LINEAR DRIVE

Abstract

Linear drive (100), in particular for converting a rotational movement into a linear movement for actuating a valve including a shut-off slide, having a crank mechanism, the linear drive (100) comprising a first crankshaft (6) associated with a piston rod (10) via a first connecting rod (8), a second crankshaft (7) associated with the piston rod (10) via a second connecting rod (9), and a planetary gear for rotationally driving the first crankshaft (6) and the second crankshaft (7).

Claims

1. A linear drive in particular for converting a rotational movement into a linear movement for actuating a valve including a shut-off slide, having a crank mechanism, the linear drive comprising: a first crankshaft associated with a piston rod via a first connecting rod, a second crankshaft associated with the piston rod via a second connecting rod, and a planetary gear for rotationally driving the first crankshaft and the second crankshaft.

2. The linear drive according to claim 1, wherein the planetary gear is configured as a power-distributed gear.

3. The linear drive according to claim 1, wherein the first crankshaft is associated with an internal gear of the planetary gear.

4. The linear drive according to claim 3, wherein the second crankshaft is associated with a further internal gear of the planetary gear.

5. The linear drive according to claim 4, wherein the planetary gear comprises a first planetary set and a second planetary set, which are arranged on a common planetary carrier.

6. The linear drive according to claim 5, wherein the planetary wheels of the first planetary set are each associated with a respective planetary wheel of the second planetary set in a torque-proof manner.

7. The linear drive according to claim 5, wherein the planetary carrier is in engagement with a driving shaft.

8. The linear drive according to claim 5, wherein the driving shaft is in engagement with the planetary carrier by means of a bevel pinion.

9. The linear drive according to claim 5, wherein the planetary carrier is configured as a crown wheel or integrally comprises a crown wheel.

10. The linear drive according to claim 1, wherein the rotational axis of the planetary gear is coaxial to the respective rotational axes of the crankshaft.

11. The linear drive according to claim 1, wherein the first crankshaft has a first transmission ratio, and the second crankshaft has a second transmission ratio, which is different with respect to the first transmission ratio.

12. The linear drive according to claim 1, wherein the crankshafts rotate in opposite directions during operation.

13. The linear drive according to claim 1, comprising a first slotted link and a second slotted link respectively limiting the rotation range of the first crankshaft and the rotation range of the second crankshaft to a maximum of 180°.

14. The linear drive according to claim 1, wherein the linear drive is used for actuating a valve including a shut-off slide.

15. The linear drive according to claim 14, wherein the linear drive is used for controlling the flow in an oil or gas production facility in a water depth of at least 30 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further advantages and features of preferred embodiments of the invention will be explained below on the basis of the attached schematic drawings. The Figures show:

[0027] FIG. 1 a typical embodiment of a linear drive in a schematic sectional view,

[0028] FIG. 2 the embodiment of FIG. 1 in a schematic side view; and

[0029] FIG. 3 a slotted link of the embodiment of FIGS. 1 and 2 in a schematic perspective view.

DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

[0030] Typical embodiments will be described in the following on the basis of the Figures, wherein the invention is not restricted to the exemplary embodiments, the scope of the invention being rather determined by the claims.

[0031] In FIG. 1, a typical embodiment of a linear drive 100 is shown in a schematic sectional view.

[0032] The linear drive 100 serves for linearly driving a piston rod 10 associated with a seating. In the representation of FIG. 1, the piston rod 10 is moved upwards and downwards in the drawing plane. In typical embodiments, the piston rod 10 is in association with a shut-off slide of a valve, in particular of a subsea valve.

[0033] The linear drive 100 is driven by a motor (not illustrated), the shaft of which is associated with a bevel pinion 15 in a torque-proof manner. The bevel pinion 15 is in engagement with a crown wheel configured to be in one piece with a planetary carrier 1 and drives this planetary carrier 1 by means of the crown wheel.

[0034] In the planetary carrier 1, a first planetary set having first planetary wheels 2, and a second planetary set having second planetary wheels 4 are arranged. The first planetary wheels 2 (only one being illustrated in FIG. 1) of the first planetary set are each in torque-proof association with the respective planetary wheel 4 (only one being illustrated in FIG. 1) of the second planetary set. However, the planetary wheels 2 and 4 of the two planetary sets, which are each in torque-proof association, in turn are mounted to be rotatable within the planetary carrier 1 via a planetary shaft configured in one piece with one of the planetary wheels 2 and 4.

[0035] The first planetary wheels 2 of the first planetary set engage into a first internal gear 3. The second planetary wheels 4 of the second planetary set engage into a second internal gear 5 here also referred to as a further internal gear.

[0036] The first internal gear 3, and the second or further internal gear 5 are mounted rotatable on a common axis with the planetary carrier 1 in a housing having the housing parts 11 and 12.

[0037] The tooth number ratios, and thus the first transmission ratio of the first planetary wheels 2 of the first planetary set, to the first internal gear 3 are different from the tooth number ratios and the second transmission ratio of the second planetary wheels 4 to the second internal gear 5. A rotation of the planetary carrier 1 during operation corresponding to the different transmissions ratios results in a relative movement of the first internal gear 3 with respect to the second internal gear 5. In the exemplary embodiment illustrated in FIG. 1, the first internal gear 3 has 108 teeth, and the second internal gear 5 has 109 teeth. The first planetary wheels 2 have 41 teeth, and the second planetary wheels 4 have 42 teeth. In further exemplary embodiments, other combinations may be used so as to achieve different transmission ratios.

[0038] In typical embodiments, the crankshafts are configured to be rather disc-shaped, namely having an axial thickness which is smaller than their respective diameter. This enables a compact construction form.

[0039] A first crankshaft 6 is in torque-proof association with the first internal gear 3. A second crankshaft 7 is in torque-proof association with the second internal gear 5. The two crankshafts 6 and 7 are in articulated association with the piston rod 10 via respectively one coupling rod or connecting rod 8 and 9. This association provides for the two crankshafts 6 and to rotate synchronously, thus at the same speed, but, if necessary, in different directions.

[0040] The pivot angle of the crankshaft 6 is limited to 180° between an upper and a lower dead point by a slotted link 13. The pivot angle of the crankshaft 7 is limited to 180° between an upper and a lower dead point by a slotted link 14. The stops of the slotted links 13 and 14 are arranged so that the two crankshafts 6 and 7, when turning from the respective upper dead point to the respective lower dead point, are required to rotate in opposite directions.

[0041] The drive of the planetary carrier in typical embodiments results in a rotation of the internal gears taking place synchronously in opposite directions. This rotational movement is converted into a linear movement of the piston rod via the crankshafts and the coupling rods.

[0042] In FIG. 2, a side view of the embodiment of FIG. 1 is shown. The reference numerals used in FIG. 1 and also in FIG. 3 correspond to those of FIG. 1, wherein not all of the parts need to be provided with a reference numeral again, and in the text, not all of the elements provided with a reference numeral are described again.

[0043] In FIG. 2, the rotational angle limitation caused by the slotted link 13 can be recognized. At the opposite side (namely at the rear side of the linear drive 100 in FIG. 2), an oppositely mounted slotted link (reference numeral 14 in FIG. 1) is arranged allowing a rotational movement in the opposite direction.

[0044] FIG. 3 shows the slotted link 13 in a schematic perspective view. The slotted links 13 and 14 are configured to be structurally identical but will be mounted oppositely in an opposite axial orientation so as to achieve the opposite movement of the crankshafts.

[0045] The construction form of the planetary gear enables a very high transmission ratio. The output torques in the two internal gears thus are almost identical. At the output side, no reaction moment is introduced into the housing from the planetary gear.