PIVOT ARM DEVICE AND BRIDGE

Field of the invention

The invention relates to a pivot arm device in accordance with the preamble of claim 1 and a bridge comprising a pivot arm device.

Background of the invention

From prior art movable bridges, for example in the form of bascule bridges, are known. Such bridge is used, for example, for bridging crossing shipping routes. A supporting structure of the bridge is movable in this case about an axis of rotation, for example. Hydraulic cylinders may be provided for moving the supporting structure. Such movable bridge is disclosed, for example, in US 3,376,795 or in US 5,454,127.

Moreover, bascule bridges are known in which a compensating mass or a compensating weight is provided for the supporting structure. The compensating weight then reduces the load acting on the hydraulic cylinders. In this way, less, especially electrical, energy is required to drive the hydraulic cylinders and thus to move the supporting structure. It is a drawback of the compensating weight that complicated mechanical constructions and construction work, especially for a base, are required, which entails high costs.

Disclosure of the invention

In contrast, the object underlying the invention is to provide a pivot arm device and a bridge which eliminate the afore-mentioned drawbacks.

This object is achieved with respect to the pivot arm device according to the features of claim 1 and with respect to the bridge according to the features of claim 12.

Advantageous developments of the invention are the subject matter of the subclaims.

In accordance with the invention, a pivot arm device comprising a pivot arm is provided. The latter may be rotatably, especially pivotally, supported especially at a distance from the center of gravity of the pivot arm. The pivot arm may further be connected to a hydraulic cylinder which acts on the pivot arm especially at a distance from the pivot bearing. The pivot arm then can be pivoted or rotated via the hydraulic cylinder in a raising direction and in a lowering direction. The hydraulic cylinder preferably rests, especially rotatably, on a fixed bearing. The hydraulic cylinder preferably has a first effective area which acts in a raising direction of the pivot arm and to which pressure medium or oil can be applied. Moreover, a second effective area may be provided which can act in the lowering direction of the pivot arm and to which pressure fluid can be applied. Furthermore, a third effective area acting especially in the raising direction to which pressure medium can be applied may be provided for load compensation or gravitational force compensation of the pivot arm.

This solution offers the advantage that the hydraulic cylinder or actuating cylinder includes a third surface or effective area adapted to be used for load compensation, wherein a compensating weight as explained in the beginning can be dispensed with and, in this way, raising forces to be applied by the hydraulic cylinder via the first effective area are reduced. Thus, for raising the pivot arm less energy is required as compared to a hydraulic cylinder having two effective areas only. Moreover, the hydraulic cylinder requires comparatively small amounts of pressure medium to operate the former. These amounts are comparable when using a hydraulic cylinder having two chambers.

Preferably, in another embodiment of the invention the third effective area may delimit a cylinder chamber within the hydraulic cylinder. The cylinder chamber then may be connected to a gas-loaded hydraulic accumulator. Thus, a hydraulic accumulator having a predetermined closed gas volume is provided and can be biased in this way. Accordingly, in a technically simple manner the hydraulic accumulator may be used as a gas spring so as to replace a compensating weight, for example. The hydraulic cylinder along with the cylinder chamber then can be passively used in a technically simple manner without any control valves, for example, being provided. Preferably, the flow path between the hydraulic accumulator and the cylinder chamber is in the form of a closed system and is not in fluid communication with the other effective areas. Hence, in a fluidic respect, the cylinder chamber is separated from the first and second effective areas.

The hydraulic accumulator may have a separating element for separating a gas volume from pressure medium for the third effective area. The gas volume is preferably designed so that the compensating force applied via the third effective area through the hydraulic accumulator is adapted to the holding force of the pivot arm during lowering/raising the pivot arm. Thus, only low forces have to be applied via the first effective area for raising the pivot arm. This is also applicable to lowering the pivot arm, wherein a force for lowering the pivot arm can be applied via the second effective area, where needed. The holding force for retaining the pivot arm which has to be applied by the hydraulic cylinder is dependent on the position of the pivot arm. The more the pivot arm is pivoted upwards, the less the holding force and vice versa. Thus, the compensating force applied via the hydraulic accumulator is not constant but depending on the holding force. The gas volume of the hydraulic accumulator is preferably designed so that the compensating force applied via the third effective area through the hydraulic accumulator increases when lowering the pivot arm and drops when raising the pivot arm. In particular, the gas volume is chosen to be comparatively small so that, when retracting the hydraulic cylinder and when lowering the pivot arm, a curve of the compensating force is provided as a strongly rising characteristic line which at least approximately matches the increasing holding force of the pivot arm. In other words, the optimization of the effective areas of the hydraulic cylinder, of the gas volume and of the filling pressure of the hydraulic accumulator results in a very steep pressure curve. Thus, a steep stroke-dependent pressure may be made available to the connected hydraulic accumulator. In other words, the gas volume is comparatively small, which may result in a steep pressure curve. The size of the hydraulic accumulator thus may be selected by way of the desired pressure characteristic on the actuating cylinder or hydraulic cylinder.

