Land vehicles – Wheeled – Running gear
Reexamination Certificate
2000-04-21
2001-11-06
Dickson, Paul N. (Department: 3618)
Land vehicles
Wheeled
Running gear
C280S124128, C280S124158
Reexamination Certificate
active
06312006
ABSTRACT:
The present invention relates to a two-axle vehicle suspension arrangement, comprising a pair of support members for each axle, means for fixing the wheel axles between the ends of each support member, and spring elements disposed at or in the vicinity of the ends of the support members and joining the support members to a frame.
A commonly occurring wheel suspension arrangement with spring elements at either end of a support member has spring elements in the form of two identical air springs arranged symmetrically in relation to the axle position, i.e. the axle is arranged midway between two springs having the same spring force. The various parameters determining the length of the support arm include the desired spring properties and the space required by other system components.
For space reasons there may be a need to have a relatively short distance between the axle and the spring element on one side of the axle to provide space for other system components, while there is no corresponding requirement for space on the other side. If the larger space requirement on one side of the axle is made the determining dimension and the support member parts on either si equal length, then the deformation will be the same and balance will be obtained during the spring sequence, but at the same time this will result in a total length of the support member which is greater than what would be optimum if there were not differing space requirements on either side of the axle.
One method of avoiding this is to make the axle asymmetrical in relation to the spring mountings, as is known by EP-A-0 137 957. In this case the support member portion on one side of the axle has been extended relative to the support member portion on the other side of the axle, to provide space for a lifting device by means of which the wheel axle and thus the wheels can be raised from the road surface when the vehicle load is low. However, the air spring elements on either side of the axle are identical, i.e. they have the same spring force, and his results in imbalance during the spring action by uneven deformation in the spring elements due to moment arms of unequal length.
The purpose of the present invention is to achieve a wheel suspension arrangement of the type described by way of introduction, which makes it possible to reduce the total installation space required on the frame side, compared with known symmetrical wheel axle suspensions, at the same time as the problems with imbalance in previously known asymmetrical wheel axle suspension systems are eliminated.
This is achieved according to the invention by virtue of the fact that the wheel axles are fixed in an axle position asymmetrically between the outer ends of the support members, and that the support members of one axle are reversed in relation to the support members of the other axle, so that the spring elements located closest to the respective axle position are directed towards each other, the spring elements being so selected that the spring force of the spring elements located closest to the axle position is greater than the spring force of the other spring elements.
Preferably, the spring elements are selected so that the product of the spring force and the distance from the axle position to the point of attachment of the spring elements in the support member is at least approximately equal on both sides of the axle position, thus providing optimal spring properties.
The basic principle of the invention is particularly easy to apply to wheel suspensions with air springs, where the spring elements consists of cylindrical air cushions of elastic material. The spring forces of the air springs are adapted by selecting an area differential between the air cushions so that the difference between the effective cross sectional areas of the air cushions is inversely proportional to the difference between the distances to the axle.
REFERENCES:
patent: 2903256 (1959-09-01), Weiss
patent: 2998261 (1961-08-01), Bartlett
patent: 4132432 (1979-01-01), Raidel
patent: 4378935 (1983-04-01), Brown et al.
patent: 4756550 (1988-07-01), Raidel
patent: 0 137 953 (1985-04-01), None
Dickson Paul N.
Volvo Lastvagnar AB
Young & Thompson
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