EP0156304B1 - Apparatus for the inspection of the underside of bridges - Google Patents

Abstract

The invention relates to a bridge bottom inspection apparatus which includes an operating chassis movable along the edge of the bridge. A lift tower (6) is raisably and lowerably supported by chassis and can extended downwards past the edge of the bridge. A work platform (5 ) is attached to the lift tower and can be cantilevered beneath the bridge. In order to permit the apparatus to be erected simply, to reduce its overall weight and therefore the load upon the bridge, and to overcome high sound insulation walls located in the guard rail region, the operating chassis has a guide tower (8) located on the bridge, on which the lift tower (6) is guided for up and down movement by means of cantilevered support elements (10). The operating chassis may be a rail or transport vehicle (1). The guide tower (8) is mounted on a turntable (3) of the vehicle pivotably about a horizontal axis (9). Particular further developments of the bridge bottom inspection apparatus described serve to permit it to be moved past masts arranged at the edge of the bridge in such a manner that the lift tower (6) and the work platform (5) can remain in their work position.

Description

The invention relates to a bridge underside device with an operating chassis standing on the bridge and movable along the edge of the bridge, and a lifting and lowering lifting tower held and carried by the latter, which extends downwards past the edge of the bridge and attached to the lower end of which a work platform projecting under the bridge is. Such devices are used instead of scaffolding or lifting lifts in the inspection or renovation of concrete bridges in particular to get to the underside of the bridge.

Known bridge underside devices, for example according to DE-OS 33 05 384, have a box-like ring construction which comprises the lifting tower and which projects from the operating chassis beyond the edge of the bridge and holds the lifting tower and guides it in its lifting and lowering movement. Accordingly, the entire length of the lifting tower must be particularly rigid and thus heavy. The lifting drive, usually a hydraulic working cylinder, is arranged in the lifting tower. However, since the parts located outside the bridge must correspond to the parts of the operating chassis on the bridge as a counterweight for reasons of stability, this known construction is relatively heavy.

Many bridges on expressways that lead through residential areas have soundproof walls up to 3.5 m high above or in place of the railing. The use of the known bridge underside devices requires the dismantling of these soundproof walls.

The invention has for its object to provide a light bridge underside device that loads the cap area (cantilevered edge area) of the bridge less in weight and also allows to overcome the high soundproofing walls running along the bridge edge.

According to the invention it is proposed that the operating chassis has a guide tower located on the inside of the edge barrier of the bridge and that the lifting tower is guided up and down on the guide tower by means of supporting members projecting over the edge barrier.

The guide tower is located on the bridge within the perimeter barrier, e.g. B. the bridge railing, so that its weight does not generate an outward tilting moment. Heavy I-profile rails are preferred for guiding, which are weight-related. Furthermore, the usually very heavy hydraulic cylinder for lifting drive can be arranged on the guide tower and thus on the bridge. The lifting tower can be so long (high) that in the operating position (work platform swung under the bridge) the bottom support elements reach over the soundproof wall so that it does not form an obstacle during work. A floor can be provided in the area of the supporting members, so that access to the work platform can be made easily through the guide tower upwards, over this floor and through the lifting tower downwards. Finally, the lifting tower can also be dimensioned more easily because the forces are not introduced at changing locations, but at the same location via the supporting members.

The bridge underside device can be constructed using a crane. However, in order to make crane help unnecessary and to design the device to be self-assembling and to facilitate the transport to the bridge, it is proposed that the service chassis be designed as a transport vehicle suitable for transporting the entire bridge inspection device over longer distances and have a turntable that can be rotated about a vertical axis which the guide tower by a horizontal, in the. Operating position in the longitudinal axis of the bridge is pivotally mounted.

In the case of road transport, the transport vehicle can be a trailer or a truck, each of which is parked in the longitudinal direction near the edge of the bridge. In the case of railway bridges, however, it is advantageous to build the entire device on a rail-bound wagon. Railroad cars can be very heavy, e.g. B. 60 to, so that the stability of the device is guaranteed. In addition, railway bridges are usually narrow.

In order to increase the footprint of these vehicles and to avoid vibrations of the work platform due to the vehicle suspension, the turntable can be equipped with support rollers that can be lowered onto the bridge surface and run in the longitudinal direction of the bridge, the axes of which cross the swivel axis of the guide tower perpendicularly. Instead of the turntable, the chassis of the transport vehicle can also have cross arms provided with corresponding support rollers. As usual, these booms can be height-adjustable or foldable and can be arranged on both sides of the vehicle.

