Dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle

A dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle including a housing having two axially elongated members. A dual rate spring package is disposed in the housing. Such spring package includes a first spring assembly for absorbing, dissipating and returning a first predetermined level of energy imparted to the shock absorbing apparatus. One end of the first spring assembly acts against a closed end of the housing and a second end acts against a spring seat. A second spring assembly absorbs, dissipates and returns a second predetermined level of energy. One end of the second spring assembly acts against an opposed closed end of the housing and a second end acts against the spring seat. An axially elongated guide assembly, extending substantially the cumulative length of the first and second spring assemblies, controls axial compression of the first and second spring assemblies. An operable length of the guide assembly is automatically adjustable to the length of the housing during operation of the shock absorbing apparatus. An apparatus for monitoring loads applied to the shock absorbing apparatus is also provided.

FIELD OF THE INVENTION DISCLOSURE

The present invention disclosure generally relates to heavy off-road vehicles and, more particularly, to a dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle.

BACKGROUND OF THE INVENTION DISCLOSURE

Heavy off-road vehicles or trucks which are designed to carry heavy loads of cargo typically include a wheeled frame and a truck body portion supported by the frame. The truck body portion of such vehicles can carry loads in the range of 35 to 300 tons. Out of necessity, such vehicles employ some sort of shock absorbing device as part of the suspension system.

During operation, such vehicles operate in either of two conditions: empty or loaded. In these applications, the difference in weight or load acting on the vehicle suspension system can be quite substantial and a single element suspension system will perform poorly in one or the other condition. In the 1990's there was a change in the industry regarding suspension design. The OEM's all perceived a need and desire for better ride quality with an emphasis on when the vehicle was operating in an empty condition. It is most desirable to the vehicle driver to have a suspension system which offers a relatively soft ride when the load is at a minimum but yet is stiffer when the supported load is at a maximum whereby improving load stability.

Moreover, the OEM's of such vehicles desired the ability to monitor and record the actual loads being carried in the truck body portion of each vehicle. As such, it would be possible to optimize the amount of loading of the vehicle and thereby increase component life, maximize productivity and monitor vehicle activities, i.e., rough road conditions, and the like.

Thus, there is a continuing need and desire for a dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle which works in a first or relatively soft condition when the supported load is at a minimum and a second relatively stiff condition when the supported load being carried by the vehicle is significantly greater. Moreover, there is a continuing need and desire for such a dual rate shock absorbing apparatus for a off-road heavy duty vehicle suspension system which has the ability to monitor and provide an indication of the loads acting on the suspension system.

SUMMARY OF THE INVENTION DISCLOSURE

In view of the above, and in accordance with one aspect, there is provided a dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle. Such shock absorbing apparatus includes a housing having an axially elongated outer member and an axially elongated inner member. Each housing member has a closed end and an open end. Moreover, structure is provided toward the closed end of each housing member for facilitating connection of the shock absorbing apparatus between two parts on the vehicle. Lengthwise portions of the open ends of the inner and outer housing members are arranged in sliding relation relative to each other in response to loads being exerted on the absorbing apparatus.

A dual rate spring package is disposed in the housing to provide superior suspension performance when the vehicle is operated in either empty or loaded conditions. Such spring package includes a first or “soft” elastomeric spring assembly for absorbing, dissipating and returning a first predetermined level of energy imparted to the shock absorbing apparatus when the closed ends of the housing members are compressed toward each other within a predetermined range of axial movement. One end of the first spring assembly acts against a closed end of the inner housing and a second end acts against a spring seat. A second elastometic spring assembly is provided for absorbing, dissipating and returning a second predetermined level of energy, different from the first predetermined level of energy, imparted to the shock absorbing apparatus when the closed ends of the housing members are compressed toward each other. One end of the second spring assembly acts against a closed end of the outer housing and a second end acts against the spring seat disposed between opposed ends of the spring assemblies. An axially elongated guide assembly, extending substantially the cumulative length of the first and second spring assemblies, is provided for controlling compression of the spring assemblies. An operable length of the guide assembly is automatically adjustable to the length of the housing during operation of the shock absorbing apparatus.

