DE102018100516B4 - MEASUREMENT DEVICE, ESPECIALLY LINEAR POSITION MEASUREMENT DEVICE - Google Patents

Abstract

Measuring device based on an internal linear displacement sensor for determining the position of an actuator that can be guided in a straight line and in the direction of the longitudinal axis of the measuring device:i) with a main housing, formed by a light metal profile (2) that is open on one long side and the two end faces, and a closed but closed one at the two end faces Open plastic profile (1) with almost identical linear dimensions and different thermal expansion coefficients, where j) the thermal expansion coefficient of the plastic profile (1) is greater than that of the light metal profile (2) k) the plastic profile (1) and the light metal profile (2) have parallel or identical longitudinal axes l) the plastic profile (1) is fixed in the light metal profile (2), in particular latched, preferably via an integrated outer profile and a corresponding inner profile, but has longitudinal axial mobility with respect to the light metal profile (2), so thatm) the profiles (1, 2) , seen longitudinally, be i changes in the ambient and/or material temperatures and can therefore be moved longitudinally and axially relative to one another based on friction,n) each with an end cap (13) which closes the corresponding end face of the plastic profile (1), is mechanically fixed to it and which is larger than the cross-sectional area of the plastic profile (1), whereino) the respective end cap (13) is designed in such a way that the light metal profile (2) at least at a certain ambient or device temperature directly or indirectly via a seal, in particular a flat seal, onto correspondingly protruding areas of the cap (13), p) the light metal profile (2) has at least one spring integrated into it, which is designed in one piece with the light metal profile (2) and is formed by at least two contrary, in particular parallel slots (5, 6) with an overlapping area, wherein the angles to the longitudinal axis of the light metal profile (2) are greater than 45 degrees, in particular approximately or ge Exactly 90 degrees, so that when the temperature drops, the spring can compensate for part of the increase in length of the light metal profile (2) due to the different thermal expansion coefficients.

Description

The invention relates to a measuring device, in particular a linear path measuring device

Linear displacement measuring devices are preferably used for industrial applications. These systems measure distances with a very high level of precision under harsh environmental conditions.

The general state of the art is that an inductive measuring principle is used up to measuring lengths of around 1000 mm, while for measuring lengths above around 1000 mm the so-called magnetostrictive measuring method is used.

As a rule, housings are used that are made of aluminum or aluminum alloy profiles in operative connection with plastic elements. Above measuring lengths of 1000 mm, changes in expansion of the materials involved and their disturbing differences (metal to plastic) become particularly effective. This is particularly noticeable with the plastic element, since the latter has a greater coefficient of expansion than the aluminum profile. In the temperature range between -40° C and +85° C, the different coefficients of expansion can have such a negative effect that leaks (in the area of the front sides) or even the destruction of the housing or the linear displacement measuring device can occur.

1. 1) Polyamid 6 mit 30 % Glasfaser (PA 6 GF30): α = 50 - 100 x 10-b m/mk Längenausdehnung längs/quer zur Fließrichtung ISO 11359
2. 2) Alu: 23,8 x 10-6 m/mk ä 0,024 mm/k für ein 1-m-Gerät Differenz: Faktor 3 = 0,048 mm/mk: Delta: 20 bis -40 Grad: 60 x 0,05 mm = 0,3 mm für ein 1-m-Gerät, 0,6 mm für ein 2-m-Gerät ä 80 bis -40 Grad = 1,2 mm für ein 2-m-Gerät

Kunststoff - PB 0,150 Kunststoff - PE 0,200 Kunststoff - PE-X 0,220 Typical linear expansion coefficients α are given as follows:

1. 1) Polyamide 6 with 30% glass fiber (PA 6 GF30): α = 50 - 100 x 10-bm/mk linear expansion longitudinal/transverse to the flow direction ISO 11359
2. 2) Alu: 23.8 x 10-6 m/mk ä 0.024 mm/k for a 1 m device Difference: Factor 3 = 0.048 mm/mk: Delta: 20 to -40 degrees: 60 x 0.05 mm = 0.3mm for a 1m device, 0.6mm for a 2m device ä 80 to -40 degrees = 1.2mm for a 2m device

Plastic - PB 0.150 Plastic - PE 0.200 Plastic - PE-X 0.220

• Der DE 10 2010 053 217 A1 ist ein Hall-basierter Linearwegsensor für mittellange Wege zu entnehmen. Vorgeschlagen wird eine Sensoranordnung, ausgebildet zur Erfassung der Position eines linear bewegbaren Elementes, wobei die Sensoranordnung einen Magneten sowie ein, die Position des Magneten erfassendes Sensorelement aufweist, wobei ein ortsfester Träger vorgesehen ist und der Träger zur Aufnahme des Sensorelements und zur Aufnahme des linear und relativ zu dem den Magneten umfassenden bewegbaren Elementes ausgebildet ist.

