ROTARY ACTUATOR, CONVERTING ACTUATOR AND METHOD FOR PRODUCING ROTATION

Abstract

The invention relates to a rotary actuator, converting actuator and method for producing rotation. The rotary actuator includes at least two rotation units for producing stepped angular displacements (Rs). The rotation unit includes a cylinder for producing linear movement (L) and a converter for converting the linear movement to rotation. The stepped rotary movements of the rotation units are transmitted by transmission elements to an output shaft.

Claims

1. A rotary actuator for producing rotation, and comprising: a frame; at least one output shaft; and at least one pressure medium operated rotation unit; at least a first rotation unit and a second rotation unit, which are series connected regarding produced rotation (R); the first rotation unit having a first pressure medium cylinder for providing first axial movement and a first converting arrangement for converting the first axial movement (L) to first angular displacement (Rs); the second rotation unit having a second pressure medium cylinder for providing second axial movement (L) and a second converting arrangement for converting the second axial movement (L) to second angular displacement (Rs); control means for directing pressure medium selectively to the pressure medium cylinders for operating selected ones of the rotation units individually for producing stepped angular displacements; and transmission means for transmitting produced rotation movements of the rotation units to the output shaft, whereby rotation (R) of the output shaft is an outcome of the stepped angular displacements (Rs) produced by at least two selectively controlled rotation units.

2. The rotary actuator as claimed in claim 1, wherein operation of each of the pressure medium cylinders of the rotary actuator is independently controllable.

3. The rotary actuator as claimed in claim 1, wherein the pressure medium cylinders of the rotary actuator are provided with two fixed operational positions, an extreme shortened first operational position and an extended second operational position, whereby the cylinders are without any intermediate positions between the extreme operational positions; and each of the cylinders are configured to produce two stepped angular displacements, whereby a total number of possible angular displacements of the rotary actuator is determined by formula 2.sup.n, wherein n is number of cylinders of the rotary actuator.

4. The rotary actuator as claimed in claim 1, wherein the pressure medium cylinders of the rotary actuator are arranged successively on a same axial line.

5. The rotary actuator as claimed in claim 1, wherein the rotary actuator comprises: at least two rotation units which are configured to produce angular displacements with differing magnitudes.

6. The rotary actuator as claimed in claim 1, wherein each rotation unit is configured to produce specific angular displacement with different magnitude compared to angular displacements of other rotation units.

7. The rotary actuator as claimed in claim 5, wherein stroke lengths of the pressure medium cylinders of at least two rotation units are dimensioned to be different in order to produce different angular displacements.

8. The rotary actuator as claimed in claim 5, wherein the converting arrangements are configured to convert produced axial movement (L) to angular displacement (Rs) according to their converting ratio; and the rotary actuator having at least two converting arrangements provided with differing converting ratios in order to produce different angular displacements (Rs).

9. The rotary actuator as claimed in claim 8, wherein the at least two rotation units provided with differing converting ratios of the converting arrangements are configured to generate equal or substantially equal torques; and the torques of the rotation units provided with differing converting ratios are compensated for by dimensioning sizes of surface areas of working pressure surfaces of the pressure medium cylinders relative to the converting ratios.

10. The rotary actuator as claimed in claim 1, wherein the rotary actuator comprises: one single frame inside which at least two rotation units are arranged.

11. The rotary actuator as claimed in claim 1, wherein the frame of the rotary actuator comprises: at least two frame parts, and inside each frame part is at least one rotation unit; the frame parts are arranged axially one after each other; and between successive frame parts are transmission means for transmitting produced angular displacements.

12. Method for producing rotation with a rotary actuator, comprising: using a rotary actuator provided with at least two individually operable rotation units, wherein each of the rotation units is provided with a pressure medium operated cylinder and a converting arrangement; producing axial movement (L) in selected pressure medium cylinders by feeding and discharging pressure medium to and away from at least one pressure space of the selected pressure medium cylinders; converting the produced axial movements (L) of the selected pressure medium cylinders to stepped angular displacements (Rs); transmitting the produced angular displacements to an output shaft; and controlling operation of one or more rotation units individually for producing desired rotation (R) of the output shaft.

