EP2128455A1 - Pneumatic actuator - Google Patents

Abstract

The pneumatic actuator (1) has a bendable compression unit (10) and a bendable tension unit (13), which cooperates at a spaced printing body (18) in a longitudinal manner for operation. The compression unit and the tension unit are connected with each other in a node (15) at a movable end (3) of the actuator.

Description

The present invention relates to a pneumatic actuator according to the preamble of claim 1.

Pneumatic actuators of the type mentioned have the advantage that they can generate comparatively large force in relation to their weight or can be operated with a large working distance. In other words, with proper interpretation, they have eg. favorable overall characteristics with regard to the parameters of weight, manpower and working distance.

The low weight is a consequence of the usable materials, since the pressure body from a fluid-tight membrane, z.Bsp. can consist of a tissue; Compression and tension members may consist of plastics such as GRP etc or of metal, but in one way or another have a comparatively low mass.

Pneumatic actuators can also be used in a variety of sizes for a variety of purposes, once z.Bsp. as a gripper, whether in the laboratory or in industrial production, or as an architectural element, z.Bsp. for extending a sunroof.

The operating pressure is generated by a fluid, usually a gaseous, but may also be a liquid such as water, when the compressibility of the gas is undesirable.

The EP 1 664 552 shows a pneumatic actuator of the type described above, which is used as a cantilever. A disadvantage of this concept is that the working path is not linear in dependence on the operating pressure, so that a control of the working path on the pressure can be implemented only with difficulty; Furthermore Nachtellig is that when using a non-rigid pressure member in the pressure-relieved state of the pressure hull, but under load attack of the actuator, a state can be reached, which is unstable, and when exceeded, puts the actuator in a dysfunctional state in which it is no longer functional.

The latter is the case when the actuator is deflected by the load attack so far that the tension members no longer attack from the original side of the pressure member by the excessive curvature of the pressure member. Although this can be counteracted by a stiffening of the pressure member, but this is undesirable in view of the working path of the actuator or the resulting design effort, and this is only an increase in mass, depending on the intended use of the actuator.

Accordingly, it is the object of the present invention to provide an improved pneumatic actuator.

The invention is explained below with reference to the figures.

• Fig. 1 schematisch eine Ansicht eines erfindungsgemässen Aktors,
• Fig. 2 eine bevorzugte Ausführungsform des erfindungsgemässen Aktors im Längsschnitt,
• Fig. 3a und 3b schematisch den Verformungsmechanismus des Aktors von Fig. 2
• Fig. 4a bis 4d die Verformung des Aktors von Fig. 2 während dem Anheben (oder Absetzen) einer Last
• Fig. 5a und 5b einen Längsschnitt durch den Aktor von Fig. 2 unter Last, der zusätzlich einen Verdrängungskörper aufweist.

It shows:

• Fig. 1 1 is a schematic view of an actuator according to the invention;
• Fig. 2 a preferred embodiment of the inventive actuator in longitudinal section,
• Fig. 3a and 3b schematically the deformation mechanism of the actuator of Fig. 2
• Fig. 4a to 4d the deformation of the actuator of Fig. 2 while lifting (or stopping) a load
• Fig. 5a and 5b a longitudinal section through the actuator of Fig. 2 under load, which additionally has a displacement body.

Fig. 1 shows the inventive actuator 1 in a view from the outside, obliquely from the front. It can be seen a supported end 2 (in the view "back") and a relative to the supported end 2 to be moved end 3 (lying in the view "front"). At the end 3 to be moved, a load in the form of a weight 5 is attached, for example via a cable 4. The actuator is able to lift the weight 5 in the direction of the double arrow 6, ie upwards and lower it down.

A bendable pressure member 10 is connected via a support 11 with (for the purpose of the present illustration) a wall 12, as well as a bendable tension member 13 via a corresponding support 14. The pressure member 10 and the tension member 13 are at the end 3 to be moved of the actuator 1 with each other connected in a node 15, but separated from each other at the supported end 2.

