Patent Description:
Beam-type axle/suspension systems have been used in heavy-duty vehicles for many years. Beam-type axle/suspension systems typically include a pair of suspension assemblies. In some heavy-duty vehicles, the suspension assemblies are connected to a frame or subframe of the vehicle. Reference is made generally to a heavy-duty vehicle for the purpose of convenience with the understanding that such reference includes trucks, tractor-trailers and semi-trailers, trailers, and the like. Reference is made generally to a frame for the purpose of convenience with the understanding that such reference is by way of example and includes main or primary frames, movable subframes or sliders, nonmovable subframes, and the like.

A pair of laterally-spaced hangers is attached to and depends from the frame of the heavy-duty vehicle. The suspension assembly includes a pair of longitudinally-extending elongated beams. Each beam is pivotally mounted at one of its end portions to a respective hanger. An axle extends transversely between, and typically is attached to, the beams at an end or intermediate portion of the beam located opposite the pivotal connection end. The beam end portion opposite the pivotal connection end is also typically connected to an air spring, which is connected to the frame. The axle/suspension system may include a ride-height control valve mounted on the frame or other support structure to adjust the ride-height of the heavy-duty vehicle. Ride-height is defined as a static distance from the bottom of a frame member to a longitudinal central axis of the axle. The ride-height control valve is operatively connectable with the beam and the air spring in order to maintain a desired ride-height of the heavy-duty vehicle. A brake system of the heavy-duty vehicle may be mounted on the axle/suspension system, along with one or more shock absorbers that provide damping to the axle/suspension system, typically if a non-damping air spring is employed.

The axle/suspension system of the heavy-duty vehicle acts to provide ride, handling, and damping characteristics. For example, as the heavy-duty vehicle is traveling over the road, its tires and wheels encounter road conditions that impart various forces, loads, and/or stresses, collectively referred to as forces, to the respective axle on which the tires and wheels are mounted. In turn, the forces are transferred to the suspension assemblies that connect with and support the axle. In order to minimize the detrimental effect of these forces on the heavy-duty vehicle as it is operating, the axle/suspension system is designed to react and/or absorb at least some of the forces.

These forces include vertical forces caused by vertical movement of the tires and wheels as they encounter certain road conditions, fore-aft forces caused by acceleration and deceleration of the vehicle, and lateral and torsional forces associated with transverse vehicle movement, such as turning of the vehicle and lane-change maneuvers. In order to address the application of such different forces, axle/suspension systems have differing structural and operational requirements. The axle/suspension system often needs to be fairly stiff to minimize the amount of sway experienced by, and provide roll stability to, the heavy-duty vehicle. The axle/suspension system also often needs to be relatively flexible to assist in cushioning the vehicle from vertical forces. This provides compliance, allowing the components of the axle/suspension system to withstand the forces and allowing damping of the vibrations or oscillations resulting from such forces. As a result, the axle/suspension system often requires critical components, such as air springs and/or shock absorbers, to cushion the ride of the vehicle from vertical impacts and provide damping characteristics.

Air springs of the type utilized in heavy-duty axle/suspension systems typically include a flexible bellows mounted to the frame and operatively connected to a piston mounted to the beam. Shock absorbers of the type utilized in heavy-duty axle/suspension systems are typically mounted on and extend between the elongated beam and the hanger or the frame of the heavy-duty vehicle and include a cylinder and a piston rod reciprocating within the cylinder. Both air springs and shock absorbers have structural limitations, which limit their ability to extend with downward pivotal movement of the axle.

