EP2331446B1 - Gantry crane - Google Patents

Description

The invention relates to a gantry crane, which has a serving for moving the gantry crane along a rectilinear, formed by parallel rails roadway comprising a plurality of chassis groups, each having at least two spaced apart in the longitudinal direction of the respective rail rotatably mounted on a subframe wheels and of which at least two, preferably all, are rotatably connected to a head support of the gantry about a vertical axis, wherein for at least one of the associated head carrier about the vertical axis rotatably connected chassis group, preferably for all with the respectively associated head support to the respective vertical Axle rotatably connected chassis groups, at least one measuring device is present, from which the tracking of at least one of the wheels of the chassis group with respect to the rail on which it rolls, can be detected and a respective track position corresponding tracking position is dispensable.

Trolleys of rail cranes movable on rails comprise landing gear groups for a respective leg of the gantry crane. The chassis groups have wheels for moving the crane, some or all of which are equipped with drive motors.

Another genre than the gantry cranes are the bridge cranes (= overhead cranes or overhead cranes), which have elevated lanes and in which the support structure and the chassis of the crane are in one plane.

In a conventional embodiment of a gantry crane, the individual chassis groups are connected to a head support of the steel structure of the crane with only one degree of freedom, namely a pivotability about a horizontal axis transverse to the rails. In practice, this results in more or less large inclinations of the axes with respect to their exact alignments perpendicular to the longitudinal extent of the rail, due to tolerances and deformations of the components. The resulting horizontal forces and their unfavorable distribution to the individual wheels lead to suspension restrictions and thus to increased wear of the wheel flanges of the wheels and also the wheel treads and the rails.

To reduce wear, constructions are known in which an additional degree of freedom is provided for the articulation of the chassis group on the head support, namely a rotation about a vertical axis. Such a gantry crane is from the EP 1 911 716 A2 known. For pivotable connection of a respective chassis group on the associated head support both about a horizontal axis lying transversely to the rails and about a vertical axis are a central joint, which is designed as a floating bearing in the vertical direction, and relative to the direction perpendicular to the longitudinal extent of a respective rail Arranged on opposite sides of the central joint arms are provided, which are each connected on the one hand to the chassis group, on the other hand to the head support by superimposed joints, of which both compressive and tensile forces are transferable. The central joint may in particular be designed in the manner of a ball joint.

In addition, other constructions for the pivotable connection of a chassis group with the head support are known both about a horizontal transverse axis to the rails and about a vertical axis. For example, such constructions provide the use of a ball or roller slewing ring, a sliding bearing with an additional counter support, an axial ball bearing with additional counter bearing or a central joint in the form of a spherical thrust bearing with tie rods arranged on both sides of the central joint between head support and chassis group. These constructions are sometimes quite expensive.

Despite the rotatable about the vertical axis connection of the chassis groups with the associated headrests, it comes, especially in cranes with long driveways, usually to the concerns of the wheel flanges of the wheels on the rail flanks, depending on the flange clearance and the axle deviations of the wheels. In the best case, which is practically unavailable, the chassis group drives a sinusoidal curve, whereby the wheel flanges of the wheels start alternately with relatively low forces on both rail flanks. In practice, due to deviations of the axles of the wheels of a chassis group from their exactly parallel orientations to each other, which are referred to as "inclinations of the wheels", to horizontal forces acting in the sense of a rotation of the chassis group about the vertical axis. This leads to a tarnishing of one of the two wheel flanges, in particular of the front wheel for the respective direction of travel of a respective chassis group, to the relevant rail flank and thus to an increased wear of this wheel flange. Even deviations in the exact rectilinear alignment of the rails can cause a tarnish of the respective ones Wheel flanges come. The renovation of worn flanges in practice leads to significant costs in the operation of gantry cranes.

An increase in the service life can be achieved by rotating about vertical axes tracking rollers, by means of which the wheels are guided relative to the rails. However, original equipment costs a great deal and, due to roller wear, there are also considerable consequential costs and such equipment is not always possible, e.g. at floor level installed rails.

Also known is an attachment of lubricating pins to reduce the friction between the flanges and the rail edges. However, the effectiveness is not very high and the rapid wear of the lubricating pins leads to a high maintenance.

