Quick release coupling device

A quick release coupling device for securing end flanges of two adjacent pipes includes a clamp assembly. The clamp assembly has a plurality of clamping members disposed to straddle the two end flanges therearound so as to generally circumscribes the two end flanges. Each clamping member either has a spring or is of spring nature for resiliently urging the clamping member radially outwardly of the end flanges. The clamp assembly also has a plurality of connecting members for connecting respective adjacent pairs of clamping members so as to form an annulus provided a gap between two end clamping members. Coupling means is disposed in the gap for releasably connecting one end clamping member and the other end clamping member against the bias of the clamping members so as to complete the annulus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention pertains to a quick release coupling device mainly 
for use in a marine loading arm installation which is particularly 
designed to transfer very low temperature fluid products such as liquefied 
natural gases. 
2. Prior Art 
A marine loading arm installation is conventionally employed for unloading 
petroleum products from a tank vessel to a storage tank on land or for 
loading the same from the storage tank to the tank vessel. The loading arm 
installation includes an assembly of articulated pipe sections carrying a 
flanged end connector and is mounted on a sea berth for bolted connection 
of the end connector to a similar flanged connector on the manifold of the 
tank vessel. During the transfer of the fluid cargo, the vessel moves due 
to wind, tide or wave, and the level of the deck thereof changes. Then, 
the pivotal arms of the loading arm installation can move following the 
movement of the vessel. However, an excessive movement of the vessel may 
cause the intervening space between the vessel and the sea berth to exceed 
the safety reach of the loading arm. In such a case, since the bolted 
connection of the loading arm to the manifold is unyielding, one of the 
pipe sections or other parts of the loading arm will break. Consequently, 
in the conventional loading arm, in order to prevent the breakage and a 
serious hazard in that case, a quick release coupling device is provided 
for the flanged pipe connections of the loading arm and the manifold of 
the tank vessel. 
A prior art quick release coupling device includes a plurality of clamping 
members disposed to straddle the end flanges of two pipes to be coupled, a 
plurality of connecting rods hinged at their ends to respective pairs of 
clamping members so as to form an articulated succession of the clamping 
members, the clamping members and the connecting rods being disposed about 
the end flanges in the form of a ring provided with a gap between two end 
clamping members thereof, and connecting means for releasably coupling the 
two end clamping members to complete the ring. In the coupling device of 
this type, the connecting means works to release the two end clamping 
members and hence the plurality of the clamping members from the end 
flanges in case of emergency. 
However, when very low temperature fluid cargo such as liquefied natural 
gas is transferred through the loading arm installation, a layer of ice 
forms on the outside of the quick release device. In such a case, even 
though the connecting means might work in emergency, it is possible that 
the ice formed on the clamping members prevents them from being released 
from the end flanges and uncoupling of the loading arm cannot be effected. 
SUMMARY OF THE INVENTION 
It is therefore the object of the present invention to provide a quick 
release coupling device for securing together the end flanges of two pipes 
which device operates to reliably release the pipes even in the presence 
of ice formed thereon when an emergency arises. 
According to the present invention, there is provided a quick release 
coupling device for securing end flanges of two pipes together comprising 
a clamp assembly including a plurality of clamping members disposed to 
straddle the two end flanges therearound in circumferentially distributed 
relation so as to generally circumscribe the two end flanges, each 
clamping member having urging means for resiliently urging the clamping 
member radially outwardly of the end flanges, and a plurality of 
connecting members together for connecting respective adjacent pairs of 
clamping members so as to form an annulus provided with a gap between two 
end clamping members, and coupling means disposed in the gap for 
releasably connecting one end clamping member of the clamp assembly and 
the other end clamping member thereof together against the bias of the 
urging means of the clamping members so as to complete the annulus.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
Referring to FIGS. 1 to 8, there is illustrated one embodiment of a quick 
release coupling device in accordance with the present invention, in which 
reference numerals 10 and 12 indicate a pair of couplings which are 
secured to the ends of a pair of pipes 14 and 16, respectively. Each of 
the couplings 10 and 12 includes a connecting flange 18, 20 at one end 
thereof and a radial end flange 22, 24 at the opposite end thereof, the 
connecting flange 18, 20 being coupled to a flange 26, 28 of the end of 
the pipe 14, 16 by bolts (not shown). The couplings 10 and 12 are 
connected together by the quick release coupling device, with the end 
flanges 22 and 24 being confronted with each other. The end flanges 22 and 
24 have forward end faces 30 and 32 held in contact with each other to 
form a radial sealing interface therebetween, circumferential surfaces 34 
and 36, and rearward surfaces 38 and 40 tapering toward the connecting 
flanges 18 and 20 and extending rearwardly from the circumferential 
surfaces 34 and 36, respectively. 