A piston-type accumulator is preferably provided as hydraulic accumulator. Said piston-type accumulator is extremely pressure-tight and thus most advantageously suited for the pivot arm device so as to serve as a substitute for a compensating weight. It is also imaginable to provide a bladder accumulator as a hydraulic accumulator. It is further imaginable to use plural hydraulic accumulators in parallel in a fluidic manner.

It is imaginable that a valve is fluidically provided between the hydraulic accumulator and the cylinder chamber. Said valve may be used to block the pressure medium communication, for example. Alternatively or in addition, it is imaginable that pressure medium can be relieved by the valve in a restricted manner from the cylinder chamber to the hydraulic accumulator, when the pivot arm is lowered, so as to adapt the compensating force to the holding force of the pivot arm.

In another configuration of the invention, a set of hydraulic accumulators having differently sized gas volumes may be provided. One of said hydraulic accumulators may be selected for being connected to the cylinder chamber by way of a desired pressure characteristic of the hydraulic cylinder.

Preferably, the hydraulic cylinder and the at least one hydraulic accumulator form a unit and are, for example, mechanically connected to each other. This results in an extremely compact configuration, as e.g. in that case the hydraulic accumulator is rotatably supported along with the hydraulic cylinder on a fixed bearing.

The first effective area of the hydraulic cylinder may delimit a first cylinder chamber which may then be connected to a hydraulic machine. Via the latter pressure medium may be adapted to be conveyed into the first cylinder chamber so as to raise the pivot arm, for example. The second effective area may delimit a second cylinder chamber of the hydraulic cylinder which is connected, for example, to a tank or accumulator or to the hydraulic machine. If a connection to the hydraulic machine is provided, the latter may be in fluidic arrangement between the first and second cylinder chambers. If the second cylinder chamber is connected to a tank, it is imaginable that the hydraulic machine is equally connected to a tank so as to be capable of conveying pressure medium via the same to the first cylinder chamber. The hydraulic machine may be used as a hydraulic pump, for example. If the latter is arranged between the first and second cylinder chambers, it may convey pressure medium, for example, from the first into the second cylinder chamber to lower the pivot arm. For raising the pivot arm, the hydraulic pump can convey pressure medium from the second into the first cylinder chamber. It is further imaginable that the hydraulic machine can additionally be used as hydraulic motor so that the latter then may be provided for energy recovery, for example. If, for instance, the pivot arm is lowered on the basis of its weight force, pressure medium may flow from the first cylinder chamber via the hydraulic motor to the second cylinder chamber in order to use the hydraulic motor for driving a generator.

The effective areas are configured in a technically simple manner on a piston of the hydraulic cylinder which in turn may be connected to the pivot arm. Preferably, the first and second effective areas are, especially approximately, equal. This offers the advantage that no device or at most a small device for compensating a difference in the pressure medium volume has to be provided, which allows to configure the pivot arm device in an extremely compact and simple manner.

Preferably, the piston of the hydraulic cylinder is guided in a cylinder housing. A piston rod which may protrude from the cylinder housing and may be connected to the pivot arm may extend away from the piston. An axial blind hole recess is introduced to the piston and to the piston rod, for example, from a piston side of the piston facing away from the piston rod. A guiding rod tightly connected to the cylinder housing may then extend in the axial direction, wherein the piston and the piston rod are guided on the same via the blind hole recess. The first effective area is a bottom area of the blind hole recess, for example. A fluid path may axially pass through the guiding rod, wherein the first cylinder chamber delimited by the first effective area can be communicated with the hydraulic machine via said fluid path. A piston area provided on the side of the piston rod then may form the second effective area. Moreover, the piston area facing away from the piston rod may be provided as a third effective area.

It is also imaginable to connect the piston rod to the fixed bearing and, instead, to connect the cylinder housing to the pivot arm.

