third exemplary embodiment air spring <NUM>, and also attaches the piston of the air spring to the beam of the axle/suspension system (not shown). Once attached, disc vertical sidewall <NUM> sealingly mates with piston sidewall <NUM>, as will be discussed below.

More particularly, vertical sidewall <NUM> of circular disc <NUM> matingly engages sidewall <NUM> of piston <NUM> to provide a sealing engagement of the disc to the piston. More specifically, an outer surface <NUM> of vertical sidewall <NUM> of circular disc <NUM> mates with an inner surface <NUM> of lower portion <NUM> of sidewall <NUM> to form an airtight seal. Optionally, the attachment of circular disc <NUM> to piston <NUM> may be supplemented by additional attachment means such as welding, soldering, crimping, friction welding, an O-ring, a gasket, adhesive or the like. Alternatively, the attachment of circular disc <NUM> to piston <NUM> may be accomplished via alternative means, such as fasteners, welding, soldering, crimping, friction welding, adhesives and the like, without changing the overall concept or operation of the present invention. Circular disc <NUM> may be composed of metal, plastic, and/or composite material or other materials known to those skilled in the art, without changing the overall concept or operation of the present invention. As a result of the sealing engagement of circular disc <NUM> to the bottom of piston <NUM>, the disc, piston top plate <NUM>, and piston sidewall <NUM> define a sealed piston chamber <NUM> having an interior volume V<NUM>. Piston chamber <NUM> generally is able to withstand the required burst pressure of the axle/suspension system (not shown) during vehicle operation. Piston chamber <NUM> preferably has a volume of from about <NUM><NUM> (<NUM> in. <NUM>) to about <NUM><NUM> (<NUM> in. More preferably, piston chamber <NUM> has a volume of about <NUM><NUM> (<NUM> in.

In accordance with another of the primary features of the present invention, threaded rod <NUM> is formed with opening <NUM> that extends through the entire length of the threaded rod. A conduit <NUM> having a continuous opening is in fluid communication with the bottom end of threaded rod opening <NUM>, and is disposed through and attached, by any suitable means, to opening <NUM> formed in circular disc <NUM>. Conduit <NUM> and threaded rod opening <NUM> provide fluid communication between bellows chamber <NUM> and piston chamber <NUM>. The opening in conduit <NUM> and threaded rod opening <NUM> each have a cross sectional area of from about <NUM><NUM> to <NUM><NUM> (<NUM> in. <NUM> to about <NUM> in. More preferably, the opening in conduit <NUM> and threaded rod opening <NUM> each have a cross sectional area of about <NUM><NUM> (<NUM> in.

It is contemplated that the ratio of the cross-sectional area of the opening in conduit <NUM> and threaded rod opening <NUM> measured in in. <NUM> to the volume of piston chamber <NUM> measured in cm<NUM> (in. <NUM>) to the volume of bellows chamber <NUM> measured in cm<NUM> (in. <NUM>) is in the range of ratios of from about <NUM>:<NUM>:<NUM>,<NUM> to about <NUM>:<NUM>,<NUM> :<NUM>,<NUM>. This is an inclusive range that could be alternatively expressed as <NUM>:<NUM>-<NUM>,<NUM> :<NUM>,<NUM>-<NUM>,<NUM>, including any combination of ratios in between, and, for example, would necessarily include the following ratios <NUM> :<NUM>:<NUM>,<NUM> and <NUM>:<NUM>,<NUM>:<NUM>,<NUM>.

More specifically, when the axle (not shown) of the axle/suspension system (not shown) experiences a jounce event, such as when the vehicle wheels encounter a curb or a raised bump in the road, the axle moves vertically upwardly toward the vehicle chassis. In such a jounce event, bellows chamber <NUM> is compressed by the axle/suspension system (not shown) as the wheels of the vehicle travel over the curb or the raised bump in the road. The compression of air spring bellows chamber <NUM> causes the internal pressure of the bellows chamber to increase. Therefore, a pressure differential is created between bellows chamber <NUM> and piston chamber <NUM>. This pressure differential causes air to flow from bellows chamber <NUM>, through threaded rod opening <NUM>, through conduit <NUM> and into piston chamber <NUM>. The flow of air between bellows chamber <NUM> into piston chamber <NUM> through threaded rod opening <NUM> and conduit <NUM> causes damping to occur. As an additional result of the air flow through threaded rod opening <NUM> and conduit <NUM>, the pressure differential between bellows chamber <NUM> and piston chamber <NUM> is reduced. Air continues to flow through threaded rod opening <NUM> and conduit <NUM> until the pressure of piston chamber <NUM> and bellows chamber <NUM> have equalized.