The quick release coupling device generally includes a clamp assembly A and 
coupling means B. The clamp assembly A includes a plurality of clamping 
members 42A to 42E disposed around the end flanges 22 and 24 of the 
couplings 10 and 12 in circumferentially spaced relation to each other. 
Each of the clamping members 42A to 42E includes an elongated arcuate 
plate 44 having arcuate inner and outer surfaces 46 and 48, and two pairs 
of opposed standards 50A and 50B integrally mounted on and outwardly 
projecting from the outer surface 48 of the arcuate plate 44 at opposite 
ends thereof, respectively, each pair of opposed standards 50A, 50B being 
disposed on the lateral marginal portions of the outer surface 48. An 
arcuate groove 52 of a trapezoidal cross-section is formed in the inner 
surface 46 of the arcuate plate 44 and extends along the inner surface 46 
thereof so that the arcuate plate 44 is fitted on the outer periphery of 
the end flanges 22 and 24 of the couplings 10 and 12 with the inclined 
side walls of the groove 52 being held in contact with the tapered 
rearward surfaces 38 and 40 thereof, respectively. Consequently, when the 
clamping members 42A to 42E are disposed around the end flanges 22 and 24, 
each of the clamping members 42A to 42E straddles the end flanges 22 and 
24 and is held in firm engagement therewith. 
Each of the clamping members 42A to 42E also includes an arcuate recess 54 
of a square cross-section and a bore 56 of a circular cross-section both 
of which are formed in the arcuate plate 44. The recess 54 has a width 
generally equivalent to the sum width of the circumferential surfaces 34 
and 36 of the end flanges 22 and 24 and extends along the groove 52 with 
appropriate length and depth. The bore 56 extends from the outer surface 
48 toward the inner surface 46, and has an upper portion adjacent the 
outer surface 48 and a lower portion adjacent the recess 54, the lower 
portion having a smaller diameter than that of the upper portion. Thus, 
the bore 56 and the groove 52 are communicated with each other through the 
recess 54 disposed therebetween. Housed in the recess 54 of the arcuate 
plate 44 is a pressing plate 58 which has a thickness smaller than the 
depth of the recess 54 and is slidable along the recess walls 60. The 
pressing plate 58 has an arcuate inner surface 62 which is brought into 
contact with the circumferential surfaces 34 and 36 of the end flanges 22 
and 24 when the clamping members 42A to 42E are disposed around them. The 
pressing plate 58 also has a small bore 64 formed therethrough to 
accommodate a hexagon socket head cap screw 66. A cylindrical housing 68, 
which includes a tubular portion 70 having an exteriorly threaded upper 
portion 72 adjacent its open top end and a hub portion 74 formed on the 
bottom end of the tubular portion 70 in coaxial relation thereto, is 
fixedly secured to the arcuate plate 44, with the hub portion 74 and the 
bottom end of the tubular portion 70 firmly received in the lower portion 
and the upper portion of the bore 56, respectively. The housing 68 also 
includes a bore 76 extending through the bottom end of the tubular portion 
70 and the hub portion 74 coaxially therewith. A pushing rod 78 of a 
circular cross-section is received in the tubular portion 70 of the 
housing 68. The pushing rod 78 includes a radial flange ring 80 mounted 
integrally around the peripheral surface thereof intermediate opposite 
ends thereof, the flange ring 80 being received in the tubular portion 70 
of the housing 68 for sliding movement therealong. The pushing rod 78 
extends outwardly through the bore 76 of the bottom end of the tubular 
portion 70 and the hub portion 74 into the recess 54 of the arcuate plate 
44. The pressing plate 58 is fixedly secured to the inner end of the 
pushing rod 78 by the screw 66. An interiorly threaded cap 82 is threaded 
onto the upper portion 72 of the tubular portion 70 of the housing 68 and 
firmly secured thereto by a locking nut 84 threaded on the upper portion 
72. A compression coil spring 86 is wound around the pushing rod 78 and 
acts between the radial flange ring 80 thereof and the inner end face of 
the cap 82 to urge the pushing rod 78 toward the circumferential surfaces 
34 and 36 of the end flanges 22 and 24 to hold the pressing plate 58 
against them when the clamping members 42A to 42E are disposed around the 
end flanges 22 and 24. The urging force of the coil spring 86 can be 
suitably adjusted by moving the cap 82 along the threaded upper portion 72 
of the housing 68. 