Regarding the state of the art, reference is made to the following publications, for example:

• the DE 10 2010 053 217 A1 is a Hall-based linear displacement sensor for medium-length displacements. A sensor arrangement is proposed, designed to detect the position of a linearly movable element, with the sensor arrangement having a magnet and a sensor element that detects the position of the magnet, with a stationary carrier being provided and the carrier for accommodating the sensor element and for accommodating the linear and relative to the movable element comprising the magnet.

through the DE 10 2016 207 880 A1 a sensor arrangement for contactless position detection and a method for determining a relative position have become known. A target is used which has a measuring value sensor running along a measuring path with at least one electrically conductive measuring track and an eddy current sensor with a measuring value sensor which comprises at least two detection coils, the measuring value sensor being arranged at a distance from the measuring value sensor and relatively movable along the at least one electrically conductive measuring track and this is at least partially covered, with at least one of the detection coils acting as a measuring coil whose measuring signal is evaluated by an evaluation and control unit for path determination.

The invention is based on the object of providing a measuring device, in particular a linear displacement measuring device, which is able, independently of different coefficients of expansion of the materials used, to realize precise measurement results even with measurement lengths of more than 1000 mm, without causing damage or leaks on or in the housing .between the housing components, or the measuring device, in particular the linear displacement measuring device.

The invention is also based on the object of providing a unit, in particular a machine, which is equipped with a measuring device, in particular a length measuring device.

• i) mit einem Hauptgehäuse, gebildet durch ein an einer Längsseite und den beiden Stirnseiten offenes Leichtmetallprofil sowie ein geschlossenes, aber an den beiden Stirnseiten offenes Kunststoffprofil mit nahezu identischem Längenmaß und verschiedenen thermischen Ausdehnungskoeffizienten, wobei
• j) der thermische Ausdehnungskoeffizient des Kunststoffprofils größer ist als der des Leichtmetallprofils
• k) das Kunststoffprofil und das Leichtmetallprofil parallele oder identische Längsachsen aufweisen,
• l) das Kunststoffprofil im Leichtmetallprofil fixiert, insbesondere verrastet ist, vorzugsweise über ein integriertes Außenprofil und ein korrespondierendes Innenprofile, jedoch Längsaxialbeweglichkeit bzgl. des Leichtmetallprofil aufweist, so dass
• m) die Profile, in Längsrichtung gesehen, bei Änderungen der Umgebungs- und/oder Materialtemperaturen und dadurch relativ zueinander reibungsbasiert längsaxialbeweglich sind,
• n) mit je einer Endkappe, die die entsprechende Stirnseite des Kunststoffprofils verschließt, an dieser mechanisch fixiert ist und die größer ist als die Querschnittsfläche des Kunststoffprofils, wobei
• o) die jeweilige Endkappe so gestaltet ist, dass das Leichtmetallprofil zumindest bei einer bestimmten Umgebungs- bzw. Gerätetemperatur direkt, oder indirekt über eine Dichtung, insbesondere eine Flachdichtung, auf entsprechend überstehende Bereiche der Kappe drückt,
• p) das Leichtmetallprofil mindestens eine in diese integrierte Feder aufweist, die einstückig mit dem Leichtmetallprofil ausgebildet ist und durch mindestens zwei konträre, insbesondere parallele Schlitze mit Überlappungsbereich gebildet ist, wobei deren Winkel zur Längsachse des Leichtmetallprofils größer als 45 Grad sind, insbesondere annähernd oder genau 90 Grad, so dass
• q) bei Temperaturerniedrigung die Feder aufgrund der unterschiedlichen thermischen Ausdehnungskoeffizienten einen Teil der Längenzunahme des Leichtmetallprofils ausgleichen kann.

