Land vehicles – Body elevation or tilt
Reexamination Certificate
1999-07-19
2002-08-13
Dickson, Paul N. (Department: 3618)
Land vehicles
Body elevation or tilt
C280S006157, C280S006159, C280S005507
Reexamination Certificate
active
06431557
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for adjusting the driving mode ride height of a vehicle having a pneumatic suspension system.
BACKGROUND OF THE INVENTION
When load-carrying vehicles (LCV's) are to be loaded and unloaded, they are normally brought to a loading dock. In order to facilitate and to increase the efficiency of such loading and unloading, the height of the loading dock should be adapted to the elevation of the loading platform of the LCV. One way of achieving this result is to construct a loading dock having a variable elevation. Such an approach may be economically feasible with highly utilized loading docks, such as goods terminals, where loading and unloading are very frequent.
Another method of solving the problem of adapting the height of the loading dock and the elevation of the LCV loading platform is to control the elevation of the vehicle loading platform. Such an approach has the advantage of allowing for adaptation to loading docks having a fixed height.
Such a system is described, for example, in British Patent No. 2,237,780.
This patent describes a system in which the LCV loading platform is located at a predetermined height when the vehicle is operated in its normal driving mode. When the vehicle is parked for loading and unloading, however, the elevation of the LCV loading platform is adjustable so as to allow for adaptation of its elevation to the height of the loading dock, thus enabling efficient loading and unloading. When the LCV is to once again be operated in a normal driving mode, the original fixed elevation of the LCV loading platform is restored.
PCT Application No. WO 91/07291 discloses another apparatus of the type disclosed above.
One problem exhibited by the prior art is that the height assumed by the LCV loading platform, when restoring the elevation of the LCV loading platform for normal operation of the LCV, after performing height adjustment during loading and unloading, is fixed and cannot be varied. Therefore, when the vehicle is operated in a normal driving mode, i.e. when the vehicle is not parked or is driven at a speed exceeding a relatively low speed, the elevation of the LCV loading platform in most cases cannot be adjusted, and in those cases where the elevation is adjustable, it is adjustable within the same range as the permitted range for loading and unloading. This initially means that control possibilities are not available, which is a disadvantage with this type of prior art, and secondly that the ride height in the driving mode is adjustable within a range where a risk of damage to the load and the LCV exists.
It has been determined by tests and calculations that the aerodynamic properties of an LCV are dependent on the elevation of the LCV loading platform. Such tests and calculations have shown that is preferable, for obtaining an LCV having a lower air resistance, and thus a lower fuel consumption, for the elevation of the LCV loading platform to be as low as possible when the vehicle is operated in a driving mode.
Thus, it is an object of the present invention, by providing the LCV with a possibility of adjusting the elevation of the LCV loading platform, to permit the vehicle to be operated in the driving mode with a low set driving mode elevation or ride height, thereby reducing both the air resistance and the fuel consumption.
A second advantage of being able to lower the elevation of the LCV loading platform is, in those cases where the absolute height of the LCV is limited by regulations or accessibility, that a larger loading height can be utilized, thereby improving the financial strength of the LCV.
Thus, another object of the present invention is, by providing the LCV with a mechanism to control the height of the loading platform, to ensure that the LCV can be driven with a low ride height, whereas the LCV can carry further load, which improves the economy for the LCV.
A further advantage of being able to lower the ride height of the LCV framework is that this lowers the cab instep height which increases driver comfort.
Thus, it is another object of the present invention, by providing the LCV with the ability of adjusting the ride height of the LCV framework, and thereby that of its loading platform and cab, which are affixed to the framework, to lower the cab instep height thereby increasing driver comfort.
An LCV loading platform is resiliently suspended by the structure carrying wheel axles and wheels. Thus, when the LCV is operated in the driving mode, the LCV loading platform will oscillate around the height level that the loading platform has assumed in an equilibrium position, when standing still. The amplitude of loading platform oscillations around its equilibrium position is dependent of the quality of the road, the load weight, the vehicle speed, and the characteristics of the loading platform suspension.
As discussed above, the loading platform of an LCV is fitted to the wheel-carrying structure by resilient means. Such resilient means display elastic properties within a certain range of expansion and compression. If the resilient means are compressed excessively, they will then act like a rigid connection. Such excessive compression will occur if the loading platform has been adjusted to an excessively low position when the LCV is operated in a driving mode. This means that the harmonic oscillation which, when the loading platform elevation is correctly adjusted, occurs around the equilibrium position of the loading surface height level, is replaced by an interrupted oscillation when the resilient means is compressed past its elastic range. When interrupted oscillatory motions take place, large accelerations occur, leading to the load, the resilient means, and the LCV as a whole, being subjected to very high stress forces. If the loading platform is adjusted to an excessively high position, problems will also occur, in that the resilient means may be extended in excess of the elastic range. In such cases, an interrupted oscillatory motion also occurs leading to high stress forces on the load, the resilient means, and on the LCV as a whole.
Yet another object of the present invention is to provide the LCV with a means of adjusting the elevation of its loading platform, thus allowing for adjustment within a first, larger range when the vehicle has taken up a parking or marshalling position, and adjustment within a second, smaller range when the vehicle has taken up a driving mode. Adjustment of the ride height will thus be allowed when the vehicle is in a driving mode, but the elevation or ride height in this mode can only be adjusted within a range which is not detrimental to either the load or the vehicle.
One advantage of allowing the ride height of the vehicle framework and loading platform to be adjusted to as high a level as possible is that the framework ground clearance increases. This is of importance when the vehicle is driven over bad ground and when the vehicle is driven across angled ramps and steep structures.
Still another object of the present invention is, by providing the LCV with a means of adjusting the elevation of the vehicle framework and loading platform, that the driver will be able to selectively adjust the ride height in accordance with various conditions. Thus, if the vehicle is to be driven on a flat road as low a ride height as possible is of interest, or if the vehicle is driven over bad ground or across steep ramps and structures, as high a ride height as possible is of interest.
A still further advantage of having the vehicle framework and loading platform adjustable within a first, larger range when the vehicle has taken up a parking or marshalling position and a second smaller range when the vehicle has taken up a driving mode is that the vehicle cardan shaft, which is provided for connecting an output shaft of a transmission arranged in the vehicle to a driving wheel axle, is connected to the driving wheel axle in a certain angular position. When the vehicle is standing still or being driven at low speed, a relativel
Brandt Per-Olof
Terborn Bengt
Dickson Paul N.
Lerner David Littenberg Krumholz & Mentlik LLP
Phan Hau
Volvo Lastvagnar AB
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