Releasable coupling assembly

A releasable coupling assembly is provided for secure retention and controlled reliable release of a releasable structure with respect to a base structure, such as a releasable spacecraft with respect to a mother spacecraft or launch vehicle. The releasable coupling assembly comprises a latch housing on the base structure and supporting a pair of pivotal latches for locking engagement with oppositely projecting locking tabs of a pawl rotatably supported on a locking shaft mounted on the releasable structure. The two latches are respectively coupled to a pair of control pistons movably disposed within cylinders in the latching housing and biased by springs toward normal positions in locked engagement with the pawl. Supply of a fluid under pressure to the cylinders displaces the control pistons in directions retracting the latches to release positions disengaged from the pawl thereby releasing the locking shaft and the releasable structure from the base structure. In the event one of the latches fails to move to the release position, the pawl is free to rotate with respect to the locking shaft for disengagement from the failed latch.

This invention relates generally to devices for releasable mechanical 
coupling of two structures with respect to each other. More specifically, 
this invention relates to an improved and relatively compact releasable 
coupling assembly designed for secure locked retention and substantially 
fail-safe remote release of a releasable structure with respect to a base 
structure. 
Mechanical coupling assemblies designed for remote control actuation are 
known for use in releasably locking a releasable structure with respect to 
a base structure. Such coupling assemblies have typically comprised 
multiple latch components movable between normal latched or locked 
positions securely retaining the releasable structure in place and release 
positions permitting separation of the releasable structure. In many 
operating environments, displacement of the latch components occurs in 
response to supply of a pressurized fluid to the coupling assembly wherein 
pressurized fluid supply is controlled by a valve or other appropriate 
means adapted for remote control actuation. For example, such 
fluid-actuated coupling assemblies have been used for releasable mounting 
of munitions and the like onto aircraft. More recently, such coupling 
assemblies have been used for controlled remote release of a spacecraft or 
other hardware from a mother spacecraft, a launch vehicle, or the like. 
Typical fluid pressure sources have included, for example, a liquid under 
pressure from an hydraulic power system or the like or a pressurized gas 
from a pneumatic system or derived from a pyrotechnic device. 
In previous fluid-actuated coupling assemblies, proper operation of all of 
the multiple latch components has been a prerequisite before the 
releasable structure can be separated from the base structure; a failure 
of one of the latch components to move to its release position has 
prevented releasable structure separation. This limitation upon coupling 
assembly operation has generally been due to use of a single fluid 
pressure-responsive actuator device coupled to the various latch 
components by a relatively complex mechanical linkage, wherein any 
operational failure of the actuator device or any portion of the linkage 
results in nonseparation of the releasable structure. While this type of 
coupling assembly operation may be desirable in some environments for 
safety purposes, such as releasable mounting of munitions on aircraft, it 
can be highly undesirable in other operating environments, such as a 
spacecraft environment wherein the coupling assembly can be extremely 
difficult or impossible to access in the event of failed separation of the 
releasable structure. Previous coupling assemblies have not provided 
satisfactory redundant release means for insuring separation of the 
releasable structure in the event of partial coupling assembly 
malfunction. 
There exists, therefore, a significant need for an improved releasable 
coupling assembly of the fluid-actuated type designed for secure locked 
retention of a releasable structure and including substantially fail-safe 
redundant release means for reliable separation of the releasable 
structure from a base structure. The present invention fulfills these 
needs and provides further related advantages. 
SUMMARY OF THE INVENTION 
In accordance with the invention, an improved fluid-actuated releasable 
coupling assembly is provided for securely locking a releasable structure 
onto a base structure and for controlled, redundant separation of the 
releasable structure from the base structure. The coupling assembly 
comprises a pair of latches pivotally mounted on a latch housing which is 
in turn mounted onto the base structure. The latches are normally 
positioned in locking engagement with oppositely projecting locking tabs 
of a single pawl supported for rotation within a locking shaft mounted on 
the releasable structure. The two latches are remotely actuatable for 
independent retraction to release positions disengaged from the pawl 
thereby permitting separation of the releasable structure. In the event 
one of the latches fails to disengage from the pawl, the pawl may rotate 
relative to the still-engaged latch to separate the associated locking tab 
therefrom for releasable structure separation from the base structure. 
