Fluid suspension system

Claim 2

A fluid suspension system in which a fluid motor having a cushioning end and a normally vented opposite end is disposed in elevational supporting relation between a sprung mass and an unsprung mass, said fluid suspension system comprising; resiliently biased fluid pressure means in constant communication with said cushioning end of said fluid motor to resiliently support said sprung mass at substantially a predetermined elevated cushioning position relative to said unsprung mass when said opposite end is vented; and lockout valve means operative selectively to communicate said opposite end of said fluid motor with said fluid pressure means and simultaneously to block the venting thereof to equalize pressure in said ends of the motor and minimize said resilient supprt whereby the weight of the sprung mass is operative temporarily to move the sprung mass to a lower predetermined fixed position.

Claim 3

The fluid suspension system of claim 1 including fluid flow restricting means disposed between said fluid pressure means and said opposite end of said fluid motor to control the lowering rate of the sprung mass.

Claim 4

The fluid suspension system of claim 1 including a non-return valve disposed between said fluid pressure means and said opposite end of said fluid motor to prevent flow of fluid from said opposite end toward said fluid pressure means temporarily to lock said sprung mass in said predetermined fixed position.

Claim 5

The fluid suspension system of claim 1 including; a reservoir; and separate valve means having open and closed positions for controlling communication between said opposite end and said reservoir and operative to move to said open position communicating said opposite end with said reservoir responsive to operation of said lockout valve means to block communication of said opposite end with said fluid pressure means and return said sprung mass to said predetermined cushioning position.

Claim 6

A fluid suspension system in which a fluid motor having a cushioning end and a normally vented opposite end is disposed in elevational supporting relation between a sprung mass and an unsprung mass, said fluid suspension system comprising; resiliently biased fluid pressure means in constant communication with said cushioning end of said fluid motor to resiliently support said sprung mass at substantially a predetermined elevated cushioning position relative to said unsprung mass when said opposite end is vented; lockout valve means operative selectively to communicate said opposite end of said fluid motor with said fluid pressure means and simultaneously to block the venting thereof to equalize pressure in said ends of the motor whereby the weight of the sprung mass is operative temporarily to move the sprung mass to a lower predetermined fixed position; a reservoir; separate valve means having open and closed positions for controlling communication between said opposite end and said reservoir and operative to move to said open position communicating said opposite end with said reservoir responsive to operation of said lockout valve means to block communication of said opposite end with said fluid pressure means and return said sprung mass to said predetermined cushioning position; a source of fluid pressure; and leveling valve means, having a neutral position normally blocking communication of said cushioning end of said fluid motor with said source of fluid pressure and said reservoir and being responsive to predetermined variations in the relative position of said sprung mass to said unsprung mass to control communciation of said cushioning end with said source of fluid pressure and said reservoir to maintain said sprung mass substantially in said predetermined cushioning position.

Claim 7

A fluid suspension system in which a fluid motor having a cushioning end and a normally vented opposite end is disposed in elevational supporting relation between a sprung mass and an unsprung mass, said fluid suspension system comprising; resiliently biased fluid pressure means in constant communication with said cushioning end of said fluid motor to resiliently support said sprung mass at substantially a predetermined elevated cushioning position relative to said unsprung mass when said opposite end is vented; lockout valve means operative selectively to communicate said opposite end of said fluid motor with said fluid pressure means and simultaneously to block the venting thereof to equalize pressure in said ends of the motor whereby the weight of the sprung mass is operative temporarily to move the sprung mass to a lower predetermined fixed position; a reservoir; separate valve means having open and closed positions for controlling communication between said opposite end and said reservoir and operative to move to said open position communicating said opposite end with said reservoir responsive to operation of said lockout valve means to block communication of said opposite end with said fluid pressure means and return said sprung mass to said predetermined cushioning position; a source of fluid pressure; and leveling valve means, having a neutral position normally blocking communication of said cushioning end of said fluid motor with said source of fluid pressure and said reservoir and being responsive to predetermined variations in the relative position of said sprung mass to said unsprung mass to control communciation of said cushioning end with said source of fluid pressure and said reservoir to maintain said sprung mass substantially in said predetermined cushioning position.

Claim 8

The fluid suspension system of claim 5 wherein said unsprung mass is a tractor and said sprung mass is a trailer, and said fluid suspension system is a cushion hitch which couples said trailer to said tractor for relative vertical movement therebetween, said cushion hitch being tuned and damped to generate out-of-phase vertical movement of said trailer relative to vertical movement of said tractor to suppress bounce of said tractor and said trailer as a unit.

Claim 9

The fluid suspension system of claim 6 including link means pivotally coupling said trailer and said tractor for vertical relative movement therebetween with said fluid motor connected between said link means; a valve spool movably disposed in said leveling valve means for controlling said communication of said cushioning end of said fluid motor with said source and said reservoir to maintain a preselected elevational relationship between said trailer and said tractor; detent/release means in said leveling valve means engaging said valve spool in a neutral blocking position and requiring a selected minimum break-out force for moving said valve spool; and resilient lost motion linkage means for connecting said valve spool to said link means to exert an increasing actuating force on said valve spool in response to relative vertical movement of said tractor and trailer so that limited relative movement of said trailer from said preselected elevational relationship can occur without exceeding said selected minimum break-out force required to move said valve spool from said neutral blocking position.

