Abstract:
A shock and vibration mount includes a resilient elastomeric member arranged to act with two spaced spring units, each of which includes a group of stacked, disc-shaped annular springs. Low level impacts and vibrations are transmitted from a rod, that is movable with the impacted member or with a member reacting to an impact, to the elastomeric member through either of the stacked units, high intensity shocks being attenuated first by the elastomeric member and then by one of the stacked units.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a vehicle suspension system and more particularly to a vehicle suspension system composed of elements consisting of a number of spring systems arranged in series to attenuate and damp vertical or horizontal shock waves. 
     Off the road vehicles, such as four wheel drive recreational vehicles, earth moving equipment and treaded vehicles such as tanks and tractors have in general compromised the ability of the vehicle&#39;s road suspension system to supply an isolation system over a wide range of road conditions by a requirement to protect the suspension system itself against damage from high intensity off the road shocks. The compromise in general has taken the form of limiting the travel of the suspension system by rubber bumpers that are contacted under high shock conditions by the vehicle&#39;s suspension system before the suspension system is damaged. Under unusually severe shock conditions, the rubber bumpers are not only contacted but compressed to the point where the rubber is no longer compressible and &#34;hard bottoming&#34; occurs. &#34;Hard bottoming&#34; results in the transmission of high shock loads to the vehicle&#39;s chassis and the vehicle&#39;s occupants. 
     Most vehicle suspension systems use helical, leaf or torsion bars to provide road shock isolation. Since only the leaf spring of these three types provides a small amount of damping, the vehicle&#39;s suspension must also include some type of damping device which may be hydraulic or a friction device. Since both of these damping devices are nonlinear, the suspension system becomes nonlinear and possibly subject to &#34;hard bottoming&#34; even if the limit of travel of the suspension system has not been reached. 
     Therefore, it is a primary object of this invention to provide a vehicle suspension element that will not only provide for the normal road isolation of a vehicle suspension system, but also for the abnormal condition of high shock load imposed by unusually rough terrain. It is also an object of this invention to provide a high degree of damping so that additional damping services, hydraulic or other types, are not required. 
     The patent to Blake, U.S. Pat. No. 3,770,232, discloses the combined use of an elastomeric annulus and sets of annular metal springs to absorb shocks received by a support member before they reach a platform on which a gas turbine or the like is mounted. The elastomeric annulus is connected directly to the shock-receiving support member so that the annulus immediately responds to such shocks. While this patent does disclose an elastomeric annulus and annular metal springs acting together to absorb shocks and vibration, it does not teach or suggest how these spring members could be applied to absorb shocks received by the two control arms of a vehicle. 
     SUMMARY OF THE INVENTION 
     The shock and vibration absorbing arrangement of this invention includes an elastomeric member connected to a member, such as the chassis of a vehicle, that is to be protected from shock and a set of annular springs operatively connected to each of two shock-receiving members, such as the upper and lower control arms of a wheel suspension system, for transmitting forces to the elastomeric member. 
    
    
     DESCRIPTION OF THE DRAWING 
     The single FIGURE of the drawing is a diagrammatic side elevation, partly in section and partly broken away, of the mechanism of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The heavy duty vehicle suspension system of the present invention includes an elongate rod having an upper section 10 and a lower section 11 threaded together to form a single rod that is adjustable in length. At its upper end the rod has an annular flange 12 and, at its lower end, a flange 13. A sleeve 16, which is slidably disposed on the rod, is provided with two spaced annular flanges 17 and 18, and a resilient elastomeric annulus or grommet 20 is disposed between the flanges 17 and 18 in engagement with the inner walls of the flanges. The annulus 20 is preferably composed of rubber, and includes a groove 22 around the outer periphery thereof. A flat ring 24 is embedded within the groove and is provided with a plurality of circumferentially spaced holes 26 which are aligned with holes 32 in a member 28 to receive nut and bolt units 30 for clamping the ring 24 to the member 28. THe member 28 is the structural member which is to be protected from shocks, as for example the frame or chassis of the vehicle. 
     A first set of disc-shaped annular metal springs 34, which are vertically stacked to engage each other along alternating inside and outside edges, is disposed between the lower flange 13 of the rod and the flange 18 of the sleeve 16. The annular springs 34 are of the type generally known as &#34;Belleville&#34; springs. A second set of similar, stacked, disc-shaped annular springs 56 is disposed between the flange 17 of the sleeve and the upper flange 12 of the rod. A casing 50 encloses the second set of springs 56, and the flanges 12 and 17, and a casing 51 encloses the set of springs 34 and the flanges 13 and 18. 
