Multi-ratio transmission and control with downshift inhibitors

Claim 2

A transmission and control comprising multi-ratio planetary gear means; fluid operated drive establishing means for establishing first, second and third drive ratios in said planetary gear means; a fluid source; a pair of shift control valve means in fluid communication with said source and said drive establishing means being shiftable for selectively controlling said drive establishing means and having a shift control chamber and an inhibitor chamber; transmission governor means for providing a signal responsive to the speed of the transmission; first inhibitor valve means in fluid communication with one of said shift control valve means, said governor means and the third ratio drive establishing means for directing fluid pressure from said source to said inhibitor chamber of said one shift control valve means for preventing downshifting of said one shift control valve means when said planetary gearing means is in the third ratio and said transmission speed is above a predetermined value to prevent a drive ratio change from the third ratio to the second; and second inhibitor valve means in fluid communication with the other shift control valve means, said governor means and the second ratio drive establishing means for directing fluid pressure from said source to said inhibitor chamber of said other shift control valve means when said planetary gear means is in said second ratio and said transmission speed is above a predetermined value to prevent a drive ratio change from the second ratio to the first ratio.

Claim 3

A transmission and control comprising multi-ratio planetary gear means; fluid operated drive establishing means for establishing first, second and third drive ratios in said planetary gear means; a fluid source; a first shift control valve having a valve bore in fluid communication with said source and said drive establishing means, a valve spool slidably disposed in the valve bore for selectively directing fluid from said source to said drive establishing means to control the establishment of the first, second and third drive ratios, a shift control chamber adjacent one end of the valve spool, and an inhibitor chamber adjacent the opposite end of the valve spool; a second shift control valve having a valve bore in fluid communication with said first shift control valve and said drive establishing means, a valve spool slidably disposed in the valve bore for selectively directing fluid from said first shift control valve to said drive establishing means to control the establishment of the first and second drive ratios, a shift control chamber adjacent one end of the valve spool and an inhibitor chamber adjacent the opposite end of the valve spool; transmission governor means for providing a signal responsive to the speed of the transmission; first inhibitor valve having a valve bore in fluid communication with the inhibitor chamber of said first shift control valve and the drive establishing means controlling the third ratio, a valve spool slidably disposed in the valve bore for directing fluid from the drive establishing means to the inhibitor chamber, and a governor chamber adjacent the valve spool in fluid communication with said governor means for inhibiting downshifting of said first shift control valve when said planetary gearing means is in the third ratio and said transmission speed is above a predetermined value to prevent a drive ratio change from the third ratio to the second; and second inhibitor valve having a valve bore in fluid communication with the inhibitor chamber of the second shift control valve and the first shift control valve, a valve spool slidably disposed in the valve bore for directing fluid from the first shift control valve to the inhibitor chamber, and a governor chamber adjacent the valve spool in fluid communication with said governor means for inhibiting downshifting of said second shift control valve when said planetary gear means is in said second ratio and said transmission speed iS above another predetermined value to prevent a drive ratio change from the second ratio to the first ratio.

Claim 4

A transmission and control comprising multi-ratio planetary gear means; fluid operated drive establishing means for establishing first, second and third drive ratios in said planetary gear means; a fluid source; a first shift control valve having a valve bore in fluid communication with said source and said drive establishing means, a valve spool slidably disposed in the valve bore for selectively directing fluid from said source to said drive establishing means to control the establishment of the first, second and third drive ratios, a shift control chamber adjacent one end of the valve spool, and an inhibitor chamber adjacent the opposite end of the valve spool; a second shift control valve having a valve bore in fluid communication with said first shift control valve and said drive establishing means, a valve spool slidably disposed in the valve bore for selectively directing fluid from said first shift control valve to said drive establishing means to control the establishment of the first and second drive ratios, a shift control chamber adjacent one end of the valve spool and an inhibitor chamber adjacent the opposite end of the valve spool; transmission governor means for providing a signal responsive to the speed of the transmission; first inhibitor valve having a valve bore in fluid communication with the inhibitor chamber of said first shift control valve and the drive establishing means controlling the third ratio, a valve spool slidably disposed in the valve bore for directing fluid from the drive establishing means to the inhibitor chamber, and a governor chamber adjacent the valve spool in fluid communication with said governor means for inhibiting downshifting of said first shift control valve when said planetary gearing means is in the third ratio and said transmission speed is above a predetermined value to prevent a drive ratio change from the third ratio to the second; and second inhibitor valve having a valve bore in fluid communication with the inhibitor chamber of the second shift control valve and the first shift control valve, a valve spool slidably disposed in the valve bore for directing fluid from the first shift control valve to the inhibitor chamber, and a governor chamber adjacent the valve spool in fluid communication with said governor means for inhibiting downshifting of said second shift control valve when said planetary gear means is in said second ratio and said transmission speed iS above another predetermined value to prevent a drive ratio change from the second ratio to the first ratio.