Bridging span structure

A bridging span structure intended in particular for the crossing of ditches by vehicles and a system for transporting and depositing such a structure, wherein each connecting arm is rotatably mounted in relation to a bridging span about a pivoted bolt and wherein an arrangement is provided for urging the connecting arm automatically back to its normal position of use and for holding this connecting arm in this normal position, the invention being applicable to military armoured vehicle of the Engineering Corps.

BACKGROUND OF THE INVENTION 
The present invention relates to a bridging span structure intended in 
particular for the clearing of ditches by vehicles such as armoured 
vehicles of the Engineering Corps and a system for the transport on a 
vehicle of at least two bridging span structures intended for the clearing 
of ditches and for laying down the bridging span structures over the 
ditches from the vehicle. 
A system has been proposed for laying down from a vehicle a bridging span 
of short length or of greater length after the end-to-end assembly of two 
or more bridging spans of short length. 
Such a system is described in the document FR-B-2,683,837 in the name of 
the applicant and essentially comprises a beam for supporting and 
launching a bridging span or assembled bridging spans, displaceable in 
relation to the vehicle towards an overhanging position; means for the 
displacement of the bridging span or of the assembled bridging spans in 
relation to the beam to an overhanging position forward of the beam; and a 
plate supporting in a guided manner the beam and which may tilt in 
relation to the vehicle together with the beam to permit the laying down 
of the bridging span or of the assembled bridging spans over a ditch to be 
cleared. 
In the inactive position or position of transport on the load vehicle, the 
beam has its portion behind the supporting plate accommodated between two 
superposed bridging spans and the connecting arms forming braces of both 
bridging spans, each one being U-shaped and pivotally connected at its 
ends to two internal side-walls, respectively, of two central boxes of two 
bridging span elements. Both connecting arms of the lower bridging span 
assume a downward swung or lowered position permitting to increase the 
space for the accommodation of the beam and these connecting arms may be 
simultaneously swung upwards by a lifting table to a position 
substantially parallel to the frame of the vehicle, in which they are 
locked to the lower bridging span. 
The hereabove known system has thus the major inconvenience to require a 
complex structure of lifting table mounted onto the chassis of the vehicle 
and associated control means for raising it from an inoperative position, 
after withdrawal of the beam from above the lower bridging span and acting 
upon the lower ends of the U-shaped connecting arms of this bridging span 
to move them away from each other to their position of locking to the 
lower bridging span. 
SUMMARY OF THE INVENTION 
The present invention has as its object to remove the hereabove 
inconvenience of the known system by proposing a bridging span structure 
intended in particular for the clearing of ditches by vehicles such as 
armoured vehicles of the Engineering Corps, comprising two parallel 
bridging span elements with upper treadways and connected to each other by 
two connecting arms forming braces and which is characterized in that each 
connecting arm has approximately a .OMEGA.-shape, both coaxial base 
elements of which comprise bolts having each one of their ends connected 
to the body of the corresponding bridging span element by a 
ball-and-socket pivotal connection; each pivoted bolt is rotatably mounted 
oppositely from its ball-and-socket pivotal connection in a bearing held 
against rotation at the body of the bridging span element and which may 
slide in relation to the latter so as to permit the displacement of the 
pivoted bolt in a plane perpendicular to the bridging span elements about 
the centre of pivotal connection of this bolt; and in that means are 
provided for automatically returning each connecting arm to its normal 
position of use in a plane substantially perpendicular to both bridging 
span elements and to hold the connecting arm in this normal position of 
use. 
Preferably the returning and holding means of each connecting arm comprise 
two identical parallel cams made fast to the connecting arm at both ends 
of the pivotally connected bolts opposite to the ball-and-socket pivotal 
connections and the axes of rotation of which are coaxial with the axes of 
rotation of the pivotally connected bolts; and two rollers held in bearing 
relationship by an elastic means upon the lower portion of the eccentric 
shape of each cam according to a force providing the holding of the 
connecting arm in its normal position of use, the eccentric shape of the 
cam being such that during the rotation of the connecting arm in one 
direction or in the other one, either one of the two rollers exerts upon 
this cam a torque for the rightening of the connecting arm to its normal 
position. 