The plurality of the clamping members 42A to 42E disposed around the end 
flanges 22 and 24 are connected to each other by a plurality of connecting 
rods 88A to 88D so as to form an articulated succession in the form of an 
annulus with a gap G between two end clamping members 42A and 42E. Each 
pair of opposed standards 50A, 50B of the clamping members 42A to 42E 
except for the pair of end standards 50B of the end clamping member 42E, 
journals a shaft 90. Each of the connecting rods 88A to 88D has one end 
pivotally connected to the shaft 90 journalled by the standards 50A of 
each of the clamping members 42B to 42E and the opposite end to the shaft 
90 journalled by the standards 50B of each of the clamping members 42A to 
42D. A pair of mounting flat bars 92 are welded at their one ends to a 
rear face of the end flange 22 in diametrically opposite relation. 
Pivotally connected to the flat bars 92 by pins 94 at the free ends 
thereof are a pair of links 96 which are pivotally connected further to 
the shafts 90 journalled by the standards 50A of the end clamping member 
42E and the standards 50B of the clamping member 42B, respectively. Thus, 
the plurality of the clamping members 42A to 42E and the connecting rods 
88A to 88D are supported by the flat bars 92 and the links 96 on the end 
flange 22 of the coupling 10 in such a manner that the clamping members 
42A to 42E are retained in place around the end flange 22 even when the 
clamp assembly A is in a released condition to be hereinafter explained. 
Provided in the gap G between the two end clamping members 42A and 42E is 
the coupling means B which releasably couple them. The coupling means B 
includes drive means 100 in the form of a hydraulic cylinder, a coupling 
rod 102 and a rocker lever 104. The hydraulic cylinder 100 is pivotally 
connected to trunnions 106 extending, respectively, from a pair of opposed 
mounting ears 108 which are secured on the pair of standards 50A of the 
end clamping member 42E by bolts 110. The hydraulic cylinder 100 has a 
piston, not shown, slidably received in its cylinder body 112 and has a 
piston rod 114 connected to the piston and extending from the cylinder 
body 112. The piston rod 114 has a clevis 116 at the outer end which 
receives therein a clevis pin 118. The coupling rod 102 includes a pair of 
block 120 and 122 respectively mounted thereon at opposite ends thereof, 
the block 120 being pivotally mounted on the shaft 90 journalled by the 
pair of standards 50A of the end clamping member 42A. The block 122 at the 
free end of the coupling rod 102 has a pair of integral stubs 124a and 
124b at opposite sides thereof, the pair of stubs 124a and 124b extending 
along the common axis of the end flanges 22 and 24 and constituting an 
engagement shaft 124. The rocker lever 104 includes a pair of parallel 
opposed rocker plates 126 which are pivotally connected to a pair of stub 
shafts 128 secured to the pair of standards 50B of the end clamping member 
42E, respectively. Each of the rocker plates 126 has an elongated upper 
portion 130 and a generally square lower portion 132, and an end plate 134 
is secured to both rear end faces 136 of the lower portions 132 of the 
rocker plates 126 by mounting screws 138 so as to connect the pair of 
rocker plates 126 together to define a space S therebetween. A pair of 
opposed slots 140, which constitute an engagement groove 142, are formed 
in the inner surfaces 144 of the rocker plates 126, respectively. Each 
slot 140 extends generally from a center of the lower portion 132, where 
each stub shaft 128 is mounted, toward upper end face 146 of the upper 