A further improvement of this construction is that the turntable is arranged on a cross slide that is movable horizontally and transversely to the direction of travel with respect to the vehicle chassis. As a result, the bridge underside device can be adjusted precisely in relation to the bridge edge in the transverse direction of the bridge without having to maneuver the transport vehicle. The changing distance from railings, guardrails or the like from the edge of the bridge can thus be taken into account. The cross slide will be placed in a stable guide and driven by means of a hydraulic cylinder. The adjustment range can e.g. B. 0.5 m on both sides.

In the case of narrow bridges, in particular if guardrails are provided at a distance from the edge of the bridge, so that the transport vehicle cannot move all the way to the edge of the bridge, the transport vehicle impedes traffic. In such cases, a special company chassis is preferred, the wheels of which run partly in front of and partly behind the crash barriers, as well as a special road transport vehicle. The empty road transport vehicle, however, must be moved away after the bridge inspection device has been set up in order to clear the traffic lane. This takes time and personnel. In addition, the vehicle is missing as a counterweight.

As a special construction, it is proposed that the guide tower is pivotally mounted on the operating chassis about a horizontal axis and has a turntable on its lower side in the horizontal transport position, which is rotatably connected to a transport chassis, the turntable axis being perpendicular to the guide tower and perpendicular to the standing surface of the Transport chassis extends. The transport chassis can in particular be a four-wheel trailer. The solution to the problem is that the transport frame is lifted off the road by swiveling it up and is thus completely removed from the traffic area. It hangs 90 ° on the guide tower and acts as a counterweight. Further details can be found in the description of an exemplary embodiment.

With some bridges, the use of the device described is hindered by the fact that masts are attached at relatively short intervals along the edge of the bridge, for example for the roadway lighting or for the electrical overhead line wires of electric buses or trains. In order to be able to drive past such obstacles with the company chassis without having to take the work platform and the lifting tower back onto the bridge surface, it is proposed that an up and down movable sliding frame be provided on the guide tower, to which projecting rigid support arms are attached, and that on a non-liftable part of the operating chassis, two swivel arms are pivotably mounted about vertical axes, the support arms, the swivel arms and the lifting tower having coupling parts that can be engaged and disengaged in the vertical direction for mutual connection. This proposal is described in detail. There are four support arms with hooks on the slide frame and two swivel arms, each with two hooks on the turntable, i.e. at the base of the guide tower. An advantage of this solution is that the weight of the lifting tower falls into the coupling members and a safe coupling is thereby possible. The vertical mobility of the sliding frame is used for coupling.

Another preferred embodiment, also with sliding frame on the guide tower up and down, is that three parallelogram frames are arranged on the sliding frame, each having a plurality of superposed, up and down swiveling arms, which are connected to each other by a vertically arranged articulated bracket and by means of a rotary actuator. can be actuated, and that the arms can be connected to the lifting tower with the aid of plug-in coupling parts. Here, the swivel arms of one of the three frame levels can be released without any risk to stability. The coupling process takes place here with the help of the swivel drive. The arms are coupled to the lifting tower in the horizontal position and released in the pivoted down position. They each give space for the mast to drive past. Incidentally, this construction has the advantage that the distance between the lifting tower and the guide tower can be varied if desired by the common inclination of all pivot arms. This can be of particular importance in road transport because it is possible in this way to reduce the overall height of the bridge inspection device loaded for transport.

Finally, with a view to overcoming bridge masts, it is proposed as a third embodiment that two pivoting frames are pivotally mounted about vertical axes on the sliding frame of the guide tower as supporting members, each of which can carry the lifting tower alone. The operation of such a device is easier because the operating chassis only has to stop once in order to couple one swivel frame and to release the other. The direction of movement of the coupling elements is horizontal. It can therefore be advantageous to give the coupling members a limited height adjustment, for example driven by short hydraulic cylinders, for easy insertion and locking of the coupling members on at least one swivel frame.

In order to rule out incorrect operation of the support members which can be separated from the tower and which can be taken back to the operating chassis, it is proposed that a safety control device is provided which prevents the simultaneous actuation of all the support members and prevents the separation of further support members as long as one support member is disconnected.

