Three-position actuator piston assembly and actuator system utilizing same

A pressurized fluid-operated, three-position actuator assembly for selectably positioning a controlled device clutch in a selectable one of a first position, a second position axially offset said first position in a first axial direction, or a third position axially offset said first position in a second axial direction opposite said first axial direction, said assembly comprising:

• a shaft operatively associated with said controlled device;
• a differential area piston fixed for axial movement with said shaft, said differential area piston having a larger face exposed to pressurized fluid in a selectably, variably pressurized first chamber and an opposed smaller face exposed to pressurized fluid in a constantly pressurized second chamber pressurized fluid on said larger face causing a force urging said shaft in said first axial direction and pressurized fluid on said smaller face causing a force urging said shaft in said second axial direction;
• and
• a secondary piston having a face opposed to said smaller face of said differential area piston and exposed to pressurized fluid in said second chamber, said secondary piston effective to apply a force in said first axial direction to said shaft only if said controlled device was previously displaced n said second axial direction from said first axial position.

A pressurized fluid-operated, three-position shift actuator assembly (12) for selectably positioning a controlled double-acting jaw clutch in a selectable one of a neutral position, a first engaged position axially offset said neutral position in a first axial direction, or a second engaged position axially offset said neutral position in a second axial direction opposite said first axial direction, said assembly comprising:

• a body (14) defining a bore (16) having a large interior diameter portion (16A), a small interior diameter portion (16B), and an intermediate interior diameter portion (16C) axially interposed therebetween;
• a shaft (18) operatively associated with said jaw clutch and slidably received in said bore;
• a differential area piston (20) slidably and sealingly received in said large interior diameter bore portion and fixed for axial movement with said shaft, said differential area piston having a larger face (20A) exposed to pressurized fluid in a selectably, variably pressurized first chamber (26) defined by said larger face and said larger interior diameter bore portion, and an opposed smaller face (20B) exposed to pressurized fluid in a constantly pressurized second chamber (30) defined by said smaller face and said larger diameter bore portion, pressurized fluid on said larger face causing a force urging said shaft in said first axial direction and pressurized fluid on said smaller face causing a force urging said shaft in said second axial direction;
• and
• a generally tubular secondary piston (22) having an outer diameter surface (22B) slidably and sealingly received in said intermediate interior diameter bore portion and an interior diameter surface (22A) slidably and sealingly carried by the outer diameter surface (18A) of said shaft, said secondary piston having a face (22C) opposed to said smaller face of said differential area piston and exposed to pressurized fluid in said second chamber, said secondary piston limited in axial movement in said first axial direction relative to said shaft by a first stop member (24) and relative to said body by a second stop member (16E), said secondary piston engaging both said stop members (24 and 16E) when said shaft causes said clutch to be in the first position, whereby said secondary piston is effective to apply a force in said first axial direction to said shaft only if said clutch was previously displaced in said second axial direction from said neutral position.

A compound splitter-type mechanical transmission (110) comprising a double-acting splitter jaw clutch (180) for engaging a selected one of two splitter gears (174, 176) to shaft (146) and a pressurized fluid-operated, three-position shift actuator assembly (12) for selectably positioning said clutch in a selectable one of a neutral (N) position, a first engaged position (D) axially offset said neutral position in a first axial direction for engaging one of said splitter gears, or a second engaged position (OD) axially offset said neutral position in a second axial direction opposite said first axial direction for engaging the other of said splitter gears, said shift actuator assembly comprising:

• a shaft (18) operatively associated with said clutch (180A/180);
• a differential area piston (20) fixed for axial movement with said shaft, said differential area piston having a larger face (20A) exposed to pressurized fluid in a selectably, variably pressurized first chamber and an opposed smaller face (20B) exposed to pressurized fluid in a constantly pressurized second chamber, pressurized fluid on said larger face causing a force urging said shaft in said first axial direction and pressurized fluid on said smaller face causing a force urging said shaft in said second axial direction;
• and
• a secondary piston (22) having a face (22C) opposed to said smaller face of said differential area piston and exposed to pressurized fluid in said second chamber, said secondary piston effective to apply a force in said first axial direction to said shaft only if said clutch was previously displaced in said second axial direction from said neutral position.

A vehicular transmission system (10) comprising:

• a compound splitter-type mechanical transmission (110) comprising a double-acting splitter jaw clutch (180) for engaging a selected one of two splitter gears (174, 176) to shaft (146), a pressurized, fluid-operated, three-position shift actuator assembly (12) for selectably positioning said clutch in a selectable one of a neutral (N) position, a first engaged position (D) axially offset said neutral position in a first axial direction for engaging one of said splitter gears, or a second engaged position (OD) axially offset said neutral position in a second axial direction opposite said first axial direction for engaging the other of said splitter gears, said shift actuator assembly comprising a shaft (18) operatively associated with said clutch (180A/180);
• a differential area piston (20) fixed for axial movement with said shaft, said differential area piston having a larger face (20A) exposed to pressurized fluid in a selectably, variably pressurized first chamber and an opposed smaller face (20B) exposed to pressurized fluid in a constantly pressurized second chamber, pressurized fluid on said larger face causing a f said shaft in said first axial direction and pressurized fluid on said smaller face causing a force urging said shaft in said second axial direction;
• and a secondary piston (22) having a face (22C) opposed to said smaller face of said differential area piston and exposed to pressurized fluid in said second chamber, said secondary piston effective to apply a force in said first axial direction to said shaft only if said clutch was previously displaced in said second axial direction from said neutral position;
• an onboard source of regulated, compressed air (44/B) regulated to a predetermined regulation pressure connected directly to said second chamber (30);
• and
• an onboard source of selectably variably pressurized, compressed air (A) connected to said first chamber (26).