portion 130 and opens to the upper end face 146. Each slot 140 has a width 
slightly larger than a diameter of each stub 124a, 124b of the block 122 
of the coupling rod 102 so that each stub 124a, 124b is received in each 
slot 140 for sliding movement therealong, the block 122 being disposed in 
the space S between the pair of rocker plates 126. Those corners defined 
by the upper end face 146 of the upper portion 130 of the rocker plates 
122 and inner opposed side walls 148 of the slots 140 are removed to 
provide chamfered corners 150 to facilitate the introduction of the stubs 
124a and 124b into the slots 140 and the release of them therefrom. Both 
rear ends 152 of the upper portion 130 of the rocker plates 126 are 
pivotally connected to the clevis pin 118. Those corner portions of the 
lower portions 132 of the rocker plates 126 defined by front and inner end 
faces 154 and 156 thereof are truncated to provide truncated corners 158 
so as to clear the end portion of the outer surface 48 of the arcuate 
plate 44 of the end clamping member 42E, and thereby to permit the pivotal 
movement of the rocker lever 104 about the stub shafts 128. Both front end 
faces of the upper portions 130 of the rocker plates 126 serve as abutment 
means or surfaces 162 which are brought into abutment with the outer 
periphery of the end flanges 22 and 24 when the rocker plates 126 are 
pivoted, as shown in a two dots-and-dash line in FIG. 3. Two pairs of 
aligned bores 164 and 166 for selectively receiving a set pin 168 is 
formed through the pair of rocker plates 126 adjacent the rear chamfered 
corners 150, the bores 164 being closer to the slots 140 than the bores 
166. Bores for receiving a shear pin 170 are also formed through the pair 
of rocker plates 126 and the pair of standards 50B of the end clamping 
member 42E, respectively, and are brought into alignment with each other 
when the rocker lever 104 is in a closed position to be hereinafter 
explained. 
When the piston rod 114 of the hydraulic cylinder 100 is, as shown in FIG. 
1, in a retracted position, the coupling means B is in the closed position 
corresponding to a coupled condition of the clamp assembly A in which the 
clamping members 42A to 42E are disposed around the two end flanges 22 and 
24 to straddle them and the two end clamping members 42A and 42E are 
connected together. In the closed position, the rocker lever 104 is in 
such a position that the groove 142 is open and extending generally 
radially outwardly of the end flanges 22 and 24, and the engagement shaft 
124 of the block 122 of the coupling rod 102 is received in the inner end 
of the groove 142. In the embodiment, the axis O of the engagement shaft 
124 of the block 122 lies closer to the end flanges 22 and 24 than the 
common axis P of the stub shafts 128 supporting the rocker lever 104 in 
the closed position, where the distance D between the axes O and P is 
preferably selected to be, for example, 3 mm. Therefore, it will be noted 
that the force acting on the coupling rod 102 axially thereof toward the 
end clamping member 42A, as designated by an arrow E in FIG. 3, will cause 
the rocker lever 104 to pivot counterclockwise in FIG. 3 about the stub 
shafts 128 to firmly retain the engagement shaft 124 in the inner end of 
the groove 142, so that the block 122 is biased toward the end flanges 22 
and 24 in the closed position. Also in the closed position, the set pin 
168 is received in the bores 166 remote from the engagement groove 142 so 
as to permit the release of the block 122 from the space S, and the shear 
pin 170 is received in the bores to prevent accidental pivotal movement of 
the rocker lever 104. 
