Levelling device for a rotatable superstructure

Abstract

 Levelling device (10) for a turntable ladder, a boom or similar, with a multi-part rotating frame, one part of which is formed by a base (14), which is mounted on an understructure by means of a first turntable (20), which can be rotated around an upright axis by means of a rotary drive (26) attached to the understructure, and a further part formed by a superstructure (12) supporting the ladder or similar, which is connected with base (14) in such a manner that it can be pivoted around a connecting axis which is inclined relative to the upright axis, said superstructure (12) being pivotable relative to base (14) by means of a pivot drive, characterised in that base (14) has an approximately wedge-shaped cross-section, and in that superstructure (12) is mounted on base (14) by means of a second turntable (32), which lies in a plane (E₁) that is inclined relative to the first turntable (20).

Description

[0001] The present invention relates to a levelling device for a rotatable superstructure according to the preamble of claim 1.

[0002] Levelling devices of this type are used in vehicles fitted with turntable ladders, for example. With their help, one can ensure that, even if the vehicle is parked on a slope, the plane of erection within which the ladder set is erected around a pivoting axis remains vertical in all operating modes.

[0003] Such a device is disclosed in German utility model DE 21 35 341 U1, for example. It comprises a two-part rotating frame consisting of a base and a superstructure which is pivotably connected to the base, and supports the turntable ladder. The base is mounted on the vehicle understructure by means of a turntable which can be rotated, by means of a rotary drive attached to the understructure, around an upright axis which is perpendicular to the understructure. The pivotal connection between the superstructure and the trailer is achieved by means of a horizontal connecting axis. A pivot drive controlled by a regulating unit ensures that when the base rotates in relation to the understructure, the plane of erection is maintained vertical, thereby compensating for any inclination of the vehicle caused by a slope.

[0004] This device is not suitable for heavy, telescopic ladders due to the large forces to be absorbed and the unfavourable force transmission relationships. Alternative levelling devices as disclosed in DE 35 40 666 C2, for example, comprise rotating frames with two-part bases, of which each base part is contrived to be approximately wedge-shaped and can be rotated in relation to the other base part by means of a turntable. The ladder superstructure is mounted on this base by means of a top turntable, the inclination of which relative to a bottom turntable, used to mount the base on the understructure, can be modified by rotating the base elements relative to each other.

[0005] In total, three independently operated drive connections are required. Once levelling out is complete, only the uppermost rotary drive and turntable are used; hence not only the plane of erection, but also the axis around which the plane of erection rotates during positioning of the ladder, are positioned vertically. This is a complex and costly construction as it offers more than the required degree of freedom. Furthermore, the weight of this system is high, and increases with the weight of the turntable ladder for guiding.

[0006] The task of the present invention is therefore to create a levelling device of the aforementioned type, which is suitable for achieving level compensation for large and heavy superstructures in combination with a comparatively low own weight, high stability and relatively low costs.

[0007] This task is solved according to the invention by means of a levelling device with the features of claim 1.

[0008] According to the invention, the base itself has an approximately wedge-shaped cross-section. The superstructure is mounted on the base by means of a second turntable positioned in a plane which is inclined relative to the first turntable for rotating the base on the understructure. This means the base can be formed by a single wedge-shaped element.

[0009] To drive the second turntable one may provide a simplified pivot drive in the form of a push rod system, for example. This means the superstructure can be pivoted, by means of the pivot drive, around the axis of rotation of the top turntable, said axis of rotation being inclined relative to the axis of rotation of the bottom turntable. As the ladder rotates relative to the understructure, the pivot drive has to make a continual series of corrections in order to keep the plane of erection vertical. A smooth rotation for moving the turntable ladder can be achieved by compensating the movements of the pivot drive by means of the rotary drive.

[0010] Compared to the construction described in DE 21 35 341, the advantage is that the superstructure is directly supported by the base, so that even larger forces can be absorbed. The pivot axis of the superstructure relative to the base, and the upright axis around which the first turntable rotates are not vertical, but form a relatively small angle with each other, which, however, has to be greater than the inclination to be compensated. This has proved sufficient for the functioning of the present invention. Further, there are obvious benefits to be derived from the simplicity of the construction and the positive force transmission relationships. There is no need for heavy and costly drive constructions as used in the context of DE 35 40 666 C2.

[0011] In a preferred embodiment of this invention, the levelling device comprises a second push rod extending between a third point of contact on the base, which lies directly adjacent the first point of contact of the first push rod, or coincides with this latter, and a fourth point of contact on the superstructure.