13. A converting actuator for converting linear movement to rotation movement and vice versa, the actuator comprising: a frame; at least one output shaft; and at least one pressure medium operated rotation unit; at least a first rotation unit and a second rotation unit, which are series connected regarding their movements, and which are individually operable; the first rotation unit having a first pressure medium device for providing first axial movement (L) and a first converting arrangement for converting the first axial movement (L) to first angular displacement (Rs) and vice versa; the second rotation unit having a second pressure medium device for providing second axial movement (L) and a second converting arrangement for converting the second axial movement (L) to second angular displacement (Rs) and vice versa; transmission means for transmitting rotation movements between the at least two rotation units and also between the output shaft and the rotation units; and wherein the stepped angular displacements (Rs) produced by the at least two rotation units are configured to generate a rotation outcome (R) for the output shaft, and correspondingly an input torque directed to the output shaft is configured to produce rotation of the output shaft and is configured to be converted into axial movements (L) in the at least two rotation units.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0041] Some embodiments are described in more detail in the accompanying drawings, in which

[0042] FIG. 1 is a schematic side view of a rotary actuator comprising several rotation units integrated inside one frame part,

[0043] FIG. 2 is a schematic side view of another rotary actuator comprising several differing rotation units,

[0044] FIG. 3 is a schematic diagram showing basic features of producing stepped rotatory movements by means of the disclosed rotary actuator,

[0045] FIG. 4 is schematic and sectional half-view of a rotary actuator comprising two rotation units,

[0046] FIG. 5 is a schematic side view of a feasible rotary actuator comprising two or more parallel rotation units,

[0047] FIG. 6 is a schematic side view of a feasible rotary actuator comprising several rotation units arranged within each other,

[0048] FIG. 7 is a schematic side view of a feasible rotary actuator comprising at least two rotation units arranged within each other, and further comprising one or more rotation units arranged consecutively, and

[0049] FIG. 8 is a schematic side view of a converting actuator capable to convert input rotary movement into pressure energy, and vice versa.

[0050] For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0051] FIG. 1 shows in a simplified manner a rotary actuator 1 by means of which rotation R may be generated. The rotary actuator 1 comprises two, three or more rotation units 2a-2c, each of which comprises a pressure medium cylinder 3 for producing axial movement L and converting means 4 for converting the axial movement to angular displacement or stepped rotary movement Rs. Number of the rotation units 2 may be selected according to the need. The rotary actuator 1 may comprise a frame 5 for supporting the rotation units 2a-2c. The rotation units 2 may be arranged inside the frame 5. The rotary actuator 1 is connected to a hydraulic system and comprises needed pressure medium ducts 8 for directing pressure medium to the cylinders 3 and away from them. The rotary actuator 1 may also comprise needed control means such as valves and other control elements for controlling the flows of the pressure medium. The rotary actuator 1 may be hydraulically or pneumatically operated. The rotary actuator 1 further comprises transmission means 7 for transmitting the produced stepped rotary movements Rs to an output shaft 8, which may be mounted by means of bearings 9 to the frame 5. The rotation units 2 are connected to each other by means of the transmission means 7 so that the produced rotation steps are transmitted between them and further to the output shaft 8. The produced axial movements L of the cylinders 3 are not transmitted from one rotation unit to another. Thus, the rotation units 2 are series connected regarding the produced rotary movements. The cylinders 3 of the rotation units 2 may be independently controlled, whereby varying stepped rotary movements may be generated. The rotations units 2 of the rotary actuator 1 may be similar or they may all be configured to produce specific angular displacement.

[0052] FIG. 2 illustrates that the rotary actuator 1 may be composed of two or more different rotation units 2a-2c. The station units 2 may be provided with pressure medium cylinders 3 having differing stroke lengths and they may also be configured to produce linear forces having different magnitude, for example. Alternatively, or in addition to, the converting means 4 of the rotation units 2 may be structurally different and/or their converting ratios may be different.

