GB2097737A

GB2097737A - Apparatus for adjusting ramps on ferries, floating bridges or the like

Info

Publication number: GB2097737A
Application number: GB8203329A
Authority: GB
Original assignee: GOEPPNER KAISERSLAUTERN EISEN
Current assignee: GOEPPNER KAISERSLAUTERN EISEN
Priority date: 1981-02-07
Filing date: 1982-02-05
Publication date: 1982-11-10
Also published as: DE3104361A1; DE3104361C2; GB2097737B; FR2499499B1; FR2499499A1

Abstract

An apparatus adjusts ramps to obtain a better adaptation of the bending- moment curve in the vicinity of the connection of the ramp to a support and adjusts the bending moment in the centre part of the floating bridge. A load-dependent switching means is associated with the ramp-adjusting cylinder (4) in its hydraulic circuit, so as to interrupt and/or reverse the flow of hydraulic medium between the two sides of the piston (8) of the ramp- adjusting cylinder. This means may either be a pressure accumulator (7) with low pretension pressure and the same piston: piston rod ratio as in the ramp-adjusting cylinder or, in a simpler embodiment, a float-controlled hydraulic compensating switch (20). In either case, a safety valve (17) without intermediate lines and adjusted to the desired bending moment is directly associated with the ramp cylinder. <IMAGE>

Description

SPECIFICATION Apparatus for adjusting ramps on ferries, floating bridges or the like The invention relates to an apparatus for adjusting ramps on ferries, floating bridges or the like, in which the bridge support and the ramp forming the connection with the bank or shore are pivotably connected to one another via a pivot, in which case for adjusting the ramp inclination hydraulic cylinders are provided in the vicinity of the pivot, the piston faces of which hydraulic cylinders can be acted upon by a pressure adapting automatically to the respective loading of the ramp.

For spanning shallow bank slopes an adequately long bank ramp is required. The long supporting length thereof leads, however, to undesirably or even inadmissibly high bending moments, particularly at the rigid connection to the bridge support of the floating bridge under load. In any case, these bending moments are considerably greater than the normal bending moment in the middle zone of the floating bridge. For reasons of standardisation and interchangeability of the floating-bridge parts, in was thus necessary hitherto for all floating-bridge parts, even those parts which were used as the centre part of floating bridges or ferries, to be designed for this higher connection bending moment of the ramp thickness.

It is not practicable for the connection of the ramps to the bridge supports to be of articulated design, so as to overcome the above-mentioned deficiencies. In this case, a kink would be formed in the roadway at the connection point, when heavy loads pass thereover. The floating bodies or pontoons beside the bank would be submerged considerably more than those in the centre part of the floating bridge. This would again have the result, because of the already mentioned necessary standardisation and interchangeability, that also the pontoons in the centre part of the floating bridge would have to be given the larger dimensions necessary for the pontoons close to the bank. These larger dimensions would be necessary, in the case of the pontoons close to the bank, so as to increase their buoyancy and thus keep the kink in the roadway within certain limits.

Accordingly, the invention is based on the object of so designing the connection of the ramp to the bridge support that, on the one hand, the bending moment of the centre part of the floating bridge or ferry is not exceeded and, on the other hand, the submersion of the pontoons close to the bank is kept to a smali extent.

The resilience of the ramp connection required here would most simply be achieved by providing safety valves at the hydraulic cylinders serving as adjusting elements for the ramp, which safety valves limit the maximum oil pressure and thus also the maximum bending moment. When these valves open, the ramp supports then lift from the bank after the return journey of the load over the ramp connection and, therefore, when the next load approaches, it would be necessary to lowerthe ramp again with the hydraulic system provided, via a manual switch. Thispersesimple measure has thus proven to be very disadvantageous in the operation of a floating bridge, particularly when used at night.

The Applicants have themselves carried out tests with a gas-pressure accumulator or reservoir in the hydraulic circuit of the ramp-adjusting cyclinders which were mounted on the ramp cylinder ahead of the safety valves. In this case, the gas-pressure spring accumulators were so designed that, upon exceeding the pretension pressure in the accumulator, the oil emerging from the ramp cylinders at a relatively low pressure increase could be taken up by the accumulator. After the departure of the load, the gas-pressure spring accumulator returned the pressure oil again to the ramp cylinders. Therefore, the disadvantage was at least avoided that after relieving the ramp connection of load the ramp tips lifted from the bank. However, even with this embodiment it was necessary for a series of drawbacks to be taken into consideration.Thus a gas-pressure spring accumulator can only be used within narrow temperature limits. Its use is no longer possible even at the 0 C limit. Furthermore, the gas pressure in the accumulator varies considerably with the outside temperature, so that in particular, but also quite generally, constant maintaining and monitoring of the set gas pressure is thus necessary. Any rupture of the feed pipes to the accumulator or failure of the accumulator itself can result in the capsizing of the ferry or the inundation of the floating bridge to which such a device is applied. Finally, in the case of long feed pipes to the tank for the hydraulic fluid, resuction problems occur on the cylinder head side, which lead to vacuum formation. This means that the seals of the ramp-adjusting cylinders are endangered.Moreover, an incalculable elasticity can arise in the entire system.

