Abstract:
A kneeling valve assembly for transport vehicles to enable a quick and convenient kneeling operation to permit safe ingress and egress from the vehicle. The kneeling valve assembly employs a suspension member positioned between the vehicle body and the axle of the transport vehicle to raise and lower the transport vehicle relative to a ground level. The kneeling valve assembly includes a first valve that is operable to selectively permit fluid flow between the inlet passage and the suspension member to raise the transport vehicle relative to the ground level. A second valve is provided that is operable to selectively permit fluid flow between the suspension member and the exhaust passage to lower the transport vehicle relative to the ground level. A leveling trigger is fluidly coupled to the inlet passage and is operable to determine a height of the transport vehicle relative to the ground level. Finally, a third valve is provided that is operable to selectively permit fluid flow between the inlet passage and the suspension member to maintain a predetermined height above the ground level.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/373,061, filed on Apr. 16, 2002 The disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to vehicle suspensions and, more particularly, relates to vehicle suspension capable of providing a kneeling function. 
     BACKGROUND OF THE INVENTION 
     As is well known, transit vehicles, such as buses, occasionally employ means to aid the elderly or handicap board the vehicle. Although ramps and lifts have often been used, recently there has been a renewed interest in systems that enable the transit vehicle to be lowered. Theses systems are often known as kneeling systems, since they enable the transit vehicle to “kneel” toward the ground. 
     Kneeling systems often include a control device that actuates a plurality of pneumatic or hydraulic members to lower the step height of the transit vehicle to permit easy ingress and egress and later raising the vehicle back up for conventional locomotion. These kneeling systems may serve a dual purpose of also providing a leveling mechanism that automatically maintains a predetermined relationship between the vehicle chassis and the road wheels. Although these systems are generally satisfactory, there is a desire to provide a simplified and cost effective alternative to the conventional, rather complicated systems. 
     Accordingly, there exists a need in the relevant art to provide a kneeling valve assembly for use in a transit vehicle that is capable of lowering and raising a transit vehicle to aid in ingress to and egress from the vehicle. Furthermore, there exists a need in the relevant art to provide a kneeling valve assembly that is simplified and cost-effective to operate and maintain. Still further, there exists a need in the relevant art to provide a kneeling valve assembly that overcomes the disadvantages of the prior art. 
     SUMMARY OF THE INVENTION 
     According to the principles of the present invention, a kneeling valve assembly for transport vehicles is provided having an advantageous construction so as to enable quick and convenient kneeling operation of the transport vehicle to permit safe ingress and egress from the vehicle. The kneeling valve assembly employs a suspension member positioned between the vehicle body and the axle of the transport vehicle to raise and lower the transport vehicle relative to a ground level. The kneeling valve assembly includes a first valve that is operable to selectively permit fluid flow between the inlet passage and the suspension member to raise the transport vehicle relative to the ground level. A second valve is provided that is operable to selectively permit fluid flow between the suspension member and the exhaust passage to lower the transport vehicle relative to the ground level. A leveling trigger is fluidly coupled to the inlet passage and is operable to determine a height of the transport vehicle relative to the ground level. Finally, a third valve is provided that is operable to selectively permit fluid flow between the inlet passage and the suspension member to maintain a predetermined height above the ground level. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit,the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a plan view illustrating a kneeling valve assembly according to the principles of the present invention; 
     FIG. 2 is a cross sectional view illustrating the kneeling valve assembly of FIG. 1 taken along lines  2 — 2 ; 
     FIG. 3 is a cross sectional view illustrating the kneeling valve assembly of FIG. 1 taken along lines  3 — 3 ; 
     FIG. 4 is a fluid circuit of a kneeling system of the present invention incorporated into a transit vehicle shown in a normal run position; 
     FIG. 5 is a fluid circuit of the kneeling system incorporated in the transit vehicle shown in a high position; 
     FIG. 6 is a fluid circuit of the kneeling system incorporated in the transit vehicle shown in a low position; 
     FIG. 7 is a fluid circuit of the kneeling system incorporated in a transit vehicle during a kneeling operation; 
     FIG. 8 is a fluid circuit of the kneeling system incorporated in a transit vehicle being held in the kneeling position; 
     FIG. 9 is a fluid circuit of the kneeling system incorporated in a transit vehicle during a raising operation; and 
     FIG. 10 is a fluid circuit of the kneeling system incorporated into a transit vehicle having been returned to a normal run position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown a kneeling system, which is designated generally by the reference numeral  10 . Kneeling system  10  is intended for use in a transit vehicle  12 , such as a bus or van; however, kneeling system  10  may be provided in any vehicle where there is a desire to provide a kneeling function. Accordingly, although the specific recitation contained herein is directed to a kneeling incorporated into a bus, it should be understood that the present invention may find utility in a wide variety of applications. 
