WO2005017392A1

WO2005017392A1 - Protection device for a spindle drive

Info

Publication number: WO2005017392A1
Application number: PCT/EP2004/008741
Authority: WO
Inventors: Karl Hehl
Original assignee: Karl Hehl
Priority date: 2003-08-06
Filing date: 2004-08-04
Publication date: 2005-02-24
Also published as: DE102004005209A1

Abstract

The invention relates to a protection device, for a spindle drive, comprising a spindle (10) and a nut (11), which has an elastic element (13) as safety element. The rotating part of the spindle drive is driven by means of a drive unit (12), in order to thus generate a linear movement of one component relative to another component (16). The elastic element (13) is arranged between the spindle drive and at least one of the components. A reliable free-space for the decay of moments of inertia is guaranteed when a nominal force on the spindle drive (S) given by the selected or selectable spring force of the elastic element (13) is exceeded, by the embodiment of the elastic element (13) as safety element for the decay of moments of inertia of the part of the spindle drive subjected to a linear movement and by arrangement of the elastic element in the vicinity of the spindle drive.

Description

Protection device for a spindle drive

description

Related to related applications

The present application claims the priority of the German patent application 103 35 854.4, filed on August 6, 2004, the disclosure content of which is hereby expressly made the subject of the present application.

Field of the Invention

The invention relates to a protective device for a spindle drive according to the preamble of claim 1.

State of the art

Such a device is used in EP 0 675 300 B1 for two-stage closing during an injection process on a plastic injection molding machine. Two drives are connected in series, the first drive essentially accomplishing the closing movement, while the second drive is intended to generate the closing force. Since the drive can be dimensioned considerably smaller for the mere approach movement than for the application of the considerable closing force, this device largely decouples the first drive from the power flow or at least from the further power flow when the closing force is applied. For this purpose, there is a rotationally secure, non-positive fixing. Protection of the spindle drive against overstressing, in particular as a result of moments of inertia, is therefore not achieved, especially since the parts come into engagement with one another to a large extent at a standstill.

Basically, the problem with electrical drives with the conversion of a rotation into a linear movement is that a mechanical overrun of the spindle system can lead to the destruction of the spindle. So far so far Protective devices known electrical circuits, which are to avoid such overload conditions by current limitation. In many cases, however, this is not sufficient because the current limitation only takes effect when the end point of motion has actually been reached. However, in the case of spindle drives in particular, there are still moments of inertia in the masses to be moved that the system "continues to run", which can lead to the destruction of parts of the machine. Studies have shown that a clearance of the order of millimeters may be required for this ,

Summary of the invention

On the basis of this prior art, the object of the present invention is to develop a protective device of the type mentioned at the outset in such a way that a reliable free space for reducing moments of inertia is ensured.

This object is achieved by a protective device for a spindle drive with the features of claim 1.

The elastic element provided does not represent a force limitation, but is intended to provide the system with the "run-out" that is required if the nominal force of the spindle drive is exceeded. For this purpose, the elastic element is arranged in the area of the spindle drive in such a way that an additional linear movement is intercepted if necessary can.

This additional mechanical fuse is advantageously arranged in the drive train in which the direct force is applied. As a result, a safety spring travel of the order of millimeters can be made available in the shortest possible way before the entire system is damaged.

A preferred application is z. B. in injection molding machines and especially in plastic injection molding machines. Spindle drives of this type are increasingly being used there, the region of the ejector for removing ejecting injection molded parts from the injection mold is mentioned. In this area, the manufacturer does not know the tool-related dimensions from the outset. It is up to the operator to specify the appropriate freedom of movement. If incorrect entries are made here, the spindle drives will inevitably collide and possibly be damaged.

Brief description of the figures:

The invention is explained in more detail below with reference to the attached figures. Show it:

1 shows a three-dimensional view of a spindle drive with associated protective device, FIG. 2 shows a section through the spindle drive according to FIG. 1, FIG. 3 shows an enlarged detail from FIG. 2 in the area of the protective device, FIG. 4 shows a section through a protective device according to 5 shows a section through a hollow shaft motor provided with the protective device.