A similar ramp-adjusting apparatus is known from DE AS 2 900 861. In the hydraulic system provided here, the piston faces of a cylinder/piston unit are acted upon with an elastic pressure acting progressively under load. It is to be achieved thereby, for example, thatthe first pontoons, adjacentthe bank, of a floating bridge are not pressed too deep into or underthe water, when a vehicle is travelling thereon.

A pressure accumulator filled with compressed gas is likewise provided so as to achieve the progressively acting elastic pressure.

To achieve the object set and, in particular, to obviate the further disadvantages mentioned above in known or at least tested apparatus, it is proposed in acordance with with the invention that, starting from the initially described apparatus, both piston faces of the hydraulic cylinder can be acted upon by an automatically adjusting pressure via a hydraulic line connecting both piston sides, as a function of the respective loading of the ramp, that a safety valve is provided directly on the hydraulic cylinder in the hydraulic line, which safety valve is adjustable to the bending moment which can be taken up in the connection zone of the ramp to the pontoon, and that in the hydraulic line there is provided loaddependent switching means for the automatic interruption and/or reversal of the flow of the hydraulic medium between the two sides of the piston of the cylinder.

In a preferred embodiment, this load-dependent switching means is designed as a pressure reservoir or accumulator with low pretension pressure, wherein a double-acting piston is provided which has the same piston: piston rod ratio as the hydraulic cylinder for adjusting the ramps.

Upon exceeding the pressure set in the safety valve, the hydraulic medium displaced from the ramp-adjusting cylinder is displaced into this loaddependent switching means at low pretension pressure. As a result of the same piston:piston rod ratio, it is immediately possible for the deficient hydraulic volume to be replaced on the opposite side of the piston of the ramp-adjusting cylinder, so that the aforementioned resuction problems are avoided.

After the departure of the load, as a result of the ramp's own weight it continues to lie with the ramp tip on the bank.

To assist the action of the load-dependent switching means, it is additionally possible to provide in its cylinder a spring acting on one piston side.

The pretensioning of this spring assists the tendency of the ramp to continue to rest with its ramp tip on the bank. Accordingly, it is also possible to overcome inherent friction, possibly also to be taken into consideration, in the mountings and pistons.

The hydraulic medium flows back, after the ramp has been relieved of load, into the region of the ramp-adjusting cylinder, whence it had been previously displaced.

In a simpler embodiment, the load-dependent switching means can be designed as a float controlled hydraulic compensating switch which has a compensating valve which is disposed in the hydraulic line and which opens or closes depending on the position of a control float.

When the ramp connection is without load, a free articulation is formed by an open connection between the ramp cylinder and the hydraulic-medium tank. Under load, the connection is closed after a preset degree of submersion, so that a rigid ramp connection is achieved with the precalculated or predetermined admissable bending moment. In this embodiment it is necessary, however, for the ramp to have sufficiently high inherent weight, so that even after the load has departed it is ensured that the ramp tip remains in contact with the bank. Moreover, to avoid resuction problems it is necessaryforthe hydraulic-medium tank to be disposed at a short distance from the ramp-adjusting cylinder.

In any case, according to the invention, starting from a given angular position of the ramp relative to the pontoon associated therewith, depending on the respective contact point of the ramp end on the bank and depending on the respective loading of the ramp or of the articulation zone of the ramp to the pontoon, there is achieved automatic adjustment of the angle between ramp and pontoon and, therefore, a flattening of the bending moment in the articula tion zone is attained.

According to the invention, both embodiments can be inserted in the overall hydraulic circuit which is already provided with corresponding valves.

Furthermore, the arrangement of additional servocontrolled non-return valves directly on the cylinders is possible so as to further increase safety in the event of pipe rupture.

The invention will be further illustrated below on the basis of the description of two embodiments of the subject-matter of the invention illustrated in the attached drawings merely by way of example and diagrammatically.

Figure 1 shows a pontoon, situated adjacent the bank, of a floating bridge with ramp and rampadjusting cylinder: Figure 2 shows a similar pontoon with a control float; Figure 3 is a hydraulic circuit diagram of an adjusting hydraulic circuit with spring accumulator; Figure 4, finally, is a hydraulic control diagram utilising a control float.

In Figure 1 the pontoon 1, illustrated merely by way of example and associated with the ramp 2, is articulatedly connected to the ramp 2 at the connection point 3. Between the ramp 2 and pontoon 1, the adjusting cylinder 4 is articulated to both parts, adjacent to the connection point 3. The adjusting cylinder 4 makes it possible to adjust the angular position of the ramp 2 relative to the deck of the pontoon 1, to which it is articulated. This angular position is dependent on the bank condition and bank height, when the free ramp end 5 is supported on the bank 6.