In addition to "straight-ahead chassis" for moving a gantry crane along rails laid in a straight line, non-generic corner bogies are also known which serve to move a crane along a roadway which has at least one bend.

In chassis of overhead cranes a synchronization device is known in which a leading wheel is scanned and the two rails associated drives are controlled so that the desired orientation of the crane chassis is achieved to the rails. Such a synchronization device is made possible by the usually rigid design of overhead cranes.

From the DE 25 28 293 A1 goes from one of the described embodiments, a gantry crane of the type mentioned, the speed of the motors of the two rails associated drives are regulated for Geradelauf control.

The object of the invention is to achieve a substantial cost reduction over the service life of the gantry crane. According to the invention, this is achieved by a gantry crane having the features of claim 1.

In a gantry crane according to the invention, an actuator is provided for at least one of the associated head carrier rotatably connected to the vertical axis group, of which the chassis group with a torque which is determined by the control of the actuator by means of a control device to the vertical Axis can be acted upon. It is therefore a force-controlled actuator, which causes a torque about the vertical axis about which the chassis group is rotatable, according to its force generated by it. Preferably acts on each of the chassis groups, which are rotatable about a vertical axis relative to the associated head carrier, at least one force-controlled actuator.

To control the actuator by the control device of the control device is supplied by a measuring device, a tracking value. As a tracking in the context of the present document, the position of the wheel relative to the rail with respect to the direction perpendicular to the longitudinal extent of the rail is referred to. This tracking is detected by the measuring device for at least one of the respective direction of travel in front of the vertical axis about which the landing gear group is rotatable relative to the head carrier, lying wheels of this suspension group on which the actuator acts, and a respective current track position corresponding measured value (= Tracking value) is output from the measuring device to the control device as a controlled variable. Depending on the track position value, which is supplied to the control device, this is set by this the moment-loading of the force acting on this chassis group actuator. The force acting on the vertical axis, caused by the actuator torque thus represents the manipulated variable of the control loop. Preferably, the tracking of the front wheel for the respective direction of travel is detected by the measuring device.

By applying torque according to the invention, the wheel flanges of the wheels can be kept at a distance from the rail flanks, completely or at least substantially (for example over more than 90% of the driving distance). As a result, a significant reduction in wear is achieved, in a very simple manner without carrying out a rotational position of a chassis group with respect to the vertical axis compulsorily adjusting forced control. The torque application of a respective chassis group is effected by a control, wherein the actual value of the tracking of the detected by the measuring device for the present direction of travel wheel is used as a controlled variable.

In an advantageous embodiment of the invention is for a central region of the tracking of the detected by the measuring wheel, wherein in this central region the flanges are spaced from the rail edges, for example at least 3mm, the force exerted by the actuator on the Fahrververksgruppe torque from the control device to the Value 0 is set, ie no torque is applied to the chassis group by the actuator exerted or the landing gear group is released with respect to a rotation about the vertical axis. If, during the process of the gantry crane, the track position of the wheel comes to lie on one side outside this middle range, a torque is exerted on the chassis group by the actuator. In this case, it can be advantageously provided that the amount of torque applied is a constant value, regardless of how far the track position of the wheel is outside this middle range. For left and right deviations with respect to the central region, the direction of the force exerted by the actuator is reversed, ie, the direction of rotation of the torque is reversed. The amount of applied torque may be the same as or different than the left and right deviations from the middle range. In this way, a very simple control can be achieved.

