Load compensation device for lifting applications with objects to be lifted or lowered

Abstract

The invention relates to a load compensation device for lifting applications with objects to be lifted or lowered, having a movable platform, wherein the platform carries the objects, wherein the platform is supported for load compensation purposes by at least one spring element (5). The spring element (5) acts on an expansion unit (4, 6, 7), which, for the purpose of expansion, guides the spring force of the spring element (5) into a scissor device (3), wherein the spring force is implemented as a resultant lifting force via the scissor device on the platform for lifting action and provides a substantially constant lifting force over the essential lifting travel of the platform by means of the lifting geometry formed by the expansion unit (4, 6, 7) and the scissor device (3). By adjusting the geometry, in particular the length / dimension of the structural elements of the expansion unit and the length of the legs of the scissor device, the size and linearity or stability of the support force (lifting force) can be set in a simple manner. The load compensation device is further characterized by a compact size, flexible operation and high performance with little manufacturing, installation and maintenance outlay.

Description

Technical Field

[0001] The present invention relates to a load compensating device for use in lifting mechanisms and similar applications.

[0002] The present invention relates to a mechanically acting load compensation device for improving the performance and efficiency of vertical lifting applications. The load compensation device should be flexible enough to be integrated into existing or newly designed lifting systems, thereby reducing the load on the drive train or the entire lifting mechanism and significantly improving the efficiency of the overall system. This load reduction not only reduces drive power and energy consumption, but also allows the entire lifting mechanism to be correspondingly smaller and lighter, increasing load capacity and, consequently, the power density of the overall system. Background Art

[0003] Document US 2011 / 0240409 A1 (“Scissor lift assembly” by Bacon) shows a lift table with a scissor mechanism, in which a motor-driven spindle is arranged between the two legs of a scissor pair, wherein the lift table has a small overall height in the lowered state.

[0004] Document US 5,833,198 A (“Mechanically operated lifting platform” by the inventor Graetz) likewise shows a lifting platform with a scissor mechanism, in which spring elements are arranged between the legs of a pair of scissors, wherein the spring characteristic curve is selected such that when loaded with a load assembly, the lifting platform is lowered essentially by the total height of the load assembly, resulting in an overall height of the loaded lifting platform that is essentially independent of the load.

[0005] Publication JP H07 267594A ("Motor-driven platform lifter" by inventor Mizouchi Seiji) shows a scissor lift platform on which a compression spring is provided for supporting a drive via a drive spindle.

[0006] Until now, in lifting devices such as those described in document DE 10 2012 020 264 B4, compression spring elements have been placed between the lower frame and the upper frame or lifting platform to reduce the load on the lifting mechanism and the drive train. This direct connection has several disadvantages. For example, it requires solid guide elements and complex spring supports to prevent longitudinal bending of the compression spring elements. This significantly reduces the service life if lateral forces act on the spring elements. To achieve significantly reduced load on the lifting mechanism even in the raised position, a high spring prestress must be applied to the spring elements due to the flat spring characteristic curve. However, when performing maintenance work on the lifting system, the energy stored in the spring prestress must be reliably separated, decoupled, or isolated from the lifting system, which leads to complex maintenance plans and may require additional equipment.

[0007] A further disadvantage is that, in the case of a direct connection to a spring element, a constant force curve cannot be produced over the entire stroke, since the spring force increases during the joint displacement according to the spring characteristic curve.

[0008] Solutions with counterweights, such as known passenger elevators, do provide constant support over the entire lifting height, but such solutions are generally not usable in mobile applications and have large moving masses and are therefore unsuitable for many industrial applications. Summary of the Invention

[0009] The object of the present invention is therefore to provide a load compensation device for lifting applications (lifting equipment, lifting mechanisms, lifting and lowering conveyors, lifting tables, etc.) that provides a supporting force that is as linear as possible and at the same time as constant as possible over the lifting height. The desired solution should also be lightweight and can be safely maintained after being moved to the maintenance position.

