EP3164610B1 - Piston and a positioner fitted with the piston - Google Patents

Description

The invention relates to a piston for a fluid operable adjusting device, in particular for a fluid-actuated linear actuator having a one-piece piston body in the region of its radial outer circumference coaxial to the longitudinal axis of the piston annular receiving groove with two mutually facing side groove flanks, in the one for position detection usable permanent magnet assembly is received, wherein the permanent magnet assembly consists of a bent into a ring structure elastic permanent magnetic magnetic tape. The invention further relates to a fluid operable adjusting device, which is in particular a fluid-operated linear drive and which is provided with a housing in which a piston is arranged linearly displaceable.

An equipped with a piston of the aforementioned type actuator is known from DE 20 2005 005 508 U1 known and is designed for example as a linear drive or shock absorber. During operation of the actuator, the piston moves relative to a housing of the actuator, wherein the integrated into the piston permanent magnet assembly is available to allow by cooperating with external position detection means, a position detection of the piston. In order to produce the piston inexpensively, it contains a one-piece piston body with a peripheral receiving groove into which the permanent magnet assembly is inserted. The latter consists of several arcuate Magnetic segments, which are used in the assembly of the piston from radially outside into the receiving groove. However, the production and assembly of the magnet segments is relatively expensive.

The in the above DE 20 2005 005 508 U1 described piston is additionally equipped with a ring structure having a guide band, which is inserted into a formed on the outer circumference of the piston body annular retaining recess. The guide band is formed as a hollow cylindrical guide ring, which is interrupted at one point of its circumference, so that it can be temporarily expanded due to its elasticity during assembly. The radially outer surface of the guide band defines a guide surface which slidably engages the inner peripheral surface of the housing housing the piston so that the piston can perform a precisely guided linear movement relative to the housing.

From the DE 19715858 A1 a piston for a working cylinder is known, which is equipped for position detection with an annular permanent magnet. In order to allow the mounting of this ring magnet, a multi-part construction of the piston body is provided. The piston body consists of two mutually attached to form the receiving groove piston elements which are coated in the region of the receiving groove with an elastomeric material to clamp the permanent magnet and to fix it in a gentle manner.

The EP 0 307 569 A2 describes a piston-cylinder unit whose piston has a one-piece piston body, on the peripherally a broken at one point of its circumference guide belt is placed. The guide band has elastic properties and is in one on the outer circumference the piston body formed annular groove spring-like snapped. In order to enable a position detection of the piston, the piston body has at a position of its outer periphery via a recess in which a permanent magnet piece is inserted, which is covered by the guide band.

From the US 3639868 a fluid operable adjusting device is known which has a piston with a one-piece piston body, wherein in the piston body in the region of its radial outer circumference an annular receiving groove is formed, in which an annular permanent magnet is received.

The invention has for its object to provide measures that allow a cost-effective equipment of a piston with a usable for position detection permanent magnet assembly.

To solve this problem is provided in a piston of the type mentioned that the magnetic tape has two in the circumferential direction of the receiving groove facing Bandendabschnitte and whose width is less than the distance between the two groove flanks of the receiving groove, each of the two Bandendabschnitte by clamping in one of two in the circumferential direction of the receiving groove adjacent clamping zones of the receiving groove is held, in which the piston body has at least one under local narrowing of the receiving groove with respect to a groove flanks projecting and pressing on the side surface of the magnetic tape clamping projection.

The invention is further achieved in an operable with fluid actuator of the type mentioned in that it is equipped with a trained in the aforementioned sense piston.

In this way, can be a cost-producible one-piece piston body very easy with an example equip the position detection usable permanent magnet assembly. As a permanent magnet arrangement, an elastically bendable, over permanent magnetic properties possessing magnetic tape is used, which is placed around the piston body for mounting on the piston body and thereby inserted into the receiving groove. The magnetic tape is positioned so that its two mutually facing Bandendabschnitte come to rest in a clamping region of the piston body, in which the receiving groove has two adjacent clamping zones in the circumferential direction of the receiving groove. Each of the two band end sections is placed in one of the two clamping zones. Each clamping zone is characterized in that at least one of the two groove flanks of the receiving groove is provided with a clamping projection which projects beyond the associated groove flank. In this way, the width of the receiving groove in the region of each clamping projection is less than the clear distance between the two mutually facing groove flanks, which is greater than the width of the magnetic tape. Consequently, the magnetic tape can be easily inserted into the receiving groove by lying around or bending around the piston body in the areas outside of the clamping area, while the two Bandendabschnitte are pushed into the receiving groove with slight pressure during insertion into the respective associated clamping zone. By the at least one located in the clamping zone clamping projection, the magnetic tape is applied laterally and clamped in the receiving groove. If the magnetic tape is fixed in this way in the receiving groove, the band end sections can no longer be unfolded, so that the piston can then be easily inserted into the housing of an associated adjusting device. It is not necessary to hold the magnetic tape by hand or by means of a mounting device until the piston into the housing of a Actuator is introduced. Further advantages of the embodiment according to the invention are that the relevant components can be inexpensively manufactured by chipless shaping if desired. Through a targeted shaping tolerance compensation can also be created over a wide tolerance range, which ensures a secure holding the magnetic tape in the receiving groove. Since the mounting of the magnetic tape is very simple, the necessary assembly steps can also be automated if necessary, which further reduces the manufacturing cost of the piston.