• Fig. 1 die Seitenansicht einer Brückenuntersichtvorrichtung im Transportzustand,
• Fig. 2 die Vorrichtung nach Fig. 1 nach Durchführung einer 90°-Drehung des Drehschemels in Fahrtrichtung bzw. Brückenlängsrichtung gesehen,
• Fig. 3 eine Ansicht der Vorrichtung wie Fig. 2 in einem weiteren Aufbaustadium,
• Fig. 4 eine Ansicht der Vorrichtung wie Fig. 2 in Arbeitsstellung,
• Fig. 5 eine weitere Ansicht wie Fig. 2 mit zurückgeschwenktem Führungsturm beim Passieren eines Mastes,
• Fig. 6 Teile der Brückenuntersichtvorrichtung in der Stellung nach Fig. 4 in Draufsicht,
• Fig. 7 Teile der Brückenuntersichtvorrichtung in der Stellung nach Fig. 5 in Draufsicht,
• Figuren 8 und 9 eine andere Ausführungsform der den Hubturm und den Führungsturm verbindenden Tragorgane in Ansicht und Draufsicht,
• Figuren 10 und 11 eine weitere Ausführungsform der den Hubturm und den Führungsturm verbindenden Tragorgane in Seitenansicht und Draufsicht,
• Fig. 12 eine andere Brückenuntersichtvorrichtung in halb aufgebauter Stellung in Brückenlängsrichtung gesehen.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. In detail shows

• 1 is a side view of a bridge underside device in the transport state,
• 2 seen the device of FIG. 1 after a 90 ° rotation of the turntable in the direction of travel or longitudinal direction of the bridge,
• 3 shows a view of the device like FIG. 2 in a further construction stage,
• 4 is a view of the device like FIG. 2 in the working position,
• Fig. 5 shows another view like Fig. 2 with back swiveled guide tower when passing a mast,
• 6 parts of the bridge underside device in the position according to FIG. 4 in plan view,
• 7 parts of the bridge underside device in the position according to FIG. 5 in plan view,
• FIGS. 8 and 9 show another embodiment of the support members connecting the lifting tower and the guide tower in a view and a top view,
• 10 and 11 show a further embodiment of the support members connecting the lifting tower and the guide tower in side view and top view,
• Fig. 12 seen another bridge underside device in a semi-assembled position in the longitudinal direction of the bridge.

The bridge underside device according to FIGS. 1 to 7 uses a three-axle truck 1 as a combined operating and transport chassis. On its chassis 2 there is a turntable 3, the axis of rotation of which is designated 4. A lifting tower 6, which is surrounded at the top and on the sides by a work platform 5, is connected to a guide tower 8 by means of a sliding carriage 7. This guide tower 8 is pivoted about a horizontal axis 9 on the turntable 3 The towers and the work platform consist of a lattice structure, for. B. made of aluminum.

The sliding carriage 7 consists of four rigidly connected support arms 10, the gripping hooks 11 (FIG. 5) of which engage in corresponding hook eyelets 12 on the lifting tower 6. On the other hand, the sliding carriage 7 is guided so that it can be moved in two I-shaped rails 14 of the guide tower 8 by means of rollers 13. The drive is formed by a hydraulic telescopic cylinder 15 attached to the outside of the guide tower. A transport support, not shown, which is removed in the operating state, supports the lifting tower 6 on the truck 1 with respect to the guide tower 8.

The lifting tower 6 is divided into an upper part 16 and a lower part 17, which are connected to one another by a turntable 18, the axis of which is aligned with the axis of the tower. The drive of the slewing ring is not shown. The work platform 5 consists of a main web 19 which is pivotably articulated about an axis 20 on the lower part 17 of the lifting tower and an additional web 21 which can be telescoped in the longitudinal direction. From the tabs 22 attached to the lower part 17, two hydraulic cylinders extended by tubes 23 extend to the end of the main web 19. The two webs have a U-shaped cross section and therefore include the lifting tower 6 in the folded state.

The bridge underside device further comprises two triangular bent swivel arms 24 (FIG. 6) which are articulated on the turntable 3 so as to be pivotable about vertical axes 25. The axes of rotation are formed by stable hinges stiffened with triangular support walls 26. Two gripping hooks 27 are arranged on the swivel arms 24, which can grip the lifting tower 6 on lateral cross bars 28.

For better support of the pivoted-out turntable 3, two extension rails 29 (FIG. 4) which can be pulled out laterally from the chassis 2 and on which support legs 30 are hinged are used. The support legs are provided with roll rolls 31 which run parallel to the truck 1. A slow drive for the movement of the assembled device on the bridge can be installed in the truck or act on the support rollers 31.