[0012] These two push rods may be disposed symmetrically around the centre axis of the second turntable between superstructure and base. If one of the two push rods is extended, the other push rod is automatically shortened. Overall, this results in an approximately V-shaped arrangement in which one side of the V shortens during the rotational movement, whilst the other is extended.

[0013] The push rods are preferably hydraulically driven telescopic cylinders.

[0014] The levelling device according to the invention preferably comprises a sensor for measuring the lateral inclination of the plane of erection of the superstructure relative to the verticals, and a control unit to control the pivot drive and the rotary drive, which is there to ensure that, when the superstructure rotates in relation to the understructure, the lateral inclination of the plane of erection is brought to zero.

[0015] Using the measured signal from the sensor, the control unit can thus convert a target rotary movement specified by an operator into a complex movement which is carried out by the pivot drive and the rotary drive, and, all in all, delivers the desired ladder movement whilst keeping the plane of erection vertical at all times.

[0016] In one preferred embodiment, the control unit is provided to generate a specified rotation speed of the superstructure relative to the understructure by overlapping of two variable rotation speeds of the pivot drive and the rotary drive. The rotation speed then compensates for the pivot speed.

[0017] A preferred embodiment of the invention will be described in more detail below with reference to the enclosed drawings.

Fig. 1

is a diagrammatic side view of one embodiment of the levelling device according to the invention; and

Fig. 2

is a view of the levelling device of Fig. 1 from below; and

Fig. 3

is a diagram showing the angle positions of various parts of the levelling device of Fig. 1 and 2.

[0018] The levelling device 10 shown in Fig. 1 serves to orient the plane of erection of a turntable ladder, a boom, a telescopic mast or similar, vertically. In this particular case, it is a ladder set for a fire-fighting vehicle, rotatably mounted on an understructure fixed to the vehicle and not shown in more detail.

[0019] Levelling device 10 comprises an essentially two-part rotating frame 11, formed by a base 14 as the bottom part, which is rotatably mounted on the vehicle understructure, and a superstructure 12 as the top part which supports the ladder set and is in turn supported by base 14. Superstructure 12 is pivotably mounted on base 14, as will be illustrated in more detail below. Base 14 is contrived as a wedge ring, i.e. it has a wedge-shaped lateral cross-section. Thus the upper edge 16 of base 14 lies in a plane E₁ which is inclined relative to plane E₂ of the ring-shaped lower edge 18 of base 14.

[0020] Base 14 is mounted on the understructure by means of a bottom turntable 20. This latter is an annular gear 22, which is fixed to the lower edge 18 of base 14 and is rotatably mounted in a ring-shaped bearing 24 attached to the understructure. Annual gear 22 can be driven and made to rotate by a bottom rotary drive 26, also attached to the understructure. This rotary drive 26 comprises a motor, 28, on whose output shaft a pinion 30 is attached, which engages in annular ring 22 on the inside. Hence rotation of pinion 30 leads to rotation of annular gear 22 within its bearing 24. Base 14 then rotates together with annular ring 22, being attached to it.

[0021] Superstructure 12 is mounted on base 14 by means of a second turntable 32. This latter comprises an outer ring 34, which is attached to superstructure 12 and is mounted concentrically around an inner ring 36, which is connected to base 14. The top turntable 32 lies in plane E₁, which is inclined relative to bottom turntable 20 in plane E₂.

[0022] Top turntable 32 is driven to rotate relative to base 14 by means of a pivot drive 38. Pivot drive 38 comprises two hydraulically driven telescopic cylinders 40, of which only one telescopic cylinder 40 can be seen in Fig. 1. As is generally usual, telescopic cylinders 40 comprise an inner rod 44 which is extensibly mounted in a piston sleeve 46. The end of inner rod 44 is connected with the inner wall of base 14 by means of a hinge 48 on the side on which the wall of base 14 is highest. The end of piston sleeve 46 is in turn connected to the top turntable 32 by means of another hinge 50, i.e. is attached to outer ring 34 of superstructure 12.

[0023] Hinge 48 is essentially formed by a loop 52 at the end of the inner rod, which is traversed by a bolt that is not shown in more detail in Fig. 1, which is held at its ends in two parallel flanges 54 projecting from the inside wall of base 14, and which enclose loop 52 on both sides. Telescopic cylinder 40 can therefore be pivoted around the bolt. In a similar manner, a loop 56 is contrived at the end of piston sleeve 46, and is traversed by another bolt 58 which is connected to outer ring 36 of top turntable 32.