Advantageous developments of the invention will become apparent from the dependent claims.

Preferably, in each clamping zone of the receiving groove, the piston body is equipped with a plurality of clamping projections acting on the respectively assigned band end section.

An embodiment is possible in which at least one pair of clamping projections in the axial direction of the piston is directly opposite each clamping zone. In this way, the associated Bandendabschnitt is clamped between directly opposite clamping projections. However, since such a measure has a relatively high degree of tolerance with regard to the safety of clamping, it is considered more advantageous if the piston body has clamping openings in each clamping zone of the receiving groove over a plurality of clamping projections arranged at a distance from each other in the circumferential direction of the receiving groove. Per clamping zone so several, in the circumferential direction of the receiving groove spaced from each other arranged clamping projections are present.

Particularly advantageous is an embodiment is considered in which in each clamping zone at least two and in particular exactly two in the circumferential direction of the receiving groove at a distance adjacent to each other arranged clamping projections are provided, which are assigned to different groove flanks. Thus, if a first clamping projection is arranged on one groove flank, the clamping projection spaced in the circumferential direction of the receiving groove in this respect is located on the opposite groove flank. It is very advantageous if none of these clamping projections opposite to the respective other groove edge associated clamping projection. In the region of each clamping projection, therefore, the assigned band end section is respectively clamped between on the one hand one of the clamping projections and on the other hand the opposite groove flank. The alternate arrangement of the clamping projections on the two groove flanks has the consequence that the band end portion quasi swings through the clamping zone or has a slightly wavy longitudinal course. Such a design of the clamping zone is extremely insensitive to tolerances and ensures a secure clamping each Bandendabschnittes even with a large tolerance range, which can make the production costs very low.

It has proven to be advantageous if, in the respective clamping zone, the projected clear distance, measured in the longitudinal direction of the piston, between the two projections which are spaced apart in the circumferential direction of the receiving groove is smaller than the width of the magnetic tape. Nevertheless, since the clamping projections are spaced from one another, the band end section can be relatively easily threaded or pushed into the receiving groove from radially outward.

Preferably, the clear distance between each clamping projection and the opposite groove flank of the receiving groove is equal to or greater than the width of the magnetic tape.

Furthermore, it has proved to be advantageous if in each clamping zone the distance measured in the circumferential direction of the receiving groove between the clamping projections arranged on different groove flanks is at least as large as the width of the magnetic tape, but at most twice the width of the magnetic tape. In this way one obtains a particularly reliable clamping effect.

The clamping projections can be designed arbitrarily and can be structured, for example, knob-shaped. It is considered particularly expedient if the clamping projections are each formed rib-shaped with an elongated shape and each extending starting from the region of the groove base in the direction of the radial groove opening of the receiving groove.

It is also advantageous if the clamping projections are chamfered at their end facing the radial groove opening end to the associated groove flank. In this way, the clamped Bandendabschnitt can very comfortably push into the receiving groove.

For the magnetic tape, a cost-producible rectangular cross section is recommended. The magnetic strip is preferably a strand body bent to the desired ring shape, the two strip end sections of which either rest loosely against one another or are arranged at a small distance from one another.

Preferably, the magnetic tape consists of a strand-shaped band body made of an elastically deformable plastic material, which is provided with permanent magnet means. The permanent magnet means are preferably ferromagnetic particles which are integrated in the band body and magnetized as required.

The one-piece piston body is preferably made of a rigid material. This then applies correspondingly for the one-piece component of the piston body performing clamping projections. For example, the piston body made of metal, ceramic, glass or a hard plastic material.

It is advantageous if the piston body not only has a single clamping area provided with two adjacent clamping zones, but has two such clamping areas which are assigned to diametrically opposite peripheral areas of the piston body. In this way, there is a greater variability in the insertion of the magnetic tape in the receiving groove.

It is advantageous if, in addition to the magnetic tape, the piston is equipped with a guide strip suitable for the linear guidance of the piston in a housing of an actuating device. The guide band is like the magnetic tape arranged coaxially to the piston body.

The guide band is expediently located in an annular holding recess formed in the piston body, which concentrically encloses the annular receiving groove and which has a greater axial width than the receiving groove. In this way, the receiving groove opens with its radially outer groove opening in the recess bottom of the holding recess. A mounted in the retaining recess, annular structured guide tape encloses the magnetic tape radially outside and covers the magnetic tape expediently.

The guide band is particularly easy to mount on the piston body when it is inserted into a coaxial to the longitudinal axis of the piston annular retaining recess and is thereby held in the radial direction with respect to the longitudinal axis of the piston positively in the retaining recess. Although the guide band has a ring structure in the assembled state, but overall is a finite, over two opposite Bandendabschnitte disposal strand body, which can be put around the piston body for mounting in the retaining recess simply. The two mutually facing recess flanks of the holding recess have in cross-section each an undercut profiling, wherein they each have a radial distance from the recess bottom of the retaining recess in the direction of the opposite recess flank projecting annular retaining projection. The two holding projections are able to engage in a form-fitting manner with the facing side edge of the guide strip pressed into the holding recess and thereby hold the guide strip in a form-fitting manner in the radial direction of the piston.