[0010] The solution to this problem involves the combination of a mechanically acting spring element and a scissor mechanism actuated by an expansion unit, which in turn supports a load-bearing device (hereinafter referred to as a "platform"). The solution according to the invention comprises a combination of a mechanically acting spring element and a scissor mechanism actuated by an expansion unit, which produces a uniform lift / force curve between two platforms that are vertically movable relative to one another. This load-compensating device is characterized by compact dimensions, flexible operation, and high performance with minimal manufacturing, assembly, and maintenance effort.

[0011] This object is achieved, in particular, by the device according to the present invention. A load compensation device for lifting applications with an object to be lifted or lowered is proposed, comprising a movable platform, the platform carrying the object, and the platform being supported by at least one spring element for load compensation purposes. The spring element acts on an expansion unit, which, to achieve the expansion, directs the spring force of the spring element into a scissor mechanism, wherein the spring force acts as a resultant lifting force on the platform via the scissor mechanism, and wherein a substantially constant lifting force is provided over the substantial lifting travel of the platform by means of a lifting geometry formed by means of the expansion unit and the scissor mechanism. By adapting the geometry, in particular the length / size of the structural elements of the expansion unit and the length of the legs of the scissor mechanism, the magnitude and linearity or stability of the supporting force (lifting force) can be easily adjusted. The load compensation device is also characterized by compact dimensions, flexible operation, and high performance with minimal manufacturing, installation, and maintenance effort.

[0012] According to the invention, the spring element (5) is configured as at least two parallel-acting tension springs and is preloaded with a spring prestressing force of such magnitude that the spring element (5) acts in the form of a stop in the raised lifting position, thereby ensuring that no additional measures have to be taken for separating the force or energy of the energy storage device in the event of maintenance.

[0013] The lifting geometry is advantageously designed so that the spring force that varies in the lifting curve is essentially compensated by the lever effect that varies in the lifting curve. This results in essentially constant support, i.e., optimized load compensation, even with steep spring characteristic curves, and in many cases allows for the omission of high spring preloads for use in a working range that is as linear as possible.

[0014] In a design of simple design, the expansion unit comprises a push rod, wherein the push rod is respectively articulated between a spring energy storage device and a scissor arm of the scissor device.

[0015] Advantageously, the expansion unit acts on a bending geometry, wherein the bending geometry predetermines the direction of the expansion unit's levering effect on the scissor mechanism. This allows for compensation of nonlinear spring force curves. Furthermore, by appropriately configuring the bending geometry, variable support forces in the lifting curve, as desired in certain applications, can be configured. In a simple and compact variant, the bending geometry is formed by at least one curved surface of the scissor arm of the scissor mechanism, with the spring force of the expansion unit acting on the curved surface via a slide or roller arrangement.

[0016] In one variant, the expansion unit has an expansion wedge geometry on at least one side. This allows for a particularly compact design. Furthermore, a flat spring characteristic curve can be easily converted into a constant load compensation or a constant support force. Depending on the application, it may be advantageous to provide an expansion wedge at one end of the tension spring and a push rod at the other end of the spring. Combinations of curved geometry with a push rod or an expansion wedge are also possible.

[0017] If the load compensating device is dimensioned accordingly, it can also perform a vertical guidance function. The supported lifting mechanism can thus be designed more simply in terms of construction and the lifting function can be limited.

[0018] Exemplary embodiments and advantageous embodiments of the load compensation device according to the invention are described below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings show:

[0020] Figure 1Schematic diagram showing two embodiments A1, A2 of a kinematic mechanism according to the invention with a load compensation device of a push rod as an expansion device,

[0021] Figures 2 to 5 Schematic diagrams show further embodiments B, C, D, E of the kinematic mechanism according to the invention with a load compensation device having an optional expansion device,

[0022] Figure 6 shows the technical embodiment of variant A1 with vertical guidance in the lowered (lowered) and extended (raised) positions,

[0023] Figure 7 shows the technical embodiment of variant D with vertical guidance in the lowered (lowered) and extended (raised) positions,

[0024] Figure 8 shows the technical embodiment of variant D without vertical guidance in the lowered (lowered) and extended (raised) positions,

[0025] Figure 9 The technical embodiment of the integration of variant D into an existing lifting and lowering conveyor mechanism is shown.