When the ramp 2, or the connection zone 3 of the ramp 2 to the pontoon or floating body 1 of the amphibious vehicle associated therewith, is placed under load, for example by an approaching or departing heavy hand vehicle, considerable bending moments occurs in the articulated zone 3. These bending moments can be substantially flattened if an adjustment of the ramp 2 is possible dependent upon the load. According to Figure 3, this is effected by a spring accumulator 7 provided in the hydraulic circuit of the ramp-adjusting cylinder 4. The ramp adjusting cylinder 4 has a double-acting piston 8; likewise, a double-acting piston 9 is provided in the spring accumulator 7.The cylinder chamber 10 of the ramp-adjusting cylinder 4 is in communication via a line 11 with the cylinder chamber 12 of the spring accumulator 7, wherein in the illustrated example of embodiment a spring 13 acting on the piston 9 is arranged. A compressed-gas accumulator is not very suitable, since such compressed-gas accumulators are not suited to low temp2ratures; moreover, it is necessary for the gas pressure to be constantly monitored. The cylinder chamber 14 of the ramp-adjusting cylinder 4 communicates via a line 15 with the second cylinder chamber 16 of the spring accumulator 7, via a safety valve 17.

If the ramp 2 is now loaded, hydraulic fluid flows from the cylinder chamber 14 of the ramp-adjusting cylinder 4 into the cylinder chamber 16 of the spring accumulator 7. Correspondingly, hydraulic fluid flows from the cylinder chamber 12 of the spring accumulator 7 into the cylinder chamber 10 of the ramp-adjusting cylinder 4. The spring 13 in the spring accumulator 7 is thereby loaded. A prerequisite for the aforementioned flow of hydraulic fluid is that the safety valve 17, which is provided in the hydraulic circuit and which is arranged directly in the ramp-adjusting cylinder 4, opens at a predetermined pressure.

It is now possible, depending on the respective load, for the ramp to vary its angular position and the bending moment is advantageously influenced in the sense of a flattening of the bending-moment curve.

When the load is removed, the flow of hydraulic fluid is reversed. In this case, the inherent weight of the ramp and also the spring 13 have a supporting effect.

The hydraulic fluid flows almost pressurelessly to and fro between the different cylinder chambers.

This takes place fully automatically, depending on the loading pressure of the ramp 2. The assembly is practically completely maintenance-free.

Another possibility, as shown in Figures 2 and 4, lies in providing the pontoon 1 at a suitable location with a control float 18 on a pivoting lever 19, by way of which it is possible to open or close a compensating valve 20 in the hydraulic circuit between the two cylinder chambers 10 and 14 of the ramp-adjusting cylinder 4. This opening and closing takes place depending on the angular position of the lever 19 and, therefore, on the position of the control float 18 disposed at its free end.

The other valves illustrated in the two hydraulic circuit diagrams are associated with the conventional hydraulic circuit for actuating the ramp-adjusting cylinder 4 and, therefore, do not require any further description.

Claims

1. Apparatus for adjusting ramps on ferries, floating bridges or the like, in which the bridge support and the ramp forming the connection with the bank or shore are pivotably connected to one another via a pivot, in which case for adjusting the ramp inclination hydraulic cylinders are provided in the vicinity of the pivot, the piston faces of which hydraulic cylinders can be acted upon by a pressure adapting automatically to the respective loading of the ramp, characterised in that both piston faces of the hydraulic cylinder (4) can be acted upon by an automatically adjusting pressure via a hydraulic line (15,11) connecting both piston sides, as a function of the respective loading of the ramp, in that a safety valve (17) is provided directly on the hydraulic cylinder (4) in the hydraulic line (15), which safety valve is adjustable to the bending moment which can be taken up in the connection zone of the ramp (2) to the pontoon (1), and in that in the hydraulic line (15, 11) there is provided load-dependent switching means for the automatic interruption and/or reversal of the flow of hydraulic medium between the two sides of the piston of cylinder (4).

2. Apparatus as claimed in Claim 1, characterised in that the load-dependent switching means is designed as a pressure reservoir or accumulator (7) with low pretension pressure, wherein a doubleacting piston (9) is provided which has the same piston:piston rod ratio as the hydraulic cylinder (4) for adjusting the ramps.

3. Apparatus as claimed in Claim 2, characterised in that a spring (13) acting on one piston side is provided in the pressure accumulator (7).

4. Apparatus as claimed in Claim 1, characterised in that the load-dependent switching means is designed as a float-controlled hydraulic compensating switch which has a compensating valve (20) disposed in the hydraulic line (11, 15) and opening and closing depending on the position of a control float (18).

5. Apparatus for adjusting ramps on ferries, floating bridges or the like substantially as herein described with reference to and as shown in Figures 1 and 3 or with reference to and as shown in Figures 2 and 4 of the accompanying drawings.