In a further configuration, the pivot arm may be provided to be a supporting structure of a movable bridge or a pivot arm for raising a supporting structure of a movable bridge. Preferably, the bridge is a bascule bridge with hydraulic actuation. The use of the hydraulic cylinder having three chambers allows to dispense with a compensating weight in the bridge or allows to at least reduce a compensating weight. Accordingly, construction expenditure and a demand of space are extremely low. Bridges including a compensating weight have to be designed to be extremely stable because of the large additional movable mass, which results in high expenditure on material and constructional design. The small available space required and the simpler configuration of the movable bridge, on the one hand, renders the same cheaper and, on the other hand, effects on a landscape where the bridge is provided are definitely reduced due to the smaller overall size and the simplified configuration. By reason of the small amounts of pressure medium required, also a hydraulic drive may be designed to be appropriately small, which is more cost-efficient and saves available space. In contrast, movable bridges known from prior art including a compensating weight usually exhibit extremely expensive and large-scale steel constructions which are cost-intensive and affect the overall appearance of the landscape.

It is also possible that the pivot arm is part of an A frame. Usually, an A frame includes two pivot arms each of which is synchronously operable by a hydraulic cylinder. The use of the pivot arm device according to the invention allows to considerably reduce the energy required when using the A frame.

In an alternative embodiment of the invention, it is imaginable that the pivot arm is employed, especially on a vessel, for raising and lowering a suction pipe system. In this way, an energy input can equally be considerably reduced as compared conventional systems.

Moreover, it is alternatively imaginable that the pivot arm is a loading bridge of a transport vehicle. This offers the advantage that, on the one hand, energy can be saved and, on the other hand, a pressure medium accumulator can be designed to be very small due to the small amounts of pressure medium required. This is extremely advantageous in a transport vehicle, for example in the form of a truck.

It may further be provided to use the pivot arm in a fairground ride. This entails an extremely low energy input, which is of great advantage to the operator of such ride.

It is imaginable as an alternative to provide the pivot arm in a dredger. In particular, the pivot arm may be provided in a backhoe dredger used on a vessel, for example. It is of advantage in this case that low energy is required and, besides, minimum space is required for the hydraulic system due to the small amount of pressure medium.

Preferably, the pivot arm may also be used in a crane, especially in a knuckle boom crane, in order to save energy costs.

It is also imaginable to design the pivot arm as an, especially motion-compensated, gangway, in particular for a vessel, so as to save energy costs.

Furthermore, it is further to provide the pivot arm in a mobile work machine to save fuel due to the reduced energy demand.

Applicant reserves itself the right to direct an independent claim to the A frame, to the suction pipe system, to the loading bridge, to the fairground ride, to the dredger, to the crane, to the gangway or to the mobile work machine each comprising the pivot arm device according to any one of the preceding aspects.

In accordance with the invention, a movable bridge comprising a pivot arm device according to one or more of the preceding aspects is provided. The pivot arm constitutes the supporting structure and/or the pivot arm or a further pivot arm is provided for raising a supporting structure of the bridge.

Brief description of the drawings

Preferred embodiments of the invention shall be illustrated hereinafter in detail by way of schematic drawings, wherein:

• Figure 1 shows a side view of a movable bridge according to an embodiment,
• Figure 2 shows a pivot arm device for the movable bridge of Figure 1,
  
  

  each of Figures 3 to 11 shows a use of a pivot arm device according to Figure 2.

In Figure 1 a movable bridge 1 is shown. It has a pivot arm in the form of a supporting structure 2. The supporting structure 2 is rotatably supported about a horizontal axis via a pivot bearing 4. For rotating the supporting structure 2 about the pivot bearing 4 a hydraulic cylinder 6 comprising a hydraulic accumulator 8 is provided. The hydraulic cylinder 6 acts on a lower side 12 of the supporting structure 2 with its piston rod 10. Moreover, the hydraulic cylinder 6 is supported by a pivot bearing 14. The pivot bearings 4, 14 are stationary in this case.

When the supporting structure 2 is rotated upwards out of the horizontal position shown in Figure 1 via the pivot bearing 4 by the hydraulic cylinder 6, the holding force to be applied by the hydraulic cylinder 6 decreases with the rotational distance. When, on the other hand, the supporting structure 2 is pivoted downwards from an upper initial position, the holding force increases with the rotational distance.