Further, the pressure member 10 and the tension member 13 between them include a distance pressure body 18 which is pneumatically regulated and extends from the supported end portion 19 to the end portion 20 of the actuator 1 to be moved. The distance pressure body 18 is elongated and responds to changes in pressure with a change in its thickness, so that a pressure change causes a relative movement of the pressure member 10 and tension member 13, wherein this relative movement takes place in the plane defined by the pressure member 10 and tension member 13. The pressure body 18 acts as a variable spacer element between the pressure member 10 and the tension member 13.

The distance pressure body 18 does not necessarily extend exactly from the supports 11,14 to exactly the node 15; However, it extends from the supported end region 19 to the end region 20 to be moved. In other words, it is somewhat longer or somewhat shorter to conceive, which the person skilled in the art can do in a suitable manner without difficulty.

The node 15 connects the pressure member 10 and the tension member 13 firmly together, be it in the form of a screw, a welding point, a splice or other connection such. a hinge. Here too In the specific case, the expert will determine a suitable connection, in particular with regard to the materials used and the necessary mechanical properties of the node 15.

The supports 11 and 14 symbolize a fixed clamping or articulation of the pressure member 10 and the tension member 13 on the wall 12; In addition, it is possible to firmly clamp one of the members 10, 13 and to articulate the respective other member 13, 10. Again, the skilled person can determine the appropriate form of attachment of pressure member 10 and tension member 13 in the specific case.

The tension member 13 can be used as a rope or, for example, as a flexible rod 30 (FIG. FIG. 2 ) be formed; conceivable is a plastic rope, a wire rope, a rod or strip of metal, for example made of spring steel (with elastic properties), or plastic or other configurations. Essential is its tensile strength, which must meet the requirements of the operation of the actuator, and the blegeweiche design that allows to perform during the operation of the actuator 1 necessary, described in more detail below movement.

The pressure member 10 must be able to absorb pressure and thus have a certain resistance to buckling. In operation, it is supported to some extent by the distance pressure body 18 against kinking. Also conceivable here is a rod or strip of metal or plastic, or another configuration of suitable material.

As mentioned above, the skilled person can design the pressure member 10 and the tension member 13 in a concrete case in terms of configuration, material and dimensioning suitable.

The distance pressure body 18 is pneumatically adjustable, so a pneumatic element, which by a fluid such. Water or a gas can be applied and thus pressurized. It consists for example of a substantially strain-resistant fabric (coated textile or film, as z.Bsp. a tent maker used) is the fluid-tight, or of a stretch-resistant shell, in which a fluid-tight bladder is inserted. In principle, it can not be ruled out that the distance pressure body 18 consists of a stretchable material that expands under pressure. To relieve the figure, a pressure source for the fluid and a supply line to the distance pressure body 18 is omitted; these are conventional and readily provided by the skilled person.

Since the distance pressure body 18, which is under operating pressure, presses the pressure member 10 and the tension member 13 away from one another, it bulges laterally slightly above it, as shown in FIG FIG. 1 is represented by the lines 21, which illustrate the curvature of the distance pressure body 18. In other words, it is such that under load, the pressure member 10 and the tension member 13 cut into the distance pressure body something. The pressure member 10 or the tension member 13 can also be arranged on the inside of the distance pressure body 18 and then run, for example, in pockets 35, 36 (FIG. FIG. 2 ), which are sewn on the inside, so that the distance pressure body 18 transmit the forces originating from the fluid pressure ago on the pressure member 10 and tension member 13, that can cooperate with these operatively. Again, the particular training in a specific case is the expert.

Imagine the arrangement of Fig. 1 initially without distance pressure body 18 and loaded by only a small weight 5, so that the buckling stiffness of the bendable pressure member 10 is not exceeded, results in a simple and rigid suspension for the weight 5. Enlarged mentally, the weight 5 continues, the pressure member 10 buckle, whereupon the structure collapses (the tension member 13 is always sufficient tensile strength dimensioned).

