DE3319522A1 - Piston/cylinder unit with magnetic shoe as anti-rotation locking means - Google Patents

Abstract

Piston/cylinder unit actuated by pressure medium and having a piston which carries one or more permanent magnets. The permanent magnets project in a radial direction from the piston and are guided in a longitudinal groove (12) of the cylinder (1) so that they serve as an anti-rotation locking means for the piston. Sensors (5) sensitive to a magnetic field are arranged radially opposite the longitudinal groove (12) on the periphery (4) of the cylinder (1). The sensors (5), as limit switches, can affect among other things a control unit (11) which is sunk in the cylinder shell and is connected to working spaces of the cylinder via lines (18) integrated in the wall. The limit switches are displaceable on a rail-shaped holding device (6). Furthermore, a magnetic displacement gauge is provided which works according to the principle of the transit-time measurement of a travelling wave excited by magnetostriction. …<IMAGE>…

Description

May 26, 1983 D 9059-rns

Festo machine factory Gottlieb Stoll, 7300 Esslingen.

Piston-cylinder unit with magnetic shoe to prevent rotation

The invention relates to a piston-cylinder unit actuated by pressure medium with a piston, which carries a permanent magnet, and one or more, magnetic field sensitive Sensors on the periphery of the cylinder.

Working cylinders, their pistons with one or more permanent magnets is equipped are known per se. The field built up by the magnets enables it, when in use suitable sensors to passively detect the piston position; it is also possible, depending on the piston position trigger certain changes in the state of a solenoid-operated switch or relay. In particular, the Arrangement of magnetically sensitive limit switches that are used in A signal is given when a certain piston position is reached output a control unit, which causes a reversal of the pressure medium acting on the piston-cylinder unit. The magnet-sensitive detectors used and switches are arranged according to the prior art on the outer surface of the cylinder, and the cylinder itself consists of a non-ferromagnetic material.

There are also various forms of mechanical anti-twist protection a piston in a piston-cylinder unit is known. They are used for areas of application in which a rotation of the piston or a piston rod of the working cylinder usually connected to it is not tolerated can be. To prevent rotation, the piston is generally given a central longitudinal axis with respect to its longitudinal axis not rotationally symmetrical shape and arranges it in a cylinder liner, the guide bore of which is negative in shape Piston contour is formed.

Based on this prior art, it is the object of the invention to provide a magnet-equipped, anti-twist device To create a piston-cylinder unit that can be produced easily and inexpensively with little material requirement, Requires minimal assembly work and with constant or reduced field strength of the permanent magnets a greater switching accuracy achieved.

This object is achieved according to claim 1 in that one or more permanent magnets in the radial direction of protrude from the piston on which the cylinder jacket is guided and serve as an anti-twist device for the piston. The piston is thus in the form of a guide shoe Provided permanent magnet, which blocks the piston against turning inside the cylinder and it at the same time allows solenoid-operated switching operations to be carried out depending on the piston position or the piston position

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to eat. In other words, the piston is covered with a magnetic marking part, which is also a mechanical one Has a leadership role.

The inventive double action of a magnet as a position transmitter and anti-twist protection of a piston-cylinder unit has a number of advantages. Opposite in known manner anti-rotation piston-cylinder units according to the invention, the possibility of magnetic monitoring and reversal of the piston movement is created, and on the other hand a magnet-equipped piston-cylinder unit an anti-twist device, which significantly expands the areas of application of the respective units. The arrangement according to the invention is characterized by a very little assembly effort, since a guide shoe and magnetic marker carrier in a single work step is attached to the piston. The permanent magnet can give the piston a non-round shape, what had to be avoided according to the prior art; one that is not rotationally symmetrical with respect to the longitudinal center axis Piston contour is even desirable for anti-twist guidance. It can therefore use standard magnets in the form of Rods, rods or blocks are used, and the production of special magnetic molded parts can be omitted.

