High stability latch mechanism

#This invention relates generally to actuated mechanical interlock mechanisms and, more particularly, to high stability latching of deployable optical metering structures.

#To extend the range of astronomical telescopes, it is necessary to increase the effective aperture. This implies that larger diameter primary mirrors must be employed. Unfortunately, the current state of the art is at the practical size limit of monolithic mirrors. As a result, segmented primary mirrors comprising a plurality of petals surrounding a monolithic center segment must be devised. A space born telescope of this configuration will require deployment after being placed in orbit. Linear, stable, high stiffness precision latches must be used to interlock the metering structure once the mirror is deployed to maintain mirror performance. Current latching technology does not address the need for high stiffness, linearity, and precision. Latch technology as used in satellite antennae does not meet optical tolerance requirements. Their repeatability and stability are typically two orders of magnitude below optical system requirements.

#Latching mechanisms commonly found can be categorized either as a retaining type or a mating type. Retaining types are preset in the latched position and release in their operating state. Examples of this type are illustrated in U.S. Pat. No. 4,682,804 to Palmer, et al. and U.S. Pat. No. 4,508,296 to Clark. These devices are used to retain payloads during transport, preventing damage due to shock and vibration. Remote release of the latch allows the payload to be removed from the support structure. High reliability and preload are their key performance requirements.

#FIGS. 1, 2 and 3 are perspective illustrations of the latching sequence of the latch mechanism of the present invention in conjunction with an exemplary deployed member and an exemplary reference structure.

#FIG. 4 is a perspective view of the latch and flexured ball assembly removed from the exemplary deployed member and the exemplary reference structure shown in FIGS. 1 through 3.

#FIG. 5 is a cross-sectional view of the latch mechanism and flexured ball assembly taken along line 5-5 of FIG. 4.

#To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

#Referring to FIGS. 1 through 3 there are three distinct stages which occur during the deployment operation in a large optical system. A single comer of a typical deployed optical system is illustrated in FIGS. 1 through 3. During the first stage as illustrated in FIG. 1, the deployed member 10 has attached to it a flexured ball assembly 12. The flexured ball assembly 12 (shown in greater detail in FIGS. 4 and 8) is in alignment with the latch mechanism 14 (shown in greater detail in FIGS. 4, 5 and 10) which is mounted in the reference structure 16. Any number of common methods can be used to maintain axial alignment. Latching pawls 18 are driven to their open position, providing clearance for the approaching flexured ball assembly 12. As deployment proceeds, the flexured ball assembly 12, makes contact with the latch mechanism 14 as shown in FIG. 2. Position sensing of the deployed member 10 is generally provided by an external system (not shown), and indicates when the flexured ball assembly 12, is in its mated position with latch mechanism 14. At this point the latch mechanism 14 is actuated, which causes the latching pawls 18 to engage the flexured ball assembly 12, as illustrated in FIG. 3. Applying a large force, typically about 1000 pounds, to seat the ball assembly 12 completes the latching operation.

#Turning to FIG. 4 there is shown more detailed views of the latch 14 and flexured ball assembly 12 removed from their respective structures 10, 16. Mounting plate 20 serves as the interface between the latch 14 and the reference structure 16 to which it is mounted. Drive motor 22 moves the latching pawls 18 in or out and supplies clamping force when the latching pawls 18 are in the latched state. The latch mechanism 14 is capable of locking the pawls 18 tightly in an open position as well as applying a large clamping force when the latching pawls 18 are in the fully latched position. The latching pawls 18 are supported within a main housing 24 to which mounting plate 20 is mounted.