During operation, the heavy-duty vehicle may strike a pothole or may be lifted onto a railroad car, resulting in the beam of the suspension assembly pivoting or rotating downwardly about the hanger. Similarly, when the heavy-duty vehicle, such as a trailer, is reversing, the trailer brakes may be actuated, referred to as reverse braking, causing the suspension assembly to extend downwardly. In such situations, the air spring and/or shock absorber greatly extend or stretch between the beam and the frame. Both the air spring and shock absorber may be capable of limited extension. Thus, the air spring and/or shock absorber provides some restriction on the relative pivotal movement of the beam of the axle/suspension system. However, the air spring and shock absorber can be damaged if the tensile load produced by the extension exceeds the structural limitations of the air spring and/or shock absorber. As a result, the air spring, shock absorber, and/or other critical components of the axle/suspension system may be damaged. Thus, it is desirable for the axle/suspension system to minimize damage to such critical components. Specifically, it is desirable to limit pivotal movement of the beam about the hanger to prevent over-extension of the air spring and/or shock absorber.

In some heavy-duty vehicles, devices that operate in tension, such as chains, straps, cables, wire ropes, or the like, have been used to minimize the possible damage to the air spring and/or shock absorber as a result of over-extension. These devices are generally disposed between the hanger or frame of the heavy-duty vehicle and the beam of the suspension assembly to act as positive mechanical limiting structures, or down stops. The devices limit the pivotal movement of the beam of the suspension assembly, reducing the extension or stretching that the air spring and/or shock absorber may experience. These devices minimize the possibility of potential damage to the air spring, shock absorber, and/or other components of the axle/suspension system. Because these devices are disposed beneath the heavy-duty vehicle, they may be exposed to road splash and debris that could damage the devices. The devices are often manufactured to be relatively robust in order to withstand the weight of and forces acting on the axle/suspension system. This results in the devices increasing the weight and cost of operating the heavy-duty vehicle while decreasing available space in the already limited undercarriage of the heavy-duty vehicle and axle/suspension system.

Thus, a need exists for an axle/suspension system for a heavy-duty vehicle that provides a positive mechanical down stop that is simple, durable, light weight, and compact and that limits pivotal movement of the beam to avoid potential damage to the air spring, shock absorber, and/or other components of the axle/suspension system during operation of the vehicle.

<CIT> suggests a semi-elliptical spring suspension system with automatic spring rate varying capacity. <CIT> suggests a zero spring rate suspension system using an air bag disposed at an end of a pivoting arm attached to a vehicle frame. <CIT> suggests a suspension system comprising a rocker having a pivot joint disposed at one end and a spring element at an opposite end, with an axle disposed therebetween. <CIT> suggests a suspension system comprising a control arm pivotable about a vehicle frame hanger at one end and having an axle disposed at the opposite end, with a spring element disposed therebetween. <CIT> suggests a leaf spring suspension system pivotably attached to a vehicle frame at either end thereof. <CIT> suggests a suspension system for a vehicle that includes at least one beam, a support spring extending between the vehicle frame and the support beam and a lift spring extending between a lift bracket welded to the beam and the vehicle frame. <CIT> suggests an auxiliary lift axle wheel assemblies for load carrying vehicles, in which an auxiliary axle and wheel assemblies carried by the vehicle can be moved down toward load-bearing engagement with the road surface when the vehicle is heavily loaded, or can be lifted upwardly away from the road surface when there is little or no load carried by the vehicle. <CIT> suggests an independent suspension unit for a vehicle which does not require an axle.

This summary is provided to introduce concepts that are in the description. This summary is not intended to identify key factors or essential features of the subject disclosure, nor is it intended to be used to limit the scope of the subject disclosure.

The axle/suspension system for a heavy-duty vehicle of the subject disclosure solves problems associated with prior art axle/suspension systems utilizing chain stops or other devices that operate in tension. The axle/suspension system of the subject disclosure provides a mechanical down stop for limiting the downward movement of the axle/suspension system while operating in a compression mode. The axle/suspension system of the subject disclosure provides a mechanical down stop that is positioned to be better protected from exposure to road splash and debris. The axle/suspension system of the subject disclosure provides a mechanical down stop that is more compact with fewer components, is less costly to manufacture, requires less assembly time and complexity, and is relatively lighter in weight than prior art down stops, reducing the weight of the heavy-duty vehicle and occupying less space in the undercarriage or axle/suspension system.