Particularly useful is an embodiment in which the guide band has elastically deformable properties, so that the holding projections can press under local deformation of the guide band and to form a positive engagement in the respective associated side edge of the guide band. In the unassembled state, the guide band expediently has a rectangular cross-section.

Alternatively, it is also possible to design the side edges of the guide strip with an engagement structure such that the guide strip can be latched or clipped into the holding recess.

Figur 1

einen Längsschnitt durch eine bevorzugte Ausführungsform der erfindungsgemäßen Stellvorrichtung, die mit einer ebenfalls vorteilhaften Ausführungsform des erfindungsgemäßen Kolbens bestückt ist,

Figur 2

den in Figur 1 strichpunktiert umrahmten Ausschnitt II des Kolbens in einer vergrößerten Darstellung, wobei die Schnittebene den in den Figuren 4 und 5 eingezeichneten Schnittlinien II-II entspricht,

Figur 3

einen Querschnitt durch den Kolben gemäß Schnittlinie III-III aus Figur 1, wobei die übrigen Bestandteile der Stellvorrichtung nicht abgebildet sind und wobei sowohl das Führungsband als auch das Magnetband nur gestrichelt angedeutet sind,

Figur 4

eine Seitenansicht des Kolbens mit Blick in der radialen Richtung gemäß Pfeil IV aus Figur 2, wobei der strichpunktiert umrahmte Ausschnitt zusätzlich vergrößert abgebildet ist und wobei das Führungsband der besseren Übersichtlichkeit wegen nicht gezeigt ist, und

Figur 5

in einer der Figur 4 entsprechenden Darstellungsweise eine weitere radiale Ansicht des Kolbens mit Blickrichtung gemäß Pfeil IV, wobei hier das Führungsband im montierten Zustand gezeigt ist.

The invention will be explained in more detail with reference to the accompanying drawings. In this show:

FIG. 1

a longitudinal section through a preferred embodiment of the adjusting device according to the invention, which is equipped with a likewise advantageous embodiment of the piston according to the invention,

FIG. 2

the in FIG. 1 dash-dotted framed section II of the piston in an enlarged view, the sectional plane of the in the FIGS. 4 and 5 Plotted section lines II-II corresponds,

FIG. 3

a cross section through the piston according to section line III-III FIG. 1 , wherein the remaining components of the adjusting device are not shown and wherein both the guide tape and the magnetic tape are indicated only by dashed lines,

FIG. 4

a side view of the piston with a view in the radial direction according to arrow IV FIG. 2 , wherein the dash-dotted framed neckline is additionally shown enlarged and wherein the guide band is not shown for the sake of clarity, and

FIG. 5

in one of the FIG. 4 corresponding representation, a further radial view of the piston with Viewing direction according to arrow IV, wherein here the guide band is shown in the assembled state.

The FIG. 1 shows in longitudinal section a fluid operable adjusting device 1 in one embodiment as a fluid-operated linear actuator 1a. However, the scope of the invention is not limited to linear drives, but extends to all other types of usable in connection with fluid applications actuators, such as for use in shock absorbers.

The adjusting device 1 has a housing 2 which defines a housing chamber 3 extending in a linear manner and preferably having a circular cross-section, in which a piston 4 is arranged to be linearly displaceable back and forth. The longitudinal axis 5 of the piston 4 extends in the direction of movement of the piston 4 and preferably coincides with the longitudinal axis 6 of the housing chamber 3.

The housing chamber 3 is closed at both end sides by a respective end wall 7a, 7b of the housing 2. The peripheral, radially outer boundary of the housing chamber 3 takes over a one-piece or multi-part tubular body 8 extending between the two end walls 7a, 7b, the inner surface of which defines a cylindrical piston running surface 9. The end walls 7a, 7b are expediently designed as a housing cover which is separate relative to the tubular body 8 and connected to the tubular body 8 by fastening means. However, it is also possible to form at least one of the end walls 7a, 7b in one piece with the tubular body 8.

The radial outer contour of the piston 4 is adapted to the inner contour of the housing chamber 3, so that it slides along the piston running surface 9 during its linear movement. Preferably the piston 4 is provided at its radially outer circumference with a preferably cylindrical guide surface 10 which slidably rests against the piston running surface 9, so that the piston 4 undergoes a linear guide with respect to the housing 2 during its linear movement by the interaction between the guide surface 10 and the piston running surface 9 ,

By the piston 4, the housing chamber 3 is divided axially into two working spaces 12 a, 12 b, in each case one outside the cutting plane of the FIG. 1 lying fluid channel opens, so that a controlled fluid admission of the two working spaces 12a, 12b is possible. In this way, the piston 4 can be driven to a linear movement relative to the housing 2 in the axial direction of the longitudinal axis 6.

The fluid used for the operation of the adjusting device 1 is preferably compressed air. However, the use of another gaseous medium or a hydraulic medium is possible.