Preferably, the elongated guide assembly of the shock absorbing apparatus axially extends generally centrally through the first and second spring assemblies and the spring seat. In one form, the elongated guide assembly of the shock absorbing apparatus includes two axially elongated guides arranged in at least partially telescoping relation relative to each other.

In one form, a follower is carried on and moves with the inner housing member. After the “soft” spring assembly has been compressed a predetermined amount, the follower on the inner member “bottoms out” and engages with the spring seat so as to allow the shock absorbing apparatus to transition operation between when the vehicle operates in an empty or unloaded condition and a loaded condition.

In one embodiment, the shock absorbing apparatus further includes a stop for inhibiting inadvertent axial separation of the housing members relative to each other. In a preferred form, the shock absorbing apparatus further includes structure for guiding and aligning the outer housing member and inner housing member relative to each other.

The shock absorbing apparatus is preferably designed to further include an apparatus for monitoring compressive loads applied to the shock absorbing apparatus during operation of the vehicle. In one form, the apparatus for monitoring compressive loads includes a load cell capable of monitoring and providing an electric signal indicative of the load applied to the shock absorbing apparatus. In another form, the apparatus for monitoring compressive loads includes a piston head slidably sealed to an inner periphery of at least one of the inner and outer members such that a pressurized fluid chamber is defined between the piston head and the closed end of the at least one of the inner and outer members. The piston head is operably coupled to and movable with the guide of the respective spring assembly. A device is provided for monitoring and producing an electric signal indicative of the level of pressure in the chamber. In one form, the device for monitoring the level of pressure in the chamber includes a pressure transducer.

According to another aspect, there is provided a dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle including an axially elongated housing having first and second axially spaced ends. Each end of the housing has structure for facilitating connection of the shock absorbing apparatus operably between first and second body parts on the vehicle. The housing includes an axially elongated inner member having a closed end and an open end and an axially elongated outer member having a closed end and an open end. Lengthwise portions of the open ends of the inner and outer members are arranged in sliding relation relative to each other. An axially elongated elastomeric spring assembly is arranged within an interior chamber defined by the housing between the closed ends of the inner and outer housing members. The spring assembly includes a first elastomeric spring assembly for absorbing, dissipating and returning a first predetermined level of energy imparted to the shock absorbing apparatus when the housing members are axially compressed toward each other within a predetermined range of axial movement. A second elastomeric spring assembly is provided for absorbing, dissipating and returning a second predetermined level of energy after the first predetermined level of energy imparted to the shock absorbing apparatus is exceeded. A spring seat is disposed between the first and second elastomeric spring assemblies. An axially elongated guide assembly substantially extends a cumulative length of and generally centrally through the first and second spring assemblies for controlling axial compression of the first and second spring assemblies. An operable length of the guide assembly is automatically adjustable to the length of the housing during operation of the shock absorbing apparatus.

Preferably, the elongated guide assembly axially includes two axially elongated guides arranged in at least partially telescoping relation relative to each other. In a preferred form, the shock absorbing apparatus further includes a follower arranged between the spring seat and the closed end of the inner housing member for moving with the inner housing member in response to axial loads being exerted upon the shock absorbing apparatus. In one embodiment, the shock absorbing apparatus further includes a stop for inhibiting inadvertent axial separation of the housing members relative to each other. In another form, the shock absorbing apparatus further includes structure for guiding and aligning the housing members relative to each other and about a central axis of the shock absorbing apparatus. The structure for guiding and aligning the housing members preferably includes at least two axially spaced bushings.

In one embodiment, the shock absorbing apparatus further includes an apparatus for monitoring compressive loads applied to the shock absorbing apparatus during operation of the heavy off-road vehicle. In one form, the apparatus for monitoring compressive loads includes a load cell arranged toward the closed end of the outer housing member for monitoring and providing a signal indicative of the load applied to the shock absorbing apparatus. In another form, the apparatus for monitoring compressive loads includes a piston head slidably sealed to an inner periphery of the outer member such that a pressurized fluid chamber is defined between the piston head and the closed end of the outer member. The piston head is operably coupled to and movable with the guide of the first spring assembly. A device is provided for monitoring the level of pressure in the fluid chamber. Preferably, such device is further capable of generating a signal indicative of the level of pressure in the chamber. In one form, the device for monitoring the level of pressure in the chamber includes a pressure transducer.