In one preferred form of the invention, the two latches are pivotally 
supported in spaced relation within an outwardly open latch chamber in the 
latch housing. A pair of connector links respectively couple the two 
latches to a pair of control pistons reciprocal within cylinders formed in 
the latch housing and biased by springs toward positions retaining the 
latches in their normal positions for respective locking engagement with 
the tabs on the pawl. Fluid pressure ports at one side of the latch 
housing are provided for guiding a fluid under pressure from redundant 
sources to the housing cylinders for displacing the control pistons in 
directions retracting the latches toward their release positions. 
The releasable structure carries the locking shaft to project outwardly 
therefrom for engagement with the pivoting latches, wherein this locking 
shaft preferably is supported within a compact shaft housing and is biased 
by a spring for axial movement toward a disengaged position recessed into 
a cavity in the shaft housing. The outboard end of the locking shaft 
terminates in a yoke within which the pawl is rotatably supported in a 
position with the tabs thereon projecting in opposite directions for 
locking engagement with the pivoting latches within the latch housing. 
The coupling assembly is engaged by inserting the outboard end of the 
locking shaft into the latch chamber between the two pivoting latches. 
During such insertion, the pawl is rotated to orient toward a position 
with the tabs thereon projecting somewhat in-line with the locking shaft 
to facilitate pawl movement between the closed latches. Pins within the 
latch chamber bear against curved lower faces of the pawl tabs to orient 
said pawl for proper locked engagement with the latches. When the pawl is 
engaged, mating serrated surfaces on the latch housing and the shaft 
housing secure the releasable structure with respect to the base structure 
in a position fixed against displacement in response to shear forces. 
Supply of a fluid under pressure to the cylinders in the latch housing 
displaces the control pistons in directions retracting the associated 
latches to their release positions. Such latch movement disengages the two 
latches from the pawl thereby permitting the spring-loaded locking shaft 
to retract from the latch chamber and further permitting the releasable 
structure to separate from the base structure. In the event, however, one 
of the latches fails to disengage from the pawl, the retracting spring 
force on the locking shaft urges the pawl to rotate within the shaft yoke 
to swing the still-engaged pawl tab free from the failed latch thereby 
permitting releasable structure separation. 
Other features and advantages of the present invention will become more 
apparent from the following detailed description, taken in conjunction 
with the accompanying drawings, which illustrate, by way of example, the 
principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As shown in the exemplary drawings, a releasable coupling assembly referred 
to generally by the reference numeral 10 is provided for secure locked 
retention of a releasable structure 12 with respect to a base structure 
14. The coupling assembly 10 is adapted for remote control actuation in 
response to supply of a fluid under pressure through conduits 16 (FIG. 1) 
for controlled and reliable independent operation of a pair of latches 18 
(FIG. 2) to permit separation of the releasable structure 12 from the base 
structure 14. 
The releasable coupling assembly 10 of the present invention advantageously 
provides a compact and relatively simple unit for secure mechanical 
coupling of a variety of structures, wherein the coupling assembly is 
adapted for substantially fail-safe fluid pressure actuation particularly 
by remote control means for reliable structure separation. For example, 
the coupling assembly 10 is particularly adapted for use in an aircraft or 
spacecraft environment to securely retain virtually any releasable or 
jettisonable structure with respect to an aircraft, spacecraft, launch 
vehicle, or the like. The couplng assembly is advantageously compact and 
lightweight while securely and positively locking the releasable structure 
in palce with high mechanical advantage. When releasable structure 
separation is desired, however, the coupling assembly is conveniently 
actuated by remote control supply of a fluid under pressure from any 
convenient and preferably redundant source to insure substantially 
fail-safe structure separation. In this regard, the coupling assembly is 
designed for releasable structure separation notwithstanding partial 
malfunction of the coupling assembly, thereby rendering the invention 
particularly desirable in spacecraft or other environments wherein human 
access to the coupling assembly might be extremely difficult or 
impossible. 
As shown in one preferred form in FIGS. 1-6, the releasable coupling 
assembly 10 comprises a relatively compact latch housing 20 which may be 
formed from virtually any convenient material by a casting or machining 
process wherein the housing material is chosen to withstand the particular 
intended operating environment for the coupling assembly. This latch 
housing 20 is securely mounted onto the base structure 14 by a pair of 
mounting bolts 22 passed through appropriate openings in bolt bosses 24 
formed on opposite sides of the latch housing. In the illustrative 
embodiment, these mounting bolts 22 are shown secured into the base 
structure 14 to position the latch housing 20 on an exterior or skin 
surface of the base structure. Alternatively, if desired, the latch 
housing 20 can be securely mounted within an outwardly open recess in the 
base structure 14 to avoid protruding components. Still further, the latch 
housing 20 can be installed onto the releasable structure 12, if desired. 