• Fig. 1 und Fig. 2 eine Vorderansicht und eine Draufsicht eines Portalkrans gemäß einem Ausführungsbeispiel der Erfindung, stark schematisiert und vereinfacht;
• Fig. 3 eine Seitenansicht (Blickrichtung A in Fig. 1) einer mit einem Kopfträger verbundenen Fahrwerksgruppe mit der Schiene;
• Fig. 4 einen Abschnitt des Kopfträgers und der mit dem Kopfträger verbundenen Schwinge in Ansicht, Blickrichtung B in Fig. 3 (ohne die Gelenkelemente zur Verbindung des Kopfträgers mit der Schwinge);
• Fig. 5 eine schematische vergrößerte Darstellung eines Abschnitts eines Fahrschemels im Bereich der Messeinrichtung, in einer Seitenansicht entsprechend Fig. 3 (ohne den Antriebsmotor);
• Fig. 6 eine schematische Darstellung der Messeinrichtung in Ansicht (entsprechend der Blickrichtung B in Fig. 3);
• Fig. 7 eine schematische Darstellung eines Teils des für die jeweilige Fahrtrichtung vordersten Rades mit einem oberen Abschnitt der Schiene, in einer der Blickrichtung B in Fig. 3 entsprechenden Ansicht;
• Fig. 8 eine schematisierte Darstellung des Regelkreises in einer möglichen Ausbildung;
• Fig. 9 beispielhafte Diagramme der Spurlage gegen die Zeit (Diagramm oben) und des vom Stellglied ausgeübten Drehmomentes gegen die Zeit (Diagramm unten) zur Verdeutlichung der Regelung.

Further advantages and details of the invention are explained below with reference to the accompanying drawings. In this show:

• Fig. 1 and Fig. 2 a front view and a plan view of a gantry crane according to an embodiment of the invention, highly schematic and simplified;
• Fig. 3 a side view (viewing direction A in Fig. 1 ) connected to a head carrier chassis group with the rail;
• Fig. 4 a section of the head support and the rocker connected to the head support in view, viewing direction B in Fig. 3 (without the hinge elements for connecting the head carrier with the rocker);
• Fig. 5 a schematic enlarged view of a portion of a subframe in the region of the measuring device, in a side view accordingly Fig. 3 (without the drive motor);
• Fig. 6 a schematic representation of the measuring device in view (corresponding to the viewing direction B in Fig. 3 );
• Fig. 7 a schematic representation of a portion of the front for the respective direction of travel wheel with an upper portion of the rail, in one of the viewing direction B in Fig. 3 corresponding view;
• Fig. 8 a schematic representation of the control loop in a possible training;
• Fig. 9 exemplary diagrams of the tracking against time (diagram above) and the torque exerted by the actuator against time (diagram below) to illustrate the scheme.

An exemplary embodiment of a gantry crane ("gantry crane") designed in accordance with the invention is shown in the figures. The gantry crane is movable on a straight roadway, which is formed by two mutually spaced, parallel rails 1. The gantry crane has four legs 2, 3,4, 5 in the illustrated embodiment. Also constructions with three legs are known. Furthermore, two supports can be provided. The legs 2-5 and supports support the cross member 6 or 7, along which a trolley 8 is movable or which are provided with another type of movable or fixed lifting device. In the case of training with two or more cross members 6, 7 run between these connection carrier. 9

At the lower ends of the arranged on a respective side of the portal legs 2, 3; 4, 5, a connecting this head carrier 10 is attached. Such a head carrier 10 is also referred to as a "chassis carrier" or "moving beam". The head carrier 10 serve to connect the steel structure of the crane with the individual chassis groups 11 of the crane chassis. The crane chassis is a straight-ahead chassis for moving along the rectilinear rails 1.

Preferably, a landing gear group 1 is arranged directly below each of the legs 2-5. It would also be conceivable and possible, for example, to provide a separate head carrier 10 for each leg 2-5. Pro rail 1 are preferably at least two spaced apart in the longitudinal direction of the rail 1 chassis groups 11 are present. An arrangement below a respective leg 2 - 5 is preferred.

All wheels 12 of a respective chassis group 11 are arranged one behind the other on a straight line formed by the rail 1. The axes 13 of the wheels 12 are aligned approximately at right angles to the rails 1 (the deviation in all possible rotational positions of the chassis group 11 with respect to the below explained vertical axis 23, for example, less than 3 °, which value depends on the geometry of the chassis group, deviations the axial positions of the wheels 12 of a chassis group 11 with respect to their orientations parallel to each other are preferably less than 0.05 °).

In the exemplary embodiment shown, a respective chassis group 11 has eight wheels 12 which are spaced apart from one another in the longitudinal direction of the rail 1.

In each case two longitudinally of the rails one behind the other wheels 12 are rotatably mounted on a subframe 16. In the illustrated embodiment, four subordinate in the longitudinal direction of the rails subframe 16 per suspension group are thus available.

