Reduction of coil spring load height variability

Details Reduction of coil spring load height variability Reduction of coil spring load height variability

2000-09-20

2002-11-19

Dickson, Paul N. (Department: 3613)

Spring devices

Vehicle

Mechanical spring and nonresilient retarder

C267S166000, C029S896910, C029S896930

Reexamination Certificate

active

06481702

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention includes a method of assembling coil springs under load to isolators of varying height to provide a more consistent overall assembled height. Coil springs are used in vehicle suspension systems at various locations and for various functions. Springs may be used to isolate the vehicle interior from bumps, dips, unevenness and other obstacles in the roadway. Generally, springs in a suspension provide a dampening effect and a more comfortable ride for the occupants.
Suspension coil springs typically used in large vehicles also tend to be of large diameter and height. There are always possible manufacturing tolerances or inconsistencies in springs. The larger the spring, the greater the potential inconsistency in the manufacturing process.
Coil springs are typically made out of steel wire. No matter how tightly manufacturing tolerances are controlled in the manufacturing process the overall spring height may vary. One common variation is the spring height under a given load. That is, two springs manufactured together may each have an individual reaction to a particular load that changes the height of the spring. Vehicle manufacturers would like a consistent height under a given load. However, the different height springs make this difficult. The varying spring heights can effect other components such as moving the frame too low or too high.
One current method of accommodating the variation of coil spring height under load is to measure and test each spring under a given load. After each spring is tested a tolerance height is set. Springs that do not meet the required tolerance under load are not used. The springs may be sorted into categories and grouped by load height (i.e. low, medium, high). Springs of one group are used on a vehicle such that the reaction of the springs on the vehicle is at least somewhat consistent. This process is cumbersome and time consuming.
SUMMARY OF THE INVENTION AND ADVANTAGES
This invention generally includes methods of controlling the load height variability in coil springs used in a vehicle suspension system. The methods involve placing springs under load and then assembling an isolator to the spring. The isolators are of varying heights to compensate for different spring heights. The isolator and spring are then assembled into the suspension. Isolators can be assembled to the top, bottom or both the top and bottom of the spring.
Different methods of forming the spring to the isolator can be used. The springs can be placed into molds with a preset dimension in the mold cavity to represent the isolator. The mold cavity may also be an adjustable so that a single mold can be used to mold the isolator to the spring. In a mold with an adjustable mold cavity the spring is placed under a load and the height of the mold cavity is adjusted. Adjusting the mold cavity to the desired position ensures an overall constant height when the spring and isolator are assembled together under load. Alternatively, the isolators can be formed separately from the springs and then added to the spring.
Adding isolators to the spring ensures a more consistent overall load height for each spring and isolator assembly.


REFERENCES:
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patent: 3578279 (1971-05-01), Scheldorf
patent: 3862751 (1975-01-01), Schwaller
patent: 4162064 (1979-07-01), Bouton et al.
patent: 4475725 (1984-10-01), Niemann
patent: 5090657 (1992-02-01), Dreiman
patent: 5467970 (1995-11-01), Ratu et al.
patent: 5772191 (1998-06-01), Nakano et al.
patent: 6254072 (2001-07-01), Bono et al.

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