The linear movement of the piston 4 can be tapped outside of the housing 2 on a force-tapping part 14 coupled in a motion-coupled manner to the piston 4. The latter is in the embodiment of a piston rod 15, which passes through at least one of the end walls 7b slidable under sealing and which is fixed with its lying within the housing chamber section 3 on the piston 4. The piston 4 and the piston rod 5 thus form a moving unit.

In an embodiment not shown, the linear actuator 1a is a rodless linear drive, in which the piston 4, for example, magnetically with an outside of the Housing 2 slidably mounted Kraftabgriffsteil is motion coupled.

The piston 4 has a preferably disk-shaped piston body 16. The piston body 16 has a piston body radial plane 16 a that is perpendicular to the longitudinal axis 5 of the piston 4. About the piston body 16 of the piston 4 is fixed to the piston rod 15 in the embodiment. By way of example, the piston body 16 is circular-disk-shaped and is penetrated by a central fastening hole 17, with which it is plugged onto the piston rod 15.

The piston body 16 is expediently a one-piece component. It is preferably made of a rigid material and is made in the embodiment of metal, in particular die-cast aluminum. As alternative materials for the piston body 16, for example, ceramic, glass or hard plastic may be mentioned, with composite materials are also possible.

The piston body 16 carries in the region of its outer periphery to the longitudinal axis 5 concentric sealing means 18, which rest in the built-in adjusting device 1 state of the piston 4 on the piston running surface 9 slidably. They prevent a fluid transfer between the two working spaces 12a, 12b. By way of example, the sealing means 18 consist of two sealing rings 18a, 18b which are fixed to the piston body 16 at an axial distance from each other. Preferably, each sealing ring 18a, 18b held in a radially outwardly open mounting groove 19a, 19b, which are formed in the piston body 16 at its radially outer periphery. Each attachment groove 19a, 19b is arranged coaxially with the longitudinal axis 5.

The guide surface 10 is expediently formed by the radially outwardly oriented outer circumferential surface of a guide band 22 having a ring structure which is fixed to the piston body 16 in the region of the radial outer circumference. The piston body 16 has in the region of its radial outer circumference via a coaxial to the longitudinal axis 5 annular retaining recess 23 into which the guide belt 22 dips radially and in which the guide belt 22 is held.

Conveniently, the piston 4 is equipped with a permanent magnet assembly 24 which is usable for detecting the position of the piston 4. The permanent magnet assembly 24 is fixed in place on the piston 4 and makes its linear movement with. With the help of next to the trajectory of the permanent magnet assembly 24 and in particular outside of the housing chamber 3 arranged, not shown in the drawing position detection means responsive to the magnetic field of the permanent magnet assembly 24 can be in operation of the actuator 1, the current axial position of the permanent magnet assembly 24 supporting Determine piston 4. The position detection means comprise, for example, one or more sensors, for example Hall sensors, and / or they belong to a displacement measuring system.

The permanent magnet arrangement 24 expediently has an annular structure and is arranged coaxially to the longitudinal axis 5 on the piston body 16.

In combination with at least one guide band 22, it would be possible, with a corresponding configuration of the piston body 16, to mount the guide band 22 and the permanent magnet arrangement 24 axially next to each other on the piston body 16. However, in favor of a narrow construction of the piston 4, it is advantageous if the permanent magnet assembly 24 on the same axial height is arranged with the guide belt 22, in such a way that the permanent magnet assembly 24 is concentrically enclosed by the guide belt 22. The latter applies to the embodiment.

In the exemplary embodiment, the permanent magnet arrangement 24 is received in an annular receiving groove 25 of the piston body 16 formed in the region of the radial outer circumference of the piston body 16. This receiving groove 25 has a radially outwardly oriented, extending around the piston body 16 around extending slot-shaped groove opening 26 which is narrower in the axial direction of the piston 4 than the retaining recess 23. The receiving groove 25 is surrounded by the holding recess 23 radially outside, wherein it opens with its groove opening 26 in the recess bottom 27 of the retaining recess 23. The recess base 27 is the radial base of the retaining recess 23.

Preferably, the radially oriented groove opening 26 of the receiving groove 25 opens into the holding recess 23 in the axially central region. In this way, axially on both sides of the groove opening 26 in each case an annular recessed base portion 27a, 27b, which is preferably contoured cylindrical.

The arranged in the holding recess 23 guide belt 22 covers the slot opening 26 and consequently also arranged in the receiving groove 25 permanent magnet assembly 24th

The retaining recess 23 for the guide band 22 has two in the axial direction of the longitudinal axis 5 of the piston 4 spaced apart and facing each other side recess flanks 28a, 28b. Each of these depression flanks 28 adjoins the depression bottom 27, with each depression flank being exemplified 28a, 28b merges into one of the two recess base sections 27a, 27b. The holding recess 23 is open at the recess bottom 27 opposite radial side, ie radially outward.

The receiving groove 25 for the permanent magnet arrangement 24 has a groove base 32, radially outwardly facing groove base surface, which lies opposite the groove opening 26 radially outward.

The diameter of the groove bottom 32 is smaller than the diameter of the recess bottom 27.

