WO2009155945A1

WO2009155945A1 - Fluidic device

Info

Publication number: WO2009155945A1
Application number: PCT/EP2008/005198
Authority: WO
Inventors: Gerald Müller; Albrecht Wagner
Original assignee: Festo Ag & Co. Kg
Priority date: 2008-06-26
Filing date: 2008-06-26
Publication date: 2009-12-30
Also published as: DE112008003894A5

Abstract

In a fluidic device, comprising a housing, which has at least one piston receiving element (13), in which the at least one piston (14) is supported in an axially displaceable manner, wherein sealing means (20) that enclose the piston (14) and provide a fluidic sealing effect are disposed between a circumferential side (18) of the piston (14) and the inside (19) of the piston receiving element (13) facing the circumferential side (18), the piston and/or the inside (19) of the piston receiving element (13) facing the piston (14) are provided with fibrous material in order to produce the sealing means (20).

Description

June 25, 2008

FESTO AG & Co. KG, Ruiter Strasse 82, 73734 Esslingen

Fluid technical device

The invention relates to a fluid power device, comprising a housing which has at least one piston receptacle in which at least one piston is mounted axially displaceable, wherein between a peripheral side of the piston and the inner side of the piston receiving side facing the circumferential side fluid-tight, sealing the piston enclosing sealant are arranged.

Such a fluidic device in the form of a valve device is known for example from EP 1 564 458, wherein here a valve spool is provided, which is associated with a sealing device having a plurality of elastomer sealing elements. The elastomer sealing elements each have an inner sealing area, which serves as a dynamic sealing edge for sealing against the valve spool.

The problem of elastomeric sealing elements with dynamic

Sealing edge is the friction between the sealing element and the associated movable component, in this case the

P 26695 / PCT 25 June 2008 Valve slide, is generated. Furthermore, during prolonged standstill of the valve slide, a so-called "stick-slip effect" occur, that is, elastomer sealing element and valve slide are connected by increased static friction with each other, which must be overcome first, so that the valve spool can set in motion only possible by a relation to the operating pressure increased fluid pressure.

The object of the invention is to provide a fluid power device of the type mentioned, which is reliable compared to conventional fluid power devices and less susceptible to wear.

This object is achieved by a fluid power device having the features of independent claim 1. Further developments of the invention are presented in the subclaims.

The fluidic device according to the invention is characterized in that the piston and / or the inner side of the piston receptacle facing the piston is provided with fiber material for forming the sealing means.

Compared to elastomer sealing elements occurs when using fiber material significantly less friction in the relative movement between the piston seat and piston. There-

P 26695 / PCT 25 June 2008 by the wear of such a fluid power device, in which is used to form the sealant fiber material, less than in conventional fluid power devices with elastomer sealing elements. In addition, the above-mentioned "stick-slip effect ^{w is} avoided because the fiber material does not lead to increased static friction between the relatively movable components of the fluid power device even with longer downtime.

Although a brush seal arrangement for a fluid power device in the form of a pump is already known from WO 03/036097 A1, the brush seal arrangement is used for sealing the annular gap between a rotating component in the form of a shaft and a stationary housing.

Obviously, it has previously been assumed that such arrangements are not suitable for linear arrangements due to the relatively uniform stresses in rotating applications in which due to oscillating movements high alternating stresses occur.

As already mentioned, the piston can be provided peripherally with fiber material. Alternatively, the inside of the piston receptacle facing the piston can be provided with fiber material.

P 26695 / PCT 25 June 2008 be. However, it is also a combination of fiber material exhibiting piston and fiber material exhibiting inside of the piston seat possible. In the case of a fibrous material piston, the fibrous material may extend substantially substantially the entire axial length of the piston. Preferably, however, only at least a portion of the piston is provided with fiber material in the axial direction. It is also possible to provide a plurality of partial regions of the piston arranged one behind the other in the axial direction at a distance from one another with fiber material.

As fiber material, natural and / or synthetic fibers can be used. In the case of synthetic fibers, these may be man-made fibers, in particular polymer fibers, or industrial fibers, for example glass fibers and / or carbon fibers and / or metal fibers.