     Briefly, with reference to FIG. 4, transit vehicle  12  generally includes a front and rear axle  14  (only one shown) and a pair of wheels  16  disposed on opposing ends of axle  14 . Additionally, transit vehicle  12  includes a chassis  18 , a body structure  20  disposed on and coupled to chassis  18 , and a pair of suspension members  22  disposed between axle  14  and chassis  18  for use in accordance with the principles of the present invention. It should be understood that suspension members  22  may be hydraulically, pneumatically, or mechanically based actuators, such as airbags, air shocks, hydraulic lift assemblies, screw drives, and the like. 
     Referring in particular to FIGS. 1-3, kneeling system  10  primarily contains a kneeling valve assembly  24 , a plurality of fluid passages interconnecting kneeling valve assembly  24  to suspension members  22 , and a mechanical leveling trigger  26  (FIG.  4 ). Kneeling valve assembly  24  includes a main body portion  28  and an upper end cap  30 . Upper end cap  30  is positioned adjacent to and in contact with main body portion  28 . A seal  32  is disposed between upper end cap  30  and main body portion  28  to seal the interface therebetween. 
     Kneeling valve assembly  24  further includes an inlet supply  33 , a first fluid outlet passage  34  (FIG.  4 ), a second fluid outlet passage  36  (FIG.  4 ), and a plurality of valve bores disposed within main body portion  28 . Specifically, kneeling valve assembly  24  includes a supply valve bore  38 , a leveling valve bore  40 , and an exhaust valve bore  42 . First fluid outlet passage  34  and second fluid outlet passage  36  each extend between kneeling valve assembly  24  and suspension members  22  to provide fluid communication therebetween. 
     A supply poppet member  44  is slidably disposed within supply valve bore  38  to form supply valve  45 . More particularly, supply poppet member  44  includes a base portion  46  disposed in an upper chamber  48  of supply valve bore  38 . A seal  50  is disposed alongside base portion  46  in upper chamber  48 , which seals upper chamber  48  from first fluid outlet passage  34 . Supply poppet member  44  further includes a face portion  52  slidably disposed in a lower chamber  54  of supply valve bore  38 . A seal  56  is disposed alongside face portion  52  in lower chamber  54 , which seals upper chamber  48  from first fluid outlet passage  34 . Face portion  52  further includes a seal  58  that engages a seat  60  of main body portion  28  to isolate supply pressure  33  from suspension members  22 . 
     Supply poppet member  44  is normally biased via a spring  62  and backpressure into a seated position wherein face portion  52  of supply poppet member  44  contacts seat  60  of main body portion  28  to prevent fluid flow between supply pressure  33  and first fluid outlet passage  34  and second fluid outlet passage  36 . As will be described below, supply poppet member  44  is further positionable to an unseated position where face portion  52  of supply poppet member  44  is spaced apart from seat  60  of main body portion  28  to enable fluid flow between inlet supply  33  and first fluid outlet passage  34  and second fluid outlet passage  36 . Supply poppet member  44  still further includes a fluid passage  64  formed through face portion  52  to enable fluid to flow between inlet supply  33  and upper chamber  48 . However, a restrictor  66  is disposed within fluid passage  64  to restrict fluid flow therethrough. A supply valve solenoid  68  is further provided in fluid communication with upper chamber  48  of supply valve bore  38  via an outlet pilot passage  69  to rapidly exhaust fluid pressure in upper chamber  48 . As may be readily appreciated by those skilled in the art, varying style pilots may be used in place of supply poppet member  44 . 