The latch housing 20 is shaped to include a pair of generally identical 
cylinders 26 in spaced relation to each other and having opposite sides 
interconnected by an integrally formed pair of sidewalls 28 spanning the 
distance between the cylinders 26. These sidewalls 28 cooperate with 
facing portions of the cylinders 26 to define an outwardly presented open 
latch chamber 30 within which the two latches 18 are mounted. 
More specifically, the two latches 18 comprises a pair of generally 
identical, somewhat elongated mechanical links of inverted, generally 
U-shaped configuration with lower ends pivotally supported in spaced 
relation within the latch chamber 30 on a respective pair of generally 
parallel pivot pins 32 extending between and supported by the sidewalls 28 
of the latch housing 20. From their respective pivot pins 32, each of the 
latches 18 extends upwardly (as viewed in FIG. 2) with a sufficient width 
defining a central, generally vertically elongated slot 36 formed to 
extend from the lower end of the latch upwardly to terminate in a 
downwardly presented locking surface 38 formed near the latch upper end. 
A pair of curved connector links 40 are associated respectively with the 
latches 18 to control pivoting latch movement between normal or locked 
positions with the upper ends of the latches pivoted toward each other and 
retracted release positions with said latch upper ends pivoted away from 
each other. These connector links 40 each have one end extending into a 
middle portion of the slot 36 in the associated latch 18 and pivotally 
connected to the latch by a short latch pin 42 carried by the latch to 
extend through said slot 36. From the latches 18, the connector links 
project away from each other and into the respective cylinders 26 through 
aligned cylinder openings 44. The opposite ends of the connector links are 
pivotally secured by pins 46 respectively to the head 48 of a control 
piston 50 carried for reciprocal movement within the associated cylinder 
26. Springs 52 react compressively between the cylinder head portions 48 
and a housing faceplate 54 fastened onto the latch housing 20 by screws 55 
or the like to close the upper ends of the cylinders 26. 
The compression springs 52 apply a downwardly directed spring force to the 
control pistons 50 thereby urging the control pistons toward normal 
positions resting upon baseplates 56 closing the lower ends of the 
cylinders 26. In these positions, as shown best in FIGS. 2 and 4, lower 
grooved peripheries of the pistons 50 respectively define a pair of lower 
annular pressure chambers 58 within the cylinders 26. Fluid under pressure 
is controllably supplied to these pressure chambers 58 via the conduits 16 
which are coupled to the latch housing 20 in flow communication with 
appropriate internal flow ports 61 (FIG. 4) for independently coupling of 
fluid from the conduits 16 to the respective cylinders 26. Supply of fluid 
under pressure to the chambers 58 urges the control pistons 50 to displace 
upwardly within the cylinders 26, with peripheral seal rings 63 being 
conveniently provided about the pistons above the pressure chambers 58 to 
prevent significant fluid leakage around the pistons. 
The latches 18 within the open latch chamber 30 of the latch housing 20 are 
thus normally supported by the spring-loaded control pistons 50 in 
generally vertical and generally parallel locked positions (FIG. 4), as 
will be described in more detail. In these locked positions, the axes of 
the pivot pins 42 and 46 associated with the connector links 40 are 
generally aligned in a common plane oriented substantially perpendicular 
to the latches 18, as viewed in FIG. 4. As a result, external forces 
applied to the latches 18 and tending to separate the latches are 
generally ineffective to retract the latches away from each other toward 
their release positions. Alternatively stated, the latches 18 are retained 
in their locked positions with a high mechanical advantage, thereby 
permitting high locking forces in a compact coupling assembly. Supply of 
fluid under pressure to the annular chambers 58 beneath the control 
pistons 50, however, displaces the pistons within the chambers 26 and 
correspondingly moves the connecting link pivot axes out of coplanar 
alignment (FIG. 5) progressively toward positions of decreasing mechanical 
advantage to facilitate disengagement and separation of the releasable 
structure 12. 