[0024] In the view shown in Fig. 2, the V-shaped arrangement of the two telescopic cylinders 40,42 can clearly be seen. The two base-side contact points 60,62 of telescopic cylinders 40,42, which are formed by hinges 48, by means of which inner rods 44 are connected to base 14, are closely neighboured, whereas the remaining contact points 64,66 on superstructure 12, which are formed by hinges 50 for connecting piston sleeves 46 with the outer ring 34 of top turntable 32, are relatively distanced. In the situation shown here, superstructure 12 occupies a middle position between two outermost rotary positions relative to base 14.

[0025] If, starting from this position, for example top telescopic cylinder 42 shown in Fig. 2 is extended, the two contact points 60,64 move away from each other, and outer ring 34 of top turntable 32 is rotated relative to inner ring 36. Simultaneously, the two contact points 62,66 of bottom telescopic cylinder 44 move closer together, and the inner rod 44 of the latter is pushed into piston sleeve 46. This extending and retracting can easily be achieved by means of a hydraulic drive. Overall, this arrangement of two telescopic cylinders 40,42 means superstructure 12 can be pivoted by approx. 60° relative to base 14.

[0026] By pivoting superstructure 12 relative to base 14 by means of pivot drive 38, the lateral inclination of the plane of erection of the turntable ladder, relative to which the axis of erection S (Fig. 1) is perpendicular, can be changed and corrected as required. If, for example, the vehicle is parked on ground which is inclined relative to the horizontal plane, this results in an inclination of plane E₂ of bottom turntable 20, which can lead to the plane of erection of the ladder set being inclined relative to the vertical plane. To compensate for this inclination, one of telescopic rods 40 or 42 is slightly extended, i.e. pivot drive 38 is activated whilst rotary drive 26 attached to the understructure is activated in the opposite sense. As this happens, the orientation of the ladder relative to the understructure remains virtually constant, the plane of inclination, however, is tilted left or right relative to the vertical plane. With appropriate control of pivot drive 38 and bottom rotary drive 26, one can therefore ensure that the plane of erection is oriented absolutely vertically. During this action the wedge-shaped base 14 is rotated between the understructure and superstructure 12, as it were.

[0027] The inclination of the plane of erection requiring compensation can be detected by a sensor, for example. The measured result of this sensor can be fed into a corresponding control unit which controls pivot drive 38 and rotary drive 26 in the manner described above. If the vehicle is parked on a slope and a rotary movement of the ladder set relative to the understructure is required, this movement can be completed whilst the orientation of the plane of erection is kept vertical. This is accomplished in that the control unit represents a target rotation speed of superstructure 12 relative to the understructure in one direction by overlapping two variable rotation speeds of pivot drive 38 and rotary drive 26. In Fig. 3, the torsion angle of bottom turntable 20 γ_positioning and top turntable 32 γ_levelling is shown in degrees against time in seconds. In this example, superstructure 12 and the ladder set complete a full 360°C rotation within 60 seconds. However, this rotation is represented by an overlapping of two different rotary movements, namely a rotation of top turntable 32 and bottom turntable 20. In the diagram in Fig. 3 one can see that during a continuous rotation of bottom turntable 20, i.e. of base 14 on the understructure, pivot drive 38 completes a pendulum movement between base 14 and superstructure 12, in a range of 60°. This to and fro movement accomplishes the compensation of the lateral inclination of the plane of erection of superstructure 12.

[0028] For each position of bottom turntable 20 one can calculate what position the top turntable 32, i.e. superstructure 12, must adopt relative to base 14 in order for the plane of erection to remain vertical. Thus one can calculate a pivot function S as a function of the formation of wedge 14 and the angle of inclination of the understructure on the slope. If γ_levelling is the angle position of top turntable 32 and γ_positioning is the position of bottom turntable 20, γ_levelling can be expressed as

[0029] The derivation of pivot function S according to the positioning angle gives a precontrol function V, which represents a relationship between the rotation speeds of positioning and rotary angles.

[0030] Using the approximation that the total rotation speed ω_spd is the total of the partial rotation speeds of the two turntables ω_positioning and ω_levelling, the rotation speed of the bottom and top turntables can be calculated as a function of the total rotation speed and rotation position.