Figures 3 and 4 show the so-called cap area of a bridge 32 in cross section. A bridge pier 33 is indicated. A railing 34 is shown in FIG. 2 and a soundproof wall 35 is shown in FIG. 3 as examples of edge barriers. 4 and 5, on the other hand, a mast 36 is shown in the same place, which carries a lamp housing 37 for street lighting. It is explained with the aid of FIGS. 6 and 7 how the bridge underside device can drive past such masts in the assembled state.

In Fig. 3 it is indicated that the turntable 3 can be mounted on a cross slide 39 which can be adjusted within the vehicle width by means of a hydraulic cylinder. Thus, however, the axis 4 of the turntable 3, the turntable itself and all other structures with respect to the truck 1 to the bridge edge can be adjusted precisely.

The structure of the bridge underside device is as follows: The truck 1 in the transport state acc. Fig. 1 moves parallel to the edge of the bridge. First, the support rollers 31 are positioned between the truck and the edge barrier. The boom rails 29 now serve as support for the turntable 3, which is rotated 90 ° into the position shown in FIG. 2. By means of two hydraulic drive cylinders 38, which are articulated on the turntable 3 and on the other hand on the guide tower 8, the guide tower with all attachments and superstructures is pivoted up about the pivot axis 9 with respect to the turntable. This construction phase must take place at a point on the bridge where the edge barrier is not too high. In order to keep the swiveling torque within limits at the beginning of the movement, the lifting tower 6 can be moved with the work platform 5 on the guide tower a little way beyond the edge of the bridge. An intermediate position with an inclination of approximately 45 ° is indicated by dash-dotted lines in FIG. 2.

FIG. 3 shows the position of the bridge underside device from the viewing direction as in FIG. 2 after the guide tower 8 has been erected. The lifting tower 6 is held outside the bridge edge on the guide tower and can now be lowered. Advantageously, a possibly existing cross slope of the bridge can be compensated for by measuring the swivel angle of the guide tower 8 to somewhat more or less than 90 °. As a further step in the construction, the work platform 5 is folded down, namely in that the built-in in the tubes 23 Lift cylinders are extended. Fig. 3 shows the work platform in an inclined position. Possibly simultaneously with the pivoting movement of the work platform 5, the lifting tower 6 is lowered by retracting the telescopic cylinder 15 and the lower part 17 of the lifting tower together with the work platform on the slewing ring 18 is rotated by 180 °. The work platform 5 thereby pivots under the bridge, which is shown in FIG. 4. Depending on the width of the bridge, the additional web 21 can be extended to the right. To bypass the bridge pillars 33, the work platform is swiveled out parallel to the bridge by means of the turntable 18 and swung in again behind the pillar.

In the present example, it will depend on the height of the bridge box how high the soundproof wall 35 may be. Lower bridge boxes allow higher soundproof walls and vice versa. The working height between the bottom of the work platform 5 and the lower surface of the bridge box can be set as desired on the telescopic cylinder 15. The device is highly resilient; the weight of the guide tower 8 and the truck 1 guarantee that no dangerous tilting moments occur even when the work platform is pivoted outwards in the construction phase (FIG. 3).

The following description of the mode of operation of those parts of the bridge underside device, which makes it possible to drive past masts, makes particular reference to FIGS. 4 to 7. Starting from FIG. 4 and the associated top view according to FIG. 6, the device moves in the direction of the arrow towards the edge of the bridge along towards the masts 36 (Fig. 7). The lifting tower 6 and the guide tower 8 are connected to one another by the sliding carriage 7. The lifting tower hangs in the four gripping hooks 11 of the support arms 10. The two swivel arms 24 are folded forward from the transport position into a middle waiting position, but only to the extent that at least the left swivel arm does not impede the approach to the mast 36.

Thus, the device moves into the position shown in solid lines in FIG. 7. The mast is now immediately in front of the sliding carriage 7. In this position, the travel drive stops and the lifting tower 6 is raised so far that the swivel arms 24 with their Gripping hook 27 can grip from the side under the cross bars 28 of the lifting tower. This position of the swivel arms is shown in FIGS. 5 and 7. Now the lifting tower is set back a little by means of the sliding carriage so that the gripping hooks 27 engage the cross bars and the swivel arms take on the full weight of the lifting tower 6 and the work platform 5. The sliding carriage 7 moves further downward, however, so that its gripping hooks 11 detach from the hook eyelets 12. Now the guide tower 8 is tilted back slightly, as shown in FIG. 5, and in this position the sliding carriage 7 can be moved higher, the lower support arms 10 with their gripping hooks coming past the lower hook eyelets 12.