     At its upper end, the rod section 10 carries a ball unit 57 that is disposed in a partially spherical recess in a shock-receiving member 46, such as the upper control arm of the suspension of the vehicle. A lower extension 57&#39; of the ball 57 is threaded and is engaged in a tapped opening in the upper end of rod section 10. A nut 58 which is threaded on the upper end of the ball unit 57 engages a lock washer 59 and urges it against the upper surface of flange 12, thus locking the ball unit 51 to the rod section 10. Similarly, a ball unit 61 has a shank portion 61&#39; threaded into a tapped opening in the lower end of rod section 11 and is locked to the flange 13 of rod section 11 by a lock washer 62 and a nut 60, that is threaded onto the ball unit 61. 
     In normal operation, the heavy duty vehicle suspension system operates as a vibration isolator absorbing the minor vibration and shock loads generated by operation of a military tank or &#34;off road&#34; type vehicles on pavement or smooth terrain. These type of vibrations are attenuated by the resilient rubber annulus 20 while the stacked metal springs remain substantially rigid. However, under high shock conditions generated by operation of a vehicle over rough terrain the metal springs become active and compress, limiting the overall or combined spring rate to a satisfactory soft value instead of the infinite spring constant that would result from the rubber annulus acting alone. Impingement of a high intensity shock load on the bogie (military tank) or wheel (off road vehicle) would initially effect a rapid acceleration of the control arms 44, 46 in a vertical upward direction. Rapid acceleration of the arms 44, 46 correspondingly effects an acceleration of the peripheral flange 13 which is fixedly attached thereto through the rod 10, 11. The acceleration is initially transmitted through flange 13 to the lower metal springs 34 to peripheral flange 18. Flange 18 rapidly compresses the resilient rubber annulus 20 in the area between peripheral flange 18 and flat ring 24 which is rigidly attached to the vehicle structure 28. The rubber annulus within a few milliseconds becomes substantially incompressible in the area between the flat ring 24 and the peripheral flange 18, changing the spring constant of the rubber annulus from a low spring constant to an infinite spring constant. Further acceleration of flange 18 is halted so that acceleration of flange 16 in a vertical upward direction is impacted to the lower stack of springs 34 and acts to compress the disc-shaped metal springs 34 and further damp the high intensity shock transmitted to the platform 28 through flat ring 24. The disc-shaped metal springs have a variable incremental deflection which is a function of shock loading, so that high shock loads are increasingly attenuated with a high degree of damping to assure soft bottoming. Also it is readily apparent that the disc-shaped metal springs have a sufficiently high initial spring constant so as not to deflect until after the spring constant of the rubber annulus 20 becomes substantially infinite. 
     The shock and vibration mount of this invention must also include the ability to attenuate the shock rebound which is manifest as a deceleration and subsequent reversal of the vehicle support arms in the upward direction as the shock and vibration mount is actuated. 
     The present system damps any shocks that are incident to the downward movement of the control arms 46 and 44 after their upward movement has been arrested. Such rebound shocks are transmitted to the annulus 20 by the rod section 10 and the springs 56. As a result, the part of the annulus 20 between the ring 24 and the flange 17 is first compressed and then the shock is further attenuated by the springs 56. If the resilient rubber annulus were non-symmetrical with respect to the flat ring 24 the two stacks of disc-shaped metal springs 34, 56 would have to be individually tailored in order to obtain similar load/deflection characteristics for both the initial shock direction and the rebound direction. Precise tailoring may not be necessary, however, because the initial shock and rebound direction curves are generally different. 
     The stacked disc-shaped metal spring 34, 56 arranged in series with the resilient rubber annulus permit a wide variety of load versus deflection performances so that shock loads can be attenuated for a range of conditions and to a predetermined degree. Under high intensity shock conditions, high loads and large displacements, the stacked disc-shaped metal springs 34, 56 become effective in limiting the overall spring rate to an extended linear value rather than the hard spring rate that would result from the rubber mounts alone. The high degree of damping, together with the high attenuation value for damping-of accelerating forces supplied by the shock and vibration mounts of the invention, will reduce the moment and shear loads imposed on the tank or vehicle suspension system and associated equipment mounted thereon. Also, the high damping will require less space for the mounting system due to the smaller deflections of the platform that will occur under shock conditions. 
     In the following claims, the term &#34;structural member&#34; will be used to indicate the portion or member of the civilian or military vehicle that is to be protected from shocks, such as the chassis or frame of the vehicle. Also, the term &#34;control arm&#34; will be used to indicate a member that connects the bogie or wheel of the vehicle to the structural member. 
     While a preferred embodiment of the present invention has been shown and described, it will be appreciated by those skilled in the art that modifications and substitutions may be made thereto without departing from the invention&#39;s fundamental theme.