     An exhaust poppet member  70  is slidably disposed within exhaust valve bore  42  to form exhaust valve  71 . More particularly, exhaust poppet member  70  includes a base portion  72  disposed in an upper chamber  74  of exhaust valve bore  42 . A seal  76  is disposed alongside base portion  72  in upper chamber  74 . Exhaust poppet member  70  further includes a face portion  78  slidably disposed in a lower chamber  80  of exhaust valve bore  42 . A seal  82  is disposed alongside face portion  78  in lower chamber  80 . Face portion  78  further includes a seal  84  that engages a seat  86  of main body portion  28  to isolate suspension members  22  from an exhaust port  87 . 
     Exhaust poppet member  70  is normally biased via a spring  88  and backpressure into a seated position wherein face portion  78  of exhaust poppet member  70  contacts seat  86  of main body portion  28  to prevent fluid flow between first and second fluid outlet passages  34  and  36  and exhaust port  87 . As will be described below, exhaust poppet member  70  is further positionable to an unseated position where face portion  78  of exhaust poppet member  70  is spaced apart from seat  86  of main body portion  28  to enable fluid flow between first and second fluid outlet passages  34  and  36  and exhaust port  87 . Exhaust poppet member  70  still further includes a first fluid passage  90  and an interconnecting fluid passage  92 , formed in a T-shape through face portion  78  to enable fluid to flow between upper chamber  74  and first and second fluid outlet passages  34  and  36 . However, a restrictor  94  is disposed within fluid passage  90  to restrict fluid flow therethrough. An exhaust valve solenoid  96  is further provided in fluid communication with upper chamber  74  of exhaust valve bore  42  via an outlet pilot passage  98  to rapidly exhaust fluid pressure in upper chamber  74 . 
     A leveling poppet member  100  is slidably disposed within leveling valve bore  40  to form leveling valve  101 . More particularly, leveling poppet member  100  includes a base portion  102  disposed in an upper chamber  104  of leveling valve bore  40 . A seal  106  is disposed alongside base portion  102  in upper chamber  104 , which seals upper chamber  104  from first and second fluid outlet passages  34  and  36 . Leveling poppet member  100  further includes a face portion  108  slidably disposed in a lower chamber  110  of leveling valve bore  40 . A seal  112  is disposed alongside face portion  108  in lower chamber  110 , which seals upper chamber  104  from first and second fluid outlet passages  34  and  36 . Face portion  108  further includes a seal  114  that engages a seat  116  of main body portion  28  to fluidly isolate suspension members  22  from mechanical leveling trigger  26 . 
     Leveling poppet member  100  is normally biased via fluid pressure from mechanical leveling trigger  26  into an unseated position wherein face portion  108  of leveling poppet member  100  is spaced apart from seat  116  of main body portion  28  to enable fluid flow between mechanical leveling trigger  26  and first and second fluid outlet passages  34  and  36 . As will be described below, leveling poppet member  100  is further positionable to a seated position where face portion  108  of leveling poppet member  100  contacts seat  116  of main body portion  28  to prevent fluid flow between mechanical leveling trigger  26  and first and second fluid outlet passages  34  and  36 . A leveling valve solenoid  118  is further provided in fluid communication with upper chamber  104  of leveling valve bore  40  via an outlet pilot passage  120  to provide a pilot pressure to upper chamber  104 . 