The support arms 10 of the slide carriage are no longer an obstacle to the further journey, so that the device can be brought into the position shown in dash-dot lines in FIG. 7. The mast is now beyond the two towers but still within the space enclosed by the swivel arms 24. In this position, the sliding carriage 7 is lowered again, the guide tower 8 is brought into the vertical and the sliding carriage is coupled to the lifting tower 6 again by starting up again. The lifting tower is also raised a little way so that the cross bars 28 can be released from the gripping hooks 27 and the two swivel arms 24 can be folded back into the position according to FIG. 6 or the transport position.

The swivel arms 24 are preferably actuated by means of hydraulic lifting cylinders (not shown). A hydraulic or electrical safety control device ensures that the coupling and decoupling processes take place in the manner described. In particular, it is ensured that the two swivel arms can only be actuated together and only at a certain height of the lifting tower, in which the cross bars 28 are located just above the gripping hooks 27. Otherwise, a malfunction is already ruled out in that the lifting tower 6 can only be uncoupled from the sliding carriage 7 in that it rests on the swivel arms 24. Conversely, the swivel arms can only be released if the lifting tower 6 hangs in the gripping hook 11 of the sliding carriage.

Another construction for driving past a mast is sketched in FIGS. 8 and 9. The sliding carriage here has the shape of a sliding sleeve 40 surrounding the guide tower 8 with lateral widenings. On this sliding sleeve, facing the lifting tower 6, three parallelogram frames are arranged offset parallel to one another in the longitudinal direction of the bridge. Each consists of two arms 43 and 44 which are pivotably mounted about horizontal axes 41 and 42 and which are connected to one another by a vertical joint bracket 45. Each parallelogram frame can be switched between a carrying position with horizontally extended arms and a rest position with arms that are inclined downwards by means of a lifting cylinder 46 that engages the upper arm.

On the other hand, the lifting tower 6 has laterally protruding brackets 47, which make it possible to arrange a total of six hook eyelets 48 in pairs in the longitudinal direction of the bridge so that they can cooperate with the hooks provided on the arms of the parallelogram frame. In terms of strength, the arrangement is such that two parallelogram frames, i. H. four arms, carry the lift tower 6 and can absorb all occurring moments.

As indicated in FIG. 9, the device passes the mast designated here by 49 by alternately lowering the parallelogram frame. The movement takes place in In the direction of the arrow, the arms 43, 44 are first lowered and the device is moved until the mast is in the first chamber. After coupling the arms 43 and 44, the arms 43 'and 44' are lowered. Now you continue to drive the device until the mast 49 is in the second "chamber". After the arms 43 'and 44' have been re-engaged, the arms 43 "and 44" are disengaged, which means that the obstacle has been overcome and, to be on the safe side, these last ones too With the help of automatic safety control devices, the correct function can also be guaranteed here and a loosening of the hooks from the hook eyelets during assembly and disassembly of the device and during transport can be prevented.

Finally, a variant of such a construction is shown in FIGS. 10 and 11. A plate 51 and 52 is pivotally mounted on the left and right of the sliding sleeve of the guide tower, designated 50, about vertical axes 53 and 54. The panels can actually be flat lattice structures. Each plate carries four horizontally acting coupling parts 55, which laterally grip the lifting tower 6. The construction can be such that one of the two plates 51 and 52 alone gives the lifting tower 6 sufficient support. For this purpose, the coupling parts 55 must be equipped with corresponding locking devices and provision must also be made for the fixing of the respective load-bearing plate, in the example plate 51, on the guide tower 8. The particularly simple procedure is advantageous compared to the constructions described so far.

Another underside bridge device is shown in FIG. 12. It differs from the examples described so far in that the lifting tower 6 is guided up and down on the guide tower 8 by means of rigid guide arms 57 attached to it. Furthermore, there is no need for an expensive truck as a transport vehicle. Instead, a simple two-axle trailer chassis 58, the twin wheels of which are designated 59, is used for road transport. A separate company chassis is provided for operation on the bridge, consisting of a platform 60, a running frame 61 and a drive frame 62. The horizontal axis 9 of the guide tower 8 is articulated on the platform 60.

The special feature is that on the side of the guide tower 8 facing away from the lifting tower 6 there is a turntable 63 which is rotatably connected to the trailer chassis 58, the axis of rotation 64 extending perpendicularly to the base of the trailer chassis 58. The advantage of this bridge underside device lies in the extremely narrow working base on the bridge, so that it is particularly suitable for very narrow bridges or for bridges with extreme traffic loads.

