Electromechanical actuator and latch assembly for ram air turbine

This disclosure relates to an electromechanical actuator latch system used for a ram air turbine (RAT), for example.

A typical hydraulic RAT actuator includes a piston rod nested within and movable relative to a cylinder. In one example actuator, the piston rod is affixed to a housing, and the cylinder is free to slide. The cylinder moves telescopically with respect to the piston rod during a deploy sequence. The deploy sequence is initiated by triggering a latch assembly with a solenoid, thus unlocking the cylinder from the piston rod. The solenoid includes a rod that travels a small distance under reduced electrical power.

The actuator and its components are under very high stresses, and the components are designed to operate under high G-loads. Thus, the latch assembly must stay in the latched position until acted upon by the solenoid.

In one exemplary embodiment, a latch assembly for a RAT actuator includes a lever block having spaced apart first and second lateral walls interconnected to one another by a bridge wall. The first and second lateral walls provide a pivot axis at one end. A latch pin is at another end opposite the one end. The latch pin extends between the first and second lateral walls. A latch bearing is arranged in each of the first and second lateral walls. Each bearing receives an end of the latch pin and is configured to permit the latch pin to rotate relative to the lever block.

In another exemplary embodiment, a latching system for a RAT actuator includes a housing. A lever block is arranged within the housing and has first and second lateral walls interconnected to one another by a bridge wall. The first and second lateral walls provide a pivot axis at one end. The lever block provides a deploy surface. A latch pin is at another end opposite the one end. The latch pin extends between the first and second lateral walls. A solenoid is mounted to the housing and includes a rod having an end that engages the deploy surface. The solenoid is configured to push the lever block about the pivot axis during a deploy sequence.

The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a RAT system in a deployed position.

FIG. 2 is a cross-sectional view of an actuator illustrated in FIG. 2 , but in a retracted position.

FIG. 3 is bottom perspective view of a latch assembly shown in FIG. 2 .

FIG. 4 is a top perspective view of the latch assembly shown in FIG. 3 , but without a biasing member shown.

FIG. 1 illustrates a RAT system 10 secured to an aircraft structure 12 by a housing 14 . The housing 14 pivotally supports a strut 16 having a turbine 18 at one end. The turbine 18 includes blades 20 , which impart rotational drive to a generator 22 and a hydraulic pump 30 , for example. An actuator 24 is secured to the strut 16 at a first end 26 and to the housing at a second end 28 . The actuator 24 is illustrated in its deployed position.

Referring to FIG. 2 , the actuator 24 includes a housing 32 having a piston rod 34 and a cylinder 36 , unattached to housing 32 , telescopically arranged relative to one another. A deploy spring 38 is arranged between the housing 32 and the cylinders 36 in a compressed state with the actuator 24 in its retracted position, shown in FIG. 2 . The piston rod 34 is affixed to the housing 32 , and the cylinder 36 is arranged to slide over the piston rod 34 .

The piston rod 34 supports up-lock and down-lock wedges 48 , 50 . A latch assembly 52 is provided in the housing 32 near a deploy solenoid 40 that is mounted on the housing 32 . The latch assembly 52 , immersed in hydraulic fluid, is triggered by the solenoid 40 to initiate a deploy sequence. In the example, a pair of solenoids 40 is used for redundancy. A lock bolt 54 is arranged slideably within the piston rod 34 to actuate up-lock and down-lock wedges 48 , 50 during the deploy sequence. A roller assembly 58 is supported by the lock bolt 54 and arranged radially inward of the up-lock wedges 48 .

Referring to FIGS. 3 and 4 , the latch assembly 52 includes a lever block 60 having first and second lateral walls 62 , 64 spaced apart from one another. A bridge wall 66 interconnects the first and second lateral walls 62 , 64 to provide an H-shaped integral member formed from a unitary block, such as 4340 hardened steel. The lever block 60 provides a pivot axis 68 at one end defined by pivot pins 70 constructed from hardened steel, for example. Each pivot pin 70 is supported in one of the first and second lateral walls 62 , 64 by a pivot bearing 72 , which permits the lever block 60 to rotate easily in response to input from the solenoids 40 .

A recock mechanism 74 includes a plunger 76 urged toward a recock surface 80 on the bridge wall 66 by a biasing spring 78 . The biasing spring 78 acts against a plug 77 received in the housing 32 ( FIG. 2 ) and the plunger 76 . The recock mechanism 74 maintains the lever block 60 in the latched condition until acted upon by the solenoids 40 .

A latch pin 82 is supported by the first and second lateral walls 62 , 64 on an end opposite the pivot axis 68 . Ends of the latch pin 82 are supported by the block 60 with pin bearings 84 . As a result, the latch pin 82 is permitted to roll against the lock bolt 54 as the lever block 60 rotates. The pivot bearings 72 and pin bearings 84 may be provided by needle bearings in one example.

The lever block 60 includes ears 86 extending from outer sides 92 of the first and second lateral walls 62 , 64 . The bridge wall 66 interconnects to inner sides 90 of the first and second lateral walls 62 , 64 . Each of the ears 86 provides a deploy surface 88 that is arranged on an opposite side of the lever block 60 from the recock surface 80 . The solenoids 40 each include a rod 94 having an end 96 that engages and pushes directly on the deploy surface 88 . The ends 96 are radiused or spherical to reduce the friction between the rod 94 and the ears 86 .

The lock bolt 54 includes an insert 98 secured to an end of the lock bolt shaft. In one example, the insert 98 is provided hardened steel. The insert 98 abuts the latch pin 82 and includes a radius to initiate self energizing release. The lock bolt 54 includes a hole 100 receiving a pin 102 that secures the insert 98 to the lock bolt shaft.

The deploy solenoid 40 is actuated to initiate the deploy sequence within the actuator 24 . In operation, to initiate the deploy sequence, the deploy solenoid 40 pushes against the latch assembly 52 . The lever block 60 is rotated about the pivot axis 68 , and the latch pin 82 rolls along the insert 98 . The lock bolt 54 is forced to move axially to the right in FIG. 2 by a lock bolt spring 56 arranged between the piston rod 34 and the lock bolt 54 . The new position of the roller assembly 58 permits the up-lock wedges 48 to move radially inward and disengage from the end of the cylinder 36 . The deploy spring 38 is then able to urge the cylinder axially relative to and away from the housing 32 to the deployed position shown in FIG. 1 . The down-lock wedges 50 limits the axial travel of the cylinder 36 relative to the piston rod 34 .

Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.