[0026] Figure 10 The technical embodiment of variant D of the lifting table is shown as a double motor drive of electric cylinders with a lowered (lowered) and extended (raised) position, and

[0027] Figure 11 The technical embodiment of variant A1 of a lifting platform as a thrust chain dual-motor drive with a lowered (descending) and extended (raising) position is shown. DETAILED DESCRIPTION

[0028] Figure 1 On the left side, two variant embodiments A1 and A2 of the kinematic mechanism of the device with a transmission element according to the invention are schematically shown, and on the right side, the corresponding force / lift curves are shown. The figure shows two scissor arms (3) connected centrally and pivotable relative to each other, to which two push rods (4) are respectively connected, which are also pivotably supported, wherein the opposite ends of the push rods are coaxially mounted. A spring energy storage (5) acting by an attached tensile force is also coaxially mounted. For the sake of clarity, Figures 1 to 5 The schematic diagram of FIG. 1 does not show a movable platform, via which the weight of the object to be moved is introduced into the component.

[0029] The extension of the scissor arm (3) is achieved by means of the push rod (4) by the tensile force originating from the energy storage (spring assembly). A compensating force (F) thus acts on the end of the scissor arm.

[0030] If the vertical guide function of the straight line can be eliminated due to the application conditions, the floating bearing guide device (2) of the variant A1 can be omitted, which in turn leads to structural space advantages and cost advantages. Figure 1 The lower half of FIG. 1 is shown with the aid of variant A2.

[0031] It is also possible to arrange a lifting and bending geometry (7) (short: lifting curve mechanism or bending geometry mechanism) on the scissor arm (3) on the same side of the fixed bearing or floating bearing instead of the push rod, so as to achieve the extension of the scissor arm (3) by means of an expansion axis extending along the lifting curve mechanism; such variants D and E are Figure 4 and Figure 5 Note: The following reference numeral (3) indicates not only the scissor device (short: scissor element) but also the individual scissor arms.

[0032] Figure 2 、 Figure 3 and Figure 5 Variants B, C, and E are shown. These solutions each include an extended wedge in various combinations and are particularly suitable for spring accumulators with a flat characteristic curve, such as commercial tension springs or, advantageously, oval wire tension springs. Furthermore, by adapting the lift-bend geometry (variants D and E), the force / lift curve can be optimally adjusted.

[0033] The selected ratio of the scissor arm length to the push rod length, in combination with the position of the pivot axis and the spring characteristic curve and the arrangement of the optional lift curve mechanism, results in a force / lift curve that influences the device. Figure 1 As can be seen from the schematic force / lift curve shown in Figure 1, a nearly constant lifting force can be achieved. If the actual force curve is compared with an ideally functioning constant force curve, a linearity deviation of less than ±1% is technically achievable. A linearity deviation of ±15% is considered the upper limit for cost-effectiveness.

[0034] As already described with reference to variant A2, the floating bearing guidance shown in variants B, C, D and E can also be omitted if a linear vertical guidance function is not required for application reasons or if the lifting platform already has vertical guidance. This is typically the case when an existing lifting device is retrofitted with a load compensation device.

[0035] The following shows Figure 1 Variations in Figure 4 Variants B, C and E show variations in other combinations of the expansion device.

[0036] Figure 6 The technical implementation of variant A1 is shown. This explains the interaction of the transmission elements of the mechanism. The spring accumulator integrated into the lifting mechanism consists of a spring assembly consisting of two compression springs inserted into one another. These compression springs are mechanically connected between the push rods, so that the spring accumulator acts like a tension spring. The use of large compression springs allows for a particularly high power density.

