Abstract:
A cab mounting assembly attaches a cab to a chassis of a vehicle at the point of rotation of the cab when the cab is tilted. The cab mounting assembly provides two paths for the forces acting between the cab and the chassis. The static forces are supported by a bearing assembly which includes a relatively hard elastomeric member. The dynamic forces are supported by an elastomeric mount which includes a relatively soft elastomeric member. The elastomeric mount is attached to the bearing assembly and to a shock absorber. The bearing assembly is attached to the elastomeric mount and to an air spring assembly.

Description:
FIELD 
     The present disclosure relates to a cab suspension system typically used in large trucks and other vehicles. More particularly, the present disclosure relates to a mount located at the tilting point of the cab which includes a double path mounting system for isolating the cab. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     In order to provide comfort for large vehicle operators and reduce driving fatigue experienced by operators of larger vehicles, the operator&#39;s cab is suspended utilizing a vibration isolation device and a shock absorption device between the vehicle&#39;s chassis and the vehicle&#39;s cab which reduces the shock, vibration and consequent pounding the operator experiences during operation of the vehicle. Additionally, the continued application of vibration and shock forces to the cab results in structural damage which ultimately increases the costs associated with maintenance. 
     The load carried by a large vehicle is supported by the vehicle&#39;s frame which is resiliently carried by the vehicle&#39;s suspension springs and the vehicle&#39;s shock absorbers supported by the vehicle&#39;s wheels. Suspension springs typically have a high rate of stiffness which makes the ride more jarring on the operator of the vehicle. To dampen the vibration and shock transmitted to the cab, cab suspension systems have been developed utilizing cab mounting systems that include cab hydraulic shock absorbers and cab air springs to reduce the jounce and rebound movements of the cab with respect to the vehicle&#39;s frame. 
     These cab hydraulic shock absorbers and cab air springs can be mounted at both the front and rear ends of the cab. Typically, a cab is tilted by rotating around a pair of cab air springs and cab hydraulic shock absorbers which are located at the front of the vehicle. The front mounting cab hydraulic shock absorbers and cab air springs often need some type of a bearing to enable the rotational movement during the tilting of the cab. This rotational movement requirement makes it difficult from a design point of view to adequately isolate the cab from the frame. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     The present disclosure provides a cab mounting assembly which is designed for the mounting of the cab at the position where the cab rotates when it tilts. The cab mounting assembly of the present disclosure provides a double path for the loading on the cab mounting assembly such that the dynamic load is uncoupled from the static load. This uncoupling of the two loads allows for the design optimization of both paths to optimally isolate both the static loading and the dynamic loading. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a side elevation view of a truck incorporating the cab mounting assembly in accordance with the present disclosure; 
         FIG. 2  is a side cross-sectional view of one of the cab mounting assemblies illustrated in  FIG. 1 ; and, 
         FIG. 3  is an enlarged side view of the double path mounting system illustrated in  FIG. 2 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Referring now to the figures where like reference numerals designate like or similar components in the various views, there is illustrated in  FIG. 1  a vehicle which incorporates the cab mounting assembly in accordance with the present disclosure and which is designated generally by the reference numeral  10 . Vehicle  10  comprises a cab  12 , a front suspension  14  and a rear suspension  16 . 
     Front suspension  14  comprises a pair of longitudinal oscillating arms  20  mounted to oscillate about a common transverse axis  22  generally perpendicular to a vertical longitudinal plane of vehicle  10 . The free ends of oscillating arms  20  are connected to a transverse torsion bar  24 . A pair of supports  26  are rotatably mounted on torsion bar  24 . Supports  26  are rigidly connected to the structure of cab  12  allowing cab  12  to rotate about the axis of torsion bar  24 . This allows the raising of cab  12  by means of rotating about the axis of torsion bar  24  when it is necessary to gain access to an engine set underneath cab  12  for maintenance operations. A pair of cab mounting assemblies  30  are disposed between the free ends of oscillating arms  20  and the chassis of vehicle  10 . Rear suspension  16  comprises a pair of spring damper assemblies  32  which are attached to the chassis of vehicle  10  and to cab  12  through a pair of oscillating arms  34 . 
     Referring now to  FIG. 2 , cab mounting assembly  30  is illustrated in greater detail. Cab mounting assembly  30  comprises a shock absorber  40 , an air spring assembly  42  and a double path top mount  44 . Shock absorber  40  is a dual-tube shock absorber which comprises a pressure tube  54 , a piston assembly  56 , a piston rod  58 , a reserve tube  60  and a base valve assembly  62 . 
     Pressure tube  54  defines a working chamber  64 . Piston assembly  56  slidingly engages pressure tube  54  and is disposed within working chamber  64 . Piston rod  58  is adapted to be attached to piston assembly  56  and it extends out of working chamber  64  through one end of pressure tube  54  and air spring assembly  42  to be attached to double path top mount  44  which is attached to cab  12 . Reserve tube  60  surrounds pressure tube  54  to define a reserve chamber  66 . Base valve assembly  62  is attached to pressure tube  54  to control fluid flow between working chamber  64  and reserve chamber  66 . The end of reserve tube  60  opposite to piston rod  58  is adapted to be attached to the chassis of vehicle  10 . 