According to another aspect, there is provided a dual rate shock absorbing apparatus for a suspension system of a heavy off-road vehicle and including a housing with an axially elongated outer generally cylindrical member having a closed end and an open end, and with the closed end of the outer member having structure for facilitating connection of the housing to a first body part on the vehicle. The housing further includes an axially elongated generally cylindrical inner member having a closed end and an open end, and with lengthwise portions of the open ends of the inner and outer generally cylindrical members being arranged in telescopic relation relative to each other. The closed end of the inner member has structure for facilitating connection of the housing to a second body part on the vehicle. Structure is disposed between the lengthwise portions of the inner and outer members for effecting guidance and alignment of the housing members relative to each other. Moreover, a spring seat is arranged in an interior chamber defined by the inner and outer members of the housing.

In this embodiment, a dual rate spring is arranged in the interior of the housing. The dual rate spring includes a first spring assembly for allowing the shock absorbing apparatus to yield a first spring rate when the housing members are compressed toward each other within a predetermined range of axial movement. One end of the first spring assembly acts against a closed end of the inner housing and a second end acts against the spring seat. The first spring assembly includes a series of stacked spring pads. Each pad has an elastomeric member with a torodial configuration sandwiched between two plates. The series of axially stacked spring pads of the first spring assembly are axially guided by an elongated guide.

The dual rate spring also includes a second spring assembly for allowing the shock absorbing apparatus to yield a second spring rate when the first spring rate of the first spring assembly is exceeded. One end of the second spring assembly acts against a closed end of the outer housing and an axially aligned second end acts against the spring seat. The second spring assembly includes a series of axially stacked spring pads. Each pad includes an elastomeric member having a torodial configuration sandwiched between two plates. The series of axially stacked spring pads are axially guided by an elongated member axially extending substantially the length of the second spring assembly. A free end of the guide of the first spring assembly is arranged in telescoping relation with the elongated member of the second spring assembly such that axial alignment is maintained between the spring assemblies during compression of the shock absorbing apparatus.

In one form, the shock absorbing apparatus further includes a follower carried by and movable with the inner housing member. The follower is arranged between the closed end of the outer housing member and the spring seat. Preferably, the shock absorbing apparatus further includes a stop for inhibiting inadvertent axial separation of the housing members.

Preferably, the shock absorbing apparatus further includes an apparatus for monitoring compressive loads applied to the shock absorbing apparatus during operation of the heavy off-road vehicle. In one form, the apparatus for monitoring compressive loads includes a load cell arranged toward the closed end of the outer housing member for monitoring and providing a signal indicative of the load applied to the shock absorbing apparatus. In another form, the apparatus for monitoring compressive loads includes a piston head slidably sealed to an inner periphery of the outer member such that a pressurized fluid chamber is defined between the piston head and the closed end of the outer member. The piston head is operably coupled to and movable with the guide of the second spring assembly. A device is provided for monitoring the level of pressure in the chamber. Such device is also capable of generating an electrical signal indicative of the level of pressure in the chamber. In one form, such device for monitoring the level of pressure in the chamber includes a pressure transducer.

DETAILED DESCRIPTION OF THE INVENTION DISCLOSURE

While this invention disclosure is susceptible of embodiment in multiple forms, there is shown in the drawings and will hereinafter be described preferred embodiments, with the understanding the present disclosure sets forth exemplifications of the disclosure which are not intended to limit the disclosure to the specific embodiments illustrated and described.

Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views, there is shown inFIG. 1a heavy off-road self-propelled vehicle capable of carrying and transporting cargo in the range of 30 to 300 tons. Such vehicle is generally identified by reference numeral10and essentially includes two groups of components. The first is the main frame12which includes generally the frame, the cab, engine, and etc. The other main component14includes the axle system, tires, drive mechanism, and etc. Between these two main groups of components is a suspension system including, toward a rear of the vehicle, at least two shock absorbing mechanisms20. For all practical purposes, the shock absorbing mechanisms20are essentially the same and, therefore, discussion will be limited to one shock absorbing apparatus or mechanism, with the understanding that it applies to the other shock absorbing apparatus arranged toward the rear of vehicle10.