In this condition, if an emergency arises, the hydraulic cylinder 100 is 
actuated so that the piston rod 114 thereof is extended. Then, the shear 
pin 170 is broken, and the rocker lever 104 is pivoted clockwise in FIG. 3 
about the stub shafts 128. As the rocker lever 104 pivots clockwise, the 
engagement groove 142 thereof is caused to be inclined toward the end 
clamping member 42A, and the engagement shaft 124 of the block 122 which 
have been received in the inner end of the engagement groove 142 is caused 
to move along the engagement groove 142 outwardly thereof. As the rocker 
lever 104 further pivots, the abutment surfaces 162 thereof are brought 
into abutment, as shown in the two dots-and-dash line in FIG. 3, with the 
outer periphery of the end flanges 22 and 24, and the rocker lever 104 is 
still further pivoted into the open position about the abutting portion of 
the outer periphery thereof. As a result, the engagement shaft 124 is 
released from the groove 142, so that the two end clamping members 42A and 
42E are decoupled and the clamp assembly A turns to be in the released 
condition where the clamping members 42A to 42E are supported by the links 
96 and the flat bars 92 on the end flange 22 and are disengaged therefrom. 
In the release operation mentioned above, the reaction force due to the 
abutment of the abutment surfaces 162 with the end flanges 22 and 24 
facilitate the release of the clamping members 42A to 42E from the end 
flanges 22 and 24. In addition, the compression coil springs 86 mounted in 
the clamping members 42A to 42E press the pressing plates 58 against the 
circumferential surfaces 34 and 36 of the end flanges 22 and 24 to 
facilitate the release of the clamping members 42A to 42E therefrom. 
Consequently, even in the presence of a layer of ice formed on the 
coupling device and the couplings 10 and 12 of the pipes 14 and 16, the 
coupling device reliably works to release the couplings 10 and 12 of the 
two pipes 14 and 16 to prevent a serious hazard. 
For effecting the coupling operation of the coupling device, the clamping 
members 42A to 42E are disposed to straddle the end flanges 22 and 24 
therearound, and the rocker lever 104 is first pivoted in such a manner 
that the engagement groove 142 thereof extends generally along the 
circumferential surfaces 34 and 36 of the end flanges 22 and 24 and opens 
toward the end clamping member 42A. Then, the engagement shaft 124 of the 
block 122 of the coupling rod 102 is received in the engagement groove 
142, following which the set pin 168 is inserted in the bores 164 adjacent 
the groove 142 to prevent the movement of the block 122 from the space S 
and hence the release of the engagement shaft 124 from the groove 142. 
After that operation, the hydraulic cylinder 100 is actuated so that the 
piston rod 114 is retracted. As a result, the rocker lever 104 is pivoted 
so that the engagement groove 142 extends radially outwardly of the end 
flanges 22 and 24, and the engagement shaft 124 of the block 122 is moved 
along the engagement groove 142 and positioned in the inner end thereof. 
Lastly, the shear pin 170 is inserted in the bores, and the set pin 168 is 
retracted from the bores 164 adjacent the groove 142 and is inserted in 
the other bores 166 remote from the groove 142 to permit the movement of 
the block 122 from the space S. 
FIGS. 9 to 13 show a second embodiment of the coupling device in accordance 
with the present invention. In this embodiment, the plurality of clamping 
members comprise a plurality of arcuate spring plates 200A to 200C 
disposed to straddle the end flanges 22 and 24 therearound in 
circumferentially distributed relation so as to generally circumscribe the 
end flanges 22 and 24. Each of the spring plates 200A to 200C has a radius 
of curvature larger than a radius of the outer peripheral surface of each 
end flange 22, 24 in the released condition of the clamp assembly A, and 
is flexed to circumscribe the end flanges 22 and 24, as shown in FIG. 9 in 
the coupled condition of the clamp assembly A. Each of the spring plates 
200A to 200C has arcuate inner and outer surfaces 202 and 204. Formed in 
the inner surface 202 of each of the spring plates 200A to 200C is an 
arcuate groove 206 of a trapezoidal cross-section in which the outer 
periphery of the end flanges 22 and 24 of the couplings 10 and 12 is 
fitted. The spring plates 200A to 200C disposed around the end flanges 22 
and 24 are connected to each other by a plurality of connecting members 
