Guide device for a lifting device with a scissor arrangement in spreading wedge technology

Abstract

The invention relates to a guide device for a lifting device with a scissor arrangement in spreading wedge technology, wherein the lifting device has a spreading unit for lifting a load, wherein rollers (7) of the spreading unit are provided for rolling on lifting cam paths of inner and outer scissor halves of the scissor arrangement, and wherein the spreading unit is designed for moving the rollers (7) in the direction of a scissor bearing of the scissor arrangement. For stabilizing the spreading unit, the guide device comprises a doubly kinematically underdetermined three-joint coupling gear (1, 2, 3), wherein an outer hinge point (5) of the spreading unit is connected by means of the three-joint coupling gear (1, 2, 3) to a fixed bearing. This guide device reduces axial forces and moments which, in particular in the event of uneven loading of the lifting device or in cases of dynamic loading, act on the rollers and the lifting cam paths, and it thus greatly reduces the maintenance requirements, in particular of the roller arrangements.

Description

[0001] Description

[0002] Guide device for a lifting device with a scissor arrangement in expanding wedge technology

[0003] The invention relates to a lifting device with a scissor arrangement in expanding wedge technology according to the preamble of patent claim 1.

[0004] Lifting devices (lifting tables) with a scissor arrangement, which are based on the principle of the expanding wedge technology, have a high maintenance requirement in the area of ​​the rollers of the expanding unit.

[0005] The invention is intended to significantly reduce this, increase availability and expand the area of ​​application by significantly improving the lateral and parallel guidance of the spreading unit along the curved paths.

[0006] A spindle-operated scissor lift table with expanding wedge technology from the prior art is shown in Fig. 1, which is referred to in the following. In scissor lift tables that are based on the principle of expanding wedge technology, in order to expand the scissor arrangement at least one expanding unit 3 is moved longitudinally in the direction of the scissor center bearing 5 along lifting cam tracks, which are arranged on the inner and outer scissor halves 1, 2. Depending on the design of the cam tracks, both the actuating force of the expanding unit and thus also the forces in the drive train can be positively influenced and a uniform lifting movement can be achieved. Furthermore, the use of expanding wedge technology enables the lifting device to be very flat. However, the expanding unit is subject to very high loads. To ensure that it does not run off the lifting cams during the lifting movement, i.e. the rollers do not jump off the cam tracks or something similar, special measures have to be taken to ensure that it does not run off the lifting cams during the lifting movement, i.e. that the rollers do not jump off the cam tracks or something similar., a lateral guide 4 is required, for example a guide rod . In addition to the high radial loads, axial loads F also act. axiai and moments M on the spreader unit, which are caused by unequal load distributions F &x , load and lateral forces F queron the upper frame 6 in the transverse direction. Likewise, an inclination of the upper frame 6 in relation to the lower frame 7 via the scissor legs can result in an additional moment load acting on the spreading unit, which likewise leads to an inclination of the spreading unit. In the case of belt-operated lifting tables, additional moments caused by uneven belt tensions of several parallel belts must also be absorbed by the spreading unit. The superposition of the previously mentioned unfavourable load conditions results in high demands on the lateral and parallel guidance of the spreading unit. The solutions known from the prior art are very maintenance-intensive, subject to wear and sensitive to moment loads, which limits the area of ​​application of the entire lifting device and / or leads to increased maintenance expenditure.

[0007] To prevent the rollers from accidentally jumping off the curved track, it is known to use profiled rollers and cam disks to guide a spreading unit along a curved track. One such design is known, for example, from the publication DE 101 00 710 CI - Heckert et al. "Scissor lift table". However, since the rollers of the spreading unit are already subject to high radial loads, additional axial loads and moments that are directly introduced into them via the scissor arrangement and the traction device have a detrimental effect on the service life of the rollers. In addition, the relubrication intervals for the bearing pair must be kept extremely short, since dry running under high loads leads to premature wear and damage after just a short time.Likewise, profiled rollers and cam discs are very sensitive to knocks and impacts, which also cause damage and therefore excessive maintenance costs. The patent specification DE 102 09 387 Cl - Heckert "Scissor Lift Table" shows a different solution in which the spreading unit is guided linearly by means of an additional guide unit. However, with such designs, unfavorable leverage ratios arise in the lower lifting position because the spreading unit with guide rail and the guide bearing move away from each other when the scissors move together, which requires massive dimensioning of both the guide bearing and the guide rail. This has a negative impact on the dimensions of the entire scissor device. In addition, highly loaded linear sliding or rolling guides are very maintenance-intensive. This means that cost-effective production of the guide solution and maintenance-free operation are not possible.

[0008] The publication US 2003 / 0075657 Al - Joubert "SCISSORS LIFT WITH COMBINATION WEDGE AND LEVER MECHANISM" shows a spreading unit with a slide, whereby the guide function is realized by this slide construction and a spindle that guides the slide.

[0009] The publication DE 10 2006 006 467 Al - Neumann "Scissor lift table" also shows a spreading unit with a slider.