     Lastly, mechanical leveling trigger  26  is illustrated being fluidly coupled between inlet supply  33  and leveling valve bore  40 . When mechanical leveling trigger  26  is opened, fluid from inlet supply  33  flows through supply passage  122  and mechanical leveling trigger  26  and into a leveling passage  128 . Leveling passage  128  in turn is in fluid communication with normally-opened leveling valve bore  40  and, thus, suspension members  22 . Furthermore, mechanical leveling trigger  26  includes a trigger arm or switch  130  operably coupled to mechanical leveling trigger  26 . Trigger arm  130  is engaged or at least contacts chassis  18  to determine the height of chassis  18  relative to axle  14 . Trigger arm  130  is thus serves to open or close mechanical leveling trigger to achieve a predetermined height of chassis  18  relative to axle  14 . Mechanical leveling trigger  26  still further includes an exhaust  132  for exhausting fluid pressure to lower chassis  18 . Varying methods for sensing the height of chassis  18  relative to axle  14  may be used. 
     OPERATION 
     FIG. 4 illustrates kneeling system  10  in its deactuated or neutral position with only an equalized pressure supplied to both suspension members  22 . In this position, spring  62  and a constant fluid pressure in upper chamber  48  of supply valve bore  38  biases supply poppet member  44  downward such that face portion  52  of supply poppet member  44  is seated against seat  60  of main body portion  28 , thereby closing fluid communication between inlet supply  33  and first and second fluid outlet passages  34  and  36 . In the preferred embodiment, second fluid outlet passages  34  and  36  are two separate pieces as is shown in FIG. 4 to provide better fluid flow without the flow restrictions of the “T”-shaped piping of the prior art. Similarly, spring  88  biases exhaust poppet member  70  downward such that face portion  78  of exhaust poppet member  70  is seated against seat  86  of main body portion  28 , thereby closing communication between first and second fluid outlet passages  34  and  36  and exhaust port  87 . Leveling poppet member  100  is in a raised position such that face portion  108  is unseated from seat  116  of main body portion  28  as a result of increased fluid pressure within leveling passage  128  acting upon face portion  108  of leveling poppet member  100  and the general absence of fluid pressure within upper chamber  104  of leveling valve bore  40 . As should be appreciated, in this state supply valve solenoid  68 , exhaust valve solenoid  96 , and the leveling valve solenoid  118  are each deactuated. However, as can be seen in FIG. 4, supply valve solenoid  68 , when deactuated, is normally closed to prevent exhaust of fluid in upper chamber  48  of supply valve bore  38 . Moreover, in this state, first fluid outlet passage  34 , second fluid outlet passage  36 , upper chamber  74  of exhaust valve bore  42 , and leveling passage  128  are each at an equilibrium system pressure, which is typically greater than ambient. 
     FIG. 5 illustrates the state where chassis  18  is too high relative to axle  14 , thereby triggering trigger arm  30  to exhaust fluid pressure from leveling passage  128 , which is in fluid communication with first and second fluid outlet passages  34  and  36  and suspension members  22 . Accordingly, such exhaustion of fluid pressure from suspension members  22  causes suspension members  22  to deflate, thereby lowering chassis  18  relative to axle  14 . 
     On the other hand, as seen in FIG. 6, when chassis  18  is too low relative to axle  14 , trigger arm  30  opens mechanical leveling trigger  26  such that fluid from inlet supply  33  is permitted to flow through mechanical leveling trigger  26  via supply passage  122  to leveling passage  128 . Since leveling poppet member  100  is normally positioned in an upward position due to the fluid pressure acting upon face portion  108  of leveling poppet member  100 , the fluid within leveling passage  128  may flow through first and second outlet passages  34  and  36  to inflate suspension members  22 . 
     FIG. 7 illustrates the state where transit vehicle  12  assumes a kneeling position. That is, a position where suspension members  22  are deflated to lower chassis  18  relative to  14  to decrease a stepping height between the ground and transit vehicle  12 . In this kneeling position, ingress and egress is made easier for the handicapped and the elderly. To this end, leveling valve solenoid  118  is actuated to apply a pilot pressure through outlet pilot passage  120  and into upper chamber  104  of leveling valve bore  40 . This pilot pressure, which is generally equal to or greater than the outlet pressure of mechanical leveling trigger  26 , acts upon a greater surface area formed along base portion  102  of leveling poppet member  100 . The force generated by the pressure acting upon base portion  102  of leveling poppet member  100  is greater than the upward force generated by the same pressure acting upon a smaller surface area of face portion  108  of leveling poppet member  100 . Therefore, the net force is downward, thereby positioning leveling poppet member  100  in a seated position wherein face portion  108  engages seat  116 . In this position, leveling poppet member  100  isolates mechanical leveling trigger  26  from first and second fluid outlet passages  34  and  36 , thereby preventing mechanical leveling trigger  26  from commanding an inflating action. 
