Compact fluid system for shifting a transmission

Claim 2

In a fluid circuit for shifting a transmission having a plurality of fluid pressure actuated drive conditioning devices and having an operator''s shift control which has a neutral position and at least one drive position, the combination comprising means for supplying fluid under pressure, selector valve means for directing said fluid from said supply means to predetermined ones of said drive conditioning devices in response to movement of said shift control, pressure control means for producing a gradual rise of fluid pressure at said predetermined ones of said drive conditioning devices following said movement of said operator''s shift control, said pressure control means including a movable differential valve element defining a portion of the flow passage from said supply means to at least one of said predetermined ones of said drive conditioning devices and having resilient means acting on said valve element in a direction tending to close said flow passage and to shift said valve element to an initial position past that at which said flow passage is closed and having means defining a chamber wherein said fluid pressure acts on said valve element in a direction tending to open said flow passage, means defining a drain passage which is communicated with said chamber when said valve element is in said initial position and which is blocked from said chamber by movement of said valve element when said valve element moves away from said initial position, and a cut-off valve linked to said shift control and operated thereby for blocking said drain passage when said shift control is in said neutral position and for opening saId drain passage when said shift control is away from said neutral position whereby an initial buildup of fluid pressure in said chamber to shift said valve element away from said initial position thereof can only occur when said shift control is in said neutral position.

Claim 3

The combination defined in claim 1 wherein said chamber receives said fluid through a constricted passage in said valve element and further comprising a check valve disposed in said passage of said valve element.

Claim 4

The combination defined in claim 2 wherein said valve element has an additional passage for transmitting said fluid to said chamber through said check valve, said additional passage bypassing said constriction and being positioned to be closed when said valve is at said initial position.

Claim 5

A fluid circuit for shifting a transmission having a first plurality of fluid pressure actuated drive conditioning devices for selecting a speed ratio through said transmission and having a second plurality of fluid pressure actuated drive conditioning devices for selecting a drive direction through said transmission, comprising: an operator''s shift control means having a neutral position and forward and reverse drive positions and a plurality of speed ratio positions, a pump for supplying fluid under pressure, a speed ratio selector valve linked to said operator''s shift control means for directing fluid from said pump to predetermined ones of said speed ratio conditioning devices, as determined by the position of said shift control, a drive direction selector valve for directing fluid from said pump to a predetermined one of said second plurality of drive conditioning devices as determined by the position of said shift control, pressure control valve housing means defining a portion of the fluid flow path from said pump to said drive direction selector valve and having first and second bores therein wherein said fluid from said pump is transmitted to a portion of said first bore, a pressure modulating valve assembly disposed in said first bore and having a spool with an edge defining a variable flow passage communicated with said first portion of said first bore for controlling the pressure of fluid supplied to a region of said second bore, said spool being spring biased in a direction tending to increase fluid pressure at said region of said second bore and having load piston means for varying said spring biasing in accordance with fluid pressure supplied to a second portion of said first bore, a safety differential valve disposed in said second bore of said housing and having a spool movable in a first direction to block said region of said second bore from said drive direction selector valve and being further movable in the same direction to an initial position and being movable in an opposite direction to communicate said region of said second bore with said drive direction selector valve and having resilient biasing means acting thereon in said first direction, means defining a fluid chamber wherein fluid pressure acts on said spool of said safety differential valve in said opposite direction tending to open communication between said region of said second bore and said drive direction selector valve, said chamber being communicated with said region of said second bore whereby fluid pressure is transmitted to said chamber, means defining a drain passage which is communicated with said chamber when said safety-differential valve spool is at said initial position and which is blocked from said chamber when said safety-differential valve spool moves away from said initial position, and a cut-off valve responsive to movement of said shift control to close said drain passage when said shift control is in said neutral position whereby said fluid pressure in said chamber is unable to shift said safety-differential valve spool away from said initial position except when said shift control is in said neutral position.

Claim 6

A fluid circuit for shifting a transmission having a first plurality of fluid pressure actuated drive conditioning devices for selecting a speed ratio through said transmission and having a second plurality of fluid pressure actuated drive conditioning devices for selecting a drive direction through said transmission, comprising: an operator''s shift control means having a neutral position and forward and reverse drive positions and a plurality of speed ratio positions, a pump for supplying fluid under pressure, a speed ratio selector valve linked to said operator''s shift control means for directing fluid from said pump to predetermined ones of said speed ratio conditioning devices, as determined by the position of said shift control, a drive direction selector valve for directing fluid from said pump to a predetermined one of said second plurality of drive conditioning devices as determined by the position of said shift control, pressure control valve housing means defining a portion of the fluid flow path from said pump to said drive direction selector valve and having first and second bores therein wherein said fluid from said pump is transmitted to a portion of said first bore, a pressure modulating valve assembly disposed in said first bore and having a spool with an edge defining a variable flow passage communicated with said first portion of said first bore for controlling the pressure of fluid supplied to a region of said second bore, said spool being spring biased in a direction tending to increase fluid pressure at said region of said second bore and having load piston means for varying said spring biasing in accordance with fluid pressure supplied to a second portion of said first bore, a safety differential valve disposed in said second bore of said housing and having a spool movable in a first direction to block said region of said second bore from said drive direction selector valve and being further movable in the same direction to an initial position and being movable in an opposite direction to communicate said region of said second bore with said drive direction selector valve and having resilient biasing means acting thereon in said first direction, means defining a fluid chamber wherein fluid pressure acts on said spool of said safety differential valve in said opposite direction tending to open communication between said region of said second bore and said drive direction selector valve, said chamber being communicated with said region of said second bore whereby fluid pressure is transmitted to said chamber, means defining a drain passage which is communicated with said chamber when said safety-differential valve spool is at said initial position and which is blocked from said chamber when said safety-differential valve spool moves away from said initial position, and a cut-off valve responsive to movement of said shift control to close said drain passage when said shift control is in said neutral position whereby said fluid pressure in said chamber is unable to shift said safety-differential valve spool away from said initial position except when said shift control is in said neutral position.

Claim 7

The combination defined in claim 4 wherein said cut-off valve blocks said flow path to said drive direction selector valve when said shift control is in said neutral position thereof.

Claim 8

The combination defined in claim 4 wherein said spool of said safety-differential valve opens said second portion of said first bore to a drain when said safety differential valve spool is at said closed position and transmits fluid pressure to said second portion of said first bore through a flow restriction when said region of said second bore is communicated with said drive direction selector valve, whereby said load piston is gradually shifted to increase said spring biasing on said spool of said modulating valve assembly whereby a gradual pressure rise is produced at said predetermined ones of said drive conditioning devices.