In each case two in the longitudinal direction of the rails one behind the other subframe 16 are connected to a common rocker 17. In the embodiment shown thus two spaced apart in the longitudinal direction of the rails 1 wings 17 are present. The subframe 16 are pivotally connected to the wings 17 about horizontal, parallel to the axes 13 of the wheels 12 axes 18.

The two rockers 17 are connected to a common rocker 19, wherein they are each pivotable relative to the rocker 19 about a horizontal, parallel to the axes 13 of the wheels 12 axis 20.

To move the crane along the rails 1 are drive motors 21, which drive the respective wheels 12. Depending on the application, more or fewer such drive motors 21 may be present.

The respective head carrier 10 is connected to the respective chassis group 11 in such a manner that the chassis group 11 is pivotable relative to the head carrier 10 about a horizontal, perpendicular to the respective rail 1 axis 24 and about a vertical axis 23 is rotatable. For this purpose, a connecting device 25 is provided, which can be designed according to the aforementioned prior art. Particularly preferred is an education, as shown in the EP 1 911 716 A2 is known, wherein a central, preferably designed in the form of a ball joint, joint 22 is present and further between the respective head carrier 10 and the respective chassis group 11 two links 29, 30 are arranged, seen in the direction perpendicular to the rail 1 on both sides of the central joint 22 lie. Each of the two links 29, 30 is hinged to both the head carrier 10 and the rocker 19. These superimposed joints 31, 32 of the links 29, 30 are in this case designed such that both pressure and tensile forces between the respective head support 10 and the respective chassis group 11 can be transmitted via the links 29, 30. In this case, these joints 31, 32 each have a degree of freedom for pivoting the respective link 29, 30 relative to the head carrier 10 or against the rocker 19th about a plane parallel to the axes 13 of the wheels 12 axis 33 and a degree of freedom for pivoting the respective link 29, 30 relative to the head support 10 and with respect to the chassis group 11 about a perpendicular to the axes 13 of the wheels 12 standing horizontal axis 34. The central joint 22 is formed in the vertical direction as a floating bearing, ie has in this direction in the assembled state on a game.

A chassis group 11 of a gantry crane constructed in accordance with the invention may also comprise more or fewer than eight wheels 12 spaced apart in the direction of travel, at least two wheels 12 spaced apart from one another in the longitudinal direction of the respective rail 1 being rotatably mounted on a common subframe 16. In the case of the formation of the chassis group 11 with only one subframe 16, the connecting device 25 may be arranged directly between this subframe 16 and the head carrier 10. For example, in a chassis with four consecutively arranged in the direction of travel wheels 12 two wheels can be rotatably mounted on a respective subframe 16 and the subframe 16 about horizontal parallel to the axes 13 of the wheels 12 axes pivotally connected to a rocker 17. The connecting device 25 could be arranged directly between the head carrier 10 and this rocker 17 in this case.

The wheels 12 are rigid within the chassis groups 11 with respect to rotations about vertical axes, i. apart from the rotatability of the chassis group 11 as a whole about the vertical axis 23, there are no rotations about vertical axes, e.g. of individual wheels 12, given.

At least in one direction of travel and in the opposite direction of travel foremost wheel 12, that is the in Fig. 3 far left and rightmost wheel of a respective about a vertical axis 23 rotatable suspension group 11, are preferably equipped with flanges 14, 15, as in Fig. 7 can be seen. The intermediate wheels 12 may be equipped with flanges 14, 15. Instead, trackless wheels could be used for the intermediate wheels 12. In this case, a derailment protection (which may be formed by stops arranged on the subframe which cooperate with the rail flanks, as is known) is advantageously provided, whereby cost savings can be achieved in comparison to wheels with flanges. In principle, trackless wheels with derailment protection could also be used for the foremost wheels in relation to the two directions of travel, but here wheels with flanged wheels are preferred for safety reasons are. Instead of wheels 12 with flanges 14, 15 and wheels 12 could be used with tracking rollers, which are also known. However, the original equipment costs and the maintenance costs are higher.