The invention also opens up the possibility of comparing the spatial dimensions of the magnets used

to well-known, magnetically embroidered piston-cylinder units to reduce. The latter must, in the absence of an anti-rotation device, with ring-shaped or disk-shaped magnets be equipped to the arranged on the cylinder outer wall To apply detectors in any rotational position of the piston. In contrast, the invention makes it possible the position of the magnetically sensitive sensors to the in Circumferential direction invariable position of the magnetic Adapt the guide shoe. The extension of the permanent magnet in the circumferential direction can be kept correspondingly small which means that there is less need for complex, permanent magnetic alloys. In a preferred Arrangement in which the permanent magnet is recessed to fit on the inner surface of the cylinder Is guided in the longitudinal groove, the advantage is finally achieved that the surface of the magnet closer to the outer jacket of the cylinder comes to rest, on the order of the depth of the longitudinal groove. When using a and The same magnet results in a strengthening of the magnetic field at the location compared to the prior art of the respective sensor acts; this increases the measuring and switching accuracy of the magnetic detection system as well as its operational reliability. On the other hand, if you want to get on with the status you have already achieved technology, because of the guidance of the permanent magnets in a longitudinal groove on the inner surface of the cylinder Weaker magnets are used, which means the use of less expensive alloys and a corresponding one I-t enable cost advantages »

Preferred developments of the invention are in subordinate Claims described.

Further advantages of the invention emerge from the following description of exemplary embodiments with reference to the drawings. Partly show schematically:

Fig. 1 is the perspective view of the working cylinder a piston-cylinder unit with a magnetic shoe to prevent rotation;

Fig. 2 to

Fig. 5 shows other embodiments of such a working cylinder 'in an end plan view.

Referring first to Fig. 1, the cylinder 1 of a pressure medium-actuated piston-cylinder unit is shown. The cylinder 1 forms the liner for a piston, not shown in detail in the figures, which is inside of the cylinder 1 is arranged to be movable back and forth. The piston is received in a housing bore 2 of the cylinder 1 and guided in a sealing manner on an inner jacket 3 of the cylinder 1 delimiting this housing bore 2. The outer contour of the piston is thus designed according to the cross section of the housing bore 2 into which the piston is positively locked fits. The piston carries at least one permanent magnet, and on the periphery 4 of the cylinder 1 there are magnetic field sensitive Sensors 5 that respond to the field of the permanent magnet. Exemplary for such sensors

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5, two limit switches are shown in FIG be supported displaceably in the longitudinal direction by a rail-like holding device. The holding device has the shape of a rib 6 molded onto the cylinder 1, which has an outwardly protruding, rounded guide section 7 and which is located on the cylinder 1 facing, radial inside tapers to form a narrow web 8. The rib 6 protrudes from the outer jacket 9 of the cylinder 1 away in the radial direction and extends in the longitudinal direction of the cylinder; it is in Fig. 1 for clarity half drawn enlarged. The limit switches o. Ä. Sensors 5 are complementary to the guide section 7 designed housing opening drawn onto the rib 6, on which it is in the axial direction relocate and lock in preselectable positions; the latter can for example by means of a clamping screw (not shown) happen. The limit switches 5 are Connected via electrical lines 10 to a control unit, which is in the pressure medium supply circuit of the piston-cylinder device is switched. The control unit 11 can in particular take the form of a multi-way valve have, by means of which the working spaces of the cylinder 1, which are divided off by the piston, are alternately pressurized or be relieved. A switching change of the multi-way valve is triggered by an electrical signal from the sensors 5 triggered, which in turn respond to the field of the permanent magnet as soon as it has a radially opposite one Position reached at the same axial height with the sensors 5. As limit switches, for example

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Reed contacts are used. So that they are in the stray field a permanent magnet carried by the piston respond, the cylinder 1 must obviously be from a non-ferromagnetic Material. By moving the sensors 5 on the rib 6, it is possible to increase the working stroke to adjust the piston. The shape of the rib 6 is clearly not important here; alternative Embodiments of a rail-like holding device for the sensors 5 are explained below with reference to FIGS. 2 to 5.

According to the invention, a secure storage of the Piston mediated in the cylinder 1 by a permanent magnet which protrudes in the radial direction from the piston and is guided on the inner jacket 3 of the cylinder 1. According to a preferred embodiment, the permanent magnet is used for this purpose in the ready-to-use installation position of the piston in a Longitudinal groove 12 added, which is recessed on the inner jacket 3 of the cylinder 1 and located in its axial Extends longitudinally. The longitudinal groove 12 and the permanent magnet are adapted to one another in the shape that the latter runs sealingly in the longitudinal groove 12. The permanent magnet can be made in one piece as a magnetized section of the piston be trained with this. However, it is also possible and technically advantageous to use the permanent magnet to be manufactured as a plate, rod, block or other magnetic shaped piece separately from the piston. The permanent magnet is then attached to the piston afterwards

and firmly connected to it, which can be achieved, for example, by

screwing or riveting can be done. A particularly simple assembly results if you use the piston to ßefesti The permanent magnetic fitting is flattened on part of its surface, creating a flat support surface creates.

