Patent ID: 7270096

Claim:
A twin phaser comprising a drive member and two driven members arranged coaxially with one another, variable volume main working chambers defined between the members which serve to couple the drive member hydraulically to the two driven members and to vary the angular position of the drive member relative to the driven members, and locking means for locking the drive member to the driven members when the pressure in the working chambers is below a predetermined value, wherein the locking means comprise two coaxial locking pins mounted in a common bore in the centrally located member, bores in the two outer members, a resilient member for urging the pins away from one another into the bores in the two outer members, and further hydraulic chambers for urging the pins towards one another to retract them from the bores in the outer members when the hydraulic pressure in the main working chambers attains the predetermined value and wherein two pistons of the same diameter, each carrying a respective locking pin, are arranged back to back in a common cylindrical bore in the drive member, the pistons being urged apart by a spring located between them, and the space within the bore of the drive member between the two pistons is vented to allow fluids to enter and leave freely, in order to avoid hydraulic lock up of the pistons.