In Figure 2, a pivot arm device 16 of Figure 1 is illustrated. It includes the hydraulic cylinder 6 which is in the form of a differential cylinder and includes a cylinder housing 18. In the latter, a piston 20 is guided to be axially displaceable. A piston rod 10 connected to the supporting structure 2 of Figure 1 extends from the piston 20. The piston 20 has a first effective area 24 to which pressure medium can be applied in the extending direction of the piston rod 10. Via a second effective area 26 pressure medium can be applied to the piston 20 in the retracting direction of the piston rod 10. Moreover, a third effective area 28 is provided to which pressure medium can be equally applied in the extending direction of the piston rod 10. A hollow guiding rod 34 (inner tube) immersing in an axial blind hole recess 32 of the piston 20 and of the adjacent piston rod 10 extends on the bottom side of the cylinder housing 18. A bottom area of the blind hole recess 32 facing the hollow guiding rod 34 then forms the first effective area 24. The latter is supplied with pressure medium via the hollow guiding rod 34. The first effective area 24 thus delimits a first cylinder chamber that is communicated with a closed- or open-loop, especially pivotal, hydraulic machine 36 via a pressure port A. By its second effective area 26 facing in the direction of the piston rod 10 the piston 20 in the cylinder housing 18 delimits a second cylinder chamber which is equally communicated with the hydraulic machine 36 via a pressure port B. The hydraulic machine is thus arranged between the pressure ports A and B. By its third effective area 28 facing away from the piston rod 10 the piston 20 delimits a third cylinder chamber which is not in fluid communication with the hydraulic machine 36 or with the pressure ports A, B, but is communicated with the hydraulic accumulator 8 via a pressure port C. The cylinder chamber delimited by the third effective area 28 thus is a passive cylinder chamber which is not actively supplied with pressure medium by a hydraulic machine.

The hydraulic accumulator 8 includes a piston 38 as a separating element. The piston 38 separates a pressure medium chamber 40 including especially oil and being connected to the pressure port C from a pressure chamber 42 filled with gas, especially nitrogen. When air is used instead of nitrogen, the hydraulic medium used, should be adjusted to this gas to eliminate the risk of dieseling. The hydraulic accumulator 8 may be connected to the pressure port C via a valve 44. Hence, via the hydraulic accumulator 8 pressure medium can be applied to the piston 20 of the hydraulic cylinder 6 via its third effective area 28 in the extending direction of the piston rod 10, resulting in a passive compensating force which compensates the weight of the supporting structure 2 of Figure 1. The hydraulic cylinder 6 has a comparatively small pressure chamber 42. This entails the fact that upon retraction of the hydraulic cylinder 6 the curve of the compensating force shows a comparatively strongly increasing characteristic line which approximately corresponds to the increasing holding force when folding down the supporting structure 2 or is adapted thereto. Since the required holding force is substantially applied to the piston 20 via the hydraulic accumulator 8, altogether extremely little additional energy is required to rotate the supporting structure 2.

Figure 3 illustrates an A frame having two pivot arm devices 46, 48. Each of the latter includes a pivot arm 50, 52 extending at a distance parallel to each other and being connected via a beam 54. Thus, the A frame is U-shaped. Each of the pivot arm devices 46 and 48 is configured corresponding to the embodiment in Figure 2. It is imaginable that they share hydraulic accumulators or that each of them has a hydraulic accumulator.

In Figure 4 a vessel 56 is shown including a suction pipe system 58. The latter has three pivot arm devices that are used for raising and lowering a suction pipe.

According to Figure 5, a vehicle in the form of a truck 60 is shown which has a trailer including a loading bridge 62. The latter constitutes a pivot arm capable of being pivoted by two pivot arm devices 64, 66. Each of them is configured corresponding to the pivot arm device of Figure 2, wherein it is imaginable that they share a hydraulic accumulator.

Figure 6 illustrates a fairground ride. It includes a plurality of gondolas which are height-adjustable via bent pivot arms. Each of the pivot arms is pivoted via a pivot arm device according to the invention.

Figure 7 illustrates a vessel 70 comprising a backhoe dredger 72 which includes a pivot arm 74 capable of being pivoted via two pivot arm devices 76, 78. The latter are configured in accordance with Figure 2.

Figure 8 illustrates a motion-compensated gangway 80. It forms a pivot arm which is capable of being pivoted in height by a pivot arm device according to the invention.

In Figure 9 a mobile work machine 82 is illustrated which equally includes a pivot arm 84 pivotal in height which is capable of being pivoted via a pivot arm device according to the invention.

Figure 10 shows a crane in the form of a knuckle boom crane 86. The main pivot arm 88 thereof can be pivoted by two pivot arm devices, each being configured according to Figure 2. It is imaginable that the connected pivot arm can also be pivoted by a pivot arm device according to the invention.

In Figure 11 a crane 90 comprising a pivot arm 92 is shown which can be pivoted by a pivot arm device 94 according to the invention.

The invention discloses a pivot arm device comprising a pivot arm rotatable about an axis of rotation. For rotating the pivot arm a hydraulic cylinder is provided. The latter comprises a piston including a first effective area to which pressure medium can be applied in the raising direction of the pivot arm and including a second effective area to which pressure medium can be applied in the lowering direction of the pivot arm. Moreover, the piston includes a third effective area to which pressure medium can be applied in the raising direction and which serves for load compensation.