The first part of the task is solved by a measuring device based on an internal linear displacement sensor for determining the position of an actuator that can be guided in a straight line and in the direction of the longitudinal axis of the measuring device:

• i) with a main housing, formed by a light metal profile that is open on one long side and the two end faces and a closed plastic profile that is open on the two end faces and has almost identical linear dimensions and different thermal expansion coefficients, wherein
• j) the thermal expansion coefficient of the plastic profile is greater than that of the light metal profile
• k) the plastic profile and the light metal profile have parallel or identical longitudinal axes,
• l) the plastic profile is fixed in the light metal profile, in particular latched, preferably via an integrated outer profile and a corresponding inner profile, but has longitudinal axial mobility with respect to the light metal profile, so that
• m) the profiles, seen in the longitudinal direction, are longitudinally axially movable in the event of changes in the ambient and/or material temperatures and are therefore friction-based relative to one another,
• n) each with an end cap, which closes the corresponding end face of the plastic profile, is mechanically fixed thereto and is larger than the cross-sectional area of the plastic profile, wherein
• o) the respective end cap is designed in such a way that the light metal profile presses directly or indirectly via a seal, in particular a flat seal, onto correspondingly protruding areas of the cap at least at a certain ambient or device temperature,
• p) the light metal profile has at least one spring integrated into it, which is formed in one piece with the light metal profile and is formed by at least two contrary, in particular parallel slots with an overlapping area, the angles of which to the longitudinal axis of the light metal profile are greater than 45 degrees, in particular approximately or exactly 90 degrees so that
• q) when the temperature drops, the spring can compensate for part of the increase in length of the light metal profile due to the different thermal expansion coefficients.

Advantageous developments of the measuring device according to the invention can be found in the associated dependent claims.

It is of particular advantage that the cap is designed in such a way that, when assembled and at least at medium temperature (approx. 0 - 20° C.), it presses directly or indirectly via a seal, preferably a flat seal, onto the associated end face of the light metal profile but this is not fixed.

Furthermore, it is proposed that an overlap length of at least 20-50% of the slit length of each slit is given.

The first part of the task is also solved by an inductively or magnetically working linear path measuring device, containing a metal housing serving for the direct or indirect reception of at least one sensor element, in particular formed by a light metal - and a plastic profile, with the profiles viewed in the longitudinal direction relative to one another are movable, in particular when the device is functional or operating, also including end caps, which are in particular detachably connected to the plastic profile, measuring and transmission means being provided within the plastic profile and recesses in the light metal profile to compensate for different expansion coefficients of the profiles used are introduced, further including end caps, which are preferably detachably connected to the plastic profile, preferably by screwing, wherein measuring and transmission means are provided within the plastic profile and to compensate for different expansion coefficients of the profiles used, recesses are introduced in the light metal profile.

Advantageous developments of the linear path measuring device according to the invention can be found in the dependent claims.

The second part of the task is solved by a unit consisting at least of a (mechanical, electrical, pneumatic, hydraulic or electronic) machine, such as a lathe, and at least one measuring device, in particular a linear travel measuring device according to one of the preceding claims.

Advantageous developments of the unit, in particular of the machine, can be found in the associated dependent claims.

In the unit according to the invention, the actuator is attached to a part of the machine, in particular a movable part, with the measuring device, in particular the length measuring device, being positioned rigidly with respect to the basic structure and/or housing of the machine.

Alternatively, there is the possibility that the actuator is part of the measuring device, in particular the length measuring device, with the measuring device, in particular the length measuring device, being arranged rigidly with respect to the basic structure and/or housing of the machine, with the actuator being arranged in the longitudinal direction of the measuring device, in particular the length measuring device is movable.

Depending on the above variant, the actuator is in operative connection with the measuring device, in particular the length measuring device, in a non-contact or touching manner.

• - allgemeiner Maschinenbau, insbesondere Positionserfassung an schnellen Bewegungseinheiten in Fertigungslinien
• - Spritz- und Druckgussmaschinen
• - Verpackungsmaschinen
• - Blechbearbeitungsmaschinen (Pressen und Stanzen)
• - Holzbearbeitungsmaschinen
• - Automatisierungstechnik

Preferred industrial areas of application of the linear displacement sensor according to the invention are given as follows:

• - General mechanical engineering, in particular position detection on fast moving units in production lines
• - Injection and die-casting machines
• - packaging machines
• - Sheet metal processing machines (presses and punches)
• - Woodworking machines
• - Automation technology

• - glasfaserverstärktes Polyamid, z.B. PA6

The elongated housing used in the linear displacement sensor according to the invention contains a plastic profile that accommodates the measuring and transmission means and has a square or rectangular cross section, in particular, which is preferably formed from the following materials:

• - glass fiber reinforced polyamide, eg PA6

• - Aluminium bzw. Aluminiumlegierungen
• - Magnesium bzw. Magnesiumlegierungen
• - Kombinationen aus Aluminium- und Magnesiumlegierungen.