The longitudinal groove 12 according to FIG. 1 has an essentially rectangular cross section. So she's about to pick up one also rectangular, permanent magnetic block suitable from the outside of the otherwise circular cylindrical Piston protrudes. To achieve a high measurement accuracy with the sensors 5, i. H. a good spatial resolution, the permanent magnet should have the smallest possible axial extent; it can in particular in the axial direction be much shorter than the piston and thus in the form of a nose or a projection on the piston apply. In the radial direction opposite the longitudinal groove 12 is located according to FIG. 1 on the outer jacket 9 of the cylinder 1, the rail-like holding device for the Sensors 5. By this arrangement it is achieved that the sensors 5 to the permanent magnet always with the least possible Distance facing. This distance is also kept small by the fact that the permanent magnet in the longitudinal groove 12 runs sunk; its pole end comes to lie closer to the sensors 5 than, for example, at a magnetic ring running on the inner jacket 3 of the cylinder 1 would be the case. This results in a stronger magnetic field at the location of the sensors 5 and an improved Schaltbzw. Measurement accuracy; can also be used according to the invention to educate

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Development of the same field strength at the location of the sensor 5 weaker permanent magnets are used.

Alternative designs of the longitudinal groove 12 accommodating a permanent magnet of the piston are shown in FIGS. 5 shown. The longitudinal groove according to FIG. 2 is dovetail-shaped driven into the solid material of the cylinder 1; it is accordingly suitable, the dovetail-shaped Pick up magnet attachment of an associated piston. In the radial direction opposite to the longitudinal groove 12 is located an integrally formed on the outer jacket 9 of the cylinder 1 rib 6, which is shaped similarly to that in Fig. 1, but in addition is provided with an axial longitudinal bore 13. While the outside of the rib 6 in turn for pulling magnetic Can serve limit switches, the longitudinal bore 13 is for a further sensor 5 in the form of a Magnetic odometer provided, which is used as an alternative or in addition to the limit switches. This odometer makes it possible to determine the piston position even between the end positions in which the reversal the piston movement takes place. Such measurement information is necessary for the commissioning of the piston-cylinder unit of importance, which occurs from a regularly undefined piston position; likewise is a continuous Monitoring of the piston activity possible. The odometer used according to the invention can, for example work according to the principle of measuring the transit time of a traveling wave excited by magnetostriction. By the longitudinal bore 13 is stretched to a wire from

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a special alloy with magnetostrictive properties consists. This wire creates a pulse-shaped, electrical one Excitation signal sent, and at the same time with this excitation signal is an electronic timing device started. At the point of the wire that is located radially opposite the permanent magnet of the piston, the electrical excitation by magnetostriction generates a mechanical tension, which is in the form of a sound or ultrasonic wave propagates along the wire. The arrival of the traveling wave at the end of the wire is detected and the electronic timing device stopped; its final value reflects the travel time of the traveling wave along the wire. Since the speed of propagation of the mechanical If the disturbance along the wire is known and essentially constant, the distance covered can be passed through determine simple conversion very precisely; however, this distance is just a measure of the respective piston position. Measurements in the form described can be carried out with a high repetition frequency, so that one receives quasi continuous display of the piston position.

The magnetic odometer, which operates according to the principle described or another principle, is shown in FIG. 2 housed in the longitudinal bore 13 of the rib 6, where it as well as a limit switch pulled onto the rib the permanent magnet running in the longitudinal groove 12 is radially opposite. This arrangement brings the two types of sensors as close as possible to the permanent magnet, so that high field strengths are available for detection; Further-

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the arrangement according to FIG. 2 is particularly space-saving.

