1999-07-12
2001-06-19
DePumpo, Daniel G. (Department: 3611)
C280S081600, C180S024010, C180S024020
Reexamination Certificate
active
06247196
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a bogie construction particularly intended for specially heavy vehicles, such as mining vehicles, the bogie construction comprising at least two interconnected stiff axles, which form a bogie, at least some of the axles belonging to the bogie being turnable when the vehicle is steered with respect to a vertical pivoted axle mounted between the ends of the axles which are steerable with respect to the frame of the vehicle, and for interconnecting the axles belonging to the bogie. The bogie construction is provided with a rocking lever, which is arranged to turn with respect to the transverse axle of the vehicle between its ends and move in the longitudinal direction of the vehicle as a result of a steering movement of the axles in the bogie.
Stiff axles are commonly used in vehicles intended for especially heavy transports, such as heavy transport equipment, machinery, mining vehicles and the like. It is preferable to provide such vehicles with stiff axles because the loads are heavy. A structure of this kind is also simpler and thus more durable. Furthermore, the use of stiff axles is economically feasible. Usually there are more than two axles per vehicle in heavy vehicles, and axles are combined into bogie constructions using different levers and springs, which allows distribution of the load between several axles. In the case of axle constructions of specially heavy vehicles one also needs to consider the effect of the load carried by the vehicle, which may be arranged rather unevenly, and the effect of an uneven support (road) surface. Furthermore, since heavy vehicles typically also have large outer dimensions, i.e., they are long and wide, one usually needs to be able to steer more than one axle to be able to manage them easier. The turning radius can be reduced substantially if all axles are arranged to turn when the vehicle is steered.
Stiff axles which are turned during steering are typically combined with each other into a bogie construction using an equalizer lever or the like, usually by means of a rocking lever pivoted between its ends. Important design considerations include the fact that the wheels on the different sides of the vehicle move along turning circles with different radii when the vehicle is steered, and the additional fact that successive axles need to be able to turn by a different angle depending on their location in the longitudinal direction of the vehicle so that successive wheels could move along the same turning circle. In one prior art arrangement, the rocking lever interconnecting the axles is arranged to move in the longitudinal direction of the vehicle by pivoting it on a turning axle and by connecting it to other axles by various suspension rods and joints. There are also prior art proposals where the rocking lever is pivoted on the frame, and thus there are pivoted suspension rods mounted between the axles and the rocking lever, which allow the axles to move as required for steering. A disadvantage associated with the prior art structures is that a lot of space is required for the structure so that the levers can turn in the manner required for steering. A further problem is that steering causes the vehicle frame to move in the up and down direction, which requires considerable steering forces. Because the steering members have to lift the mass of the vehicle and the load carried by it when the vehicle turns, wheel suspension and steering members are loaded considerably.
An object of the present invention is to provide a new bogie construction for especially heavy vehicles, such as mining vehicles, which eliminates problems of the prior art.
SUMMARY OF THE INVENTION
The bogie construction of the invention is characterized in that the rocking lever which interconnects axles is pivoted by a joint located between its ends so that it can pivot with respect to the frame. The joint is arranged to move in the longitudinal direction of the frame so that it allows movement of the rocking lever in the longitudinal direction of the vehicle caused by steering of the axles. The first end of the rocking lever is connected to a first axle by means of a suspension rod. The first end of the first suspension rod is pivoted on the first end of the rocking lever and its second end is pivoted on the first axle. The second end of the rocking lever is pivoted by a joint on a second axle that is pivotably mounted to the joint. The second axle determines the displacement of the rocking lever in the longitudinal direction of the vehicle. The rocking lever is arranged to move substantially only in a horizontal direction during steering of the vehicle.
An essential idea of the invention is that two or more successive stiff axles are combined into a bogie construction by means of a rocking lever or several rocking levers, depending on the number of axles. The axles of the bogie are connected to a rocking lever by suspension rods or suitable ears, and the rocking lever is pivoted on the frame between its ends. Another essential feature of the invention is that the rocking lever is arranged to move in the longitudinal direction of the vehicle as required by steering so that the pivot point between its ends, around which the rocking lever is arranged to swing, is arranged to move in the longitudinal direction of the vehicle. The degree of displacement of the rocking lever in the longitudinal direction of the vehicle is preferably determined by the bogie axle that turns least. The rocking lever is pivoted on this axle by a joint, which allows movement of the ends of the rocking lever in the up and down direction, but the steering movement of the axle is transmitted to the rocking lever as its longitudinal movement. In that case the rocking lever is arranged to perform parallel transfer according to the steering movements. An essential idea of a preferred embodiment of the invention is that the rocking lever is pivoted on the free end of a supporting arm turnably pivoted with respect to the frame. An essential idea of another preferred embodiment of the invention is that the rocking lever between the axles is pivoted at least on the outermost axle below it, i.e., on the axle that turns most, using e.g., a curved C-shaped suspension rod and pivoted on the other axle with one joint. An idea of a third preferred embodiment is that the lower surfaces of at least some of the axles are provided with ears extending substantially downwards from the axles. The ear and naturally the suspension rod pivoted on the ear become longer, the further away the axle is from the longitudinal center of the vehicle. This arrangement allows to compensate for the different degrees of inclination of the suspension rods due to different turning angles. Furthermore, an essential idea of a fourth preferred embodiment of the invention is that the bogies formed by successive stiff axles are connected together on both sides of the vehicle by means of longitudinal equalizer levers. Thus the lever mechanism is arranged to distribute the loads directed to the bogies and their axles evenly in different loading and driving situations of the vehicle. Furthermore, the lever mechanisms on both sides of the frame may be connected by a transverse equalizer lever or by a corresponding arrangement which also allows rotational movement between the bogies.
An advantage of the invention is that steering of the axles does not cause significant vertical movement of the frame, and thus the loads directed to the lever mechanism and steering members will be smaller. Furthermore, the mechanical lever arrangement of the invention is simple and durable, and its features can be changed easily in various ways by changing spring stiffness, lever arms, joints, etc. A further advantage is that the levers of the bogie can be mounted in the structures of the vehicle better than in prior art solutions, which leaves more room for different actuators and components in the lower sections of the vehicle. An advantage of a suspension rod pivoted below the axle is that the suspension r
Burns Doane Swecker & Mathis L.L.P.
DePumpo Daniel G.
Sandvik AB
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