Turning toFIGS. 2 and 3, each shock absorbing apparatus20includes an axially elongated multipiece housing30defining a longitudinal axis32extending between first and second ends34and36, respectively. Housing30includes a first or outer axially elongated member40and a second or inner axially elongated member60. In a preferred form, each housing member40,60has a generally cylindrical configuration. Lengthwise portions of the housing members40and60are slidingly arranged, at least partially, in telescopic relation relative to each other. As shown inFIGS. 2,3and4, housing member40includes structure42for pivotally or articulately securing the first end34of shock absorbing apparatus20to one group of components on the vehicle10(FIG. 1). As shown inFIGS. 2,3and5, housing member60preferably includes structure62for pivotally or articulately securing the second end36of the shock absorbing apparatus20to the other group of components on the vehicle10(FIG. 1). Structures42and62can be of any suitable design and construction from that shown without detracting or departing from the spirit and scope of the invention disclosure. Moreover, any suitable connector can be employed, and in the example illustrated, a pin18is used to operably interconnect the ends34and36of the shock absorbing apparatus20to the vehicle10(FIG. 1).

Turning toFIG. 6, housing member40has a closed end43and an axially aligned open end45with a generally cylindrical body portion44extending therebetween. The closed end43and body portion44of member40combine to define a generally cylindrical blind cavity46opening only to the open end45of housing member40and having an inner periphery46′. As shown, the structure42for facilitating connection of the shock absorbing apparatus20to vehicle10(FIG. 1) is operably carried toward the closed end43of housing member40.

As further illustrated inFIG. 6, housing member60has a closed end63and an axially aligned open end65with a generally cylindrical body portion64extending therebetween and which defines a generally cylindrical blind cavity66opening only to the open end65of housing member60. Extending away from the open end65, housing member60preferably has a relatively high surface finish on the exterior surface66′ of member60. In the preferred form, lengthwise portions of the open ends45and65of housing members40and60, respectively, are arranged in telescopic sliding relation relative to each other such that the cavities46and66of the housing members40and60, respectively, combine to define a closed space67within housing30. As shown, the structure62for facilitating connection of the shock absorbing apparatus20to the vehicle10(FIG. 1) is operably carried toward the closed end63of housing member40.

Toward its free open end45, housing40furthermore preferably includes a stop47for inhibiting inadvertent axial separation of the housing members40and60relative to each other during operation of the shock absorbing apparatus20. In the embodiment shown by way of example inFIG. 7, stop47is preferably configured as a ring48which extends radially inward toward the outer periphery of housing member60and is releasably attached toward the open end45of housing member40by a series of suitable fasteners49. Ring48defines an annular shoulder50which acts as part of a stop for limiting inadvertent axial separating movements of the housing members40and60relative to each other. Preferably, ring48has an inner diameter51which is only slightly larger than the outer diameter66′ of the exterior of the open end65of housing member60. Preferably, an elastomeric ring52is carried by the ring48and acts as a wiper scraper along the exterior66′ of the open end65of housing member60which is telescopically received within the open end45of housing member40.

Each shock absorbing apparatus20furthermore preferably includes structure54for effecting guidance and alignment between those axial lengthwise portions of the housing members40and60arranged in generally telescopic relation relative to each other. As shown inFIG. 7, one portion of structure54includes an annular bushing56carried by ring48such that bushing56slides along that portion of the outer periphery66′ of housing member60arranged in telescopic and sliding relation relative to housing member40.