According to an aspect of the present invention an improved suspension assembly for a heavy-duty vehicle is provided as set forth in claim <NUM>.

The following description and drawings set forth certain illustrative aspects and implementations of the subject disclosure. These are indicative of a few of the various ways in which one or more aspects and implementations may be utilized. Further features of the subject disclosure will become apparent to those skilled in the art from reading the description with reference to the accompanying drawings, in which:.

Similar reference characters identify similar parts and directions throughout the drawings.

The present subject matter is described with reference to the drawings, in which like reference characters are used to refer to like components and constituents of orientation throughout the description. Exemplary details are set forth in order to provide an understanding of the subject disclosure. It will be understood, however, that the subject disclosure can be practiced without these specific details. It will also be understood that these specific details are not to be construed as limiting.

In order to better understand the axle/suspension system for a heavy-duty vehicle of the subject disclosure, a prior art trailing arm beam-type axle/suspension system <NUM> is illustrated in <FIG>. Reference is made generally to a trailing arm axle/suspension system for the purpose of convenience with the understanding that such reference includes beams which extend either rearward or frontward with respect to the front end of the heavy-duty vehicle. The prior art axle/suspension system is mounted to a pair of longitudinally-extending spaced-apart members of frame <NUM> of a heavy-duty vehicle (not shown). The axle/suspension system <NUM> generally includes a pair of laterally spaced suspension assemblies <NUM>. Because the suspension assemblies <NUM> are identical, for sake of clarity and brevity, only one of the suspension assemblies will be described.

The suspension assembly <NUM> includes a beam <NUM> that is pivotally connected to a hanger <NUM>. The beam <NUM> has an inverted general U-shape cross-section forming an open portion (not shown) between a pair of laterally spaced sidewalls <NUM> and a top portion <NUM>. The open portion of the beam <NUM> faces generally downward, or away from the frame <NUM> of the heavy-duty vehicle. A bottom plate <NUM> extends between and is attached to the lowermost ends of the sidewalls <NUM> by any suitable means, such as welding, to complete and close the bottom of the structure of the beam <NUM>. The beam <NUM> includes a front end portion <NUM> and a rear end portion <NUM>. The front end portion <NUM> has a pivotal connection <NUM>, such as a bushing assembly, as is known, to connect the beam with the hanger <NUM> for relative pivotal movement. A transversely extending axle <NUM> is received, supported by, and fixed to the beam <NUM> by suitable means, such as welding. The suspension assembly <NUM> also includes an air spring <NUM> mounted to and extending between the frame <NUM> and the rear end portion <NUM> of the beam <NUM>. The suspension assembly <NUM> may be supplied with a shock absorber (not shown) to provide damping, either solely or as a supplement to the air spring <NUM>, if the air spring has damping capabilities.

During operation of the heavy-duty vehicle, downward pivotal movement of the beam <NUM> and axle <NUM> may occur, such as when the axle/suspension system suddenly drops as a result of a pothole or other road hazard, reverse braking, or the trailer being lifted onto a railroad car. The air spring <NUM> and/or shock absorber may have some limited ability to restrict or prevent the beam <NUM> and axle <NUM> of the suspension system <NUM> from pivoting downward an excessive amount. However, the air spring <NUM> and shock absorber can be damaged if the tensile load produced by the extension exceeds the structural limitations of the air spring and/or shock absorber. As a result, the air spring <NUM>, the shock absorber, and/or other components of the axle/suspension system <NUM> may be damaged.