Both rollers are mounted onto a common yoke made fast to one end of a 
supporting shaft slidably mounted in a stationary casing made fast to the 
body of the corresponding bridging span element and the aforesaid elastic 
means comprises a prestressed spring accommodated in the stationary casing 
and exerting upon the supporting shaft a force for holding both rollers or 
either one thereof in bearing relationship upon the lower periphery of the 
corresponding cam. 
Advantageously the lower portion of each cam where both corresponding 
rollers are simultaneously bearing is flat and is located between two 
symmetrical portions of the eccentric shape of the cam. 
Preferably, the bearing is a parallelepipedic block accommodated in a 
rectangular guiding window of the block formed in the body of the 
corresponding bridging span element in perpendicular relation to the 
longitudinal axis of the latter. 
Each ball-and-socket pivotal connection comprises a bracket for supporting 
the female sphere in which is accommodated the male sphere made fast to 
the end of the corresponding pivotally connected bolt, the supporting 
bracket being itself fastened in a supporting part made fast for example 
by welding to the body of the corresponding bridging span element. 
The bridging span structure also comprises in association with each one of 
the two connecting arms, at least two stops made fast to both bridging 
span elements, respectively, onto which the corresponding connecting arm 
may be caused to bear in the swung down position of the latter. 
Each connecting arm comprises two pairs of riding rollers each extending 
parallel to the bridging span elements and made fast to the central 
connecting portion of the .OMEGA.. 
Protective rubber bellows are provided for tightly closing the passageways 
between the bearings and the rectangular guide windows. 
In the normal position of use of one connecting arm, the prestressed 
springs associated therewith have their maximum length. 
The invention also proposes a system for the transfer upon a road vehicle 
such as a truck of at least two bridging spans superposed on a frame of 
the vehicle and which may be assembled end-to-end and for laying down each 
one of the bridging spans or of end-to-end assembled bridging spans over a 
ditch to be cleared, each bridging span having such a structure as 
previously defined and being of the type comprising a beam for supporting 
and launching one bridging span or assembled bridging spans and 
displaceable in relation to the vehicle towards an overhanging position; 
means for the displacement of the bridging span or of the assembled 
bridging spans in relation to the beam to an overhanging position forward 
of the supporting and launching beam; and a plate supporting in a guided 
manner the beam and which may tilt in relation to the vehicle together 
with the beam to permit the laying down of the bridging span or of the 
assembled bridging spans. During the laying down of the bridging span or 
of the assembled bridging spans, that end of this bridging span or of 
these assembled bridging spans which is opposite to that already bearing 
upon the bank of the ditch opposite to the road vehicle is supported at 
the end of the laying-down and launching beam by the rear connecting arm 
of both bridging spans elements of the bridging span or of the rear 
bridging span of the assembled bridging spans during the tilting of the 
beam until the laying down of the said end of bridging span or of the 
assembled bridging spans upon the bank adjacent to the road vehicle, 
whereas the connecting arm bearing upon the laying-down beam may pivot in 
relation to the bridging span elements above the pivotally connected bolts 
so that the connecting arm may adapt itself to the different inclinations 
of the laying-down beam. 
In the transportation position on the road vehicle, the laying-down and 
launching beam is disposed between two superposed bridging spans and the 
connecting arms of both bridging span elements of the lower bridging span 
assume a downwards swung position underneath the laying-down and launching 
beam while being in contact with the latter through the medium of the 
riding rollers of the connecting arms. 
Both downwards swung connecting arms are also bearing upon the stops made 
fast to the bridging span elements. 
The connecting arms are rightened to their normal position by the returning 
means exerting a rightening torque thereupon after withdrawal of the 
laying-down and launching beam from between both superposed bridging 
spans. 
The means for the displacement of the bridging span or of the assembled 
bridging spans in relation to the laying down and launching beam comprise 
an endless drive chain extending along the longitudinal axis of the beam 
and mounted onto at least two toothed end wheels themselves rotatably 
mounted onto the beam; and at least two elements forming a fork and made 
fast to the drive chain and adapted to grip the central portion of one 
connecting arm between both pairs of riding rollers of this arm bearing 
upon the laying-down and launching beam.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to the figures, reference numeral 1 designates a road vehicle 
such as a truck permitting to transport towards a ditch 2 to be crossed by 
vehicles, such as armoured vehicles of the Engineering Corps, three 
bridging spans, namely an upper bridging span 3, an intermediate bridging 
span 4 and a lower bridging span 5, superposed on a longitudinal chassis 6 
of the vehicle. 