As shown inFIGS. 6 and 7, an annular follower68is provided toward the open end65of housing member60. Suffice it to say, the follower68moves with and in response to axial movements of housing member60. In a preferred embodiment, follower68is releasably secured toward the open end65of housing60with a series of suitable fasteners69. As shown inFIG. 7, a portion of follower68extends radially outward beyond the outer diameter of the open end65of housing member60and defines an annular shoulder70which acts as another part of the stop for limiting axial separating movements of the housing members40and60relative to each other. In the embodiment shown, follower68has an outer diameter71which is only slightly less than the inner diameter of the open end45of housing member40. Preferably, an annular elastomeric ring or cushion72is arranged between the annular shoulder50on ring48and the annular shoulder70on the follower68for dissipating impacts which may occur therebetween.

As further shown inFIG. 7, another portion of structure54includes an annular bushing76carried by and movable with follower68. During operation of the shock absorbing apparatus10, the annular bushing76on housing member40operably combines with the axially spaced annular bushing56on ring48to effect guidance and alignment of the housing members40and60relative to each other and relative to the central axis32of housing30.

Each shock absorbing apparatus20furthermore includes a dual rate spring assembly80axially disposed within the closed space67of the shock absorbing apparatus housing30. The dual rate spring assembly80includes a first axially elongated elastomeric spring assembly82arranged in stacked relation and operable in series with a second axially elongated elastomeric spring assembly92. As such, the spring assembly80permits the vehicle suspension system to function in: 1) an empty load condition; or, 2) a loaded condition.

As shown inFIG. 6, the axially elongated elastomeric spring assembly92is primarily disposed within housing member60for absorbing, dissipating and returning a first predetermined level of energy imparted or applied to the shock absorbing apparatus20when the ends34and36of housing30are axially compressed toward each other within a predetermined range of axial movement. After apparatus20is assembled and is arranged in operable combination with vehicle10(FIG. 1), one end of spring assembly92acts against the closed end63of housing member60. A second end of spring assembly92acts against a spring seat or transition plate84preferably disposed for movements within the closed space67of housing30between the opposed ends of spring assemblies82and92. More specifically, the spring seat84is disposed between the closed end43of housing member40and the follower68.

In an unloaded condition, and in the embodiment shown inFIGS. 6 and 7, the design and action of spring assembly92positions the spring seat or transition plate84in axially spaced relation from the follower68carried by, housing member60. That is, during one phase of operation of apparatus20, a predetermined axial distance or gap PD separates the follower plate68, carried by housing member60, from the spring seat or transition plate84. This design allows the elastomeric spring assembly92of spring assembly80to function when the vehicle10(FIG. 1) is operated in an empty condition and protects spring assembly92against damage when the vehicle is operated in a loaded condition.

The other spring assembly82of the dual rate spring assembly80is axially disposed within housing member40in series with the first spring assembly92for absorbing, dissipating and returning a second predetermined level of energy, different from than the first predetermined level of energy, imparted or applied to the shock absorbing apparatus20when the ends34and36of housing30are axially compressed toward each other. Notably, spring assembly82functions when the first predetermined level of energy imparted to the shock absorbing apparatus20, is exceeded, i.e. during loaded conditions for the vehicle10. As shown inFIG. 6, and after apparatus10is assembled and in arranged in operable combination with vehicle10(FIG. 1), one end of spring assembly82acts against the closed end43of housing member40. A second end of spring assembly82acts against the spring seat84.

Each spring assembly82,92has a multi-tiered construction including a series of longitudinally stacked elastomeric spring pads, generally identified by reference numeral94. As shown inFIG. 8, each spring pad94has an elastomeric member95sandwiched between two metal plates96,96′. Each plate96,96′ is operably secured to opposed ends or load faces97,97′ of the elastomeric member95. Any suitable means may be employed to accomplish the physical juncture between the elastomeric member95and each plate96,96′. In the form shown, each elastomeric member95has a donut-like or torodial configuration whereby minimizing the cross-sectional space of each spring pad. Preferably, the pads94are formed using the process and methodology disclosed in U.S. Pat. No. 5,351,844 to R. A. Carlstedt; the applicable portions of which are incorporated herein by reference. Suffice it to say, the elastomeric member95is preferably formed from a copolyester polymer elastomer such as that manufactured and sold by DuPont under the tradename “HYTREL” and the art known equivalents thereto with the resultant spring having a plastic strain to elastic strain ratio greater than 1.5 to 1. In a preferred form, member95of each spring pad94has a durometer hardness of about 55 on the D Scale.