     Because piston rod  58  only extends through one portion of working chamber  64 , movement of piston assembly  56  causes a different amount of fluid flow in the portion of working chamber  64  above and below piston assembly  56 . This difference in fluid flow is known as the “rod volume” and it flows through base valve assembly  62 . During a compression movement, fluid will flow from below piston assembly  56  to above piston assembly  56  through valving in piston assembly  56 . The “rod volume” of fluid will flow from working chamber  64  through valving in base valve assembly  62  and into reserve chamber  66 . The flow of fluid through the valving in base valve assembly  62  during a compression stroke defines the damping characteristics for shock absorber  40 . During an extension stroke, fluid will flow from above piston assembly  56  to below piston assembly  56  through valving in piston assembly  56 . The “rod volume” of fluid will flow from reserve chamber  66  through valving in base valve assembly  62  and into working chamber  64 . The flow of fluid through the valving in piston assembly  56  during an extension stroke will determine the damping characteristics for shock absorber  40 . 
     Air spring assembly  42  comprises an upper mount  70 , a lower mount  72  and a spring sleeve  74 . Upper mount  70  mates with double path top mount  44 . Upper mount  70  sealingly mates with piston rod  58  of shock absorber  40 . A dynamic air seal  76  seals the interface between air spring assembly  42  and piston rod  58  of shock absorber  40 . Lower mount  72  is sealingly attached to shock absorber  40  and acts as a piston for air spring assembly  42 . Spring sleeve  74  sealingly engages upper mount  70  and lower mount  72  to define a sealed chamber  78 . An inlet  80  extends through lower mount  72  and is utilized to insert pressurized fluid, preferably air into sealed chamber  78 . 
     Referring now to  FIG. 3 , double path top mount  44  comprises a bracket  82 , a bearing assembly  84 , and an elastomeric mount  86 . Bracket  82  is secured to and interfaces with upper mount  70  of air spring assembly  42 . Bracket  82  comprises an upright portion  88  which interfaces with bearing assembly  84 , an annular portion  90  extending generally perpendicular to upright portion  88  and which interfaces with upper mount  70  of air spring assembly  42  and an annular portion  92  extending generally perpendicular to annular portion  90  and which extends around upper mount  70  of air spring assembly  42 . 
     Bearing assembly  84  comprises an outer metal  94 , an inner metal  96  and an elastomeric member  98  disposed between outer metal  94  and inner metal  96 . Outer metal  94  is attached to upright portion  88  of bracket  82  by being press fit into a pair of holes  100  defines by upright portion  88  of bracket  82 . While outer metal  94  is illustrated as being press fit into holes  100  of upright portion  88 , outer metal  94  can be attached to upright portion  88  by any other means known in the art. The ends of outer metal  94  are rolled over as illustrated at  102  to encapsulate elastomeric member  98 . Inner metal  96  is illustrated as a tubular member defining a through hole  104  and an arcuate center section  106 . While inner metal  96  is illustrated having through hole  104  and arcuate central section  106 , other inner metal configurations known in the art can be utilized in bearing assembly  84 . Through hole  104  accepts a fastener which secures double path top mount  44  to cab  12 . The interface between inner metal  96  and elastomeric member  98  defines a bearing which allows elastomeric member  98  to rotate around inner metal  96  to allow for the tilting of cab  12 . Elastomeric member  98  can be manufactured from a self lubricating elastomer to provide for the rotation of elastomeric member  98  around inner metal  96 . Other alternatives for elastomeric member  98  include, but are not limited to, a plastic bearing bushing or a DU bushing. Elastomeric member  98  is preferably manufactured from a relatively hard elastomeric material in order to enable it to withstand and isolate the static and dynamic loading applied to dual path top mount  44 . 
     Elastomeric mount  86  comprises a piston rod mount  110 , an outer metal  112 , an inner metal  114  and an elastomeric member  116  disposed between outer metal  112  and inner metal  114 . Piston rod mount  110  comprises a piston rod interface  118  which is threadingly received on piston rod  58  or otherwise attached to piston rod  58  and an annular ring  120  which is attached to piston rod interface  118 . Outer metal  112  is attached to annular ring  120  by being press fit or otherwise secured within annular ring  120 . Inner metal  114  is a tubular member which is press fit over or otherwise secured to outer metal  94  of bearing assembly  84 . Elastomeric member  116  is disposed between outer metal  112  and inner metal  114 . Elastomeric member  116  is only loaded by the dynamic loads and therefore it can be manufactured from a relatively soft elastomeric material to provide improved Noise Vibration and Harshness (NVH) characteristics as opposed to the harder elastomeric material of elastomeric member  98  of bearing assembly  84 . 
     During operation, the static loads are transferred through bearing assembly  84  to bracket  82  and then to air spring assembly  42 . The relatively hard elastomeric material for elastomeric member  98  of bearing assembly  84  transfers the static loading between bearing assembly  84  and bracket  82 . The dynamic (damping) forces are transferred by piston rod  58 , through dynamic air seal  76  and through elastomeric mount  86  to bearing assembly  84 . The relative soft elastomeric material for elastomeric member  116  provides improved NVH characteristics for the dynamic loading and creates a barrier for the high frequency vibrations. 
     Dynamic air seal  76  allows for the movement of piston rod  58  of shock absorber  40  with respect to upper mount  70  of air spring assembly  42 . Dynamic air seal  76  comprises a rigid outer member  130 , a rigid inner member  132  and an elastomeric member  134  disposed between rigid outer member  130  and rigid inner member  132 . Dynamic air seal  76  provides a seal for sealed chamber  78  as well as allowing for the movement of piston rod  58  separate from upper mount  70  of air spring assembly  42  to permit the proper isolation by elastomeric mount  86 . 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.