COORDINATE MEASURING MACHINE WITH AN IMPROVED BELT DRIVE

Abstract

A coordinate measuring machine (CMM) having a belt drive unit for an elongated axis element of the CMM, the belt drive unit comprising a belt, the ends of which are clamped on the elongated axis element, a pulley unit, comprising a drive pulley and two idler pulleys, wherein the belt entangles the drive pulley and the idle pulleys in an omega-shaped manner, and wherein the pulley unit is configured to cause a relative linear movement between the axis element and the pulley unit, wherein a damping layer is disposed adjacent to the belt.

Claims

1. A coordinate measuring machine (CMM) having a belt drive unit for an elongated axis element of the CMM, the belt drive unit comprising: a belt, the ends of which are clamped on the elongated axis element; a pulley unit comprising a drive pulley and two idler pulleys, wherein the belt entangles the drive pulley and the idle pulleys in an omega-shaped manner, wherein the pulley unit is configured to cause a relative linear movement between the axis element and the pulley unit, and wherein the belt encompasses at least one end of the elongated axis element.

2. A coordinate measuring machine (CMM) having a belt drive unit for an elongated axis element of the CMM, the belt drive unit comprising: a belt, the ends of which are clamped on the elongated axis element; a pulley unit, comprising a drive pulley and two idler pulleys; and a damping layer disposed adjacent to the belt, wherein the belt entangles the drive pulley and the idle pulleys in an omega-shaped manner, and wherein the pulley unit is configured to cause a relative linear movement between the axis element and the pulley unit.

3. A coordinate measuring machine (CMM) according to claim 1, wherein the belt is a profiled belt.

4. A coordinate measuring machine (CMM) according to claim 1, wherein the belt is a toothed belt.

5. The coordinate measuring machine (CMM) according to claim 1, wherein the belt encompasses the axis element such that forces resulting from the prestressing of the belt which are acting on the axis element substantially neutralize themselves with regard to an overall bending moment of the axis element.

6. A coordinate measuring machine (CMM) according to claim 1, wherein the ends of the belt are clamped in two separate clamping points by a fixture means.

7. The coordinate measuring machine (CMM) according to claim 1, wherein the ends of the belt are clamped in one clamping point by a fixture means.

8. A coordinate measuring machine (CMM) according to claim 1, wherein at an end of the axis element, the belt is guided by a support pulley.

9. The coordinate measuring machine (CMM) according to claim 1, wherein at an end of the axis element, the belt is guided by an air bearing.

10. The coordinate measuring machine (CMM) according to claim 1, wherein at an end of the axis element, the belt is guided by a bush bearing with or without lubrication.

11. The coordinate measuring machine (CMM) according to claim 2, wherein the damping layer is disposed adjacent to the belt.

12. The coordinate measuring machine (CMM) according to claim 11, wherein the damping layer is arranged between the belt and the axis element.

13. The coordinate measuring machine (CMM) according to claim 2, wherein the material of the damping layer is rubber.

14. The coordinate measuring machine (CMM) according to claim 2 wherein the material of the damping layer is foamed plastic.

Description

DETAILED DESCRIPTION

[0024] In the following, the invention will be described in detail by referring to exemplary embodiments that are accompanied by figures, in which:

[0025] FIG. 1: shows an omega belt drive with vibration damping as one embodiment according to the invention;

[0026] FIG. 2: shows an omega belt drive with bending moment compensation as an embodiment according to the invention;

[0027] FIG. 3: shows an omega belt drive with bending moment compensation and vibration damping as an embodiment according to the invention;

[0028] FIG. 4: shows a further omega belt drive with bending moment compensation and vibration damping as another embodiment according to the invention;

[0029] FIG. 5: shows a further omega belt drive with bending moment compensation and vibration damping as another embodiment according to the invention;

[0030] FIG. 6: shows a further omega belt drive with bending moment compensation and vibration damping as another embodiment according to the invention;

[0031] As a first embodiment of the invention, FIG. 1 shows an axis element 1, a pulley unit 2 comprising a drive pulley 3 and two idler pulleys 4 and 4′. A belt 5 is clamped under tension preloading on the axis element 1 via two fixture means 6 and 6′. As illustrated by the arrow, the pulley unit 2 is movable forth and back by the drive pulley 3 rotating and thereby pulling its way along the axis element 1 by maintaining grip with the belt 5. This grip may be realized by a tight fit, for example by the belt being a profiled belt, particularly a toothed belt, on its lower side facing the axis element 1. The upper surface may be flat or also profiled. A tight fit on this side with the idler pulleys 4 and 4′, however, is not necessary, since they merely provide an inner prestress support for the pulley unit 2 against the drive pulley 3.