[0010] Another solution is described in the published patent application DE 10 2010 052 615 A1. Here, a guide element is assigned to the axis of the spreading unit for lateral guidance. This guide element acts between the inner and the corresponding outer shear blade. Since this guide element, as already described, is subject to high loads, the relative movement between the spreading unit and the shear blades can disadvantageously result in very high wear and, consequently, high maintenance costs.

[0011] It is therefore an object of the present invention to propose a guide device for lifting devices with a scissor arrangement in expanding wedge technology ("expanding wedge scissor lifting tables"), which is low-maintenance and effectively reduces axial forces and shear moments acting on the rollers.

[0012] The solution to this problem comprises a lifting device according to patent claim 1. A guide device for the lifting device with a scissors arrangement using expanding wedge technology is proposed, wherein the lifting device has an expanding unit for lifting a load, wherein rollers of the expanding unit are provided for rolling on lifting cam tracks of inner and outer scissor halves of the scissor arrangement and wherein the expanding unit is designed to move the rollers in the direction of a scissor center bearing of the scissor arrangement. In this case, the guide device for stabilizing the expanding unit comprises a doubly kinematically underdetermined three-bar linkage, wherein the articulation points (3, 4, 5) are designed as pivot axes, and wherein an outer articulation point of the expanding unit is connected to a fixed bearing by means of the three-bar linkage.This guide device reduces axial forces and moments which act on the rollers and the lifting cam tracks, particularly in the case of uneven loading of the lifting device or in dynamic load cases, and thus considerably reduces the maintenance requirements, in particular of the roller arrangements.

[0013] Advantageous embodiments of the device according to the invention are specified in the dependent patent claims. The features described therein and the resulting advantages can be realized both individually and in meaningful combinations with one another.

[0014] A compact, space-saving solution is achieved when the fixed bearing side articulation point is connected to one of the scissor halves. In an alternative embodiment, the fixed bearing side articulation point can be connected to a base frame of the lifting device or to the base plate. This saves space within the lifting kinematics. Advantageously, the axes of the joints of the three-bar linkage are each aligned parallel to the axis of the rollers. This design allows the rollers on the curved tracks to be largely freed from axial forces, regardless of the lifting state.

[0015] In an advantageous embodiment, the arrangement of the joints of the three-joint coupling mechanism (1, 2, 3) is selected such that they do not project beyond the lifting device when the scissors are retracted and that there is a distance to the dead centers of the coupling mechanism during operation. This ensures perfect guidance in every lifting position and prevents the three-joint coupling mechanism from collapsing with the frame of the lifting device or with a load. The distance to the dead centers can be achieved, for example, by making the coupling rods substantially longer in total than the distance between the outer joint points of the coupling mechanism in the maximum lifting position.

[0016] In advantageous variants, at least two of the joints of the three-joint coupling mechanism each have a pivot axis aligned parallel to the axis of the rollers and with at least two pivot or rotary bearings. This embodiment makes it possible, in particular, to absorb moments ("shear moments") introduced by an uneven load distribution or by the dynamic behavior of the load.

[0017] Particularly for long lifting devices, two guide devices can be provided, one on the fixed bearing side and one on the floating bearing side, to further increase stability. If necessary, the scissor arrangement can be designed in a simpler manner because lower transverse forces and moments act on the scissor arms.

[0018] Embodiments of the solution according to the invention are explained below with reference to the drawings.

[0019] Shown are: Figure 1 a lifting device (scissor lift table) according to the state of the art in side view, front view and top view,

[0020] Figures 2 - 5 show four different variants of the solution according to the invention, each in a schematic representation in the plane,

[0021] Figures 6 - 7 show a technical embodiment of the variant of a guide device explained with reference to Figure 5 in a front view and in a side view, and

[0022] Figures 8 - 9 show the technical embodiment from Figures 6 and 7 in perspective view (in raised and lowered position of the lifting device (not shown).

[0023] Figure 1 shows a spindle-operated scissor lift table with expanding wedge technology from the prior art as a lifting device. In order to expand the scissor arrangement, at least one expanding unit 3 is moved longitudinally in the direction of the scissor center bearing 5 along lifting cam tracks, which are arranged on the inner and outer scissor halves 1, 2. A lateral guide 4, for example a guide rod, absorbs axial forces to a limited extent. Figure 1 shows a lifting table with a spindle drive. The guide arrangement according to the invention described below is, however, also suitable for expanding drives using flat belt technology, as shown in Figures 6 - 9.

[0024] Figures 2 - 5 show four different variants of the invention as a schematic representation in a plane, wherein for the sake of clarity only the lifting curves with the spreading unit and the object according to the invention are arranged on the fixed bearing side of the scissors. An arrangement on the loose bearing side or on both sides is also conceivable. The invention basically comprises a guide device with a double kinematically underdetermined three-bar coupling mechanism with a joint point 4 on the fixed bearing side, which is connected to the spreading unit at the outermost joint point 5. The kinematic underdetermination of the coupling mechanism in the plane achieves a very high level of flexibility in terms of connection and design options. The guide behavior can be specifically adapted to the corresponding circumstances by designing the lengths of the coupling rods 1, 2, the position of the joint points 3 - 5 and their dimensioning.