Detailed description of preferred embodiments

The invention will now be explained in more detail by way of example with reference to the accompanying drawings. However, the exemplary embodiments are only examples which are not intended to restrict the inventive concept to a specific arrangement.

The figures show a protective device for a spindle drive S. The spindle drive has at least two parts in the form of a spindle 10 and a nut 11 which interacts with the spindle. As is customary with such a spindle drive, at least one of these parts is mounted in a rotationally fixed manner, while at least one further is rotatable Part of these parts movably loaded in the longitudinal direction of the spindle 10 device. By means of a drive device 12, such as. B. an electric motor, the further rotatable part, here nut 11 is rotated, whereby a linear movement of the non-rotatable part, here spindle 10, is achieved. This linear movement leads to a relative movement of an assembly in relation to another assembly. In the exemplary embodiment, an ejector 17 is shown as the one assembly, which can be moved relative to the assembly 16 or an injection molding tool (not shown in the drawing) connected to this assembly 16.

In this respect, the invention is explained in more detail below on the basis of these elements, which are usually located on a plastic injection molding machine. In principle, however, other assemblies on a plastic injection molding machine or also other assemblies per se, which are intended for other purposes, can be protected by such a protective device against excesses of inertia which may be unavoidable.

For protection, at least one elastic element 13 is provided in the exemplary embodiments in the form of spring washers, which is arranged between the spindle drive S and at least one of the assemblies. The elastic element 13 serves as a securing element and creates an outlet x for the non-rotatable part subject to the linear movement, here the spindle 10, or the rotatable part of the

Spindle drive, here the nut 11, in order to be able to reduce excess inertia if necessary.

Basically, there is the problem of protecting electrical spindle drives in such a way that the spindle is prevented from being destroyed when the spindle system mechanically overruns. On the injection molding machine, this occurs particularly in the area of the ejector, but not only here. In the area of ejection, the tool-related dimensions are not known to the manufacturer, so the operator must correctly enter the corresponding freedom of movement. If incorrect entries are made, the collision in question occurs. When ending such a movement there is still so much energy due to moments of inertia, for. B. the spindles or nuts and as a result of switching delays in the system that theo- infinitely high forces occur. These forces can destroy the spindle.

What exactly happens can be explained most simply with the aid of FIG. 2. If the belt wheel 22 is driven by the drive device 12 via the belt 19 so that the nut 11 rotates, this leads to a movement of the spindle 10 in the direction of the arrow 23, at least during the actual ejection process. If the collision occurs, the spindle can no longer move, which leads to an opposite movement of the nut 11 in the direction of the arrow 24 in FIG. 3. This movement leads to a corresponding movement of the bearings 14, which is intercepted by the elastic element 13. The system is therefore allowed to run out via the outlet x, so that the system can cushion itself against the preferably increasing force of the spring. The force of the elastic element 13 is dimensioned such that the predetermined or predeterminable spring force of the elastic element 13 is slightly above the nominal force of the spindle drive S. This is to allow the movement or braking of the kinematic energy to slow down gently.

The arrangement of the elastic element takes place in the area of the spindle drive, for. B. at least one end of the spindle 10 and / or the nut 11 or a storage area z. B. the bearing 14 of the spindle drive S. Advantageously, this elastic element is arranged at the end of the spindle 10 or nut 11 remote from the drive device 12 or the further rotatable part. For this purpose, as in the exemplary embodiment in FIGS. 1 to 3, the bearing 14 , 15 in the area of the outlet x against the forces of the elastic element 13 to be axially movable. This additional mechanical fuse is located directly in the drive train in which the direct force is applied. This is to reduce occurring forces and moments as quickly as possible. Depending on the system, the resulting safety spring travel can be of the order of millimeters.

In the exemplary embodiment, the part subjected to the linear movement is the spindle 10. The cushioning takes place in the area of the nut 11. The spindle drive can be a Ball screw drive, a threaded spindle with planetary drive or a comparable spindle drive.