Conveniently, the fiber material is formed by staple fibers. In a particularly preferred manner, the fiber material is formed by relatively movable fibers.

The fibers may each have a first end fixedly connected to the piston or the piston receptacle and a piston receptacle assigned to the piston or of the piston.

P 26695 / PCT 25 June 2008 Having benaufnähme associated piston aligned, free, second end. The fibers can thus be arranged like mats, for example, fibers from the piston in the radial direction, directed towards the piston receiving point, protrude.

In a development of the invention, the fiber material is formed by bristles. The bristles may be part of at least one brush element that is material or form-fitting connected to the piston and / or the piston receptacle.

In a further development of the invention, the fiber material is formed from flock fibers, with which the piston and / or the piston receptacle is flocked.

In order to support or realize an end position damping of a reciprocating piston between two end positions, it is possible to provide at least one end face, in particular both end faces, of the piston with fiber material.

In a development of the invention, the sealing means have sealing fluid which is incorporated in intermediate spaces between the fiber material. Conveniently, the sealing fluid has a relatively high viscosity, whereby it reliably holds in the interstices. By the addition of

P 26695 / PCT 25 June 2008 Sealing fluid can increase the fluid tightness of the sealant.

In a further development of the invention, the piston has at least one circumferentially extending guide band for guidance in the associated piston receptacle. As a result, lateral forces can be absorbed so that they do not have to be absorbed by the fiber material. As a result, the dimensioning of the fibers of the fiber material, for example, the choice of the appropriate fiber diameter or the fiber length, regardless of acting on the piston transverse forces can be made.

Preferably, the fluid power device is a fluidic linear drive. It can be used with at least one piston rod stocked or rodless linear drives. It is possible, for example, to use a pneumatic working cylinder, in particular, whose piston receptacle is subdivided by the piston into two working chambers, at least one of which can be acted upon by pressure medium, in particular compressed air, the working chambers being formed via the sealing material formed from fibrous material, optionally with addition sealing fluid, fluid-tight, in particular airtight sealed from each other.

P 26695 / PCT 25 June 2008 Alternatively, it is possible for the fluid-technical device to be a valve and for the piston to be formed by a valve piston designed in particular as a valve slide.

The piston receptacle can be formed directly by a housing recess formed in the housing, which is bounded by the housing wall, or by a component mounted fixedly in the housing, for example in the form of a seal arrangement in which the piston is movably mounted.

Preferred embodiments of the invention are illustrated in the drawings and will be explained in more detail below. In the drawing show:

FIG. 1 is a schematic illustration, shown in longitudinal section, of a first exemplary embodiment of the fluid power device according to the invention in the form of a fluidic working cylinder;

FIG. 2 is a schematic representation, shown in longitudinal section, of a second exemplary embodiment of the fluid power device according to the invention in the form of a valve; and

P 26695 / PCT 25 June 2008 Figure 3 is an enlarged view of the detail X of Figure 1, in which case the flock fibers are shown significantly enlarged.

1 shows a first exemplary embodiment of the fluidic device 11 according to the invention. According to the first exemplary embodiment, the fluidic device 11 is shown by way of example in the form of a fluidic working cylinder. The working cylinder has a cylinder housing 12 with a housing recess 13 in which a piston 14 is mounted so as to be axially displaceable. The working cylinder is exemplified in the form of a double-acting pneumatic cylinder, wherein the piston 14, the housing recess 13 into two working chambers 15a, 15b divided, each of which can be acted upon with compressed air. Depending on the application of one or the other working chamber 15a, 15b, the piston can be moved back and forth in the axial direction. The piston is also connected to a piston rod 16, which is guided out of the cylinder housing 12 via a housing cover 17. An interface (not shown) is located on the piston rod 16, via which the linear movement generated as a result of the compressed-air application of the piston 14 can be picked up. Between the peripheral side 18 of the piston 14 and the circumferential side 18 facing the inside 19 of the housing recess 13 limiting cylinder housing 12 are the piston