The vehicle 1 supports a system adapted for separately depositing the 
bridging spans 3, 4, 5 over ditches or for assembling at least two 
bridging spans end-to-end and depositing the assembled bridging spans 
above a ditch. 
The system for assembling bridging spans and for depositing the latter is 
in a general manner identical with the one described in French patent No 
2,683,837 incorporated herein by way of reference and will therefore not 
be discussed in detail, apart from the few differences which will appear 
subsequently in the present description. 
The bridging spans 3, 4, 5 are identical and are each formed of two 
parallel bridging span elements 3a, 3b; 4a, 4b; 5a, 5b connected to each 
other by two connecting arms forming braces 3c, 4c and 5c. Each connecting 
arm may be swung downwards from its normal position of use to a position 
permitting the passage of a beam 7 for launching and depositing a bridging 
span as shown in FIGS. 1 and 11. These figures thus show that the 
connecting arm 4c of the intermediate bridging span 4 assumes a downwards 
swung or lowered position so as to increase with respect to the connecting 
arm 3c of the upper bridging span 3 the height of accommodation of the 
beam 7 in the resting or inactive position upon the vehicle 1. 
Both bridging span elements of each bridging span 3, 4, 5 comprise two 
parallel upper trackways 3d, 4d and 5d and each bridging span element 
comprises a central rigid body or box 8 and two access jibs 9, 10 
assembled to both ends, respectively, of the central box 8 so as to extend 
the upper trackway of this box. The access jib 9 is fastened to one 
portion of the central box 8 by a transverse pivot pin 11 and to an 
opposite portion of this box by locking means 12 which are unlockable so 
as to permit the jib 9 to assume a lower position shown on FIG. 3 in the 
case where one bridging span 3; 4; 5 only should be deposited over a 
ditch, or an upward swung position as this appears from the assembled 
bridging spans 3, 4, 5 in FIGS. 17A-F and in which the upper swung jib 9 
of the bridging span is fastened by suitable locking means upon another 
stationary jib 10 of an adjacent bridging span to form a bridging span of 
greater length. 
The means for locking each liftable jib 9 of one bridging span to the 
corresponding box 8 of the latter and the means for locking each raised 
access jib 9 to a stationary jib of another adjacent bridging span may be 
of the kind described in French patent No 2,683,837. These locking means 
may also be constituted by those which have been described in French 
patent application No. 95 09 432 filed on Aug. 2, 1995 in the name of the 
applicant and incorporated herein by way of reference. 
Both elements of one bridging span 3; 4; 5 are assembled by their 
connecting arms in such a manner that the bridging span may have available 
at each one of its ends, two access jibs, namely a movable access jib 9 
and a stationary access jib 10, respectively, so that there be no 
imposition for the direction of presentation of the bridging spans during 
their coupling. 
Each bridging span 3; 4; 5 moreover comprises two pairs of front and rear 
riding rollers 14 fastened in mutually confronting relationship to both 
internal side walls located opposite each other, respectively, of two 
bridging span elements. The riding rollers 14 permit the displacement of 
the corresponding bridging span along the depositing and launching beam 7 
by riding upon two guide rails 15 formed of two side shoulders, 
respectively, of the beam 7 provided at its upper portion. 
According to the invention, each connecting arm has approximately an 
.OMEGA.-shape located in the normal position of use shown in FIGS. 1 and 
11 for the upper and lower bridging spans 3 and 5, in a plane 
substantially perpendicular to the longitudinal axes of both corresponding 
bridging span elements. Both coaxial elements of the base of the .OMEGA. 
are constituted by bolts 16 directed transversely of both corresponding 
bridging span elements in the normal position of use of the associated 
connecting arm and which are each one connected to the body of the box 8 
of one bridging span element, in the present case the element 3a of the 
bridging span 3 as shown in FIG. 4, by a ball-and-socket pivotal 
connection 17 comprising a bracket 18 for supporting the female sphere 19 
in which is accommodated the male sphere 20 made fast to the end of the 
pivoted bolt 16, the supporting bracket 18 being itself fastened in a 
female supporting part 21 made fast for example by welding to the body 8 
of the bridging span element 3a. The bracket 18 is fastened in the 
supporting part 21 by a screw 22 coaxial with the pivoted bolt 16 and the 
head of which is accommodated in a bore 23 endwise of the bolt 16. 