For each of the rotatable about the vertical axes 23 chassis groups 11 two measuring devices 26 are available. Of these, the positions of the front wheels 12 with respect to the two directions of travel are detected with respect to their orientations in the direction perpendicular to the rail 1. The orientation of a wheel 11 with respect to the rail 1 with respect to its position perpendicular to the longitudinal extent of the rail 1 is referred to as tracking in the context of this document. The tracking value a indicates the offset of the wheel from the central orientation on the rail 1. In the case of a wheel with flanges 14, 15, as is preferred for the front wheels 12 with respect to the two directions of travel, the distance between one of the wheel flanges 14, 15 with respect to the adjacent rail flank 27 could also be used as the track position value a.

The tracking of the front wheel 12 in relation to the respective direction of travel of a group of hammers 11 is largely determinative of the positions of the wheels 12 of the chassis group 11 with respect to the rails and for the forces with which wheel flanges of the wheels 12 start at the rail flanks. Instead of detecting the front wheel with respect to the present direction of travel, the measuring device could in principle also detect the tracking position of another of the wheels lying in front of the vertical axis 23 about which the chassis group 11 is rotatable. Which are relative to the respective direction of travel in front of the vertical axis 23 about which the chassis group 11 is rotatable, lying wheels are the respective "leading" wheels.

An example of a possible embodiment of a measuring device 26 is in particular from the FIGS. 5 and 6 seen. A yoke 35 slidably bears with sliding linings 36 on the two rail flanks 27. The yoke 35 is pivotally mounted on first and second pivot arms 37, 38 about horizontal axes perpendicular to the axes 13 of the wheels 12, 39, 40. The pivot arms 37, 38 are further pivotally mounted above the axes 39, 40 about horizontal, perpendicular to the axes 13 of the wheels 12 stationary axes 41, 42 which are fixedly mounted on the subframe 16, preferably in the region of the end of the subframe sixteenth The distance of the yoke 35 from the axis 13 of the front wheel 12 with respect to the direction of travel in question is relatively small, preferably smaller than the diameter of this wheel 12. The first pivot arm 37 has an extension arm 43 which projects upwards relative to the axle 41 a two-armed lever is formed. In a displacement of the wheel 12 relative to the rail 1 in the direction perpendicular to the rail 1, there is a rectified shift of lying in the region of this wheel 12 portion of the subframe 16 relative to the rail 1 and thus to a pivoting of the first and second pivot arms 37, 38th and the extension arm 43. The position of the extension arm 43 corresponding to the center position of the tracking of the wheel 12 is in FIG Fig. 6 shown in solid, two positions of the extension arm 43 for contrast, in the two transverse directions shifted track positions are in Fig. 6 indicated by dashed lines.

The pivoting position of the extension arm 43 is detected by, for example, inductive measuring sensors 44, 45. In the simplest case, it would be conceivable and possible to design the two measuring sensors 44, 45 as switches which can be actuated mechanically by the extension arm 43.

Conceivable and possible would be e.g. Also, the respective measuring device 26 on the subframe 16 on the vertical axis 23, about which the chassis group 11 is rotatable, facing side.

Between the chassis group 11 and the associated head support 10, an actuator 28 acts, which is formed, for example, as shown in the form of a piston-cylinder unit. This is arranged between a connection bracket 46 attached to the head carrier 10 and a connection tab 47 attached to the rocker 19. By a force exerted by the actuator 28, a force acting around the vertical axis 23 torque m is exerted on the chassis group 11.

The actuator 28 is controlled by a control device 48, 49 in response to the output by the measuring device 26 tracking position value. In this case, a force variable is set as the controlled variable on the actuator 28. An embodiment for the entire control loop is in Fig. 8 shown schematically. The control device has a control unit 48, which is supplied to the tracking position value detected by the measuring device 26, and an actuator drive device 49. The actuator drive means 49 is formed in the illustrated embodiment of hydraulic elements. A feed pump 50 in this case conveys hydraulic oil from a reservoir 51. By means of a pressure relief valve 52, the maximum, prevailing in the hydraulic line 53 pressure is set. A 4/3-way valve 54 is controlled by the control unit 48. Depending on the position of the 4/3-way valve 54, the actuator 28 is released or by the actuator 28, a force is exerted in one or the other direction, ie on the chassis group 11, a force acting in one or the other direction of rotation torque m is exercised. This torque m represents the manipulated variable of the control loop. The controlled system becomes, as in Fig. 8 shown schematically formed by the running on the rail 1 chassis group 11.