P 26695 / PCT 25 June 2008 14 enclosing sealing means 20 arranged. To form the sealing means, according to the first exemplary embodiment and a first variant, the peripheral side 18 of the piston 14 is flocked with fibrous material in the form of flock fibers. The flocking is of course arranged around the piston 14, in which case only a portion of the total length of the piston 14 is flocked in the axial direction. It is of course possible to flock a plurality of axially adjacent portions of the piston 14. In order to absorb transverse forces acting on the piston 14, the piston 14 can be provided on the circumference with a guide band 29 (dash-dotted representation). However, the use of a guide tape is not necessarily necessary.

Fibrous fibers are chemical fibers, in particular polymer fibers and / or industrial fibers, for example glass fibers and / or carbon fibers and / or metal fibers. To produce the flock fibers, continuous filaments of flock fiber material, for example metal, preferably steel, and / or polymer material, for example polyamide, are cut to the appropriate cutting lengths. The cut lengths of such flock fibers can range from 0.01 mm to 20 mm in length. Typical cutting lengths are in the range of 0.5 mm to 5 mm. The diameter of the flock fibers may be in the range of a few μ meters, for example 4 to 15 μ meters. The cut

P 26695 / PCT 25 June 2008 Lengths and fiber diameters of the flat fibers can vary within a wide range, in particular flocking is possible in which flock fibers of different cutting lengths and fiber diameter are combined with one another.

To apply the flock fibers, they are first charged in a flock emitter and then fly along the field lines of a strong electrostatic field in the direction of the peripheral side of the piston and / or inside of the piston receiver prepared with a binder, in particular flock adhesive. The flock fibers can be applied at any angle to the peripheral side of the piston 14, but preferably they are substantially perpendicular to the peripheral side 18. As flock adhesives are, for example, aqueous dispersion adhesive, in particular 2-component adhesive, for example polyurethane two-component -Glue . Alternatively, it is possible to use hot melt adhesive as the flock adhesive, in particular in the form of a thermoplastic or a hot-melt foil. The fibers are each adhesively bonded to the piston 14 with a first end 30, while the second end 31 is oriented towards the inside of the housing recess and is freely movable.

As shown in Figure 1, in addition to the flocking of the peripheral side of the piston 14 and at least one of

P 26695 / PCT 25 June 2008 End faces 21a, 21b of the piston 14, in the present case both end faces 21a, 21b, flocked with flock fibers. By flocking the piston 14 is damped when retracting into its respective end position, whereby a cushioning end or at least a support of realized by other means cushioning is realized.

FIG. 1 also shows the situation that the passage of the piston rod 16 is sealed by further sealing means 22. In this case, fiber material in the form of flock fibers is also used to form the further sealant.

In Figure 3, the flock fibers 23 are shown once more in an enlarged view. By means of suitable measures, the flock fibers can have an increased roughness on their outer side, whereby an additional surface is created, which contributes to the fluid-tight sealing of the two working chambers 15a, 15b. Between adjacent flock fibers 23 are intermediate spaces 24, which are at least partially filled by a sealing fluid 25. As sealing fluid is a liquid with high viscosity.

In the first embodiment shown in Figure 1, a second variant is further shown, in which the

P 26695 / PCT 25 June 2008 Fiber material of bristles 35 is formed. The bristles 35 are part of a plurality of brush elements 36, of which a single example is shown. As shown here by way of example, the brush elements have a base body 37 to which the individual bristles are attached. The base body in turn is positively connected, for example in a groove-like recess (not shown), attached to the piston 14. Of course, it is also possible to provide at least one of the end faces with a brush element for end cushioning. The sealing of the passage of the piston rod can be realized by brush elements.