Each pivoted bolt 16 of one connecting arm is rotatably mounted oppositely 
from its ball-and-socket pivotal connection 17 in a bearing or pad 24 
constituted by a generally parallelepipedic block held against rotation in 
relation to the body 8 of the bridging span element in a rectangular 
window 25 formed in the body 8 in perpendicular relation to the 
longitudinal axis of the bridging span element and in which the bearing 24 
may slide. Each window 25 is provided in the longitudinal web 8a of the 
body 8 of the bridging span element so that the bearings 24 convey the 
longitudinal forces exerted upon the bolts 16 into the longitudinal webs 
8a of the body 8. The ball-and-socket pivotal connection 17 and the 
bearing 24 of each pivoted bolt 16 thus permit a free rotation about its 
axis of rotation OX and a vertical displacement thereof along an 
orthogonal axis OZ as symbolized in FIG. 4, of the corresponding 
connecting arm 3c, 4c and 5c. Otherwise said, each bolt 16 may turn about 
the axis OX and may move about the centre of pivotal connection C of the 
ball-and-socket pivotal connection 17 in a plane perpendicular to the 
corresponding bridging span element as one will see subsequently in some 
of the cases of use of the bridging spans. 
A rubber bellows 26 is tightly fastened about the external end of the 
bearing 24 and to the longitudinal web 8a of the body 8 in a suitable 
housing of the latter so as to protect the inside of the body 8 of the 
beam from dirt such as mud. 
Each bridging span element also comprises means permitting the automatic 
return of each connecting arm of two bridging span elements to its normal 
position of use and to hold the arm in this position. 
These means comprise two identical parallel cams 27 made fast to the 
corresponding connecting arm 3c, 4c, 5c at both ends of the pivoted bolts 
16 opposite from the ball-and-socket pivotal connections 17. The axis of 
rotation of each cam 27 is coaxial with the axis of rotation of the bolt 
16 and the eccentrically shaped formation of the cam 27 extends about the 
bolt 16 over an angle of about 270.degree. as best shown in FIG. 5 while 
being symmetrical with respect to the middle plan extending transversely 
of the corresponding bridging span element and passing through the pivoted 
bolt 16. 
The means for returning and holding each connecting arm also comprise two 
rollers 28 with axes of rotation 29 parallel to the axis of rotation of 
the corresponding pivoted bolt 16 and elastically held in bearing 
relationship upon the lower portion 27a of the eccentrically shaped 
formation of the cam 27 with a force providing for the stable holding of 
the corresponding connecting arm 3c, 4c, 5c in its normal position. The 
eccentrically shaped formations of both cams 27, respectively, associated 
with one connecting arm are such that during a rotation of this arm in one 
direction or in the other one about the axis OX, either one of the two 
rollers 28 exerts upon each corresponding cam 27 a torque for rightening 
the corresponding connecting arm to its normal position as will be seen 
subsequently. 
Both rollers 28 are mounted in a common yoke 30 made fast to one end of a 
supporting shaft 31 slidably mounted in a stationary casing 32 made fast 
to the web 8a of the body 8 of the corresponding bridging span element by 
a fastening flange 33. As shown in FIG. 4, the shaft 31 is perpendicular 
to the axis of rotation OX of the corresponding pivoted bolt 16 and a 
prestressed spring 34, constituting the elastic means holding both rollers 
28 in bearing relationship upon the cam 27, is accommodated in the 
stationary casing 32 substantially coaxially with the supporting shaft 31 
which is shown in the upper high position corresponding to the maximum 
elongation of the spring 34. As shown in particular in FIG. 5, the lower 
portion 27a of each cam 27 whereupon both corresponding rollers 28 are 
simultaneously bearing in the normal position of the connecting arm is 
flat and located between both symmetrical portions of the eccentrically 
shaped formation of the cam 27. 