Thus, additional structure may be desirable or required in order to limit or prevent excessive downward movement of the beam <NUM> and axle <NUM> and overextension of and potential damage to the air spring <NUM>, the shock absorber, and/or other components of the axle/suspension system <NUM>. The additional structure is typically in the form of a chain <NUM>. Devices other than chains, such as straps, cables, wire ropes, and the like, may be similarly utilized. The chain <NUM> includes a bottom end portion <NUM>, a top end portion <NUM>, and a plurality of links <NUM>. The bottom end portion <NUM> attaches to the beam <NUM> by suitable means, such as a fastener <NUM>. The top end portion <NUM> is connected to a mounting bracket <NUM> by suitable means, such as a fastener <NUM>. The mounting bracket <NUM> is attached to the hanger <NUM> or the frame <NUM> by welding or other suitable means. The chain <NUM> acts in tension to limit the downward pivotal movement of the beam <NUM> of the suspension assembly <NUM>. The number, size, and dimension of links <NUM> establishes the range of the downward pivotal movement of the beam <NUM> permitted by the chain <NUM>. The chain <NUM> reaches its extensible limit before the air spring <NUM> or shock absorber extends beyond structural limitations. Thus, the chain <NUM> helps to prevent damage to the air spring, <NUM>, the shock absorber, and/or other components of the axle/suspension system <NUM>.

The prior art axle/suspension system <NUM>, while providing a mechanical stop that limits the pivotal movement of the beam <NUM> and axle <NUM>, has limitations, drawbacks, and disadvantages. The chain <NUM> of the prior art axle/suspension system <NUM> undesirably increases the weight and cost of operation of the heavy-duty vehicle and reduces the amount of space available in the undercarriage for other components. The chain <NUM> of the prior art axle/suspension system <NUM> is also exposed to and prone to damage from road splash and debris.

The improved axle/suspension system for a heavy-duty vehicle according to the subject disclosure overcomes the limitations, drawbacks, and disadvantages of the prior art axle/suspension system <NUM>. The axle/suspension system of the subject disclosure provides a cost-efficient, relatively simpler, lighter, and more compact mechanical down stop that is sheltered or better protected from road splash and debris.

An axle/suspension system for a heavy-duty vehicle <NUM> falling outside of the scope of the claims, but useful in understanding the present invention, is illustrated in <FIG>. The axle/suspension system <NUM> is typically mounted to, and supported by, longitudinally-extending and/or transversely-extending spaced-apart members of a frame <NUM> of the heavy-duty vehicle (not shown). The axle/suspension system <NUM> generally includes a pair of laterally spaced suspension assemblies <NUM>. Because the suspension assemblies <NUM> are identical, for the sake of clarity and brevity, only one of the suspension assemblies will be described, and it is understood that such description applies equally to all suspension assemblies <NUM>.

The suspension assembly <NUM> includes a hanger <NUM> made up of two hanger side portions (only one hanger side portion is shown for clarity and exemplary purposes in <FIG>) fixed to the frame <NUM>. The hanger <NUM> may be formed from a suitably thick and strong metal material, such as steel. The suspension assembly <NUM> includes a beam <NUM> pivotally connected to the hanger <NUM>. The beam <NUM> is illustrated in a trailing arm configuration, but may include other configurations, such as leading arm. The beam <NUM> may be formed from any suitable manufacturing method and material, such as bent plate steel. The beam <NUM> includes a top plate <NUM>, a pair of outboard and inboard sidewalls <NUM>, and a bottom wall <NUM>. Top plate <NUM>, sidewalls <NUM>, and bottom wall <NUM> may be separately formed out of any suitable rigid material, such as a metal, and joined by suitable means, such as welding. Alternatively, two or more of top plate <NUM>, sidewalls <NUM>, and bottom wall <NUM> may be formed as a single piece of steel and then bent to form two or more wall surfaces or a generally U-shaped structure to form three walls. In some configurations, top plate <NUM> and bottom wall <NUM> may overlap sidewalls <NUM>. The top plate <NUM>, sidewalls <NUM>, and bottom wall <NUM> may be formed from other materials, shaped or connected together in other ways, and/or even be formed from a single piece of composite material. The beam <NUM> also includes a front portion <NUM> and a rear portion <NUM>. A bottom wall <NUM> extends between sidewalls <NUM> to close the beam <NUM>. The front end portion <NUM> includes a pivotal connection <NUM>, such as a bushing assembly, as is known, to connect the beam <NUM> with the hanger <NUM> for relative pivotal movement, as is known. The beam <NUM> also may include an extension <NUM> located forward of the pivotal connection <NUM>. The extension <NUM> is on a side of the pivotal connection <NUM> opposite the front end portion <NUM>. The extension <NUM> may be a separate component permanently attached to the beam <NUM> by suitable means, such as welding. Alternatively, the extension <NUM> may be formed with the beam <NUM> as a single piece.