FIG. 2 shows a second exemplary embodiment of the fluid power device 11 according to the invention. As a fluidic device 11, a valve is provided here, with a valve housing 26 in which a piston receptacle 13 is in the form of a sealing device mounted in a housing recess of the valve housing. Within the piston receiving a valve slide 27 is mounted axially displaceable, wherein the valve spool control sections 28a, 28b has small and large diameter. On the circumferential sides of the large-diameter control sections 28a, there are again sealing means 20, which are formed by fiber material in the form of flock fibers 23. Regarding further

P 26695 / PCT 25 June 2008 Details regarding the manufacture, application and properties of the flock fibers are referred to the foregoing description. Here, too, the use of bristles, in particular as a component of at least one brush element, is possible instead of flock fibers.

Since the formation of the sealant fiber material, optionally with the addition of sealing fluid 25, are used, the sealing means 20 are characterized in that compared to conventional sealant in the form of elastomer sealing elements substantially less friction between the relatively movable components, ie the Piston 14 and the piston receiving occurs. Furthermore, the so-called "stick-slip effect" is prevented, since even with prolonged downtime of the piston 14 and the valve spool 27 due to the formed of fiber material, in particular flock fibers or bristles sealant no increased static friction between the relatively moving components occurs.

P 26695 / PCT 25 June 2008

Claims

claims

1. Fluid technical device, comprising a housing (12, 26) having at least one piston receptacle (13) in which at least one piston (14) is mounted axially displaceable, wherein between a peripheral side (18) of the piston (14) and the the peripheral side (18) facing inside (19) of the piston seat (13) fluid-tight, the piston (14) enclosing sealing means (20) are arranged, characterized in that the piston (14) and / or the piston (14) facing Inner side (19) of the piston receptacle (13) for forming the sealing means (22) is provided with fiber material.

2. Fluidtechnisches device according to claim 1, characterized in that are provided as fiber material natural and / or synthetic fibers.

3. fluid power device according to claim 2, characterized in that are provided as synthetic fibers man-made fibers, in particular polymer fibers.

P 26695 / PCT 25 June 2008

4. Fluid technical device according to claim 1 or 2, characterized in that industrial fibers, for example glass fibers and / or carbon fibers and / or metal fibers are provided as synthetic fibers.

5. fluid power device according to one of the preceding claims, characterized in that the fiber material is formed by relatively movable fibers.

6. fluid power device according to claim 5, characterized in that the fibers each have a fixedly connected to the piston or the piston receiving the first end and in the direction of the piston associated with the piston seat or the piston receiving the piston associated free, second end.

7. Fluid technical device according to one of the preceding claims, characterized in that the fiber material of

Bristles is formed.

8. Fluidtechnisches device according to claim 7, characterized in that the bristles are part of at least one brush element, which is material or positively connected to the KoI ben and / or the piston receiving.

P 26695 / PCT 25 June 2008

9. Fluidtechnisches device according to any one of the preceding claims, characterized in that the fiber material of flock fibers (23) is formed, with which the piston and / or the piston receptacle is flocked.

10. Fluid technical device according to one of the preceding claims, characterized in that the piston (14) is additionally provided on at least one end face (21a, 21b) with fiber material.

11. Fluid technical device according to one of the preceding claims, characterized in that the sealing means (22)

Sealing fluid (25) which is incorporated in between the fiber material (23) located intermediate spaces (24).

12. Fluid technical device according to one of the preceding claims, characterized in that the piston (14) at least one circumferentially extending guide band (29) for guiding in the associated piston receptacle (13).

13. Fluid power device according to one of the preceding claims, characterized in that it is the fluid-technical device is a fluidic linear drive.

14. Fluidtechnisches device according to claim 13, characterized in that as a linear drive a particular pneumatic

P 26695 / PCT 25 June 2008 scher working cylinder is provided, whose piston receptacle (13) by the piston (14) in two working chambers (15a, 15b) is divided, of which at least one with pressure medium, in particular compressed air can be acted upon, wherein the working chambers (15a, 15b) via made of fiber material

Sealant (22) fluid-tight, in particular airtight sealed from each other.

15. Fluid technical device according to one of the preceding claims, characterized in that it is in the fluid-technical device is a valve and the piston is formed by a slide-like valve piston, in particular valve spool (27).

P 26695 / PCT 25 June 2008