The receiving groove 25 has two in the axial direction of the longitudinal axis 5 spaced apart and at the same time facing each other lateral groove flanks 33a, 33b, which are hereinafter referred to better distinction as the first groove flank 33a and second groove flank 33b. The two groove flanks 33a, 33b go in the embodiment radially inward into the recess bottom 27 of the retaining recess 23 via. The clear distance between the two groove flanks 33a, 33b is smaller than the clear distance between the two recess flanks 28a, 28b. The receiving groove 25 preferably has an at least substantially rectangular cross-section.

The guide band 22 has a ring structure in the state fixed in the holding recess 23. However, the ring structure is not completely self-contained, but has an interruption 34. Preferably, the guide band 22 is a strand body of finite length, which has two mutually opposite Bandendabschnitte 22a, 22b. Preferably, the guide band is made as a linear extruded body, which is then bent, during assembly on the piston body 16, to the annular shape.

This is facilitated by the fact that the guide band 22 has elastically deformable properties.

When assembled, the guide band 22 is wound around the piston body 16 coaxially and inserted into the holding recess 23, with its two band end portions 22a, 22b facing each other in the circumferential direction 23a of the holding recess 23. The circumferential direction 23a of the holding recess 23 is the direction about the longitudinal axis 5 and is indicated in Figure 3 by a double arrow.

Appropriately, between the two Bandendabschnitten 22a, 22b at least a small, the interruption 34 defining distance before.

The facing each other in the circumferential direction of the holding recess 23 faces of the guide belt 22 are preferably chamfered across the entire width of the guide belt 22 away. In this case, the mutually facing beveled end faces of the two Bandendabschnitte 22a, 22b are preferably parallel to each other.

The permanent magnet assembly 24 preferably consists of an elastic permanent magnetic magnetic tape 35 bent into a ring structure. The magnetic tape 35 is expediently of finite length and has two mutually opposite band end portions 35a, 35b. Preferably, the magnetic tape 35 is made as a linear strand body, which is bent to the ring structure when it is mounted in the receiving groove 25. The magnetic tape 35 is thus bent around in its mounting on the piston body 16 expediently with simultaneous radial insertion into the receiving groove 25 to the piston body 16. This type of assembly suitably corresponds to that of the guide band 22nd

This type of assembly is facilitated by the fact that the magnetic tape 35 has elastically deformable properties. Preferably, it consists of a strand-shaped band body made of an elastically deformable plastic material, which is provided with permanent magnet means, which are responsible for the permanent magnetic properties of the magnetic tape 35. The permanent magnet means are, for example, ferromagnetic particles which are embedded in the strand-shaped band body in fine distribution during the production of the magnetic tape and subsequently magnetized.

When the magnetic tape 35 is inserted ready for use in the receiving groove 25, the two Bandendabschnitte 35a, 35b facing each other in the circumferential direction 25a of the receiving groove 25. The circumferential direction 25a of the receiving groove 25 is the direction around the longitudinal axis 5 and is in FIG. 3 indicated by a double arrow. Between the two Bandendabschnitten 35a, 35b is an interruption 36 of the ring structure of the magnetic tape 35, which manifests itself in particular in a small gap, so that the two Bandendabschnitte 35a, 35b in the circumferential direction 25a of the receiving groove 25 are opposed with a small distance. The circumferential direction 25a of the receiving groove 25 is the direction around the longitudinal axis 5 of the piston 4 around.

The magnetic tape 35 has two longitudinal side surfaces 39a, 39b which, in the state mounted in the receiving groove 25, respectively face one of the groove flanks 33a, 33b.

Although the guide band 22 in the inserted into the retaining recess 23 due to its elastic properties has the tendency to open in the region of the two Bandendabschnitte 22a, 22b and from the retaining recess 23, the guide belt 22 is held together by the piston body 16 solely because of suitable fixing measures, so that it retains its ring structure in which it is fixed in the retaining recess 23 over its entire length.

The same applies expediently for the magnetic tape 35 in relation to the receiving groove 25. The piston body 16 is formed in the region of the receiving groove 25 so that it holds the inserted into the receiving groove 25 magnetic tape 35 so that it is based on its elasticity expansion tendency on his full length away in the receiving groove 25 is arranged and in the region of the two Bandendabschnitte 35a, 35b does not open.

The presently described effect is achieved in the guide band 22 in that the two recess flanks 28a, 28b of the holding recess 23 in cross-section each have an undercut profiling, so that each recess flank 28a, 28b form-fitting with the respectively facing side edge 37a, 37b of the two in the axial direction the longitudinal axis 5 oriented side edges 37a, 37b of the guide belt 22 is engaged. The form-fit acts in a radial direction with respect to the longitudinal axis 5, so that the guide band 22 is held in the retaining recess 23 over its entire length by the profiled recess flanks 28a, 28b. It is expediently a releasable positive engagement to allow replacement of the guide band in case of need.

The undercut profiling of the recess flanks 28a, 28b manifests itself per recess flank 28a, 28b, in particular in a holding projection 38a, 38b projecting in the direction of the respectively opposite recess flank 28b, 28a is arranged concentrically to the longitudinal axis 5 of the piston 4 and extends continuously in the circumferential direction of the retaining recess 23. Each of the two holding projections 38a, 38b is arranged with a radial distance with respect to the recess base 27 of the holding recess 23 with respect to the longitudinal axis 5, so that in the area of a respective recess flank 28a, 28b located radially between a respective holding projection 38a, 38b and the recess base 27 annular self-contained holding recess 43a, 43b results, in which the guide strip 22 can engage and which is also arranged concentrically to the longitudinal axis 5 of the piston 4.