Conversely, when the axle (not shown) of the axle/suspension system (not shown) experiences a rebound event, such as when the vehicle wheels encounter a large hole or depression in the road, the axle moves vertically downwardly away from the vehicle chassis. In such a rebound event, bellows chamber <NUM> is expanded by the axle/suspension system (not shown) as the wheels of the vehicle travel into the hole or depression in the road. The expansion of air spring bellows chamber <NUM> causes the internal pressure of the bellows chamber to decrease. As a result, a pressure differential is created between bellows chamber <NUM> and piston chamber <NUM>. This pressure differential causes air to flow from piston chamber <NUM>, through conduit <NUM>, through threaded rod opening <NUM>, and into bellows chamber <NUM>. The flow of air through conduit <NUM> and threaded rod opening <NUM> causes damping to occur. As an additional result of the air flow through conduit <NUM> and threaded rod opening <NUM>, the pressure differential between bellows chamber <NUM> and piston chamber <NUM> is reduced. Air will continue to flow through conduit <NUM> and threaded rod opening <NUM> until the pressure of piston chamber <NUM> and bellows chamber <NUM> have equalized. When little or no suspension movement has occurred over a period of several seconds, the pressure of bellows chamber <NUM> and piston chamber <NUM> can be considered equal.

As a result of attaching circular disc <NUM> with openings <NUM> to piston <NUM> and providing threaded rod opening <NUM> and conduit <NUM>, a non-damping air spring such as prior art air spring <NUM>, may be converted to an air spring that includes damping characteristics such as third exemplary embodiment air spring <NUM> of the present invention. In this manner, the axle/suspension system (not shown) does not require a shock absorber to provide damping to the axle/suspension system, thus reducing the weight of the axle/suspension system. Third exemplary embodiment air spring <NUM> of the present invention provides damping characteristics without requiring a custom design and manufacturing process, as an existing designed and manufactured piston <NUM> is utilized, resulting in a desirable decrease in design and manufacturing costs when compared to a prior art air spring with damping characteristics, such as prior art air spring <NUM> (<FIG>). As a result, air spring <NUM> of the present invention converts non-damping air springs, such as prior art air spring <NUM> (<FIG>), to an air spring with damping characteristics in an economical manner, without an undesirable increase in manufacturing and design costs, and also avoiding the potential deficiencies of the "take-apart" air spring design.

It should be understood that third exemplary embodiment air spring <NUM> could also be utilized in conjunction with a "take-apart" air spring design having an open bottom, without changing the overall concept or operation of the present invention. In such an application, disc <NUM> including threaded rod <NUM> and conduit <NUM> is attached to the open bottom of the piston of the "take-apart" air spring design, and as a result, allows a non-damping "take-apart" air spring design to be converted to a damping "take-apart" air spring design that has damping characteristics similar to the "molded-in" air spring design described above.

Referring now to <FIG>, discs <NUM> and <NUM> are alternative configurations of discs that can be attached or mated to the bottom of a piston, utilizing all types of attachments including friction welding, soldering, coating, crimping, welding, snapping, screwing, O-ring, sonic, glue, press, melting, expandable sealant, press-fit, bolt, latch, spring, adhesive bond, laminate, tape, tack, adhesive, shrink fit, and the like, and/or any combination listed, without changing the overall concept or operation of the present invention. It is even contemplated that discs <NUM> and <NUM> may be composed of materials known by those in the art other than metal, plastic, and/or composite material without changing the overall concept or operation of the present invention.

The air spring for heavy-duty vehicles with damping characteristics of the present invention overcomes the problems associated with prior art air springs by eliminating the use of shock absorbers while converting a non-damping air spring with a "molded-in" end closure into an air spring that provides damping characteristics. It also allows for the use of different piston/pedestal combinations to be used in the air spring so that the volume of the piston can be varied along with the opening size between the piston chamber and the bellows chamber to optimize the damping characteristics of the air spring. Additionally, the air spring for heavy- duty vehicles with damping characteristics of the present invention provides an air spring with damping characteristics that may be optimized for different uses without requiring custom designed and manufactured air springs for a specific application as required by prior art air springs with damping characteristics.

The present invention also includes a method of converting a non-damping air spring to an air spring with damping characteristics. The method includes steps in accordance with the description and structure that is presented above and shown in <FIG>.

It is contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> of the present invention could be utilized on tractor-trailers or heavy-duty vehicles, such as buses, trucks, trailers and the like, having one or more than one axle without changing the overall concept or operation of the present invention. It is further contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> could be utilized on vehicles having frames or subframes which are moveable or non-movable without changing the overall concept or operation of the present invention. It is yet even further contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> 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. It is also contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> could be utilized on axle/suspension systems having an overslung/top-mount configuration or an underslung/bottom-mount configuration, without changing the overall concept or operation of the present invention. It is also contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> 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 further contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> could be formed from various materials, including composites, metal and the like, without changing the overall concept or operation of the present invention. It is even contemplated that exemplary embodiment air springs <NUM>,<NUM>,<NUM> could be utilized in combination with prior art shock absorbers and other similar devices and the like, without changing the overall concept or operation of the present invention.