Starting from the operating position shown in FIG. 12, the dismantling of the device into the transport position is described as follows: after the work platform 5 has been folded in, the towers are inclined to the right about the axis 9 and pivoted into the horizontal position. The twin wheels 59 come into contact with the surface of the bridge. The weight of the device is now on the turntable 63. Now the bogie 61 is lifted from the base by swiveling the support wheels up and the drive frame 62 is uncoupled from the lifting cylinder 65 attached to the platform 60. Now you turn the whole device on the turntable by 90 ° in the longitudinal direction of the bridge and the direction of travel. The drive frame 62, which is now located next to the trailer chassis and between its two axles, is finally coupled to the lifting cylinder 65 at another point and lifted up by it so far that it does not interfere with road transport. The device can now be driven off by means of a towing vehicle.

Claims (10)

1. Apparatus for viewing the underside of a bridge, with a working chassis (2) adapted for movement along the edge of the bridge while the apparatus itself is situated on the bridge (32), the apparatus comprising, supported and held by it, a raisable and lowerable tower (6) which extends downwardly past the edge of the bridge and which carries at its bottom end a working platform (5) which extends underneath the bridge, characterised in that the working chassis (2) comprises a guide tower (8) disposed on the inside of the barrier (34) along the side of the bridge (32) and in that the tower (8) is guided for movement up and down by means of supporting members (7, 10, 11, 24 ; 40, 43, 44 ; 50, 51, 52 ; 57) on the guide tower and projecting over the barrier.

2. Apparatus for viewing the underside of a bridge, according to Claim 1, characterised in that the wcrking chassis is constructed as a transporter vehicle (1) suitable for carrying the entire bridge underside viewing apparatus for relatively long distances and comprises, rotatable about a vertical axis (4), a pivoting bolster (3) on which the guide tower (8) is mounted to pivot about a horizontal axis (9).

3. Apparatus for viewing the underside of a bridge, according to Claim 2, characterised in that the rotary bolster is equipped with supporting rollers which can be lowered onto the bridge . surface, their axes intersecting at right-angles with the pivot axis (9) of the guide tower (8).

4. Apparatus for viewing the underside of a bridge, according to Claim 2, characterised in that the chassis (2) of the transporter vehicle (1) comprises transverse outriggers (29) provided with supporting wheels (31).

5. Apparatus for viewing the underside of a bridge, according to Claim 2, characterised in that the rotary bolster is disposed on a transverse slide (39) adapted for movement horizontally in respect of the vehicle chassis (2) and transversely to the direction of travel.

6. An apparatus for viewing the underside of a bridge, according to Claim 1, characterised in that the guide tower (8) is mounted on the working chassis (60) to pivot about a horizontal axis (9) and has on that side which is underneath when the apparatus is in its horizontal transit position, a rotary bolster (63) rotatably connected to a transporter chassis (58), the rotary bolster axis (64) extending at right-angles to the guide tower (8) and at right-angles to the standing area of the transporter chassis.

7. Apparatus for viewing the underside of a bridge, according to Claims 1 and 2, characterised in that there is on the guide tower (8) an upwardly and downwardly movable sliding frame (7) on which are fixed projecting rigid support arms (10) and in that there are on the rotary bolster (3) two pivot arms (24) adapted to pivot about vertical axes (25), the support arms, the pivot arms and the tower (6) having coupling parts (11, 12, 27, 28) which can be engaged and disengaged in a vertical direction in order to establish their mutual connection.

8. Apparatus for viewing the underside of a bridge according to Claim 1, characterised in that there is on the guide tower (8) an upwardly and downwardly movable sliding frame (40) on which there are three parallelogram frames each of which comprises superposed upwardly and downwardly pivotable arms (43, 44, 43', 44', 43", 44"), which are connected to one another by a vertically disposed articulated link (45, 45', 45") and which are adapted to be operated by a pivot drive (46) and in that the arms can be connected to the tower (6) by means of push-in coupling parts.

9. Apparatus for viewing the underside of a bridge, according to Claim 1, characterised in that there is on the guide tower (8) an upwardly and downwardly movable sliding frame (50) on which two pivotable frames (51, 52) are mounted to pivot about vertical axes (53, 54), of which each can by itself support the tower (6).

10. Apparatus for viewing the underside of a bridge, according to one of Claims 7 to 9, characterised in that a safety control means is provided which prevents the simultaneous actuation of all the supporting members and also prevents the separation of further supporting members so long as one supporting member is separating or isolated.

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