The guide belt 22 preferably has a rectangular cross-section in the initial state not yet inserted into the holding recess 23. The width of the guide belt 22 is slightly larger in this initial state than the measured in the axial direction of the longitudinal axis 5 clear distance between the opposing retaining projections 38a, 38b. In this way it is achieved that the holding projections 38a, 38b are pressed in the inserted into the holding recess 23 state of the guide belt 22 under local deformation of the guide belt 22 in the respective associated side edge 37a, 37b. The displaced by the impressing material of the guide strip 22 engages in the retaining recesses 43 a, 43 b. In this way, an effective in the radial direction of the piston 4 positive connection between the piston body 16 and the guide belt 22, which ensures that the guide belt 22 over its entire length at both side edges 37a, 37b by the undercut profiling of the recess flanks 28a , 28b.

During assembly of the guide strip 22, the guide strip is acted upon with radial force with respect to the longitudinal axis 5, so that it is pressed in between the two holding projections 38a, 38b and clamped therein.

It is possible to intensify the form-fitting effect by the guide band 22 at its two side edges 37a, 37b has a preformed engagement contour, which has a profiling to the profiled recess flank 28a, 28b complementary profiling, so that the guide band 22 over its entire length in the retaining recess 23 can be latched or clipped.

For fixing the magnetic tape 35 is advantageously a clamping principle is used, in which the magnetic tape 35 is not clamped over its entire length away by the piston body 16, but only in some areas, and in particular at its two Bandendabschnitten 35a, 35b. The clamping fixation of the two band end sections 35a, 35b takes place independently of one another. The two band end portions 35a, 35b are not fixed to each other, but only on the piston body 16th

The piston body 16 has at least one point of its peripheral outer circumference via a clamping region 44, on which the piston body 16 is formed so that it can hold the two Bandendabschnitte 35a, 35b independently clamped in the receiving groove 25. In this case, the piston body 16 in the clamping region 44 has two clamping zones 45a, 45b, which are adjacent to one another in the circumferential direction 25a of the receiving groove 25 and which is designed to positively hold one of the band end sections 35a, 35b in each case.

The magnetic tape 35 expediently has a constant width "B" over its entire length. This width B is in the axial direction of the longitudinal axis 5 of the piston 4 and between the both side surfaces 39a, 39b measured. Incidentally, the magnetic tape 35 desirably has a rectangular cross-sectional shape.

The width B of the magnetic tape 35 is less than the clear distance A1 between the two groove flanks 33a, 33b of the receiving groove 25. Consequently, the magnetic tape 35 is in those areas of the receiving groove 25 in which portions of the groove flanks 33a, 33b opposite, with a small Game tainted in the receiving groove 25 recorded.

On the other hand, in the area of the two clamping zones 45a, 45b, the piston body 16 has at least one clamping projection 46a, 47a protruding with respect to one of the two groove flanks 33a, 33b in the direction of the opposite groove flank 33b, 33a; 46b, 47b, which causes a local narrowing of the receiving groove 25. The local constriction ensures that the magnetic tape 35 is clamped in one or more places in the region of its two band end sections 35a, 35b in the receiving groove 25 and can not open. The constriction areas, which can also be referred to as bottlenecks, are marked by arrows at 48.

It is possible to provide in each clamping zone 45a, 45b only a single clamping projection whose distance to the opposite groove flank is slightly smaller than the width B of the magnetic tape 35, so that the clamping essentially results from the fact that the single clamping projection in the facing side surface 39a , 39b of the magnetic tape 35 is pressed.

It is also possible in each clamping zone 45a, 45b to arrange a plurality of clamping projections in the circumferential direction 25a of the receiving groove 25 at a distance from each other. For example can this multiple clamping projections on only one and thereby be formed on the same groove flank 33a, 33b.

It is also possible, in one or both clamping zones 45a, 45b, to provide two clamping projections opposite to one another in the axial direction of the longitudinal axis 5 of the piston 4 on the two groove flanks 33a, 33b, which project towards each other and a constriction 48 for clamping the associated band end section 35a, Define 35b. In this case, only one or more pairs of such opposing clamping projections may be present per clamping zone 45a, 45b.

A particularly preferred embodiment of the two clamping zones 45a, 45b is realized in the embodiment and illustrated in the drawing. Accordingly, the piston body 16 in each of the two clamping zones 45a, 45b has a plurality of clamping projections 46a, 47a spaced apart from one another in the circumferential direction 25a of the receiving groove 25; 46b, 47b, that is, via a plurality of clamping projections, which are arranged offset in the circumferential direction of the receiving groove 25 to each other. However, the clamping projections 46a, 47a; 46b, 47b in the respective clamping zone 45a, 45b are not each on the same groove flank 33a, 33b, but are arranged on different groove flanks 33a, 33b. By way of example, in each clamping zone 45a, 45b, a first clamping projection 46a, 46b is integrally formed on the first groove flank 33a and a second clamping projection 47a, 47b spaced therefrom in the circumferential direction 25a of the receiving groove 25 on the second groove flank 33b. In a respective clamping projection 46a, 47a; 46b, 47b opposite region of the respective other groove flank 33a, 33b is preferably no clamping projection, where the respective groove flank 33a, 33b is designed as a clamping projection.