It is contemplated that discs <NUM>,<NUM>,<NUM>,<NUM>,<NUM> may be attached to pistons <NUM>,<NUM>,<NUM>, respectively, utilizing other attachments such as friction welding, vibration, soldering, coating, crimping, welding, snapping, screwing, O-ring, sonic, glue, press, melting, expandable sealant, press-fit, bolt, latch, spring, adhesive bond, laminate, tape, tack, adhesive, shrink fit, and/or any combination listed without changing the overall concept or operation of the present invention. It is even contemplated that discs <NUM>,<NUM>,<NUM>,<NUM>,<NUM> may be composed of materials known by those in the art other than metal, plastic, and/or composite material without changing the overall concept or operation of the present invention.

It is contemplated that openings <NUM>,<NUM>,<NUM>,<NUM> of first and second exemplary embodiments <NUM>,<NUM> could be formed in a different location within retaining plates <NUM>,<NUM> and top plates <NUM>,<NUM> of pistons <NUM>,<NUM>, respectively, without changing the overall concept or operation of the present invention. It is further contemplated that any number of openings <NUM>,<NUM>,<NUM>,<NUM> may be formed in retaining plates <NUM>,<NUM> and top plates <NUM>,<NUM> of pistons <NUM>,<NUM>, respectively, such as multiple small openings without changing the overall concept or operation of the present invention.

It is contemplated that discs <NUM>,<NUM>,<NUM>,<NUM>,<NUM> may extend vertically further up vertical sidewalls <NUM>,<NUM> without changing the overall concept or operation of the present invention. It is also contemplated that discs <NUM>,<NUM>,<NUM>,<NUM> could have variable thicknesses being either uniform or non-uniform, without changing the overall concept or operation of the present invention. It is even contemplated that lip <NUM> may extend vertically higher without changing the overall concept or operation of the present invention. It is further contemplated that discs <NUM>,<NUM>,<NUM>,<NUM> may include structure to directly attach to each respective beam <NUM> similar to the structure of disc <NUM> without changing the overall concept or operation of the present invention. It is even further contemplated that discs <NUM>,<NUM>,<NUM>,<NUM>,<NUM> could include a groove to facilitate a sealing attachment to pistons <NUM>,<NUM>,<NUM>, respectively, without changing the overall concept or operation of the present invention.

It is contemplated that disc <NUM> may include any number of openings <NUM> and/or the openings located in a different location within the respective disc without changing the overall concept or operation of the present invention.

It is contemplated that conduit <NUM> may be composed of flexible materials such as rubber, plastic or other materials known to those skilled in the art without changing the overall concept or operation of the present invention. It is further contemplated that threaded rod <NUM> may include a conduit or other means disposed in opening <NUM> to facilitate fluid communication, without changing the overall concept or operation of the present invention
The present invention has been described with reference to specific embodiments. It is to be understood that this illustration is by way of example and not by way of limitation. Potential modifications and alterations will occur to others upon a reading and understanding of this disclosure, and it is understood that the invention includes all such modifications and alterations and equivalents thereof.

Accordingly, the air spring with damping characteristics for heavy-duty vehicles is simplified, provides an effective, safe, inexpensive and efficient structure and method which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior art air springs for heavy-duty vehicles, and solves problems and obtains new results in the art.

In the foregoing description, certain terms have been used for brevity, clearness and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed.

Claim 1:
An air spring with damping characteristics, for a suspension assembly of a heavy-duty vehicle, comprising:
a bellows (<NUM>;<NUM>;<NUM>) for attachment to a main member of a heavy-duty vehicle and a piston (<NUM>;<NUM>;<NUM>) for mounting on a said suspension assembly of the heavy-duty vehicle, said bellows including a bellows chamber (<NUM>;<NUM>;<NUM>) and being attached to said piston,
the piston having an open bottom, a top plate (<NUM>;<NUM>;<NUM>) and a retaining plate (<NUM>;<NUM>;<NUM>) for the bellows mounted on the top plate, and
a disc (<NUM>;<NUM>;<NUM>) attached to said open bottom of said piston to close it sealingly whereby the piston and said disc define a piston chamber (<NUM>;<NUM>;<NUM>),
said bellows chamber (<NUM>;<NUM>;<NUM>) and said piston chamber (<NUM>;<NUM>;<NUM>) being in fluid communication with each other via at least one opening including aligned openings (<NUM>,<NUM>;<NUM>,<NUM>;<NUM>,<NUM>) formed in said retaining plate and piston top plate, said at least one opening including a cross-sectional area of from <NUM><NUM> to <NUM><NUM> (<NUM> in.<NUM> to <NUM> in.<NUM>) wherein airflow between the bellows chamber and the piston chamber is suitable to provide damping to the suspension assembly of a said heavy-duty vehicle.