A transversely extending axle <NUM> (<FIG>) is received, supported by, and fixed to the beam <NUM> by suitable means, such as welding or fastening. The axle <NUM> is generally supported by an intermediate portion of the beam <NUM> extending rearward of the pivotal connection <NUM>. Specifically, the axle <NUM> is supported by a portion of the beam <NUM> between the pivotal connection <NUM> and the rear end portion <NUM>. In the alternative, the axle <NUM> may be supported by a portion of the beam <NUM> adjacent to, or rearward of, the rear end portion <NUM>.

The suspension assembly <NUM> also includes an air spring <NUM> mounted to and extending between the frame <NUM> and the rear end portion <NUM> of the beam <NUM>. The suspension assembly <NUM> may be supplied with a shock absorber (not shown) to provide damping. Alternatively, the air spring <NUM> may be designed and constructed to provide damping characteristics. As a result, the air spring <NUM> may work in conjunction with, or eliminate the need for, the shock absorber.

The suspension assembly <NUM> also includes a new and improved down stop assembly <NUM>. The down stop assembly <NUM> includes a bumper <NUM> and an engagement member <NUM>. The bumper <NUM> is mounted to the extension <NUM> of the beam <NUM>, such that it extends generally upwardly from the extension and is, thus, shielded from road splash and debris. Alternatively, the bumper <NUM> may be mounted to any of the beam <NUM>, the frame <NUM>, or the hanger <NUM>. The bumper <NUM> may be an existing structure of any of the frame <NUM>, the hanger <NUM>, and the beam <NUM>. The bumper <NUM> may be formed from any material with sufficient rigidity and durability, such as synthetic polymers, elastomers, rubbers, or composites. It is to be understood that bumper <NUM> may also be formed of metal or metal composite materials. The bumper <NUM> may be generally cylindrical or frustoconical in shape and may include a centralized depression or opening through which a fastener (not shown) may be inserted to attach the bumper to the extension <NUM>. Alternatively, other appropriate connectors or attachment means may be used to attach the bumper <NUM> to the extension <NUM>.

A lift bag <NUM> (<FIG>) may be used in place of the bumper <NUM>. Alternatively, the bumper <NUM> may be used in conjunction with the lift bag <NUM>, as shown. The lift bag <NUM> may be attached to the bumper <NUM> or adjacent the bumper and frame <NUM>, and extend between the bumper and components associated with the hanger <NUM> and/or the frame of the heavy-duty vehicle. The lift bag <NUM> may be operatively connected to a ride-height control valve (not shown) and the air spring <NUM>. This would allow the lift bag <NUM> and bumper <NUM> to act as a suspension assembly lift mechanism capable of altering the ride-height of the axle/suspension system <NUM>.

The engagement member <NUM> may be a separate component, such as a structure or surface, attached to the hanger <NUM>, the frame <NUM>, the beam <NUM>, or the extension <NUM>. Depending on the arrangement of the bumper <NUM> and suspension assembly <NUM>, the engagement member <NUM> may be an existing component of the frame <NUM>, the hanger <NUM>, or the beam <NUM>. The engagement member <NUM> includes a surface <NUM> for the bumper <NUM> to engage and restrict pivotal movement of the beam <NUM> and axle <NUM> about the pivotal connection <NUM>. The configuration and relative positioning of the bumper <NUM> and the engagement member <NUM> determines the range of pivotal movement of the beam <NUM> and the axle <NUM>. Specifically, downward pivotal movement of the beam <NUM> and axle <NUM> may be restricted a predetermined amount, such as to about <NUM>°, or about <NUM> inches from a ride-height of the heavy-duty vehicle. However, it is contemplated that the bumper <NUM> and/or engagement member <NUM> may allow for adjustment in order to provide a customized amount of pivotal movement of the beam <NUM> and the axle <NUM> for a particular heavy-duty vehicle application.