[0032] A guiding of the pulley unit 2 is not shown and may be realized by a further section of the axis element.

[0033] A damping layer 7 is arranged between the belt 5 and the axis element 1, wherein the material of the layer may be of a type of rubber or foam. The damping layer 7 may be fixed directly and firmly on the axis element. Relative movement between belt 5 and layer 7 has to be provided, since the layer 7 “swallows” or reduces vibrations of the belt. Between belt 5 and damping layer 7 there may be an air gap, as is shown in FIG. 1, or both elements may be abutted against each other, for example by the fixture means 6 and 6′.

[0034] FIG. 2 shows an axis element 1, a pulley unit 2 comprising a drive pulley 3 and two idler pulleys 4 and 4′. A belt 5 is clamped under tension preloading on the axis element 1 via two fixture means 6 and 6′, wherein the belt is wrapped around the axis element. As illustrated by the arrow, the pulley unit 2 is movable forth and back by the drive pulley 3 rotating and thereby pulling its way along the axis element 1 by maintaining grip with the belt 5. This grip may be realized by a tight fit, for example by the belt being a profiled belt, particularly a toothed belt, on its lower side facing the axis element 1. The upper surface may be flat or also profiled. A tight fit on this side with the idler pulleys 4 and 4′, however, is not necessary, since they merely provide an inner prestress support for the pulley unit 2 against the drive pulley 3.

[0035] A guiding of the pulley unit 2 is not shown and may be realized by a further section of the axis element.

[0036] In this configuration, on the edges of the axis element 1 the belt is supported by support pulleys 8 and 8′. With this support/bearing, the belt is free to expand, contract or slacken, respectively. The wrap-around of the belt about one of the ends of the axis element provides the resulting forces caused by the pretension of the belt to attack in such a way that a bending moment of the axis element is zero or essentially zero.

[0037] Even though pulley unit 2 is configured to drive only on the upper side of the elongated axis element 1, the belt is carried on to the lower side where it is clamped by fixture means 6′. The distance between fixture means 6′ and support pulley 8′ is arbitrary and may e.g. be maximized, as shown in FIGS. 2, 3 and 4, in order to achieve a higher overall elasticity of the belt. Since the belt is frictionless carried on to the lower elongated side of the axis element, it is of no meaning where on the lower side the belt is clamped in order to achieve the zero-sum bending moment of the axis element.

[0038] FIG. 3 shows an enhanced embodiment of the CMM axis element from FIG. 2. Here, the belt 5 is underlaid by damping layers 7, 7′, and 7″ in order to absorb vibrations of the belt. Between the belt and the damping layer there may be an air gap, or the belt may abut on the damping layer. Anyhow, with the support pulleys 8 and 8′ the belt is given chance to compensate the preload stressing distribution, so that forces acting on the support pulleys 8 and 8′ are essentially equal in both direction and amount.

[0039] FIG. 4 shows a configuration of a CMM axis element, on the edges of which the belt is supported by air bearings 9 and 9′. With this support/bearing, the belt is free to expand, contract or slacken, respectively. The wrap-around of the belt about one of the ends of the axis element provides the resulting forces caused by the pretension of the belt to attack in such a way that a bending moment of the axis element is zero or essentially zero.

[0040] FIG. 5 shows a further embodiment of a CMM axis element according to the invention, wherein the belt 5 is clamped in only one clamping point by fixture means 6. On the edges of the axis element, the belt is supported by air cushion bearings 9, 9′, 9″, and 9′″.

[0041] FIG. 6 shows a further embodiment of a CMM axis element according to the invention, wherein the belt 5 is clamped in two separate clamping points by fixture means 6 and 6′. Guiding of the belt at the edges of the axis element 1 now is realized by support pulleys 8, 8′, 8″, and 8′″.

[0042] Although the invention is illustrated above, partly with reference to some preferred embodiments, it must be understood that numerous modifications and combinations of different features of the embodiments can be made. All of these modifications lie within the scope of the appended claims.