Motor vehicles – Steering gear – Each wheel steerable
Reexamination Certificate
1999-08-18
2001-02-13
Johnson, Brian L. (Department: 3618)
Motor vehicles
Steering gear
Each wheel steerable
C180S414000, C180S236000, C280S103000, C280S091100
Reexamination Certificate
active
06186266
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally related to improved steering devices for vehicles, and more particularly to steering devices for vehicles having a steerable rear tag axle.
As the population of the world has escalated, the amount of waste produced has risen and the need for larger refuse trucks having a higher carrying capacity has intensified. However, with the increase in size and length of the trucks, it is becoming more difficult for the larger refuse trucks to maneuver through the city streets, cul-de-sacs and alleyways. Additionally, many state and federal laws limit the length between the axles and the maximum gross vehicle weight. To comply with these laws, an additional axle, otherwise known as a tag axle, is mounted rearward of the drive axle to accommodate the additional weight of the vehicle. The three conventional types of tag axles are fixed tag axles, self-steering tag axles and steerable tag axles. The conventional tag axles, however, suffer from a number of disadvantages.
Fixed axles typically do not turn and are often used as a second drive axle. Fixed axles do not reduce the turning radius, and can actually increase the steering radius of the vehicle because the fixed tag axle push the drive tires through the turn. Moreover, the fixed tag axle tires often scuff during the turning of the vehicle, which reduces the life of the tires and increases the cost of maintenance for the vehicle.
Conventional self-steering tag axles turn independently of the front steering axle and must overcome a certain amount of resistance to move from its straight orientation to a turning orientation. Because the self-steering tag axle systems must overcome the resistance, excessive tire wear and tire scuffing often occurs. Moreover, conventional self-steering tag axles must often be locked in a straight orientation or raised off of the ground entirely when the vehicle moves in reverse. Such configurations do not improve the steering radius of the vehicle, and can actually detrimentally affect the other axles when the vehicle moves in reverse.
Conventional steerable tag axle systems, such as those described in U.S. Pat. Nos. 5,364,116, 5,329,451 and 5,135,064, use a complex and expensive system of control valves and linkages to help turn the tag axle wheels. Although these steerable tag axle systems can provide a tighter turning radius than the fixed or self-steering tag axles, because these conventional steerable tag axles are so complex, additional maintenance is often required.
SUMMARY OF THE INVENTION
The present invention is broadly directed to an improved steering assembly for improving the steering of motorized vehicles, and in particular large vehicles having a tag axle. The steering system improves steering by reducing the turning radius of the vehicle and reducing tire scuffing of the tag axle wheels by using a closed, essentially valveless conduit system to move a hydraulic fluid between a front steering assembly and the tag axle steering assembly. By having a master-slave steering configuration, in contrast to conventional tag axle systems, the present invention does not require a complex system of valves, pumps and linkages to turn the wheels of the tag axle steering assembly. By using this simple steerable tag axle assembly the present invention provides a much simpler, cheaper, and more effective steering assembly than conventional fixed, self-steering and steerable tag axle assemblies.
In a first aspect, the present invention provides an improved steering assembly for a vehicle of the type having a steering axle and a tag axle assembly mounted to a frame. The steering axle assembly comprises first and second steerable wheels and a tie rod operatively connecting the first and second wheels. The tag axle assembly includes third and fourth wheels and a second tie rod which operatively connects the third and fourth wheels. The improved steering assembly has a steering axle ram assembly fluidly connected to a tag axle ram assembly through a conduit system such that a fluid moves between the steering axle ram assembly and the tag axle ram assembly in response to a turning of the first and second steerable wheels to cause third and fourth wheels to turn in unison. The steering axle ram assembly preferably comprises a first ram having a first cylinder, a first piston reciprocally housed within the first cylinder and a first shaft connected to the first piston, and a second ram having a second cylinder, a second piston reciprocally housed within the second cylinder and a second shaft connected to the second piston. The first and second cylinders are affixed to either the frame or the first tie rod, while the first and second shafts are affixed to the other of the frame and the first tie rod. The tag axle ram assembly typically includes a third ram having a third cylinder, a third piston reciprocally housed within the third cylinder, and a third shaft connected to the third piston, and a fourth ram having a fourth cylinder, a fourth piston reciprocally housed within the fourth cylinder, and a fourth shaft connected to the fourth piston. The third and fourth cylinders are typically affixed to either the frame or the second tie rod, while the third and fourth shafts are affixed to the other of the frame and the second tie rod. The diameters of the third and fourth cylinders are larger than the diameters of the first and second cylinders, so that the third and fourth wheels turn less than the first and second steerable wheels. A conduit system fluidly couples (1) the first and third cylinders, and (2) the second and fourth cylinders. A fluid moves through the conduit system between the steering axle ram assembly and the tag axle ram assembly in response to the turning of the first and second steerable wheels. The third and fourth wheels turn in unison at a lesser distance than the first and second steerable wheels.
In a second aspect, the present invention provides an improved vehicle having a steering axle assembly and a tag axle assembly mounted to a frame. The steering axle assembly comprises first and second steerable wheels and a first tie rod operatively connecting the first and second steerable wheels. The tag axle assembly comprises third and fourth wheels and a second tie rod operatively connecting the third and fourth wheels. The vehicle includes a steering axle ram assembly fluidly coupled to a tag axle ram assembly through a conduit system so that a fluid moves through the conduit system between the steering axle ram assembly and the tag axle ram assembly in response to the turning of the first and second steerable wheels, such that the third and fourth wheels turn in unison with the first and second steerable wheels. The steering axle ram assembly preferably comprises a first ram having a first cylinder, a first piston reciprocally housed within said first cylinder, and a first shaft connected to said first piston, and a second ram having a second cylinder, a second piston reciprocally housed within said second cylinder, and a second shaft connected to said second piston. The first and second cylinders are affixed to either the frame or the first tie rod, and the first and second shafts are affixed to the other one of the frame and the first tie rod. Similarly, the tag axle ram assembly comprises a third ram having a third cylinder, a third piston reciprocally housed within the third cylinder, and a third shaft connected to the third piston, and a fourth ram having a fourth cylinder, a fourth piston reciprocally housed within the fourth cylinder, and a fourth shaft connected to said fourth piston. The third and fourth cylinders are affixed to either the frame or the second tie rod while the third and fourth shafts are affixed to the other one of the frame and the second tie rod. The third and fourth cylinders have larger diameters than the first and second cylinders so that the third and fourth wheels turn a lesser distance than the first and second steerable wheels. Such a system can reduce the complexity and cost of the system, while
Marchant Alan
West William R.
Johnson Brian L.
Lerner Avraham H.
Marchant Waste Managers
Townsend and Townsend / and Crew LLP
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