As illustrated in <FIG>, the bumper <NUM> is spaced apart from, or not in contact with, the engagement member <NUM> or any component of the hanger <NUM> or the frame <NUM> of the heavy-duty vehicle when the beam <NUM> and axle <NUM> are at a typically neutral ride-height. As the beam <NUM> and axle <NUM> pivot downward in the direction D (<FIG>) and approach their downward travel limit, the extension <NUM> correspondingly pivots upward in the direction U about the pivotal connection <NUM>. As illustrated in <FIG>, this results in the bumper <NUM> engaging the surface <NUM> of the engagement member <NUM> or other components (not shown) associated with the frame <NUM> or the hanger <NUM>. This contact with the surface <NUM> restricts downward pivotal movement of the beam <NUM> and axle <NUM> about the pivotal connection <NUM>. As a result, the limited pivotal movement of the beam <NUM> and axle <NUM> helps prevent over-extension of, and avoid potential damage to, the air spring <NUM> and/or other components of the axle/suspension system <NUM> when the heavy-duty vehicle is lifted onto a railroad car, undergoes reverse braking, or strikes a pothole or other road hazard.

An axle/suspension system for a heavy-duty vehicle <NUM>, according to an aspect of the invention, is illustrated in <FIG>. The axle/suspension system <NUM> is mounted to a pair of longitudinally-extending and/or transversely-extending spaced-apart members of a frame <NUM> of a heavy-duty vehicle (not shown). The axle/suspension system <NUM> generally includes a pair of laterally spaced suspension assemblies <NUM>. Because the suspension assemblies <NUM> are identical, for the sake of clarity and brevity only one of the suspension assemblies will be described.

The suspension assembly <NUM> includes a hanger <NUM> made up of two hanger side portions (only one hanger side portion is shown for clarity and exemplary purposes in <FIG>) fixed to the frame <NUM>. The hanger <NUM> may be formed from a suitably thick and strong metal material, such as steel. A beam <NUM> is pivotally connected to the hanger <NUM>. The beam <NUM> includes a top plate <NUM>, a pair of outboard and inboard sidewalls <NUM>, and a bottom wall <NUM>. Top plate <NUM>, sidewalls <NUM>, and bottom wall <NUM> may be separately formed out of any suitable rigid material, such as a metal. Alternatively, two or more of top plate <NUM>, sidewalls <NUM>, and bottom wall <NUM> may be formed as a single piece of steel and then bent to form two or more wall surfaces or a generally U-shaped structure to form three walls. In some configurations, top plate <NUM> and bottom wall <NUM> may overlap sidewalls <NUM>. The top plate <NUM>, sidewalls <NUM>, and bottom wall <NUM> may be formed from other materials, shaped or connected together in other ways, and/or even be formed from a single piece of composite material. The beam <NUM> also includes a front end portion <NUM> and a rear end portion <NUM>. The front end portion <NUM> includes a pivotal connection <NUM>, such as a bushing assembly, as is known, to connect the beam <NUM> with the hanger <NUM> for relative pivotal movement. The beam <NUM> also includes an extension <NUM> located forward of the pivotal connection <NUM> on a side of the bushing assembly opposite the front end portion <NUM>. The extension <NUM> may be a separate component that is fixed to the beam <NUM> by suitable means, such as welding. Alternatively, the extension <NUM> may be formed with the beam <NUM> as a single piece.