If you add now thoughtfully the distance pressure body 18, the pressure member is supported by this and kinking only at significantly increased weight 5. If the pressure member 10 advantageously at the distance pressure body 18 fixed (by eg, as mentioned above, in a pocket), it is also against bending outwards, away from the distance pressure body 18, secured. The higher the pressure is in the distance pressure body 18, the higher the weight can be 5 until a buckling of the pressure member 10 takes place.

Conversely, this means that by reducing pressure, an earlier buckling or by controlled pressure, a controlled buckling takes place. With suitable dimensioning and choice of material for the pressure member 10, the buckling does not lead to failure, such as. a fracture (which may occur in an extreme case) but a curvature 41 ( FIG. 3a ), what the desired and based on the Figures 3 and 4 described deformation of the pressure member 10, and thus also of the tension member 13, thus the actuator 1 leads.

Fig. 2 shows a longitudinal section through the inventive actuator 30 in a preferred embodiment with a rod-shaped pressure member 31 and a rod-shaped tension member 32 which are firmly connected together in a node 33 and articulated on the supports 11,14 on a wall 12. Compression member 31 and tension member 32 are the same length, particularly preferably the same, flat, for example, rectangular cross-section and of the same, elastic material, and lie with the flat side on the distance pressure body 18. In such a cross section and in this position of tension member 31 and pressure member 32, a movement perpendicular to the surface of the longitudinal section is difficult and thus improves the guidance of the movement during the operation of the actuator 30. Shown are further longitudinal pockets 35,36 which extend on the inner wall of the Distanzdruckkörpers 18 and the tension member 13 and the pressure member 10 receive operable. End walls 37, 38 delimit the distance pressure body 18, which here is essentially designed as a cone with the node 33 facing the tip; he takes under maximum operating pressure in each case the predetermined by the section of the fabric shape.

Fig. 3a and 3b show two stages of the operational movement of the actuator 30, wherein the distance pressure body 18 and the weight 5 are omitted to relieve the figures. The weight is in FIG. 3a further raised (or less lowered) than in FIG. 3b ,

It is shown how the pressure member 31 bulges into the tension member 32 from the end 3 to be moved, since it is under pressure under the weight of the load and presses against the top, until it abuts the tensioned tension member 32 and contacts it. in accordance with the pressure prevailing in the distance pressure body 18 current operating pressure - located in equilibrium position. Is the operating pressure higher than that of Fig. 3a lowered even further, the marked by the dotted line 40 camber 41 of the pressure member 10 moves in the direction of the arrow 42 against the rear end 2 ( FIG. 1 ), until, as it were, it abuts the support 11, whereupon the maximum deflection of the actuator 30 is reached. An increase in the operating pressure causes the reverse movement, until the FIG. 2 corresponding elongated shape is reached. Figuratively speaking, the pressure member 32 and thus the actuator 30 rolls when lowering and when erecting. The load is lowered or lifted.

As mentioned, resulting from the flat rectangular shape of at least the pressure member 10, but also the tension member 13, a stiffening against bending perpendicular to the plane of the longitudinal section or in a different direction than in the plane defined by the members 10,13 level, which prevents in that the links 10, 13 can escape laterally and thus lead to a clean movement sequence of the actuator 30.

Preferably, one or both of the members 10, 13 are slightly pre-bent, ie slightly curved at rest. The direction of curvature corresponds to that of the curvature 41. This has a favorable effect on the rolling behavior of the actuator 30 or on how the pressure member 10 bulges during the movement of the actuator 30 into the tension member 13, so that the curvature 41 can arise and migrate. This beneficial effect is supported by an articulation of one or both members 10,13 on the supports 11,14. In addition, such a pre-curvature of the pressure member 31 in the case of a movement of the actuator 30 out of the extended state supports the intended bending into the distance-pressure body 18.

The FIGS. 4a to 4d show the complete movement of the actuator 30 from its maximum deflection in Fig. 4a to the stretched position in FIG. 4d in which the weight 5 is fully raised. In Fig. 4a is the bend 41 (line 40) far back, but does not necessarily abut the rear end of the distance pressure body 18, as it down to Fig. 5a and 5b is described.