[0025] The variants from Figures 2 and 3 show two compact, space-saving solutions in which the pivot point 4 on the fixed bearing side is connected to one of the scissor halves. The resulting short lengths of the coupling rods 1, 2 achieve advantageous guidance behavior with minimal manufacturing effort, with the attachment close to the ground on the fixed bearing side scissor leg of the variant from Figure 2 offering particularly high stability. If there is no installation space available to integrate the variants in Figures 2 or 3 into the lifting device, the two variants in Figures 4 and 5 show alternative embodiments of the invention in which the pivot point on the fixed bearing side is arranged on an upper frame of the lifting device or on a foundation / floor slab.

[0026] Figures 6-9 show an exemplary technical embodiment of the variant from Figure 5, with Figure 6 showing a front view and Figure 7 a side view (in an upper lifting position of the lifting device). Figures 8 and 9 show a perspective view.

[0027] 6 - 9, the spreading unit 5, 6, 7 is actuated on the centrally arranged deflection roller 6 by means of three parallel flat belts which wrap around it (not shown here). The four rollers 7 of the spreading unit run along the inner and outer cam tracks of the shear blades, with the object according to the invention, i.e. the coupling gear 1 - 4, taking on the guiding function. During integration, however, care must be taken to ensure that there is always a sufficiently large distance to the dead centers of the coupling gear during operation, so that the movement of the spreading unit along the cam tracks is not negatively influenced. The pivot point 4 on the fixed bearing side is designed as a bearing block and can be fastened to a base frame or a floor plate. As a result, the axial forces and moments acting on the spreading unit are transmitted into the ground or the floor via the guide mechanism according to the invention.the base plate (alternatively, the upper frame of the hoist is also suitable with restrictions).

[0028] The inventive core of the solution shown here lies in the design of a double kinematically underdetermined three-bar linkage with a fixed bearing-side articulation point and its integration into any lifting device with a scissors arrangement and expanding wedge technology in such a way that high spatially acting forces and moments can be absorbed at the outermost articulation point to which the expanding unit is attached and the lengths of the coupling rods and the position of the articulation points can be designed so flexibly that they are not higher than the upper frame when the scissors are retracted (lower lifting position of the lifting device) and there is a distance to the dead centers of the linkage during operation without negatively affecting the compact dimensions of the lifting device.

[0029] The load on the spreading unit is relieved and major misalignments are prevented, which has a positive effect on wear and therefore on the service life of the rollers in particular. In addition, the invention allows for very flexible structural design thanks to the existing flat degrees of freedom, as the connection points and the lengths of the coupling rods can be individually adapted to the existing conditions, thus enabling cost-effective retrofitting of existing systems. In contrast to solutions using maintenance-intensive, linear sliding or rolling guides or rotating plain bearing disks, the guide mechanism according to the invention can be operated maintenance-free because there are only small pivot angles in the pivot axes and these can be designed cost-effectively and with low wear using appropriate plain bearing designs.This also allows for high resistance to shocks, impacts, dirt and dust and enables cost-effective construction and operation.

Claims

Patent claims 1. Lifting device with a scissors arrangement using expanding wedge technology, the lifting device having a spreading unit for lifting a load, rollers (7) of the spreading unit being provided for rolling on cam tracks of inner and outer scissor halves of the scissor arrangement, and the spreading unit being designed to move the rollers (7) in the direction of a scissor center bearing of the scissor arrangement, characterized in that the lifting device comprises a guide device for stabilizing the spreading unit and a doubly kinematically underdetermined three-bar linkage (1, 2, 3), the articulation points (3, 4, 5) being designed as pivot axes, an outer articulation point (5) of the spreading unit being connected to a fixed bearing by means of the three-bar linkage (1, 2, 3).

2. Lifting device according to claim 1, characterized in that the coupling rods are designed without sliders.

3. Lifting device according to claim 1 or 2, characterized in that the pivot axis of the scissor-side articulation point of the three-joint coupling gear (1, 2, 3) is arranged coaxially to the axis of rotation of the rollers (7) of the spreading unit.

4. Lifting device according to one of claims 1 to 3, characterized in that the fixed bearing-side articulation point (4) is connected to one of the scissor halves.

5. Lifting device according to one of claims 1 to 3, characterized in that the fixed bearing-side articulation point (4) is connected to a base frame of the lifting device.

6. Lifting device according to one of claims 1 to 3, characterized in that the fixed bearing-side articulation point (4) is connected to a base plate.

7. Lifting device according to one of the preceding claims, characterized in that the arrangement of the joints of the three-joint coupling mechanism (1, 2, 3) is selected such that they do not project beyond the lifting device when the scissors are retracted and that a distance to the dead centers of the coupling mechanism is provided in each case during operation.

8. Lifting device according to one of the preceding claims, characterized in that the axes of the joints (3, 4, 5) of the three-joint coupling mechanism (1, 2, 3) are each aligned parallel to the axis of the rollers (7).

9. Lifting device according to one of the preceding claims, characterized in that at least two of the joints (3, 4, 5) of the three-joint coupling mechanism (1, 2, 3) each have a pivot axis aligned parallel to the axis of the rollers (7) with at least two pivot or rotary bearings.

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