3 shows a further design in which a rounded longitudinal groove 12 is used to guide the permanent magnet finds. The longitudinal groove 12 is as a section of a coaxially to the housing bore 2 and this meeting Cylinder bore is formed, the housing bore 2 being widened in the region of the longitudinal groove 12. The longitudinal groove 12 receives a correspondingly rounded permanent magnet of the piston; the permanent magnet can in particular the shape of a spherical head or spherical head section to have. As a rail-like holding device for sensors 5, there are two grooves on the outer jacket 9 of the 2-cylinder 1 14 except that in the circumferential direction side by side of the Longitudinal groove 12 are approximately opposite. As an example, one of the grooves is dovetail-shaped and the other is rectangular contoured; the dovetail groove could serve for example to guide a corresponding approach to a limit switch 5, while the rectangular Nut could accommodate the housing of a magnetic odometer. The grooves 14 are located in the circumferential direction on both sides / a longitudinal center plane through the longitudinal groove 12, which guides the permanent magnet; so one gets in the area both grooves 14 a considerable stray field.

Fig. 4 shows the cylinder 1 according to a further embodiment, in which instead of a permanent magnet on the piston two of which are provided. The permanent magnets each run in an associated longitudinal groove 12, which is mutually exclusive

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are shown diametrically opposite. But it can a different distribution of the longitudinal grooves 12 on the circumference of the cylinder 1 can also be provided, and optionally can the number of longitudinal grooves and permanent magnets also increase further. Each of the longitudinal grooves 12 is on the outer shell 9 of the cylinder 1 radially opposite a holding device assigned, which is shown by way of example as a rail 15 with a dovetail-shaped profile. It can Of course, however, other forms of a holding device for the sensors 5 can also be used, as in general the structural details in the exemplary embodiments largely are interchangeable. The rails 15 attach to flattened areas 16 of the cylinder 1, which results in a particularly compact design. The longitudinal grooves 12 are drawn as rectangular grooves, can but also have any other, polygonal or rounded contour.

Finally, FIG. 5 shows a cylinder 1, the housing bore 2 of which is the plan of a four-leaf clover Has. The housing bore 2 receives a correspondingly contoured piston with four magnetic poles, preferably the entire piston designed as a magnetic molded part and / or its poles by magnetizing such a molded part are preserved. In each case opposite the poles, guide devices for sensors 5 are provided; one recognises in detail one axial longitudinal bore 13 guided through the cylinder jacket itself and three on the outer jacket 9 of the cylinder 1 molded guide ribs 6. Instead of these

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Ribs 6 can of course also be suitable again Grooves occur (not shown). The longitudinal bore 13 is suitable to accommodate a magnetic odometer, and further sensors can be attached to the ribs 6, and in particular limit switches, arranged displaceably will. Two of the ribs 6 are dovetail-shaped Shape; they are molded onto the outer jacket 9 of the cylinder 1 without the flattening shown in FIG. The third Rib 6 has the contour shown in FIG. 1. However, this shape design is also not natural for the invention imperative.

The described, anti-twist guide of a piston by means of a permanent magnet shoe finds a preferred use for multifunctional cylinders, such as they are shown in FIG. In these, the cylinder 1 not only fulfills the task of linear guidance and to provide sealing of the piston, but rather there are various additional functions in the cylinder wall integrated. This enables better use of the material used. As mentioned earlier, are for example, the limit switch 5 on a rail-like Holding device out, which are integrally formed with the cylinder 1 acting as a liner. Farther the cylinder jacket 1 can have an axial longitudinal bore 13 at one point or another, which has a magnetic Odometer records. According to FIG. 1, the cylinder acting as a cylinder liner is also attached to the outer jacket 9 at least one flat 17 is formed which extends over

extends at least part of the cylinder length and to Attachment of the control unit 11 is used. A control unit 11 designed as a multi-way valve can in particular be suitable for connection to lines 18 which are used for supplying and / or removing pressure medium from the piston-cylinder unit are provided and are also formed in the wall of the cylinder 1. One recognizes in Fig. 1 two lines 18, which lead to the working spaces of the piston-cylinder unit on both sides of the piston and open in the area of the flat 17, which the control unit 11 receives. In the lines 18, a throttle element can optionally be installed will.