This plastic profile is in operative connection with another profile made of a light metal, approximately U-shaped, whereby the following materials are preferably used here:

• - Aluminum or aluminum alloys
• - Magnesium or magnesium alloys
• - Combinations of aluminum and magnesium alloys.

With the selected housing combination (plastic - light metal), the slits (cuts) made in the light metal profile ensure that different expansions of the materials in the temperature range of -40 - +85°C have little, i.e. no negative, effect, at least not in such a way that the tightness between the end cap and the plastic end face of the plastic profile is no longer given. This could despite vzw. intermediate elastic seal with a compensating effect, especially at low temperatures, because the difference in the coefficients of expansion of the light metal profile and the plastic profile differ greatly from one another

Advantageously, the recesses are formed by slits (incisions), a preferred embodiment of the subject of the invention providing that there are several spaced slits (incisions) in the light metal profile.

As already mentioned, the light metal profile is approximately U-shaped in cross section, with the at least two adjacent incisions (preferably transverse to the longitudinal direction) of at least one complex of incisions, preferably a pair of incisions, being provided in an alternating form in such a way that they extend from the individual wall areas into the floor area of the U-profile. This type of formation of the incisions, which according to a further idea of the invention are preferably provided in at least one of the end regions of the light metal profile, cause a kind of spring effect, because each End cap is connected to the associated end face of the plastic profile, but at the same time directly or indirectly (via a flat seal) presses against the end face of the light metal profile. Especially at low temperatures, it can happen that the incisions can be closed up to the block to compensate for the length.

In order to ensure a certain relative mobility of the housing parts when the device is in use or in its operating state, the profiles can be moved relative to one another to a small extent in the longitudinal direction. A deliberate fixation of the profiles to each other was dispensed with and instead a longitudinal mobility is used, whereby the frictional resistances with regard to the profiles touching each other are selected by construction, material selection and surface properties in such a way that sufficient mobility and spring effect can be achieved.

The measuring device according to the invention, in particular a linear displacement measuring device, can initially be used for any measuring length (also below 1000 mm).

However, preferred applications are seen with measuring lengths above 1000 mm, in particular above 2000 mm.

The measuring device according to the invention, in particular a linear displacement measuring device, works according to the inductive measuring principle, in particular for measuring lengths of more than 1000 mm. Thanks to its good dynamic behavior, the new measuring device, especially the linear position measuring device, is suitable for very fast positioning tasks over the entire measuring section.

According to a further idea of the invention, the end caps consist of plastic, in particular of polybutene (PB) and are provided with an in particular elastic flat seal. Commercially available wood screws in particular are used for detachable assembly with the end regions of the plastic profile.

Inside the plastic profile (preferably a one-piece extruded profile with open end faces) produced in particular by injection molding, there is a coil printed circuit board with several measurement tracks, preferably on a single rigid printed circuit board guided and held by the inner profile (preferably a groove), the coil printed circuit board being approximately the length of the corresponds to the plastic profile used in order to achieve the largest possible area for a given length of the device. An actuator provided outside the linear sensor housing interacts with this coil circuit board (preferably an electrical or electronic one), which together form a resonator. Preferably, the device operates according to a method as in the U.S. 2014/0 117 980 A1 is described. The actuator can either be attached directly to the upper side of the U-profile, which is open at the top, so that it can be displaced longitudinally, preferably latched, or it can be positioned on the machine side at a definable distance and without contact with the housing of the measuring device, in particular the linear displacement measuring device (fastening on a part guided on the machine side).

• 1 Einzeldarstellung des Kunststoffprofils für einen Linearwegsensor;
• 2 Einzeldarstellung des Leichtmetallprofils für einen Linearwegsensor;
• 3 Einzeldarstellung der Spulenleiterplatte für einen Linearwegsensor;
• 4 - 9 Montierter Linearwegsensor in verschiedenen Ansichten bzw. Schnitten.

The subject of the invention is illustrated by means of an exemplary embodiment in the drawing and described as follows. Show it

• 1 Individual representation of the plastic profile for a linear displacement sensor;
• 2 Individual representation of the light metal profile for a linear displacement sensor;
• 3 Individual representation of the coil circuit board for a linear displacement sensor;
• 4 - 9 Mounted linear displacement sensor in different views and sections.

1 shows a plastic profile 1 as an individual representation, which should consist of polyamide (eg PA 6) in this example. The plastic profile 1 is designed as a body that is closed in the circumferential direction but has open end faces and, when installed, takes up the 3 illustrated coil circuit board.

2 shows a light metal profile 2 as an individual representation, which in this example has a U-shaped cross section. In this example, the light metal profile 2 should consist of an aluminum alloy, for example AlMgSi.