In the illustrated embodiment, the manipulated variable can take only three values, namely, a torque 0, a torque acting in the one direction of rotation with an amount m _x or in the other direction of rotation acting torque with the amount m _y exerted. The amount m _x or m _{y of} the torque is preset here, in the illustrated embodiment by adjusting the pressure value of the pressure relief valve 52.

The default can be done after the gantry crane is completed, according to the horizontal forces caused by the deviations of the axles 13 of the wheels 12 of a chassis group 11 with respect to their mutually parallel orientations.

In a predetermined central region of the track position value, the torque value 0 is set by means of the control device, ie in the embodiment shown by setting the corresponding position of the 4/3-way valve 54 by the control unit 48. This middle region corresponds to a tracking value a which is between a value a , and a ₂ lies. In the region of the tracking value a between a, and a ₂ , the flanges 14, 15 are spaced from the rail flanks 27. If, for example, in the center position of the wheel 12 with respect to the rail 1 (= tracking value a ₀ ), the distances of the flanges 14, 15 of the rail flanks are each 20mm, so the distance of the flange 14 of the rail flange 27 in tracking position a, eg 5mm and when tracking value a _2, for example 35mm.

When the central region a, to a _{2 is} left, the 4/3-way valve 54 is adjusted accordingly by the control unit 48, so that a further approach or removal of the flange 14 to the rail edge 27 and of the rail edge 27th counteracting torque m _x or -m _{y is} exerted on the chassis group 11.

In order to determine whether the tracking position value a corresponding to the current track position lies within the range a, to a ₂ or above or below this range, the control unit 48 has a comparator part. For controlling the 4/3-way valve 54, the control unit 48 has a control part.

A control process is described below by way of example by means of Fig. 9 explained. The front wheel 12 of the chassis group 11, which is the front wheel in relation to the direction of travel, has, for example, the mean track position a ₀ at the beginning of the method of the gantry crane. As a result of occurring horizontal forces and / or tolerances in the rail position occurs when moving the crane to a change in the tracking, in the embodiment shown in the direction of the value a. Factors for the horizontal force that occurs are, in particular, the altogether non-compensating deviations of the axial positions of the wheels 12 of a respective chassis group 11 with respect to their orientations parallel to one another, and occurring wind loads. If the tracking value a, is reached, then the chassis group 11 is acted upon by the torque m _x . The distance a from the rail edge 27 thereby increases again. If an intended tracking value a is reached, for example, when the center position a ₀ is reached again, the Fahrwersgruppe 11 is again unlocked. The described control process is repeated in the sequence.

If the horizontal forces in conjunction with the orientation of the rail position so affect that the tracking value a _{2 is} reached, so acting in the reverse direction torque -m _{y is} applied to the chassis group 11.

Instead of adjusting the size of the torque exerted by a pressure relief valve 52 could for this purpose, for example, a feed pump 50 are used, the delivery pressure is adjustable.

Instead of hydraulically acting actuators 28 and other actuators could be used, for example, mechanically or electromechanically acting actuators. For example, in the case of an electrically controllable actuator, this could be controlled directly by the control part of the control unit 48.

Instead of only three different values for the manipulated variable (0, m _x , -m _y , wherein the amounts m _x and m _{y may be the} same or different), more than three values for the manipulated variable could also be provided, for example in addition to 0. Value two different strengths for the torque that are exerted in the two directions of rotation can. These can be activated at given actual values of the controlled variable a. Also, a continuous control of the torque could be provided.

Per chassis group 11, more than one actuator 28 could be provided.