Although spring assemblies82and92are generally equally compressible during operation of the shock absorbing apparatus20, the spring pads94comprising spring assembly92are designed to function for the loads typically incurred or encountered in an empty condition for vehicle10(FIG. 1). That is, the spring pads94comprising spring assembly92have a lower aspect ratio than the spring pads94comprising spring assembly82. In the embodiment shown inFIG. 6, the spring pads94comprising spring assembly92have a narrower and axially thicker cross-sectional configuration than do the spring pads94comprising spring assembly82thus yielding the differences in the aspect ratios of the two spring assemblies. As such, the spring pads94comprising spring assembly92are designed to function for the loads typically incurred or encountered in an empty condition for vehicle10(FIG. 1) while the spring pads94comprising spring assembly82are designed to function for the loads typically incurred or encountered in a loaded condition for vehicle10(FIG. 1).

The shock absorbing apparatus20illustrated by way of example inFIG. 6furthermore preferably includes an axially elongated guide assembly100. The guide assembly100extends substantially a cumulative axial length of and controls compression of the first and second spring assemblies82and92, respectively. That is, guide assembly100inhibits “snaking” and other undesirable movements of the first and second spring assemblies82and92, respectively, during compression of the dual rate spring assembly80. Moreover, and in a preferred form, an operable length of the guide assembly100is automatically adjustable to the operative length of the housing30during operation of the shock absorbing apparatus20.

Guide assembly100axially extends generally centrally through the spring assemblies82and92and through the spring seat or transition plate84. In this regard, and as shown inFIG. 9, the elastomeric member95of each spring pad94comprising spring assemblies82and92(FIG. 6) has a generally centrally disposed bore or opening98through which a lengthwise portion of the guide assembly100axially passes. The bore or opening98in the elastomeric member95of each spring pad94is sized relative to the outer diameter of that portion of the guide assembly100passing therethrough so as to accommodate the flow of elastomeric material subjected to compression whereby eliminating having the elastomeric member95“snagging” or otherwise adversely engaging with the outer diameter of guide assembly100. Moreover, and as shown inFIG. 9, the plates96,96′ of each spring pad94comprising the spring assemblies82and92, define a generally centralized opening98′ for allowing the guide assembly100unrestricted endwise passage therethrough. Additionally, and as shown inFIGS. 6 and 7, the spring seat or transition plate84also defines a generally centralized opening99for allowing the guide assembly100unrestricted endwise passage therethrough.

In the embodiment illustrated inFIG. 6, guide assembly100includes two axially elongated guides110and120arranged, at least partially, in telescoping relation relative to each other and which are generally coaxially aligned with the axis32of housing30. In the illustrated embodiment, guide110extends from the closed end63of housing member60through the spring seat or transition plate84and toward the closed end43of housing member40.

As shown inFIG. 6, guide120of assembly100extends longitudinally away from the closed end43of housing member40and toward the closed end63of housing member60for an axial distance shorter than the extended axial distance of guide110. As shown inFIG. 10, lengthwise portions of the guides110and120are arranged in telescoping relation relative to each other. In the form shown by way of example inFIG. 10, at least the end122of guide120has an elongated and generally cylindrical tubular configuration defining an inside diameter which compliments a predetermined outer diameter of a cap114, arranged toward a distal end of guide110, such that a sliding fit is established between the ends112and122of guides110and120, respectively. By this design, guides110and120of assembly100maintain the elastomeric spring pads94of the spring assemblies82and92in aligned relation relative to each other and relative to axis32while allowing for axial compression of the operative length of guide assembly100during operation of the shock absorbing apparatus20. It should be appreciated, however, the design and construction of guide assembly100can readily be inverted from that shown without detracting or departing from the spirit and scope of this invention disclosure.

