Air spring control system and method

A method for determining the force necessary to separate a first and a second mass having disposed therebetween an inflatable member comprising:

• supplying compressed gas to the member in pulses, said pulses occurring at a constant rate for a predetermined duration;
• sensing the pressure of the gas within the member at time intervals;
• comparing the pressure sensed at one time interval with the pressure sensed at least one preceding time interval to determine the pressure change;
• repeating the step of comparing;
• comparing the pressure change to at least one prior pressure change;
• generating a pressure signal when the pressure change decreases compared to at least one prior pressure change;
• and
• processing the pressure signal with the known characteristics of the inflatable member to determine the force necessary to separate the masses.

A system for determining the force necessary to separate a first and a second mass, the system comprising:

• an inflatable member disposed in a deflated state between the masses;
• a source of compressed gas;
• means for supplying the compressed gas to the member at a constant rate for inflation thereof for separating the masses;
• means for sensing the pressure of the gas within the member at substantially uniform time intervals during inflation thereof;
• means for comparing the sensed pressure with the pressure sensed at a preceding time interval to determine the pressure change per unit time and comparing the pressure change per unit time with previously determined pressure changes per unit time;
• generating a signal corresponding to pressure when the pressure change per unit time decreases in comparison to previously determined pressure changes indicating separation of the masses;
• and
• processing the pressure signal to determine the force corresponding to the pressure signal.

A control system for an inflatable spring member disposed between sprung and unsprung masses, the member inflatable from a deflated state to an inflated state to separate the sprung and unsprung masses, the system comprising:

• means for inflating the member with a compressed gas at a constant flow rate;
• means for sensing the pressure of the gas within the member at time intervals;
• means for comparing the pressure sensed at each time interval with the pressure sensed at least one preceding time interval to determine a pressure-time history, the history being of a first characteristic when the member is being inflated and is at a deflated state and changing to a second characteristic when the masses begin to separate, the comparing means issuing a pressure signal when the history changes from the first to the second characteristic;
• and
• means for processing the pressure signal to determine the force corresponding to the pressure signal issued when the masses separate.

A method for leveling a load relative to a datum comprising:

• supporting the load relative to the datum on at least one inflatable member of the type where, for a known load, pressure of a gas within the member corresponds to a height of the load relative to the datum, the member inflatable from a first non-loading supporting state corresponding to a known calibrated load height to an inflated state to elevate the load to a desired level height;
• inflating the member at the first state with compressed gas at a constant flow rate;
• sensing the pressure within the member at substantially uniform time intervals;
• comparing the sensed pressure with the pressure sensed at at least one preceding time interval to develop a pressure increase per unit time history, the history being a first characteristic when the member is inflated before the load is supported and a second characteristic when the the load is supported;
• determining the pressure at which the history changes from the first to the second characteristic;
• establishing the load borne by the air spring from the determined pressure;
• and
• based upon the established load, pressurizing the inflatable member to the pressure corresponding to elevating the load at the desired, leveling height.

A system for leveling a load relative to a datum comprising:

• at least one inflatable member to support the load, each member inflatable from a deflated state where the member has a determined length to an inflated state of a length necessary to level the load relative to the datum, each member further being of the type where, for a known load, pressure correlates to member and load height;
• a source of compressed gas;
• means for supplying compressed gas to each member at a constant rate;
• means for sensing the pressure of the gas within the member;
• means for developing from the sensed pressure a pressure per unit time history of the pressure within the member as it is inflated from the deflated state to a second state where the load is first lifted relative to the datum, the history being a first characteristic when the member is at the deflated state and a second characteristic when the load is lifted;
• means for determining from the history the pressure at which the history changes from the first to the second characteristic representing the pressure at which the load is lifted by the member;
• means for generating a pressure signal representative of the pressure at which the history changes from the first to the second characteristic and from the known deflated height of the member;
• establishing the load borne by the member;
• and
• inflating the member to a pressure which correlates to a member and load height such that the load is level relative to the datum.

A method for determining the weight of a loaded vehicle having an unloaded weight and having at least two axles with a rolling-lobe type air spring support the vehicle chassis at less than all points of support between said axles and chassis, the vehicle having a known weight distribution characteristic, the method comprising:

• inflating each air spring until the vehicle is at a predetermined height;
• sensing the pressure of the gas within each air spring;
• determining the weight on each air spring from the sensed pressure and the known pressure weight relationship for the spring;
• and
• from the known weight distribution characteristic and from the weight on each spring, determining the weight of the load.