As explained, the assemblies are preferably parts of a plastic injection molding machine that move relative to one another. In the exemplary embodiment, the assembly to be protected is an ejector 17. According to FIG. 1, this ejector 17 is guided on guides 18 which are arranged parallel to the direction of action of the elastic element 13. Only the driver and the coupling 21 can be seen in the figures.

In the embodiment of FIG. 4, which also shows a region of the ejector, a section through the coupling 21 can be seen on the right-hand side, the locking slides 26 mounted against springs 25 being visible. From the spindle drive, only the spindle 10 can be seen, the movement of which is reduced as required via the elastic means 13 designed as spring assemblies. The nut lying outside the cutting area of FIG. 4 cannot be seen. The maximum deformation path of both spring assemblies together results in the outlet x.

5 shows in a further exemplary embodiment an integration of the protective device into a hollow shaft motor 20. In the hollow shaft motor, the nut 11 can be seen, which is supported there via the bearings 14, 15. The spindle 10 is in threaded engagement with this nut. If there is an excessive load, it is intercepted by the nut 11 and the bearings 14 in the direction of the elastic element 13 using the outlet x.

It goes without saying that this description can be subjected to various modifications, changes and adaptations which range from equivalents to the appended claims. LIST OF REFERENCE NUMBERS

10 spindle

11 mother

11a Mother admission

12 drive device

13 elastic element

14, 15 bearings

16 assembly

17 ejectors

17a ejector pin

18 leadership

19 straps

20 hollow shaft motor

21 clutch

22 pulley

23, 24 arrow

25 spring

26 locking slide

S spindle drive x outlet

Claims

claims

1. Protection device for a spindle drive (S) with at least two parts in the form of a spindle (10) and a nut (11) cooperating with the spindle (10), at least one of these parts being mounted in a rotationally fixed manner, while at least one further rotatable part said parts are movably mounted in the longitudinal direction of the spindle (10), a drive device (12) for rotating the further rotatable part to produce a linear movement of the non-rotatable part together with an assembly relative to another assembly (16), at least one elastic element (13) , which is arranged between the spindle drive (S) and at least one of the assemblies, characterized in that the elastic element (13) as a securing element has an outlet (x) in the area of the spindle drive (S) in the event that one of the specified or Predeterminable spring force of the elastic element (13) certain nominal force of the spindle drive (S) to dismantle existing door gheitsmomentüberschüsse formed.

2. Protection device according to claim 1, characterized in that the elastic element (13) is provided on at least one end of the spindle (10) and / or the nut (11) and / or a bearing area of the spindle drive (S).

3. Protection device according to claim 1 or 2, characterized in that the elastic element (13) is arranged at the end of the spindle (10) or nut (11) remote from the drive device (12) or the further rotatable part.

4. Protection device according to one of the preceding claims, characterized in that the part subjected to the linear movement is the spindle (10).

5. Protection device according to one of the preceding claims, characterized in that the outlet (x) is provided for the further rotatable part designed as a nut (11).

6. Protection device according to one of the preceding claims, characterized in that the at least one in the region of the outlet (x) arranged bearing (14, 15) against the force of the elastic element (13) is axially movable.

7. Protection device according to one of the preceding claims, characterized in that the elastic element (13) is arranged in the drive train of the spindle drive (S), in which the direct introduction of force takes place when the nominal force is exceeded.

8. Protection device according to one of the preceding claims, characterized in that the spindle drive (S) is a ball screw drive or a threaded spindle with planetary drive.

9. Protection device according to one of the preceding claims, characterized in that the assemblies are parts of a plastic injection molding machine.

10. Protection device according to one of the preceding claims, characterized in that the assembly to be protected is an ejector (17).

11. Protection device according to one of the preceding claims, characterized in that the linearly moved assembly is guided on guides (18) arranged parallel to the active force of the elastic element (13).

12. Protection device according to one of the preceding claims, characterized in that the spindle drive (S) is integrated in a hollow shaft motor (20).