The present invention relates to a pneumatic actuator according to the preamble of claim 1.
A number of fluid actuators without hydraulic or pneumatic cylinders are known explicitly or implicitly, for example from WO 03/074885 (D1) from the same applicant.
In D1, the actuator is constituted for example by a plate taking up compressive forces and a web of high-strength and low-expansion textile fabric provided laterally thereto. This web is fixed to the plate along several strips. Between the strips, bubbles of elastic material are inserted into the pocket between plate and web. A bending moment is exerted on the plate when compressed air is admitted to these bubbles and the plate is bent away laterally.
A drawback with this actuator is the fact that the compressive forces are taken up by a plate and it cannot therefore fall below a certain two-dimensional extension. In addition, it is especially suitable for the deformation of surfaces and for taking up line loads.
The problem of the present invention consists in providing actuators without pneumatic or hydraulic cylinders, which are suitable for the movement of fairly large point loads.
The solution to the problem is set out in the characterising part of claim 1 with regard to its main features and in the further claims with regard to supplementary advantageous developments.
With the aid of the appended drawings, the subject-matter of the invention is explained in greater detail using a number of examples of embodiment.
a, b show diagrammatic representations of a first example of embodiment of an activated pneumatic actuator in side view and view from below,
a, b show diagrammatic representations of a second example of embodiment of an activated pneumatic actuator in side view and view from below,
a, b show a diagrammatic representation of a fourth example of embodiment in an activated state in an isometric projection and view from below,
a, b show diagrammatic representations of a seventh example of embodiment in side view,
A first example of embodiment is shown diagrammatically in
The two tension elements 4 wind around hollow body 1 in a helical manner in an opposite sense of rotation each in a half turn with constant pitch. They meet one another at a fixing point 9 lying above hing 7. The two tension elements 4 are connected in a friction-locked manner to reference system 8 at this fixing point 9.
This example of embodiment corresponds structurally to a half pneumatic structural member, as is disclosed in WO 01/73245 (D2). Half of the pneumatic beam from D2 is turned through 180 degrees about the longitudinal axis and the middle of the element from D2 is connected to reference system 8. The load force in D2 corresponds in the actuator to the supporting force and the supporting force in D2 likewise corresponds in the reverse direction to the new load force at the free end of the actuator.
The following applies for γ=L/D:
For different γ, this produces for example the following angles β: γ=10→β=4.2° or γ=5→β=8.4°.
When hollow body 1 is pressurised with a hydraulic fluid, tension elements 4 are forced by expanding hollow body 1 out of the straight connecting line between fixing point 9 and node 3 into a helical shape and therefore pull node 3 out of the deactivated initial position into the activated position as in
a, b a second example of embodiment in side view and view from below. In contrast with the first example of embodiment, compression member 2 is designed as a flexible, flexurally elastic compression element. Such flexurally elastic compression elements have already been disclosed in document PCT/CH2004/00111 (D3). At the same time, compression member 2 must be clamped in reference system 8 by means of connection piece 10 in a friction-locked manner and not be mounted in a rotary fashion.
Load force F, acting at the free end of the actuator on node 3, must not be so great that flexible, flexurally elastic compression member 2 is buckled.
Common to the two aforementioned examples of embodiment is the fact that the maximum exertable actuator force is achieved with the maximum actuator regulating path, since the buckle-stabilising effect of hollow body 1 is also greater with increasing excess pressure in hollow body 1. This is in contrast with most other pneumatic actuators, such as pneumatic muscles for example, where the actuator force diminishes with increasing actuator regulating path.
The aforementioned examples of embodiment can also be operated with constant excess pressure in hollow body 1 and thus function as very lightweight cantilevers which have at the same time a very good bearing capacity. In this function, additional compression members 2 with accompanying pairs of tension elements 4 can be arranged around hollow body 1 in order to enable loading of the cantilevers in more than one transverse direction. At least three compression members 2 are required to take up forces from all transverse directions. In the case of use as an actuator, however, the number of compression members remains restricted to a single one.
Such a cantilever also has very good damping properties and can be used as a combined damping element, spring element and bearing-structure element in the case of load variations and fluctuations.
In a fourth example of embodiment in
a, b show a seventh example of embodiment of an actuator according to the invention for an application as a belt server, for example in a motor vehicle. The arched, non-activated, i.e. non-pressurised, actuator has a flexurally elastic compression member 2 on the inside of the arc. Belt 16 stretched by a roll-up device 15 pulls the inactive actuator into an arc shape. The assumption of this arc shape can be assisted by a suitably shaped reference system 8 serving as a stop. Hollow body 1 is wrapped around helically by at least one pair of tension elements 4 in each case pairwise in an opposite sense of rotation at least in one whole convolution. In contrast with the examples of embodiment shown above, tension elements 4 are laid in a whole turn or in a multiple of complete turns around hollow body 1 and are connected at both ends of the actuator to compression member 2. Nodes 3 respectively at both ends of compression member 2 can be present for the friction-locked connection of compression member 2 and tension elements 4. The connection of tension elements 4 to compression member 2 can be provided over the whole length of compression member 2, in order to enable favourable angles of application of tension elements 4 on compression member 2 during bending of the actuator. For this purpose, more than two nodes 3 fixed to compression member 2 can also be provided. Compression member 2 or a part of the actuator can be connected at a first end to reference system 8. This fixing is not absolutely essential. A reference system 8 formed as a stop may suffice to clamp the first end of the actuator during pressurisation between belt 16 and reference system 8. It is also feasible for a first end of hollow body 1 alone or together with the first end of compression member 2 to be connected in a friction-locked manner to references system 8. Belt 16 is connected to the actuator partially or over the whole length of the actuator. At least one connection is however present between belt 16 and the actuator at moved end 17 of the actuator. Many possibilities are known to the expert for such connections, e.g. they can be produced by means of brackets, a pocket or by gluing or sewing. When hollow body 1 is pressurised with compressed air, the actuator is moved and belt 16 is thereby extended forwards, after which belt 16 can conveniently be gripped by the occupant.
It is feasible, and in accordance with the invention, to use an actuator according to the first six examples of embodiment for the application as a belt server.
Number | Date | Country | Kind |
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1644/03 | Sep 2003 | CH | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CH04/00593 | 9/21/2004 | WO | 11/10/2006 |