In the embodiment illustrated by way of example inFIG. 10, a mechanism118allows spring assembly80to be designed with opposed ends being interconnected and permits a preload condition to be imparted to spring assembly80. In one form, mechanism118includes threadably securing the cap114to the end112of guide110such that rotation of the cap114, as with a suitable tool (not shown), relative to guide110results in lengthwise adjustment of the cap114relative to the guide110. Moreover, mechanism118preferably includes an adjustment member124arranged in threaded engagement with the end122of guide120. Member124preferably includes a bushing125. Member124and bushing125journal and permits a lengthwise portion of guide110to pass therethrough. When mechanism118is assembled, inner ends of cap114and member124are arranged in linearly adjacent relation relative to each other. Preferably, a resilient washer or member126separates adjacent ends of the cap114and member124. Moreover, and when mechanism118is assembled, opposed ends of spring assembly80are joined and the ability to lengthwise adjust cap114relative to guide110and member124relative to member120permits a preload force to be imparted, if desired, to the spring assembly80.

Preferably, the shock absorbing apparatus20of this invention disclosure furthermore allows the payloads carried by vehicle10(FIG. 1) to be monitored whereby reducing overloading of the vehicle while monitoring vehicle activities such as rough roads, and etc. Toward these ends, the shock absorbing apparatus20furthermore preferably includes an apparatus140(FIG.6) for monitoring compressive loads applied to the shock absorbing apparatus20during operation of the heavy off-road vehicle10(FIG. 1).

In the embodiment illustrated inFIG. 6, monitoring apparatus140includes a piston head142arranged for sliding movements proximate to the closed end43of housing member40. Notably, a relatively small volume pressure chamber144is defined between piston head142and the closed end43of housing member40.

After the shock absorbing apparatus20is arranged in operable combination with vehicle10(FIG. 1), a suitable fluid, such as oil or the like, fills the chamber144. In the embodiment illustrated inFIG. 6, the monitoring apparatus140is designed as a closed system and includes a suitable annular seal146carried by the piston head142to prevent fluid from chamber144leaking past the piston head142toward the spring assemblies82and92when a compressive load is applied to the shock absorbing apparatus20. Because chamber144has a relatively small volume for effecting the desired ends, seal146will experience only a limited amount of travel thereby prolonging the useful life of the seal146while concurrently reducing maintenance.

In a preferred form, piston head142defines a recess or seat148concentrically arranged relative to the central axis32of housing30. Such recess or seat148is configured to accommodate and locate the plate96′ of the adjacent spring pad94whereby further promoting stability to the spring assembly82during operation of the shock absorbing apparatus20.

In the embodiment shown inFIG. 6, guide120of assembly100is secured to, projects from, and moves with the piston head142of apparatus140. Notably, the end of guide120carried by piston head142is closed by the piston head142whereby inhibiting passage of fluid from chamber144into guide120.

Preferably, and as shown inFIGS. 4 and 6, housing30defines a passage153for directing pressurized fluid between chamber144and an apparatus154during operation of the shock absorbing apparatus20. Apparatus154includes a conventional device156capable of developing and delivering an electric signal indicative of the payload applied to the shock absorbing apparatus20as a result of the pressure measured by apparatus154. In a preferred form, device156is in the form of a pressure transducer.

An alternative form of apparatus for monitoring compressive loads applied to the shock absorbing apparatus20during operation of the heavy off-road vehicle10(FIG. 1) is illustrated inFIG. 11. This alternative form of apparatus for monitoring compressive loads applied to the shock absorbing apparatus20during operation of the heavy off-road vehicle10(FIG. 1) is designated generally by reference numeral240.

With the monitoring apparatus240shown inFIG. 11, the piston head142of monitoring apparatus140is removed from housing30and replaced with a “pancake” load cell242operably coupled to a signal conditioning module244of the type manufactured and sold by Stress-Tek, Inc. of Kent, Wash. Of course, other types of load cells and signal conditioning modules could likewise be used without detracting or departing from the true spirit and scope of this invention disclosure. In the embodiment shown by way of example inFIG. 11, the “pancake” load cell242is arranged within the closed space67of housing30preferably toward the closed end43of housing member40. Like piston42of monitoring apparatus140(FIG. 6), the load cell242is operably coupled to the end of guide120of assembly100. During operation of monitoring apparatus240, loads applied to cell242are measured by and converted into an electric signal by module244such that the payload applied to the shock absorbing apparatus20can be monitored during operation of vehicle10(FIG. 1).