[0037] Figure 7 A first technical implementation scheme of the variant D is shown ( Figure 4 ), which performs the function of a linear vertical guide for the load-compensating device according to the present invention. Four high-power, elliptical wire tension springs acting in parallel serve as spring energy accumulators. Compared to round wire tension springs, these elliptical wire tension springs have a higher power density, a higher spring prestress, and a lower spring rate. The compensating load can be increased or decreased by adjusting the number of springs. A coupling element (not shown) can also be provided for this purpose to enable response to varying loads during operation. In the example shown, the lifting curve mechanism is an integral part of the scissor arm profile, with the expansion axis being guided axially by means of an intermediately mounted shaft.

[0038] Figure 8 Variant D ( Figure 4 ) technical embodiment, which has four parallel oval wire tension springs as energy storage. In this embodiment, the guide on the floating bearing side is omitted, thus eliminating the need for a linear vertical guide function. Here, the expansion shaft is advantageously guided along the centrally configured lifting curve mechanism by means of profile rollers. The compensation force is increased by adding spring elements in pairs. Therefore, it is also technically feasible to Figure 8 The embodiment shown in the FIGURE operates with, for example, only two, or with six or eight, parallel-acting tension springs. The high spring prestressing incorporated into the oval-shaped wire tension springs allows the desired compensation force to be generated without the need for additional spring prestressing. Since the tension springs move together in the raised lifting position in the manner of a stop, no additional measures need to be taken to separate the force or energy of the energy storage device during maintenance.

[0039] Figure 9 Show Figure 5 Integration of two parallel load compensation devices in an existing lifting and lowering conveyor. Such lifting and lowering conveyors are used for conveying vehicle bodies in series production of motor vehicles. In industry, there is often a desire to increase the efficiency of existing systems. In this example, by integrating Figure 4Variant D in the embodiment partially relieves the lifting mechanism with drive train and, on the other hand, increases the load-bearing capacity of the device (in this case by 40%). This provides a significant economic advantage because this retrofit is associated with relatively little effort and eliminates the need for expensive complete modifications of the lifting and lowering conveyor for higher loads.

[0040] Another application area for load compensation devices is lifting applications used on automated guided vehicles (FTFs). Here, energy savings and increased performance are particularly significant, since energy provision or energy supply is associated with high costs and lifting performance is often the limiting factor.

[0041] exist Figure 10 The load compensation device shown for an automated guided vehicle integrates both a vertical guidance function and a drive function, and thus serves as a lifting platform.

[0042] exist Figure 11 The load compensation device with guidance and drive functions shown in FIG can be used as a lifting platform for large loads of up to 3 tons on an unmanned guided vehicle. The drive function is realized by two mutually electrically synchronized thrust chain drives, and the vertical guidance and load compensation functions are realized by two Figure 6 The load compensation device is installed in the center.

Claims

1. A load compensating device for lifting applications with an object to be lifted or lowered, The load compensation device has a movable platform, wherein: The platform carries the object, wherein the platform is supported by at least one spring element for load compensation purposes, wherein the spring element acts on an expansion unit, which, for the purpose of expansion, introduces the spring force of the spring element into a scissor mechanism, wherein the spring force as a resultant lifting force exerts a lifting effect on the platform via the scissor mechanism, and wherein a substantially constant lifting force is provided over a substantial lifting travel of the platform by means of a lifting geometry formed by means of the expansion unit and the scissor mechanism, It is characterized by: The spring element is configured as at least two parallel-acting tension springs and is preloaded with a spring prestressing force, the magnitude of which causes the spring element to be in the form of a stop in the raised lifting position, the expansion unit having a push rod, wherein each of the push rods is articulated between the spring element and a scissor arm of the scissor device.

2. The load compensation device according to claim 1, characterized in that: The expansion unit acts on a bending geometry, wherein the bending geometry specifies the course of the lever effect of the expansion unit on the scissor mechanism.

3. The load compensation device according to claim 2, characterized in that: The bending geometry is formed by at least one curved surface of a scissor arm of the scissor device, wherein the spring force acts on the curved surface via the expansion unit by means of a slide or roller arrangement.

4. The load compensation device according to claim 1 or 2, characterized in that: The expansion unit has an expansion wedge geometry on at least one side.

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