In this way, per terminal zone 45a, 45b several, in the circumferential direction of the receiving groove 25 spaced bottlenecks or constrictions 48 within the receiving groove 25, which protrudes through mutually opposite groove flanks 33a, 33b ago in the receiving groove 25 clamping projections 46a, 47a; 46b, 47b.

From this arrangement, it is found that each band end portion 35a, 35b pressed into a pinching zone 45a, 45b winds with a slight wavy line in the circumferential direction 25a of the receiving groove 25 through the respective pinching zone 45a, 45b and is thereby effectively clamped. In this type of clamping, it is not necessary that the between each clamping projection 46a, 47a; 46b, 47b and the opposite groove flank 33a, 33b measured clear distance A2 is smaller than the width B of the magnetic tape 35. This clear distance A2 is suitably the same size as the width B magnetic tape 35 or even in this regard may be slightly larger. The clamping effect results mainly from the fact that the magnetic tape 35 is meander-like deformed in each clamping zone 45a, 45b, that in particular in the clamping projections 46a, 47a; 46b, 47b adjacent areas with the groove flanks 33a, 33b is clamped.

The clamping effect is essentially based on the fact that the band end portions 35a, 35b in the clamping portions 45a, 45b are forced by the alternately on different groove flanks 33a, 33b clamping projections in a meandering or wavy or at least bent longitudinal shape and due to the elasticity of the magnetic tape 35 the Have a tendency to deform back into their linear initial shape, so that they clamp in the receiving groove 25 transversely to its circumferential direction 25a.

It has proven to be advantageous if in the respective clamping zone 45a, 45b of the measured in the longitudinal direction of the piston 4 projected clear distance A3 between the two in the circumferential direction 25a of the receiving groove 25 mutually spaced clamping projections 46a, 47a; 46b, 47b is smaller than the width B of the magnetic tape.

In order to generate an optimal clamping, it has also proven to be expedient, in each clamping zone 45a, 45b, the distance A4 measured in the circumferential direction of the receiving groove between the clamping projections 46a, 47a arranged on different groove flanks 33a, 33b; 46b, 47b so that it is at least as large as the width B of the magnetic tape and at most twice the width B of the magnetic tape.

It has been shown that already two clamping projections 46a, 47a; 46b, 47b per clamping zone 45a, 45b sufficient to reliably hold the associated band end portion 35a, 35b by clamping. However, it is also possible to provide more than two clamping projections per clamping zone.

It is sufficient to provide only a single clamping region 44 of the type described along the circumference of the receiving groove 25. The magnetic tape 35 is already securely held in the receiving groove 25 when it is fixed only at its two Bandendabschnitten 35 a, 35 b.

For the speed during assembly of the piston 4, however, it may be advantageous to provide a further clamping region 44a of the described structure at at least one point spaced apart in the circumferential direction of the piston body 16 from the clamping region 44. This further clamping region 44a may then alternatively to the described clamping region 44 be used for fixing the two band portions 35a, 35b, when the magnetic tape 35 is inserted with a corresponding position in the receiving groove 25. In principle, even more such clamping areas along the circumference of the piston body 16 may be distributed, but you will keep the number of clamping areas as low as possible, as they generally complicate the insertion of the magnetic tape 35 due to the achieved clamping effect.

The clamping projections 46a, 47a; 46b, 47b can basically be designed arbitrarily. It is important that they cause a local narrowing in the course of the receiving groove 25. As a particularly expedient shape has been found in which each clamping projection 46a, 47a; 46b, 47b according to Figures 2 and 3 is formed rib-shaped with elongated shape and extending from the region of the groove bottom 32 of the receiving groove 25 in the direction of the radial groove opening 26 of the receiving groove 25 respectively. Especially in this context, it is advantageous if the clamping projections 46a, 47a; 46b, 47b have at their radial slot opening 26 facing end portion a radially outward and to the associated groove flank 33a, 33b extending chamfer 49. The chamfers 49 form oblique guide surfaces which guide the respective band end section 35a, 35b into the receiving groove 25 in a targeted manner when the same is subjected to a pressing force during assembly from the radially outside.