FIG. 12schematically illustrates the dual rate performance of the shock absorbing apparatus20when mounted to a vehicle10(FIG. 1). The horizontal line160in the graph shown inFIG. 12illustrates a load applied to the shock absorbing apparatus20when the vehicle10is empty. The horizontal line170in the graph shown inFIG. 12illustrates a load applied to the shock aborbing apparatus20when the vehicle10is loaded. Until the vehicle10(FIG. 1) is loaded, spring assembly92acts to absorb, dissipate and return energy imparted to shock absorbing apparatus20. After the vehicle10is loaded, spring assembly82acts to absorb, dissipate and return energy during operation of the shock absorbing apparatus20. Notably, and as compared to the portion of the graph illustrating performance of spring assembly82, the “softer” spring assembly92has a significantly greater suspension travel during the period between when the vehicle10is empty and when the vehicle10is loaded. As such, and with a dual rate suspension system of the type described above, suspension performance of the shock absorbing apparatus20can be optimized for the particular application by altering the ratio of empty to loaded spring assembly performance.

Apparatus20is shown inFIG. 6in its extended or unloaded state. When a force is applied to the absorbing apparatus20and ends34,36of housing30are axially compressed toward each other, spring assembly92acts to absorb, dissipate and return energy imparted to the shock absorbing apparatus20. As the ends34and36of the housing30compress and expand during operation of apparatus20, spring assembly92serves to absorb, dissipate and return a first level of energy acting on the shock absorbing apparatus20. Moreover, and as ends of the shock absorbing apparatus20are compressed toward each other during operation, spring assembly92presses against transition plate84whereby transferring energy to spring assembly82and, ultimately, to the apparatus, in whatever form, for monitoring the compressive loads applied to the shock absorbing apparatus20during operation of the vehicle10(FIG. 1). The monitoring apparatus, in whatever form, preferably delivers electric signals indicative of the loads being applied to the shock absorbing apparatus20during operation of the vehicle10(FIG. 1).

As the opposed ends34,36of housing30are compressed and expanded relative to each other, the follower68carried by housing member60axially slides and moves within the open end45of outer housing member40toward and away from the transition plate or spring seat84. As mentioned above, and as shown inFIG. 6, in an empty condition for vehicle10, the follower68carried by housing member60is axially spaced a predetermined distance PD from the transition plate84by the resiliency of spring assembly92.

When the loads acting on the shock absorbing apparatus20exceed a first predetermined level, i.e., the vehicle10(FIG. 1) is loaded with a payload, the ends34and36of housing30are compressed toward each other an extent exceeding the handling or resilient capabilities of spring assembly92. As such, the follower68on housing member60slides within the open end45of housing member40and into contact with the transition plate or spring seat84. Thereafter, the resiliency of spring assembly82acts to resist compression of the ends34and36of housing30toward each other with a second predetermined level of energy which is different from and preferably significantly greater than the first level of energy of spring assembly92.

Preferably, during operation of the shock absorbing apparatus20, the apparatus for monitoring and delivering electric signals indicative of the loads acting on the shock absorbing apparatus, in whatever form, continues to operate. Moreover, and during operation of the shock absorbing apparatus20, the guide assembly100operates to maintain the elastomeric pads comprising the spring assemblies82and92, respectively, properly orientated relative to the longitudinal axis32so as to optimize performance of the dual rate spring assembly80. The ability of the guide assembly100to automatically adjust to the operable length of the shock absorbing housing30during operation of apparatus20furthermore facilitates operation of the dual rate spring assembly80.

From the foregoing, it will be observed that numerous modifications and variations can be made and effected without departing or detracting from the true spirit and novel concept of this invention disclosure. Moreover, it will be appreciated, the present disclosure is intended to set forth exemplifications which are not intended to limit the disclosure to the specific embodiments illustrated. Rather, this disclosure is intended to cover by the appended claims all such modifications and variations as fall within the spirit and scope of the claims.