The fact that the distance pressure body 18 is not or only minimally under pressure, resulting in the Fig. 4a illustrated deformation. If the pressure is increased, this pushes the members 10, 13 away from each other via the sheath of the distance pressure body 18, so that the bulge 41 moves forward and the weight 5 rises, s. Fig. 4b , An even further pressure increase leads to the still further increased weight 5, s. Fig. 4c and finally to the maximum raised weight 5 according to Fig. 4d , Surprisingly, at still comparatively moderate pressures, ie pressures that are easily endured by the usual fabrics of the type mentioned above, the front end 3 (FIG. FIG. 1 ) almost completely straight.

In other words, the actuator 1,30 according to the invention can be better controlled by the pressure than the one mentioned at the outset Actuator of the prior art, with which a movement similar to the rolling motion can not be performed.

The conical shape of the distance pressure body 18 also results in a reduced working volume, with the result that over the entire working path less fluid must be introduced into this, which corresponds to an improved efficiency over the pneumatic actuator of the prior art. The efficiency is understood here as the ratio of the compression work for the fluid to be introduced to the work done when lifting the weight 5.

The arrangement shown also leads to an unstable state of the actuator is not possible per se; a lowering movement is stopped as soon as the curvature 41 reaches the rear support 11. As long as the pressure member 31 does not fail, a re-erecting of the actuator 1,30 is basically possible by the pressure increase.

The above-described rolling movement of the actuator 1, 30 is in an embodiment of the actuator 30, as in FIG. 2 is described, particularly gleichmässlg and thus cheap. However, it is also possible in one of the other configurations, as exemplified by FIG. 1 are mentioned.

Since the diameter of the distance pressure body at the supported end portion 19 is greater than at the end portion 20 to be moved, there is a larger, between pressure member 10,31 and tension member 13,32 acting, this apart pushing force, with the result that one on to be moved End 3 beginning rolling motion while lowering is supported. Conversely, during lifting, the straightening of the bent actuator 1, 30 from the supported end 2 is also supported.

FIG. 5a shows an inventive actuator 40 in the lowered state, in the distance pressure body 18 a in the longitudinal section of FIG. 5b shown displacement body 41 is inserted. The tensile and the pressure member are omitted to relieve the figures. The displacement body 41 occupies that volume, which remains unchanged or little changed in each operating state according to the design provided in the specific case. It is designed either as a rigid body or as a pneumatic body and causes no fluid to be supplied to the pressure body 18 when the spacer pressure body 18 is inflated for the volume occupied by the displacement body, which correspondingly improves the efficiency of the actuator 40.

Correspondingly, a displacement body 41 designed as a pneumatic body should have a constant pressure in a preferred embodiment, which is at least equal to the maximum operating pressure of the actuator 40, so that he does not lose some of the volume under the maximum operating pressure, which would still improve the efficiency, but not in the extent possible.

FIG. 5 shows a displacement body 41 in the maximum possible size. In the illustrated configuration, he additionally supports the pressure member 10,31 against kinking, so that at its end 43, a transition point results, where this effect is eliminated, which may be detrimental to the controlled deflection of the pressure member 10,31. The skilled person will therefore form the shape of the end 43 in a concrete case such that a disadvantageous effect does not occur.

In other words, the displacement body 41 used in a pneumatic actuator is such that, arranged in the predetermined alternating fluid-pressurized pressure chamber with correspondingly changing pressure and thus changing contour, dimensions that are smaller than or equal to ever the smallest corresponding dimensions of the predetermined changing Contour. Then, on the one hand, there is no collision with the pressure chamber and, on the other hand, it is possible to equip the displacement body 41 with the greatest possible volume.

Further, it is possible to provide a plurality of displacement body, which are used in the actuator and can move the movement accordingly against each other, so z.Bsp. by a filling of the pneumatic actuator with comparatively small, spherical displacement bodies, which can occupy a substantial part of its minimum volume.