[0031] This gives:

[0032] In this way one can work out a control method based on position and speed regulation, which controls both turntables as a function of a target rotation speed ω_spd specified by an operator.

[0033] The maximum required pivot angle γ_{max. levelling} can be estimated using the following equation (7).

[0034] In this, α_slope is the angle of inclination of plane E₂ of bottom turntable 20, and hence of the vehicle, and α_wedge is the wedge angle of base 14 between plane E₁ and plane E₂.

Claims

1. Levelling device (10) for a turntable ladder, a boom or similar, with a multipart rotating frame, one part of which is formed by a base (14), which is mounted on an understructure by means of a first turntable (20), which can be rotated around an upright axis by means of a rotary drive (26) attached to the understructure, and a further part formed by a superstructure (12) supporting the ladder or similar, which is connected with base (14) in such a manner that it can be pivoted around a connecting axis which is inclined relative to the upright axis, said superstructure (12) being pivotable relative to base (14) by means of a pivot drive, characterised in that base (14) has an approximately wedge-shaped cross-section, and in that superstructure (12) is mounted on base (14) by means of a second turntable (32), which lies in a plane (E₁) that is inclined relative to the first turntable (20).

2. The levelling device of claim 1, characterised in that pivot drive (38) comprises at least one telescopically extendable push rod (40), which extends between a first contact point (62) on base (14) and a second contact point (66) on superstructure (12).

3. The levelling device of claim 1, characterised by a second telescopically extendable push rod (42), which extends between a third contact point (60) on base (14), which is immediately adjacent to the first contact point (62) of the first push rod (40), or coincides with this latter, and a fourth contact point (64) on superstructure (12).

4. The levelling device of one of the preceding claims, characterised in that push rod(s) (40,42) is or are contrived as hydraulically driven telescopic cylinders.

5. The levelling device of one of the preceding claims, characterised by a sensor for measuring the lateral inclination of the plane of erection of the superstructure relative to the verticals, and by a control unit for controlling pivot drive (38) and rotary drive (26), which is provided to bring the lateral inclination of the plane of erection to zero when superstructure (12) is rotated in relation to the understructure.

6. The levelling device of claim 5, characterised in that the control unit is provided to generate a specified rotation speed of superstructure (12) in relation to the understructure by means of overlapping of two variable rotation speeds of pivot drive (38) and rotary drive (26).

Amended claims

Amended claims in accordance with Rule 137(2) EPC.

1. Levelling device (10) for a turntable ladder set, said set comprising a ladder and an understructure to which said ladder is mounted by means of said levelling device (10), the levelling device (10) comprising a multi-part rotating frame (11), one part of which is formed by a base (14), which is mounted on said understructure by means of a first turntable (20), which can be rotated around an upright axis by means of a rotary drive (26) attached to the understructure, and a further part formed by a superstructure (12) supporting said ladder, which is connected with a base (14) in such a manner that it can be pivoted around a connecting axis which is inclined relative to the upright axis; said superstructure (12) being pivotable relative to base (14) by means of a pivot drive (38), said base (14) having an approximately wedge-shaped cross-section, and said superstructure (12) being mounted on base (14) by means of a second turntable (32), which lies in a plane (E₁) that is inclined relative to the first turntable (20); the device being characterized in that said pivot drive (38), comprises at least one telescopically extendable push rod (40), which extends between a first contact point (62) on said base (14) and a second contact point (66) on said superstructure (12).

2. The levelling device of claim 1, characterised by a second telescopically extendable push rod (42), which extends between a third contact point (60) on said base (14), which is immediately adjacent to the first contact point (62) of the first push rod (40), or coincides with this latter, and a fourth contact point (64) on said superstructure (12).

3. The levelling device of one of the preceding claims, characterised in that said push rod(s) (40,42) is or are contrived as hydraulically driven telescopic cylinders.

4. The levelling device of one of the preceding claims, characterised by a sensor for measuring the lateral inclination of the plane of erection of the superstructure relative to the verticals, and by a control unit for controlling pivot drive (38) and rotary drive (26), which is provided to bring the lateral inclination of the plane of erection to zero when said superstructure (12) is rotated in relation to the understructure.

5. The levelling device of claim 4, characterised in that said control unit is provided to generate a specified rotation speed of superstructure (12) in relation to the understructure by means of overlapping of two variable rotation speeds of pivot drive (38) and rotary drive (26).

Drawing