FIGS. 8, 9 and 11 show that at least one of the bridging spans 3, 4, 5, in 
the present case the intermediate bridging span 4 also comprises two pairs 
of cylindrical rubber stops 35 fastened to both mutually confronting webs 
8a, respectively, of both elements 4a and 4b of the bridging span 4 with 
both stops 35 of each pair being located symmetrically to the plane 
orthogonal to the longitudinal axis of the corresponding bridging span 
element and passing through the axis of rotation OX of the connecting arm 
4c. Each stop 35 is fastened to a fastening lug 36 fastened in 
perpendicular relation to a plate 37 made fast to the web 8a by fastening 
screws 38. The cylindrical stops 35 of a same pair are fastened with their 
respective lugs 36 so that their longitudinal axes be inclined in relation 
to the plane of symmetry. Moreover both stops 35 facing each other of two 
bridging span elements, respectively, are positioned in relation to these 
bridging span elements so that the corresponding connecting arm be caused 
in its downward swung lower position to bear upon these two stops 35 while 
being inclined with respect to the plane of symmetry by a predetermined 
angle value for example of about 55.degree. as shown in FIG. 8. The 
putting in abutment of the connecting arms 4c of the intermediate bridging 
span has the advantage of vertically locking (or jamming) this same 
bridging span underneath the launching beam and on the same occasion the 
lower bridging span (held in the ascending vertical direction). 
Each connecting arm 3c, 4c, 5c comprises a central portion of the upper leg 
of the .OMEGA.-shaped formation of this arm, two pairs of riding rollers 
39 permitting friction between the central portion of the connecting arm 
and the upper portion of the depositing and launching beam 7 to be avoided 
during a relative displacement of this beam and of the connecting arm. 
Both rollers 39 of one pair are fastened onto yokes 4e made fast to the 
corresponding connecting arm while extending in perpendicular relation to 
the central portion of this arm. As shown in FIG. 12, both connecting arms 
4c of the intermediate bridging span 4 are held by the rollers 39 in 
bearing relationship upon the corresponding lower portions of the beam 7 
by the rightening torque of each arm exerted by one of the rollers 28 upon 
each corresponding cam 27. When the beam 7 is disengaged from its storage 
position between both upper and intermediate bridging spans 3 and 4 during 
the procedure of launching and depositing of one bridging span or of 
assembled bridging spans above a ditch, the connecting arms 4c of the 
intermediate bridging span 4 automatically assume again their normal 
vertical position. FIG. 10 shows the upwards swinging phase of one 
connecting arm in the direction of rotation shown by the arrow F1 after 
the withdrawal of the beam 7. On this figure, one of the rollers 28 is 
bearing due to the prestressed spring 34 upon the corresponding cam 37 at 
a distance d from the plane of symmetry previously defined so that the 
roller 28 exerts a rightening moment C=F.times.d, where F is the force 
exerted by the prestressed spring 34 upon the roller 28 in contact with 
the cam 27. 
The means for the displacement of the beam 7 towards its overhanging 
position in relation to the road vehicle 1 are the same as those described 
in French patent No 2,683,837 and have therefore need not be described. 
Likewise, the means for displacing a bridging span or assembled bridging 
spans in relation to the beam 7 as well as the means with a plate P 
carrying in a guided manner the beam 7 and permitting its tilting in 
relation to the vehicle to permit the depositing of one bridging span or 
of the assembled bridging spans may be identical with those described in 
French patent No 2,683,837. 
However, FIGS. 13 to 15 show a particular embodiment of the means 
permitting the displacement in translation of a bridging span or of 
assembled bridging spans upon the beam 7. 
These means comprise an endless drive chain 40 extending along the 
longitudinal axis of the beam 7 while passing over toothed wheels 41 in 
the manner shown in FIG. 13, rotatably mounted onto the structure of the 
beam 7. The chain 40 is directly driven in a suitable fashion by an 
electric motor (not shown) mounted onto the tilting plate P. The means for 
displacing one bridging span in relation to the beam 7 also comprise at 
least two elements forming a fork 42 made fast to the upper side of the 
drive chain 40 and adapted to grip the central portion of one of the two 
connecting arms of one bridging span in particular the rear connecting arm 
during the phase of launching the bridging span. Preferably both pairs of 
elements forming a fork 42 are provided to be disposed symmetrically to 
the middle transverse plane of the beam 7 while being located between both 
pairs of riding rollers 39 of the same connecting arm. FIG. 14 shows two 
pairs of elements forming a fork which may also be made fast to the lower 
side of the chain 40 so as to carry along two or more assembled bridging 
spans. As shown in FIG. 17, both elements forming a fork 42 located on a 
same side in the transverse direction of the chain 40 are rotatably 
mounted at both external ends, respectively, of a pin 43 for the 
connection of parallel links 40a of the chain 40 and are urged back to a 
position projecting above the upper side of the chain 40 by a spiral 
spring 44 mounted onto the pin 43 in the middle thereof. Each fork-forming 
element 42 comprises an inclined portion 42a permitting it to be swung 
downwards by a central portion of a connecting arm of bridge span during 
the displacement in the suitable direction of the chain 40 for gripping 
this central portion in order to carry out the phases for launching and 
depositing the bridging span or the assembling of the latter to another 
bridging span. 