208A and 208B in the form of fittings so as to form an annulus with a gap 
G between the end spring plates 200A and 200C. The end spring plate 200C 
has a pair of opposed standards 210 mounted integrally at the free end 
thereof and another pair of opposed standards 212 mounted integrally 
intermediate opposite ends thereof. The pair of standards 212 and the 
fitting 208A are disposed in generally diametrically opposite relation to 
each other, and journal shafts 214 and 216, respectively. A pair of links 
218 and 220 are pivotally connected at their one ends to the shafts 214 
and 216, respectively, the link 218 extending along the end spring plate 
200C toward the fitting 208B while the link 220 extends along the spring 
plate 200B. A pair of mounting flat bars 222 and 224 are pivotally 
connected at their one ends to the pair of links 218 and 220 at their 
opposite ends, respectively, and the pair of mounting flat bars 222 and 
224 are welded at their opposite ends to the rear face of the end flange 
22, respectively. Thus, the plurality of the spring plates 200A to 200C 
connected by the fittings 208A and 208B to each other are supported by the 
flat bars 222 and 224 and the links 218 and 220 on the end flange 22 of 
the coupling 10 in such a manner that the spring plates 200A to 200C are 
retained in place around the end flange 22 even when the clamp assembly A 
is in the released condition. Provided in the gap G between the two end 
spring plates 200A and 200C is the coupling means B similar to that in the 
first embodiment. In this embodiment, the pair of opposed mounting ears 
108 for supporting the hydraulic cylinder 100 are respectively secured on 
the pair of standards 212, and the rocker lever 104 is pivotally mounted 
on the pair of standards 210. The coupling rod 102 is pivotally mounted at 
one end thereof on a shaft 226 journalled by a fitting 228 which is 
mounted on the end spring plate 200A at the free end thereof. 
In this embodiment, when the piston rod 114 of the hydraulic cylinder 100 
is in the retracted position, as shown in FIG. 9, the coupling means B is 
in the closed position, and the spring plates 200A to 200C are flexed to 
circumscribe the end flanges 22 and 24. If an emergency arises, the 
hydraulic cylinder 100 is actuated, so that decoupling of the two end 
spring plates 200A and 200C is effected. In this condition, the spring 
plates 200A to 200C are restored to the original state where their radius 
of curvature of each of the spring plates 200A to 200C is larger than the 
radius of each end flange 22, 24, and the restoring force thereof 
facilitate the release of the spring plates 200A to 200C from the end 
flanges 22 and 24 even in the presence of ice formed on the coupling 
device and the couplings 10 and 12 of the pipes 14 and 16. 
Further explanation on the restoring force of the spring plates 200A to 
200C is hereinafter added with reference to FIGS. 11 and 12. Shown in FIG. 
11 is an arcuate spring plate 200 having one end secured to a wall K. The 
spring plate 200 has a rectangular cross-section with a thickness T and a 
width W, and has a radius Ra. When the free end of the spring plate 200 is 
subjected to pulling force N, as shown in FIG. 11, the spring plate 200 is 
flexed by flexure amount H, so that the radius decreases from Ra to Rb. In 
this condition, if the free end of the spring plate 200 is released, the 
spring plate 200 is restored with restoring force F to its original state 
where the radius is Ra. And, if the radius Ra is determined so as to be 
almost equivalent to a radius R of each end flange 22, 24 and stress 
acting on the spring plate 200 due to bending moment M is in the 
admissible range, the pulling force N will correspond to clamping force of 
the spring plate 200 on the end flanges 22 and 24, and the restoring force 
F will serve as releasing force of the spring plate 200 from the end 
flanges 22 and 24. In FIG. 12, four spring plates 200 connected to each 
other are disposed around the end flanges 22 and 24. Where, if the width 
W, the thickness T, radii Ra and R, and an angle of circumference Q of the 
spring plate 200 are 80 mm, 20 mm, 405 mm, 400 mm and 88 degrees, 
respectively, the flexure amount H, the pulling force N and the restoring 
force F are about 1.5 mm, 620 Kgf and 180 Kgf, respectively. This amount 
of the restoring force F of the spring plates 200 will be enough to 
reliably break the ice formed thereon to release them from the end flanges 
22 and 24. 