A transversely extending axle <NUM> is received, supported by, and is fixed to the beam <NUM> by suitable means, such as welding or fastening. The axle <NUM> is supported by an intermediate portion of the beam <NUM> located rearward of the pivotal connection <NUM>. Specifically, the axle <NUM> may be supported by the intermediate portion of the beam <NUM> between the pivotal connection <NUM> and the rear end portion <NUM>. In the alternative, the axle <NUM> may be supported by a portion of the beam <NUM> at the rear end portion <NUM>.

The suspension assembly <NUM> also includes an air spring <NUM> mounted to, and extending between, the frame <NUM> and the rear end portion <NUM> of the beam <NUM>. The suspension assembly <NUM> may be supplied with a shock absorber (not shown) to provide damping. Alternatively, the air spring <NUM> may be designed and constructed to provide damping characteristics, and used with or without one or more shock absorbers.

The suspension assembly <NUM> also includes a new and improved down stop assembly <NUM>. The down stop assembly <NUM> includes a bumper <NUM>. The bumper <NUM> is mounted to the extension <NUM> of the beam <NUM>, such that it extends generally upwardly from the extension and is, thus, shielded from, road splash and debris. The bumper <NUM> may be formed from any material with sufficient rigidity and durability, such as synthetic polymers, elastomers, rubbers, or composites. It is to be understood that bumper <NUM> may also be formed of metal or metal composite materials. The bumper <NUM> is generally cylindrical or frustoconical in shape and may include a centralized depression or opening through which a fastener (not shown) may be inserted to attach the bumper to the extension <NUM>. Alternatively, other appropriate connectors or attachment means may be used to attach the bumper <NUM> to the extension <NUM>. It is contemplated that a lift bag (not shown) may be used in place of the bumper <NUM>. Alternatively, the bumper <NUM> may be used in conjunction with the lift bag.

The down stop assembly <NUM> also includes an engagement member <NUM>. The engagement member <NUM> is a separate component, such as a structure or surface, fixed to a portion of the hanger 242The engagement member <NUM> may be formed by any suitable process from any suitable material. Specifically, the engagement member <NUM> may be a bracket formed from bent sheet steel. The engagement member <NUM> may be disposed between, and attached to, one or more of the walls of the hanger <NUM> by any suitable means, such as fasteners or welds. Thus, the engagement member may be at least partially sheltered or protected by the hanger <NUM> and/or frame <NUM> of the heavy-duty vehicle. The engagement member <NUM> includes a surface <NUM> for contacting the bumper <NUM> to restrict pivotal movement of the beam <NUM> and axle <NUM>. The configuration and relative positioning of the bumper <NUM> and the engagement member <NUM> determines the range of pivotal movement of the beam <NUM> and the axle <NUM>. Specifically, downward pivotal movement of the beam <NUM> and axle <NUM> may be restricted to about <NUM>°, or about <NUM> inches from a ride-height of the heavy-duty vehicle. It is further contemplated that the bumper <NUM> and/or engagement member <NUM> may be adjustable to allow for customized pivotal movement of the beam <NUM> and axle <NUM> for a particular heavy-duty vehicle application.

As illustrated in <FIG>, the bumper <NUM> is spaced apart from, or not in contact with, the engagement member <NUM> or any component of the hanger <NUM> and/or the frame <NUM> of the heavy-duty vehicle when the beam <NUM> and axle <NUM> are at neutral ride-height. As illustrated in <FIG>, as the beam <NUM> and axle <NUM> pivots downward in the direction D' (<FIG>), the extension <NUM> pivots upward in the direction U', and the bumper <NUM> contacts and engages the surface <NUM> of the engagement member <NUM> or a component associated with the frame <NUM> and/or the hanger <NUM>. The contact with the surface <NUM> restricts downward pivotal movement of the beam <NUM> and axle <NUM> about the pivotal connection <NUM>. As a result, the limited pivotal movement of the beam <NUM> and axle <NUM> may prevent over-extension of, and avoid potential damage to, the air spring <NUM> and/or other components of the axle/suspension system <NUM> when the heavy-duty vehicle is lifted onto a railroad car, undergoes reverse braking, or strikes a pothole or other road hazard.