The measuring device 26 could also be designed in another way as shown. For example, a cooperating only with a rail edge 27, rotatably mounted relative to the subframe 16 part could be present.

lying to the reference numbers:

1

rail

2

leg

3

leg

4

leg

5

leg

6

crossbeam

7

crossbeam

8th

trolley

9

connection support

10

endcarriages

11

LG group

12

wheel

13

axis

14

flange

15

flange

16

subframe

17

wing

18

axis

19

wing

20

axis

21

drive motor

22

central joint

23

vertical axis

24

horizontal axis

25

connecting device

26

measuring device

27

rail side

28

actuator

29

handlebars

30

handlebars

31

joint

32

joint

33

horizontal axis

34

horizontal axis

35

yoke

36

sliding lining

37

first swivel arm

38

second swivel arm

39

axis

40

axis

41

axis

42

axis

43

extension

44

probe

45

probe

46

connecting strap

47

connecting strap

48

control unit

49

Stellgliedansteuereinrichtung

50

feed pump

51

reservoir

52

Pressure relief valve

53

hydraulic line

54

4/3-way valve

Claims (9)

1. A gantry crane, which has a travelling gear serving for displacing the gantry crane along a rectilinear track formed by parallel rails (1), which travelling gear comprises a plurality of travelling-gear groups (11) which have in each case at least two wheels (12) which are spaced apart from each other in the longitudinal direction of the respective rail (1) and rotatably mounted on a subframe (16) and of which at least two, preferably all, are connected to a head support (10) of the gantry crane rotatably about a vertical axis (23), wherein for at least one travelling-gear group (11) which is rotatably connected to the associated head support (10) about the vertical axis (23), preferably for all the travelling-gear groups (11) which are rotatably connecled to the associated head support (10) in each case about the vertical axis (23), at least one measuring means (26) is present, by which the track position of at least one of the wheels (12) of the travelling-gear group (11) can be detected with respect to the rail (1) on which it rolls, and a track-position value (a) which corresponds to the respective track position can be emitted, characterised in that an actuating member (28) which acts between the travelling-gear group (11) and the associated head support (10) is provided, which actuating member is actuated by a regulating means (48, 49) to which the track-position value (a) emitted by the measuring means (26) is supplied, and by which the travelling-gcar group (11) can be acted upon about the vertical axis (23) with a torque (m) which is determined by this actuation.
2. A gantry crane according to Claim 1, characterised in that at least one measuring means (26) for detecting the track position of a wheel (12) of the travelling-gear group (11) which, relative to the respective direction of travel of the gantry crane, is located ahead of the vertical axis (23) about which the travelling-gear group (11) is rotatable, is present for each of the two directions of travel of the gantry crane.
3. A gantry crane according to Claim I or 2, characterised in that for a central region (a₁-a₂) of the track position of the wheel (12) detected by the measuring means (26) the torque (m) exerted by the actuating member (28) on the travelling-gear group (11) is set by the regulating means (48, 49) to a value of 0.
4. A gantry crane according to Claim 3, characterised in that for a track position of the wheel (12) which is located on one side outside the central region (a₁-a₂), the torque (m) exerted by the actuating member (28) on the travelling-gear group (11) is set to a constant, pre-settable amount (m_x, m_y), the direction of rotation of the torque (m) differing depending on the side on which the track position is located outside the central region (a₁-a₂).
5. A gantry crane according to one of Claims 1 to 4, characterised in that the actuating member (28) is a piston-cylinder unit which acts between the travelling-gear group (11) and the associated head support (10).
6. A gantry crane according to one of Claims 1 to 5, characterised in that the measuring means (26) has a part (35) mounted pivotably on the subframe (16) on which the wheel (12) which is to be detected is rotatably mounted, which part cooperates at least with one rail flank (27).
7. A gantry crane according to Claim 6, characterised in that the measuring means has a yoke (35) which cooperates with both rail flanks (27), which yoke is pivotably mounted on pivot arms (37, 38) which are pivotably mounted on the subframe (16).
8. A gantry crane according to one of Claims 1 to 7, characterised in that a respective travelling-gear group (11) has two or more subframes (16) with in each case at least two wheels (12) which are spaced apart in the longitudinal direction of the respective rail (1) and are rotatably mounted on the subframe (16), and the respective travelling-gear group (11) as a whole is connected to the head support (10) rotatably about an individual vertical axis (23).
9. A gantry crane according to one of Claims 1 to 8, characterised in that the travelling-gear groups (11) are arranged in each case directly below a respective leg (2-5) of the gantry crane.

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