FIGS. 13 to 16 show a third embodiment of the coupling device in accordance 
with the present invention. Since this embodiment is rather similar to the 
second embodiment mentioned above, only the points in which the third 
embodiment differs from the second embodiment will be hereinafter 
described. In this embodiment, first, second and third links 300, 302 and 
304 are pivotally connected at their one ends to shafts 214, 216 and 226 
journalled by the pair of standards 212, the fitting 208A and the fitting 
228, respectively. The links 300 to 304 are pivotally connected at their 
opposite ends to the rear face of the end flange 22 by pivot pins 306 to 
310, respectively. The links 300 to 304 are inclined with respect to the 
planes extending radially of the end flanges 22 and 24 in such a manner 
that each outer end is shifted in counterclockwise direction in FIG. 13 
from each inner end in the coupled condition of the clamp assembly A. In 
this arrangement, the coupling and releasing operations are effected in 
the same way as that in the second embodiment. In the releasing operation, 
the abutment surfaces 162 of the rocker lever 104 are brought into 
abutment with the outer periphery of the end flanges 22 and 24, and the 
hydraulic cylinder 100 causes the rocker lever 104 to further pivot. Then, 
the rocker lever 104 is caused to pivot about abutting portions 312 of the 
outer periphery of the end flanges 22 and 24, and the clamp assembly A is 
rotated clockwise as indicated by an arrow J in FIG. 14, so that the links 
300 to 304 also pivot about the pivot pins 306 to 310 in such a manner 
that the angles, defined by the links 300 to 304 and planes tangent to the 
circumferential surfaces 34 and 36 of the end flanges 22 and 24, approach 
right angles. These pivotal movement of the links 300 to 304 also 
facilitate the release of the spring plates 200A to 200C from the end 
flanges 22 and 24. In FIGS. 13 and 14, the abutting portions 312 formed on 
the outer periphery of the end flanges 22 and 24 have no tapered rearward 
surfaces. It is preferable to form notches or the like on the abutting 
portions 312 for preventing the sliding of the rocker lever 104 thereon. 
In this embodiment, the coupling rod 102 includes a pair of apertured yokes 
314 pivotally mounted on the shaft 226, a cylindrical housing 316 
integrally mounted on the yokes 314 and a rod body 318 received in the 
housing 316 therethrough in coaxial relation thereto. The housing 316 has 
a bottom end 320 remote from the yokes 314 and a flange member 322 
received therein for sliding therealong. The rod body 318 has exteriorly 
threaded opposite ends, the one end being secured to the flange member 322 
by nuts, the other end being secured to the block 122 which has the 
engagement shaft 124. Received in the housing 316 is spring means 324 in 
the form of Belleville springs which act between the inner face of the 
bottom end 320 of the housing 316 and the flange member 322 to urge the 
flange member 322 toward the yokes 314. Thus, in this embodiment, the 
coupling rod 102 is retractable. At the beginning of the transfer of the 
very low temperature fluid cargo through the loading arms on which the 
coupling device is provided, the end flanges 22 and 24 are first suddenly 
cooled by the fluid flowing therethrough, and subsequently the coupling 
device disposed around the end flanges 22 and 24 is cooled, so that 
shrinkage of the spring plates 200A to 200C of the coupling device due to 
the cooling differs from that of the end flanges 22 and 24. Consequently, 
it is possible that the clamping force on the end flanges 22 and 24 by the 
coupling means B is weakened. However, even if such a case, inasmuch as 
the coupling rod 102 is retractable, the coupling force of the coupling 
means B is maintained high enough to secure the end flanges 22 and 24 
together in sealed relation to each other. 
Moreover in the embodiment, the engagement groove 142 of the rocker lever 
104 has a pair of opposed side walls 148, the wall 148 adjacent the front 
end of the rocker lever 104 having an arcuate concave surface. As a 
result, in the coupling operation of the end spring plates 200A and 200C, 
since the engagement shaft 124 is received in the concave surface, the 
coupling rod 102 can be pulled by a relatively weak force of the hydraulic 
cylinder 100, thereby making it possible to employ a smaller cylinder than 
those in the aforementioned embodiments. 
Obviously many modifications and variations of the present invention are 
possible in the light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described.