[0053] As it is shown in FIG. 1 the rotation units 2 may be arranged axially on the same line. Furthermore, the rotation units 2 may be located successively. In FIG. 2 the rotation units 2 are not located inside one single frame. A further difference in FIG. 2 is that the cylinders 3 of the rotation units 2 may be of single-acting type, whereby pressurized fluid flow fed through one pressure medium duct 6 to a pressure space of the cylinder is enough to produce the first axial movement. The second axial movement in the opposite direction may be produced by means of a spring element, such as a mechanical spring or pressurized gas. Thus, the pressure medium cylinder 3 of the rotation unit may in some cases be a piston accumulator, too.

[0054] FIG. 3 is a schematic diagram showing basic features of producing stepped rotatory movements by means of the disclosed rotary actuator.

[0055] FIG. 4 shows a structure of an embodiment of the rotary actuator 1. The rotary actuator 1 comprises two rotation units 2a and 2b both provided with pressure medium cylinders 3a, 3b. A first cylinder 3a comprises a first piston assembly 10 composed of a piston ring 11 and a sleeve 12, and correspondingly, a second cylinder 3b comprises a second piston assembly 13 composed of a piston ring 14 and a sleeve 15. Alternatively, the piston assemblies 10 and 13 may be substituted by pistons having one-piece structures. Between the piston assemblies 10 and 13 is a spindle 16, which serves as a rotation transmitting element when the rotation units 2a and 2b are actuated. The spindle 16 is supported to be axially immovable. Between the first piston assembly 10 and the frame 5 are first converting means 4a and between spindle 16 and the second piston assembly 13 are second converting means 4b.

[0056] An outer surface of the sleeve 12 may comprise helical grooves or corresponding surfaces provided with pitch angles. The frame 5 may comprise a first mating element 17 arranged in contact with the helical groove and being supported immovably. The mating element 17 may be supported to the frame 5 by means of support elements 18a and 18b. Alternatively, the mating element 17 may be fastened directly to the frame 5. The mating element 17 may also comprise helical grooves matching the helical grooves of the sleeve 12, or alternatively, the mating element 17 may be a pin-like element arranged to be against the helical grooves of the sleeve 12. The first converting means 4a may then comprise at least one set of helical grooves or surfaces and at least one mating element or surface. Relative axial movement between the mating surfaces of the converting means 4a generates rotation.

[0057] An inner surface of the sleeve 12 may comprise axial splines 19 arranged to transmit rotation through axial splines 20 of the spindle 16. The axial splines 19 and 20 do not transmit axial forces, whereby they allow axial movement of the first piston assembly 10 relative to the spindle 16, which is supported to be axially immovable.

[0058] The second converting means 4b may comprise helical grooves, splines or surfaces on an outer surface of the sleeve 15 of the second piston assembly 13. The spindle 16 may comprise a second mating element 21 arranged in engagement with the helical grooves of the sleeve 15. The mating element 21 may transmit rotation movement generated in the first rotation unit 2a to the second piston assembly 3b. The second mating element 21 is arranged to be rotated with the spindle 16. The mating element 21 may be a separate piece mounted to the spindle 16 or alternatively it may be integrated to structural part of the spindle 16. Between the second piston assembly 13 and the output shaft 8 are rotation transmitting surfaces. An inner surface of the sleeve 15 may comprise axial spines 22 being in engagement with axial splines 23 of the output shaft 8. The axial spline 22, 23 allow the second piston assembly 13 to move axially relative to the output shaft 8, which is supported to the frame 5 axially immovably. In FIG. 4 the axial splines 19 and 20 serve as first rotation transmitting elements 7a, and the axial splines 22 and 23 serve as second rotation transmuting elements 7b.