Claim 10

The fluid suspension system of claim 5 further comprising; pilot circuit means including a source of pilot fluid pressure; actuation means responsive to pilot fluid pressure for actuating said lockout valve means and said separate valve means; and a pilot selector valve means interposed between said source of pilot fluid pressure and said actuation means for selectively conditioning said lockout valve means and said separate valve means to establish said preselected elevational position of said trailer and to condition said lockout valve means and said separate valve means to permit said trailer to move to said predetermined fixed position.

Claim 11

The fluid suspension means of claim 8 wherein said separate valve means comprises a poppet type check valve and is coaxially aligned with said lockout valve means; actuating means on said lockout valve for moving said separate valve means to said open position when said lockout valve is conditioned to block communication between said opposite end of said fluid motor and said fluid pressure means.

Claim 12

The fluid suspension means of claim 8 wherein said lockout valve means includes pilot fluid pressure responsive actuating means; separate actuation means, responsive to said pilot fluid pressure for actuating said separate valve means simultaneously with said lockout valve means.

Claim 13

The fluid suspension system of claim 8 wherein said leveling valve means includes a valve spool; a resilient lost motion linkage connected to said spool and responsive to movement of said sprung mass toward said predetermined fixed position to move said valve spool to a position communicating said source of fluid pressure with said cushioning end of said fluid motor; and fluid actuation means operatively associated with said valve spool and selectively communicable by said lockout valve means with said source of fluid pressure to act in opposition to said resilient lost motion linkage and return said valve spool to said neutral position.

Claim 14

In a hitch assembly coupling a tractor and a trailer through link members for vertical relative movement with a hydropneumatic support connected between the link members to improve the riding qualities by suppressing bounce, an improved, low-cost hitch control valve and linkage comprising: a control valve mounted adjacent to said hitch assembly and connected to a source of pressurized fluid; a suspension cushioning means connected to said control valve and connected across said link members of said hitch assembly allowing relative vertical movement between said tractor and said trailer, said suspension cushioning means having at least one pneumatic accumulator commonly connected thereto; a valve spool movable in said control valve to admit pressurized fluid to said suspension cushioning means and vent fluid therefrom to maintain a preselected relationship between said tractor and said trailer; a detent/release means in said valve engaging said valve spool and having a neutral engaged position requiring a selected mininum break-out force; a lost motion linkage means connecting said valve spool and one of said link members of said hitch assembly moving relative to said control valve through which vertical movement of said hitch assembly is transmitted to said valve spool and whereby limited hitch movement relative to said preselected relationship of said tractor and said trailer can occur without actuation of said control valve and smooth fluid adjustment will be available once said break-out force of said valve spool has been exceeded by forces displacing it from said lost motion linkage means.

Claim 15

In a hitch assembly coupling a tractor and a trailer through link members for vertical relative movement with a hydropneumatic support connected between the link members to improve the riding qualities by suppressing bounce, an improved, low-cost hitch control valve and linkage comprising: a control valve mounted adjacent to said hitch assembly and connected to a source of pressurized fluid; a suspension cushioning means connected to said control valve and connected across said link members of said hitch assembly allowing relative vertical movement between said tractor and said trailer, said suspension cushioning means having at least one pneumatic accumulator commonly connected thereto; a valve spool movable in said control valve to admit pressurized fluid to said suspension cushioning means and vent fluid therefrom to maintain a preselected relationship between said tractor and said trailer; a detent/release means in said valve engaging said valve spool and having a neutral engaged position requiring a selected mininum break-out force; a lost motion linkage means connecting said valve spool and one of said link members of said hitch assembly moving relative to said control valve through which vertical movement of said hitch assembly is transmitted to said valve spool and whereby limited hitch movement relative to said preselected relationship of said tractor and said trailer can occur without actuation of said control valve and smooth fluid adjustment will be available once said break-out force of said valve spool has been exceeded by forces displacing it from said lost motion linkage means.

Claim 16

The improved control valve and linkage defined in claim 12 wherein the force generated by said lost motion linkage means is proportional to its absorbed motion and the break-out force of the valve spool is sufficient to cause said lost motion linkage means to absorb some motion before it exceeds said break-out force.

Claim 17

The improved control valve and linkage defined in claim 13 wherein the lost motion linkage means includes a displaceable spring member having a force generally linear relative to its absorbed displacement.

Claim 18

The improved control valve and linkage defined in claim 13 wherein several pneumatic accumulators are connected to the suspension cushioning means, each accumulator having a different preload to increase the load range of the trailer over which said cushioning means will effectively suppress bounce.

Claim 19

The improved control valve and linkage defined in claim 13 wherein the hitch assembly is a multi-pivoted unit connecting a tractor portion with a trailer portion of an articulated vehicle.

Claim 20

The improved control valve and linkage defined in claim 16 wherein the trailer portion is an earthmoving scraper.

Claim 21

The improved control valve and linkage defined in claim 16 wherein the hitch assembly is constructed with link members arranged to cause pitch to be suppressed along with bounce by the cushioning means.

Claim 22

The improved control valve and linkage defined in claim 13 wherein the source of pressurized fluid is a pump driven by an engine in the tractor and the control valve has a pressure controlled valve operable to bleed pressure from the suspension cushioning means when said engine is stopped.

Claim 23

The improved control valve and linkage defined in claim 13 wherein the detent/release means includes cammed surfaces on opposite sides of its neutral engaged position whereby the centering force on the valve spool is increased as the hitch assembly approaches the preselected relationship between said tractor and trailer.

Claim 24

The improved control valve and linkage defined in claim 13 wherein the control valve includes controllable piston means operable to activate and deactivate the cushion means of the hitch assembly.

Claim 25

The improved control valve and linkage defined in claim 13 wherein the cushioning means is a hydraulic cylinder.