The principle of depositing a bridging span or two or three endwise 
assembled bridging spans is in a general manner identical with that 
described in French patent No 2,683,837 but some phases for the launching 
and depositing of a bridging span or of assembled bridging spans have been 
shown in FIGS. 17A to 17F to point out some unique features of the present 
invention. 
FIGS. 17A to 17F show the depositing of three endwise assembled bridging 
spans 3, 4, 5. 
According to the configuration shown in FIG. 17A, the beam 7 assumes its 
overhanging position on the tilting plate P in relation to the vehicle 1. 
In this configuration, the bridging span of great length constituted by 
the bridging spans 3, 4, 5 is bearing upon the launching beam 7 through 
the medium of the rollers 39 of the connecting arms 5c of the bridging 
span 5 so that the latter retains its geometry such as that shown in FIG. 
1. This geometry is made possible by the fact that the prestressing force 
exerted by the springs 34 associated with the cams 27, respectively, of 
the connecting arms is clearly greater than the reaction force exerted 
upon the connecting arm. 
FIG. 17B shows that the plate P has been tilted so as to lay down the end 
of the bridging span of great length upon the bank opposite to the vehicle 
1 and that the beam 7 has been moved backwards in relation to the vehicle 
1 until the three bridging spans are held upon the beam 7 by the rear 
connecting arm of the rear bridging span 5. 
After the withdrawal of the stabilizing forward jack VA from its inclined 
position shown in FIGS. 17A and B to its approximately vertical position 
shown in FIG. 17C, the beam 7 is tilted by the tilting plate P until the 
end of the bridging span of great length is laid down upon the bank of the 
ditch 2 adjacent to the vehicle 1 as shown in FIG. 17D. During the tilting 
of the beam 7, the rear connecting arm 5c of the bridging span 5 turns 
about both axes OX so that the connecting arm adapts itself to the 
different inclinations of the beam 7 and ensures the taking up of the 
bridging span of great length onto the beam 7. 
FIG. 17E shows the end or nose of the beam 7 disengaged from the rear 
connecting arm of the bridging span 5 by the backward motion of the beam 7 
on the plate P, whereas FIG. 17F shows that the beam 7 in a position 
righted by the rotation of the tilting plate P. 
FIG. 18 shows the situation in which one of the banks whereupon is resting 
the corresponding end portion of one bridging span, such as the bridging 
span 3, exhibits an inequality of height or step when viewed in cross 
section. In this case, each connecting arm 3c should allow the bridging 
span to adapt itself to this bank configuration or any other configuration 
such as that where the bank consists of two portions inclined towards each 
other. Thus in working condition, the substantial weight of the vehicles 
moving over the bridging span permits the compression of the prestressed 
springs 34 associated with the cams 27, respectively, and the whole may 
deform itself as shown in FIG. 18 by displacement along both axes OZ of 
the connecting arm 3c and therefore adapt itself to the different bank 
configurations. This function permits the optimization of the weight of 
the connecting arms which are dimensioned by the weight of the bridge 
being launched and the braking effects of the vehicles and not by the 
forces exerted during the passage of the vehicles. 
Of course the connecting arms of the bridging spans should keep both 
bridging span elements parallel and prevent them from offsetting 
themselves with respect to each other whatever the external actions 
exerted upon them such as the passages of vehicles, the braking of 
vehicles, the banking, etc. might be. For that purpose the forces are 
taken up by the ball-and-socket pivotal connections 17 and the bearings 24 
as shown by the different arrows shown in FIG. 7. 
The bridging span structure of the invention described hereinabove 
therefore allows each one of its connecting arms to be retracted into the 
configuration of transportation of superposed bridging spans, to sustain 
the moment due to the own weight of the bridging spans during the 
launching phase; to transmit the translation forces of each bridging span 
in relation to the launching and depositing beam; to bear the weight of 
the bridging span during depositing; to adapt itself to the relative angle 
during the depositing between the bridging span and the launching beam; to 
adapt itself to the different conditions of the bank and to connect both 
bridging span elements in parallel relationship with respect to each 
other.