The latches 18 lockingly engage a pawl 66 supported from the releasable 
structure 12. More specifically, the releasable structure 12 carries a 
locking shaft 64 having a yoke 65 at an outboard end within which the pawl 
66 is rotatably supported on trunnions 68 for rotation about an axis 
generally in parallel with the latch pivot pins 32. This pawl 66 includes 
integrally-formed tabs 62 projecting outwardly in opposite directions from 
the locking shaft 66 generally at a right angle to the trunnion axis for 
locking reception into the latch slots 36 in bearing engagement with the 
locking surfaces 38 at the upper extents thereof. Conveniently, the pawl 
tabs 62 each have an outwardly and downwardly curved convex lower face 70 
shaped to facilitate initial insertion of the pawl 66 downwardly between 
and past the closed latches 18 with the pawl 66 rotated on the locking 
shaft 64 to orient the tabs 62 in a nearly vertical arrangement within the 
limits of the shaft yoke 65. During such initial insertion, when the tabs 
62 clear the latches 18, the lower one of the tabs 62 contacts one of a 
pair of lower limit pins 72 mounted to extend transversely across the 
latch chamber 30 to prevent pawl overinsertion and to rotate the pawl to 
orient the tabs 62 in positions for respective locked engagement by the 
latches 18. Such engagement is shown best in FIG. 4 which depicts upper 
surfaces of the pawl tabs in bearing engagement with the locking surfaces 
38 within the latch slots 36. 
As shown in one preferred form in FIG. 4, the locking shaft 64 is 
preferably supported within a shaft housing 74 which may be formed from 
any suitable material and is secured onto the releasable structure 12 by 
bolts 75 or the like. This shaft housing 74 includes a central cavity 76 
into which the locking shaft 64 projects for threaded engagement of its 
inboard end 64' with a stop nut 78. A downwardly open reaction cup 80 is 
interposed between this stop nut 78 and a shoulder 74' on the shaft 
housing 74, and a compression spring 81 reacts between the shoulder 74' 
and the base of the cup 80 to urge the locking shaft 64 toward a normal 
position retracted into the shaft housing cavity 76. An outwardly 
presented faceplate 82 on the shaft housing 74 is appropriately serrated 
for mating locked engagement with outwardly presented longitudinal and 
transverse serrations 84 and 86 on the latch housing faceplate 54 to lock 
the releasable structure 12 against displacement relative to the base 
structure 14 in response to shear forces when the pawl 66 on the locking 
shaft 64 is in locked engagement with the latches 18. 
When it is desired to separate the releasable structure 12 from the base 
structure 14, fluid under pressure is independently supplied through the 
conduits 16 to the cylinders 26 of the latch housing 20 for independently 
retracting the latches 18 toward their release positions with upper ends 
pivoted away from each other, as viewed in FIG. 5. The pressurized fluid 
may be obtained from any convenient source, such as an hydraulic or 
pneumatic fluid shared with an appropriate hydraulic or pneumatic system 
of the base structure, or the source may constitute expanding gas from an 
exploded pyrotechnic device or the like. In any case, however, the fluid 
source is advantageously a redundant source or sources preferably adapted 
for remote control actuation by appropriate valve or signal means or the 
like (not shown). 
Retraction movement of the latches 18 disengages the latch locking surfaces 
38 from the oppositely projecting pawl tabs 62 thereby permitting the 
compression spring 81 to withdraw the locking shaft 64 to a disengaged 
position into the associated housing cavity 76. When this occurs, the 
releasable structure 12 is disengaged from the base structure 14 and may 
thus be separated therefrom manually or by other propulsion means. 
In accordance with one important aspect of the present invention, the 
coupling assembly 10 reliably releases the releasable structure 12 
notwithstanding a failure of one of the latches 18 to move to the 
retracted position in response to fluid pressure supply. More 
particularly, with reference to FIG. 6, retraction of one but not both of 
the latches 18 results in disengagement of one of the pawl tabs 62. When 
this occurs, the spring 81 in the shaft housing 74 withdraws the locking 
shaft 64 in an upward direction into the housing cavity 76. Such shaft 
withdrawal forces the pawl 66 to rotate about the axis of its trunnion 68 
thereby freeing the still-engaged pawl tab 62 from beneath the associated 
latch 18. In this manner, in spite of failure or malfunction of one of the 
latches, the releasable structure 12 is still released and may be 
separated from the base structure 14. 
The releasable coupling assembly 10 of the present invention thus provides 
a compact unit for securely locking a releasable structure in place with 
high coupling forces. However, when releasable structure separation is 
desired, the coupling assembly provides substantially fail-safe release 
means for reliable remote control actuated release notwithstanding partial 
unit malfunction. 
A variety of modifications and improvements to the invention described 
herein are believed to be apparent to those skilled in the art. 
Accordingly, no limitation on the invention is intended, except by way of 
the appended claims.