In another embodiment, not shown in the figures, the tension member is formed as part of the distance pressure body by the compressive element opposite generatrix portion of the distance pressure body tensile strength formed and connected to the node and the corresponding Auflagerbereich such that it occurs during operation of the actuator Traction forces can take over.

As mentioned above, the tension member consists of a rope or a flexible elastic rod; but it can also be done in a different configuration. It is essential that it is e.g. when the width is large, there is a symmetry to the plane of the central longitudinal section, so that the tension member is displaced by the distance pressure body with its axis of symmetry in this plane relative to the pressure member.

The deflected actuator can work during the displacement in the extended state and must always be returned to the deflected state by external load or external spring pressure. In a further embodiment of the present invention, the elastic pressure member is pre-curved in such a way that, with the minimum operating pressure in the pressure-distance body, it moves the actuator into the deflected position (see FIG. Fig. 4a and 5a ) (if the tension member 13 is not formed as a rope, this is also preferably in the same way pre-curved). At maximum operating pressure, it is then prestressed in a straight position, so that it brings the actuator back into the deflected state when the pressure is relieved.

The actuator according to the invention has been described above using the example of "lifting a weight". Its application is not limited to this, but given everywhere where work can be performed by the relative movement between the supported end and the end to be moved.

Claims (15)

Pneumatic actuator having a supported end (2) and an end (3) to be moved relative thereto, and having a pneumatically adjustable distance pressure body (18) extending from the supported end region (19) to the end region (20) to be moved, acting as a variable spacer element characterized by a bendable pressure member (10,31) and by a bendable tension member (13,32) which extend along the distance pressure body (18) and cooperate with this operatively, wherein the pressure member (10) and the tension member (13) on moving end (3) of the actuator in a node (15) connected to each other, but at the supported end (2) are separated from each other and include the distance pressure body (18) between them so that this under pressure change a relative movement of pressure member (10) and Tension member (13) causes in the direction of the plane spanned by them. Actuator according to claim 1, wherein the tension member (13,32) is designed as a flexible, preferably elastically bendable tension rod. Actuator according to claim 1 or 2, wherein the pressure member (10,31) as a preferably elastically bendable pressure rod, which is particularly preferably made of spring steel is formed. Actuator according to claim 2 or 3, wherein the pressure member (10,31) is elastically bendable and curved, such that the actuator deflects at pressure-relieved distance pressure body (18). Actuator according to one of claims 1 to 4, wherein the pressure member (10,31) bendable in the plane spanned, and is formed rigid in another direction. Actuator according to one of the preceding claims, wherein the tension member (13,32) and the pressure member (10,31) have the same length. Actuator according to claim 4, wherein tension member (13,32) and pressure member (10,31) are formed as blegbare rods. Actuator according to one of claims 1 to 7, wherein the distance pressure body (18) has a flexible, under maximum operating pressure predetermined shape engaging shell. Actuator according to claim 8, wherein the predetermined shape substantially corresponds to a cone whose tip is facing the node (15,33). Actuator according to one of the preceding claims, wherein in the distance pressure body (18) a preferably formed as a pneumatic body displacement body (41) is arranged. Actuator according to claim 10, wherein a plurality of displacement bodies are provided, which are arranged in the distance pressure body (18) against each other displaceable. Actuator according to claim 10, wherein the displacement body (41) is formed as a pneumatic body, with an operating pressure which is equal to or higher than the maximum operating pressure of the Distanzdruckkörpers. Actuator according to claim 9, wherein the distance pressure body (18) at least on the pressure member (10,31) opposite generatrix region is formed tensile strength, such that this region forms the tension member (13,32). Pneumatic actuator having a fluidbeaufschlagbaren pressure chamber which is fed during operation with predetermined alternating pressure and thereby assumes a predetermined changing contour, characterized by a pressure chamber arranged in the displacement body whose dimensions are smaller or equal than ever the smallest corresponding dimensions of the predetermined changing contour , Pneumatic actuator according to one of claims 1 to 13 with a displacement body according to claim 14.

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