Accordingly, the axle/suspension system <NUM>, <NUM> provides a new and improved, simple positive down stop assembly <NUM>, <NUM> that requires fewer components and is effective, inexpensive, lightweight, and overcomes the disadvantages, drawbacks, and limitations of prior art axle/suspension systems. The axle/suspension system <NUM>, <NUM> also provides a down stop assembly <NUM>, <NUM> that is cost-efficient, relatively simpler, lighter, more compact, and protected from road splash and debris. Moreover, it is understood that, unlike the prior art down stops, the new and improved down stop assembly <NUM>, <NUM> functions when exposed to compressive force rather than tension to limit downward pivotal movement of the beam <NUM>, <NUM> and axle <NUM>, <NUM>.

In the description, certain terms have been used for brevity, clarity and understanding. No unnecessary limitations are to be implied from those terms beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. The description and illustration of the subject disclosure is by way of example, and the scope of the subject disclosure is not limited to the exact details shown or described. The axle/suspension systems <NUM>, <NUM> of the subject disclosure could be utilized on heavy-duty trucks, trailers, buses, and the like without changing the overall concept or operation. The suspension assembly <NUM>, <NUM> of the subject disclosure could be utilized on all types of axle/suspension systems, including those having either a trailing arm or leading arm configuration, without changing the overall concept or operation. The axle/suspension system <NUM>, <NUM> of the subject disclosure could be made from other materials, have different shapes, sizes, or could be utilized on various types of heavy-duty vehicle frames or sub-frames that mount axle/suspension systems without changing the overall concept or operation.

Certain terminology is used for purposes of reference only and is not intended to be limiting. For example, terms such as "downward" refer to directions in the drawings to which reference is made. Terms such as "front", "rear", "downward", "upward", "forward", "rearward", "longitudinal", and "transverse", describe the orientation of portions of a component within a reference to the text and the associated drawings describing the subject under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms "first", "second", and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context.

Claim 1:
A suspension assembly (<NUM>) for a heavy-duty vehicle, the suspension assembly configured to be supported by a frame (<NUM>) of the heavy-duty vehicle, the suspension assembly comprising:
a hanger (<NUM>) made up of two hanger side portions configured to be fixed to the frame (<NUM>);
a beam (<NUM>) including a top plate (<NUM>), a pair of outboard and inboard sidewalls (<NUM>) and a bottom wall(<NUM>), the beam having a front end portion (<NUM>), a rear end portion (<NUM>) and an extension (<NUM>), the front end portion (<NUM>) being operatively connected to the hanger (<NUM>) at a pivotal connection (<NUM>);
an axle (<NUM>) supported by the front end portion (<NUM>) of the beam (<NUM>) for pivotal movement relative to the hanger (<NUM>) at the pivotal connection (<NUM>), the front end portion (<NUM>) of the beam (<NUM>) being located on a first side of the pivotal connection (<NUM>);
an air spring (<NUM>) configured to be connected to the frame (<NUM>) and to the rear end portion (<NUM>) of the beam (<NUM>); and
a bumper (<NUM>) or lift bag fixed to the extension (<NUM>) of the beam (<NUM>), the extension of the beam located on an opposite, second side of the pivotal connection to the front end portion, the bumper (<NUM>) or lift bag having a portion for contacting an engagement member (<NUM>) fixed to the hanger (<NUM>) to limit relative pivotal movement of the beam (<NUM>) and the axle (<NUM>) in one direction, the configuration and relative positioning of the bumper (<NUM>) or lift bag and the engagement member (<NUM>) determining the range of pivotal movement of the beam (<NUM>), the bumper (<NUM>) or lift bag functioning to limit the pivotal movement of the axle when exposed to compressive force in the one direction, the bumper (<NUM>) or lift bag being spaced apart from the engagement member (<NUM>) when the beam (<NUM>) and axle (<NUM>) are at neutral ride-height.