[0059] Pressurized fluid may be fed through a pressure duct 6a to a first pressure space 24 of the first rotation unit 2a thereby causing the first piston assembly 10 to move m direction A towards the output shaft 8. Produced axial movement L1 is converted to angular displacement or stepped rotation of the first piston assembly 10 by means of the first converting means 4a. The rotary movement is transmitted through the first transmission means 7a to the spindle 16 and further from the spindle 16 via second converting means 4b to the second piston assembly 13, and finally through the second transmission means 7b to the output shaft 8. When only the first rotation unit 2a is actuated the second converting means 4b only transmit the rotation without any conversion because no relative axial movement occurs between the sleeve 15 and the second mating element 21. The first rotation unit 2a may be actuated to the opposite direction by discharging the fluid from the first pressure space 24 and directing pressurized fluid through duct 6b to a second pressure space 25. Then, the first piston assembly 10 moves in direction B and angular displacement in an opposite direction is generated for the output shaft 8. The second rotation unit 2b may be actuated by directing pressurized fluid through duct 6c into a third pressure space 26 causing the second piston assembly 3b to produce axial movement L2 in direction A. Stroke length of the second piston assembly 13 may be shorter than the one of the first piston assembly 3a. As can be seen in FIG. 4, the length of L2 may be half of L1. The produced axial movement L2 of the second piston assembly 13 is convened to rotation by means of the second converting means 4b and the generated rotation is transmitted via rotation transmission means 7b to the output shaft 8. The second piston assembly 13 may drive in direction 8 for producing angular displacement in the opposing direction. The solution disclosed in FIG. 4 has two cylinders 3a and 3b both of them having two extreme positions, whereby four different angular displacements may be produced. However, it is possible to combine three, four or even more rotation units and to utilize the disclosed structural principle of FIG. 4.

[0060] Further, in FIG. 4 the first piston or piston assembly 10 has a first diameter D1 and pressure surface area, and the second piston or piston assembly 13 has a second diameter D2 and pressure surface area. In FIG. 4 the diameters D1 and D2 are substantially equal as well as pressure surface areas. However, it is possible to dimension surface areas of the pistons to have different size. This may be needed when the converting means 4a and 4b have different converting ratios and there exists a need to compensate for torque produced by the rotation units 2a and 2b.

[0061] FIG. 5 discloses a rotary actuator 1 comprising a first rotation unit 2a and a second rotation unit 2b arranged parallel relative to each other. The parallel assembly of the rotation units may be useful when length of the rotary actuator needs to be limited.

[0062] FIG. 6 discloses a rotary actuator 1 comprising several rotation units 2a-2n arranged within each other. Thanks to this embodiment length of the actuator may be short.

[0063] FIG. 7 discloses a feasible rotary actuator 1 comprising a set of at least two rotation units arranged within each other and a set of at least two rotation units arranged one after each other. Thus, the solution of FIG. 7 may be a combination of constructional principles of solutions of FIGS. 1 and 6.

[0064] FIG. 8 is a schematic side view of a converting actuator capable to convert input rotary movement into pressure energy and vice versa. The basic structure, features and components of the converting actuator may correspond to any one of the above disclosed embodiments of the rotary actuator. Rotary movement and torque may be input to the output shaft 8 and may be transmitted through transmission means 7 to two or more rotation units 2a, 2b. Thus, the rotation units 2 may generate angular displacement Rg. The rotation units may convert the generated angular displacement Rg into axial movements Lg by means of converting arrangements 4. The rotation units 2 may comprise cylinders or other suitable pressure medium devices for producing linear movement, and on the other hand, for generating pressure Pg when the input rotation is arranged to cause linear movement in the pressure medium cylinder or corresponding device. The generated pressure Pg may be stored in e pressure accumulator connected to a pressure space of the cylinder. Further, it may be possible to substitute the cylinder of the rotation unit with a piston accumulator. In this solution the input rotary energy may be converted into pressure energy and may be converted back into rotary movement.

[0065] The drawings and the related description are only intended to illustrate the idea of the invention. In its details, the invention may vary within the scope of the claims.