On the front side, the wall of the cylinder 1 is used for the assembly of cylinder covers (not shown), which the Close the piston-cylinder unit on both sides in the axial direction. One recognizes in Fig. 1 threaded bores 19 on the end face of the cylinder 1, namely in the form of blind bores; these take place in the assembled state of the piston-cylinder unit Retaining screws, which are supported with their heads against the cylinder cover. With larger working cylinders it may finally be advisable to provide additional recesses 20 in the wall of the cylinder 1, such as they are indicated by dashed lines in FIG. 1. Such recesses 20 lead to a further saving in material and weight. "Multifunction cylinder described in the Shape are preferably as tubular extruded parts made of aluminum. They also make it possible to avoid cumbersome, external lines and control cables

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how far protruding valves, whereby a compact design and a safe operation are achieved. Connections for the pressure medium are only at one axial end of the piston-cylinder unit provided, making the required connections simple, easy to use Manufacture, wait and release again and at the same time give the piston-cylinder unit an attractive appearance is achieved. Flat surfaces for the direct flanging of control units 11 also improve the design and bring a saving of space with them; at the same time they reduce the screwing costs and the time required for assembly the control units, valves, etc. Through the guidance of a permanent magnetic piston shoe, which is also used to Position detection and rotation lock is used in one Ultimately, a maximum degree of integration of various technical functions is achieved in the longitudinal groove of the cylinder.

Claims (15)

Expectations: fly fluid-actuated piston-cylinder unit with a piston that carries a permanent magnet and one or more sensors that are sensitive to magnetic fields the periphery of the cylinder, characterized in that the permanent magnet in the radial direction of the piston protrudes, is guided on the cylinder jacket and serves as a rotation lock for the piston. 2. Piston-cylinder unit according to claim 1, characterized characterized in that the permanent magnet is designed as a magnetized section of the piston in one piece with this 3. Piston-cylinder unit according to claim 1, characterized characterized in that the permanent magnet as a plate, rod, block or other, separate magnetic shaped piece can be attached to the piston and firmly connected to the piston. 4 · Piston-cylinder unit according to claim 3, characterized characterized in that the piston for fastening the permanent magnetic shaped piece on part of its surface is flattened. 5. Piston-cylinder unit according to one of the claims 1 to 4, characterized in that in the operational position of the piston, the permanent magnet in a is received on the inner jacket (3) of the cylinder (1) suitably recessed longitudinal groove (12). 6. Piston-cylinder unit according to claim 5, characterized characterized in that in the radial outer region of the cylinder (1) opposite the longitudinal groove (12) Rail-like holding device for the magnetic field-sensitive sensors, molded in one piece with the cylinder (1) (5) is provided on which the sensors (5) can be displaced in the axial direction. 7. Piston-cylinder unit according to claim 6, characterized characterized in that the holding device has the shape of a protruding from the outer jacket (9) of the cylinder (1), rib (6) extending in the longitudinal direction of the cylinder Has. 8. Piston-cylinder unit according to claim 6, characterized in that the holding device as in the outer jacket (9) of the cylinder (1) machined groove (14) is formed. ^9. Piston-cylinder unit according to Claim 8, characterized in that the groove (14) has a dovetail-shaped cross section. 1 ° - piston-cylinder unit according to one of the claims 1 to 9, characterized in that on the outer jacket (9) of the cylinder (1) one extends over at least a part the cylinder length extending flat (17) is formed, to which a control unit (11) can be attached. 11. Piston-cylinder unit according to claim 10, characterized in that in the wall of the cylinder (1) Lines (18) for the pressure medium supply and / or discharge of the piston-cylinder unit are formed to which the Control unit (11) can be connected. 12. 'piston-cylinder unit according to claim 11, characterized in that the lines (18) to working spaces of the piston-cylinder unit on both sides of the piston lead and open in the area of the flat (17). 13. Piston-cylinder unit according to one of claims 1 to 12, characterized in that the sensors (5) Magnetic field-operated relays or limit switches are used that influence the control unit (11) and in particular trigger a reversal of the pressure medium supply. 14. Piston-cylinder unit according to one of claims 1 to 13, characterized in that a sensor (5) magnetic odometer is provided, which determines the piston position between its end positions enables. 15. Piston ZyTinder unit according to claim 14, characterized in that the odometer according to the principle of the transit time measurement by magnetostriction excited traveling wave works.