     While leveling poppet member  100  isolates mechanical leveling trigger  26 , exhaust valve solenoid  96  is actuated to open the normally closed exhaust passed coupled to upper chamber  74  of exhaust valve bore  42 . That is, actuation of exhaust valve solenoid  96  vents the fluid pressure from upper chamber  74  of exhaust valve bore  42 , thereby allowing fluid pressure from first and second outlet passages  34  and  36  to force exhaust poppet member  70  upward against the biasing force of spring  88 , thereby opening exhaust port  87 . In this state, fluid pressure from suspension members  22  is exhausted through first and second outlet passages  34  and  36  to exhaust port  87  so as to deflate suspension members  22  and lower transit vehicle  12 . 
     As best seen in FIG. 8, transit vehicle  12  is held in this kneeling position by deactuating exhaust valve solenoid  96 , thereby equalizing the fluid pressure in upper chamber  74  of exhaust valve bore  42  relative to the fluid pressure within first and second fluid outlet passages  34  and  36  by allowing fluid flow into upper chamber  74  via passages  90  and  92 . Accordingly, with this equalized fluid pressure acting on exhaust poppet member  70 , the biasing force of spring  88  forces exhaust poppet member  70  into a seated position wherein face portion  78  engages seat  86 . In this seated position, exhaust port  87  is then closed and further evacuation of fluid pressure from suspension members  22  is prevented. However, leveling valve solenoid  118  remains in an actuated position whereby fluid pressure is applied to base portion  102  of leveling poppet member  100 , thereby seating face portion  108  against seat  116 . In this position, leveling poppet member  100  continues to isolate mechanical leveling trigger  26 , thereby preventing mechanical leveling trigger  26  from commanding a raising action. 
     FIG. 9 illustrates when transit vehicle  12  is raised from the kneeling position. To this end, leveling valve solenoid  118  is deactuated, thereby removing the fluid pressure from upper chamber  104  of leveling valve bore  40 . Accordingly, leveling poppet member  100  is forced to an unseated position by the fluid pressure acting against face portion  108  from leveling passage  128 . Simultaneously, supply valve solenoid  68  is actuated to exhaust fluid pressure in upper chamber  48  of supply valve bore  38 . Accordingly, the fluid pressure within inlet supply  33  and supply passage  122  acts upon face portion  52  of supply poppet member  44 , thereby forcing supply poppet member  44  upward against the biasing force of spring  62 . In this state, pressurized fluid from inlet supply  33  is permitted to flow to first and second fluid outlet passages  34  and  36 , finally inflating suspension members  22 , thereby raising chassis  18  relative to axle  14 . 
     Once transit vehicle  12  is raised from the kneeling position, as seen in FIG. 10, supply valve solenoid  68  is then deactuated to again prevent the exhaust of pressurized fluid within upper chamber  48  of supply valve bore  38  so as to equalize the pressure above and below supply poppet member  44 , thereby permitting spring  62  to bias supply poppet member  44  downward into the seated position. As can be seen from FIG. 10, the kneeling operation is now complete and mechanical leveling trigger  26  is again permitted to maintain the proper level of transit vehicle  12  as described above with reference to FIGS. 5 and 6. 
     Accordingly, the kneeling system of the present invention provides a number of unique advantages over conventional kneeling systems. That is, the kneeling system of the present invention provides a simple and convenient method of raising and lowering a transit vehicle to aid an ingress to and egress from the vehicle. Furthermore, the kneeling system of the present invention provides a kneeling valve assembly that is simplified and cost effective to operate and maintain. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.