Claims (16)

1. Piston for a fluid-operated adjusting device, in particular for a fluid-actuated linear drive, comprising a one-piece piston body (16) having in the region of its outer circumference a reception groove (25) coaxial with the longitudinal axis (5) of the piston (4) with two facing lateral groove sides (33a, 33b), in which groove (25) a permanent magnet assembly (24) usable for position detection is accommodated, the permanent magnet assembly (24) consisting of an elastic permanent-magnetic magnet strip (35), characterised in that the magnet strip (35) has two strip end sections (35a, 35b) facing each other in the circumferential direction of the reception groove (25), and in that its width is less than the distance between the two groove sides (33a, 33b) of the reception groove (25), wherein each of the two strip end sections (35a, 35b) is held by clamping in one of two clamping zones (45a, 45b) of the reception groove (25), which are adjacent to each other in the circumferential direction of the reception groove (25), where the piston body (16) respectively has at least one clamping projection (46a, 47a; 46b, 47b), which projects relative to one of the groove sides (33a, 33b) while locally narrowing the reception groove (25) and presses against the side face (39a, 39b) of the magnet strip (35).
2. Piston according to claim 1, characterised in that the piston body (16) has several clamping projections (46a, 47a; 46b, 47b) in each clamping zone (45a, 45b) of the reception groove (25).
3. Piston according to claim 1 or 2, characterised in that the piston body (16) has several clamping projections (46a, 47a; 46b, 47b) arranged at a distance from one another in the circumferential direction of the reception groove (25) in each clamping zone (45a, 45b) of the reception groove (25).
4. Piston according to claim 3, characterised in that in each clamping zone (45a, 45b) at least two clamping projections (46a, 47a; 46b, 47b) arranged at a distance from one another in the circumferential direction of the reception groove (25) are provided on different groove sides (33a, 33b), wherein no clamping projection on the other groove side (33a, 33b) is located opposite these clamping projections (46a, 47a; 46b, 47b).
5. Piston according to claim 4, characterised in that in the respective clamping zone (45a, 45b) the projected clearance (A3) between the two clamping projections (46a, 47a; 46b, 47b) arranged at a distance from one another in the circumferential direction of the reception groove (25), as measured in the longitudinal direction of the piston (4), is less than the width (B) of the magnetic strip (35).
6. Piston according to claim 4 or 5, characterised in that the clearance between each clamping projection (46a, 47a; 46b, 47b) and the opposite groove side (33a, 33b) is equal to or more than the width (B) of the magnetic strip (35).
7. Piston according to any of claims 4 to 6, characterised in that in each clamping zone (45a, 45b) the distance (A4) between the clamping projections (46a, 47a; 46b, 47b) located on the different groove sides, as measured in the circumferential direction of the reception groove (25), is at least equal to the width (B) of the magnetic strip (35) and maximally twice the width (B) of the magnetic strip (35).
8. Piston according to any of claims 1 to 7, characterised in that precisely two clamping projections (46a, 47a; 46b, 47b) are provided in each of the two clamping zones (45a, 45b).
9. Piston according to any of claims 1 to 8, characterised in that each of the clamping projections (46a, 47a; 46b, 47b) is rib-shaped with an elongated form and extends from the region of the groove bottom (32) of the reception groove (25) towards the radial groove opening (26) of the reception groove (25), and/or in that the clamping projections (46a, 47a; 46b, 47b) taper towards the associated groove side (33a, 33b) in their end region facing the radial groove opening (26).
10. Piston according to any of claims 1 to 9, characterised in that the magnetic strip (35) has a rectangular cross-section, and/or in that the magnetic strip (35) has a strand-shaped tape body made of an elastically deformable plastic material and provided with permanent magnet means.
11. Piston according to any of claims 1 to 10, characterised in that the piston body (16) is made of a rigid material, expediently of metal.
12. Piston according to any of claims 1 to 11, characterised in that the piston body (16) has in each of two diametrically opposite circumferential regions a clamping region (44, 44a) provided with two mutually adjacent clamping zones (45a, 45b) for the magnetic strip (35), wherein the two clamping regions (44, 44a) can be used alternatively for clamping the two strip end sections (35a, 35b).
13. Piston according to any of claims 1 to 12, characterised in that the annular reception groove (25) is concentrically enclosed by an annular holding recess (23) formed in the piston body (16), being narrower than the holding recess (23) and terminating with its radially outward groove opening (26) into the base (27) of the holding recess (23), wherein a guide strip (22) of an annular structure, which covers the magnetic strip (35) on the radial outside, is held in the holding recess (23).
14. Piston according to any of claims 1 to 13, characterised in that in the region of the radial outer circumference of the piston body (16) there is formed an annular holding recess (23) coaxial with the longitudinal axis (5) of the piston (4) and having two lateral recess sides (28a, 28b) facing each other, in which holding recess (23) a guide strip (22) of an annular structure and having two strip end sections (22a, 22b) facing each other in the circumferential direction of the holding recess (23) is held, wherein each of the two recess sides (28a, 28b) of the holding recess (23), if viewed in cross-section, has an undercut profile and, at a radial distance from the recess base (27) of the holding recess (23), an annular holding projection (38a, 38b) projecting towards the opposite recess side (28a, 28b) and in positive engagement with the facing lateral edge (37a, 37b) of the guide strip (22).
15. Piston according to claim 14, characterised in that the holding projections (38a, 38b) are pressed into the associated lateral edges (37a, 37b) of the guide strip (22) accompanied by a local deformation of the guide strip (22) and the formation of a positive engagement, wherein the guide strip (22) expediently has a rectangular cross-section if not yet installed into the holding recess (23).
16. Fluid-operated adjusting device, in particular a fluid-actuated linear drive, comprising a housing (2), in which a piston (4) capable of linear displacement is accommodated, characterised in that the piston (4) is designed in accordance with any of claims 1 to 15.

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