The plastic profile 1 and the light metal profile 2 are pushed into one another for assembly purposes and, seen in the longitudinal direction, can be moved relative to one another, so that a type of floating bearing is formed.

Δ_l - Längsausdehnung - m
l₀ - ursprüngliche Länge - m
α - Längenausdehnungszahl - K^-1 (Almost) all solid materials expand when heated. $$\mathrm{a}=1/{\text{I}}_0\times {\mathrm{\Delta }}_{\text{I}}/{\mathrm{\Delta }}_{\text{T}}$$

Δ _l - longitudinal extension - m
l ₀ - original length - m
α - coefficient of linear expansion - K ^-1

Linear expansion coefficient α material mm / mx K aluminum 0.0238 Plastic - PB 0.150 Plastic - PE 0.200 Plastic - PE-X 0.220 Plastic PP (also HT pipe) 0.180

In the end regions 3, 4 of the light metal profile 2, incisions 5, 6 (slots) are introduced according to the invention.

3 shows as a schematic diagram in the plastic profile 1 according to 1 introduced coil circuit board 7, which corresponds approximately to the length of the plastic profile 1. In one of the end regions of the coil circuit board 7 there is a circuit board 8 which is operatively connected thereto and is connected to a plug 9 .

the 4 - 9 show the assembled state of a measuring device, in particular a linear path measuring device 10, with the coil printed circuit board 7 according to FIG 3 is not recognizable. Only connector 9 is shown.

In the 4-9 are the in the 1 and 2 shown profiles 1, 2 (housing parts) recognizable. Also shown are the incisions 5, 6, which are made exclusively in the end regions 3, 4 of the light metal profile 2. In this example, the incisions 5, 6 should have a width of 1 mm and should run parallel to one another in an alternating manner.

Like the 4 - 9 can be seen, each incision 5, 6 starts in a wall area 11 of the profile 2 and runs into the bottom section 12 of the light metal profile 2.

As a result of the alternating arrangement of the incisions 5, 6 in the end areas 3, 4 of the light metal profile 2, a type of spring area F is formed. This spring area F formed by the incisions 5, 6 counteracts the different thermal expansions of the profiles 1, 2 used for different temperature ranges.

In the end areas 3, 4 of the measuring device, in particular the linear displacement measuring device 10, end caps 13, 14, in this example made of a plastic material, for example PB, are provided. The end caps 13, 14, which are preferably provided with an elastic flat seal, are connected to the open end regions of the plastic profile 1 by means of commercially available screws 15, in particular wood screws, with the flat seal being in contact with the aluminum profile 2.

The invention makes it possible to achieve devices with the following parameters with a device length of 1-2 m in a temperature range from -40 to +70° C.: Resolution: 0.2 - 0.030mm Resolution(Output): 12-16 bits Repeatability: 0.75-0.25% Linear Deviation: 0.8 - 0.3% of final value Temperature drift: <= 0.08 - 0.01% resolution 12 bits Repeatability/accuracy 0.025% Linearity deviation ≤ 0.3% FS Temperature drift ≤ ± 0.01%/K Ambient temperature -25... + 70 °C -40... + 70 °C (S97 version) resolution 0.001mm Repeatability/accuracy 18 µ (Li100... Li500), 36µ (Li600...Li1000) Linearity deviation ≤ 0.035% of full scale Temperature drift ≤ ± 0.0001%/K
http://pdb2.turck.de/repo/media/_en/Anlagen/d101791.pdf

In 4 the actuator 16 is only indicated. In this example, the actuator 16 is intended to be positioned outside the housing 1, 2 immediately thereon and to be movable in the longitudinal direction thereof. The actuator 16 works with the in 3 illustrated coil circuit board 7 together and thus forms an electrically or electronically acting resonator. The actuator 16 is preferably fastened, in particular latched, to the U-profile 2, which is open at the top, in a longitudinally displaceable manner.

In 4 It is also indicated that the profiles 1, 2 are connected to one another approximately in the region of their middle extent by suitable connecting means 18, for example screws. This connection does not have a negative effect on the different coefficients of expansion of the materials used, since the thermal balance is brought about in the front end regions 3, 4 of the profiles 1, 2.

In 7 fastening means 17 for the linear path measuring device 1ß are only indicated. These can be designed as clamps, for example, which are in operative connection with profiles molded onto the light metal profile 2 . This has the advantage that no relative movement and no asymmetrical positioning to one another are possible.

Reference List

1

plastic profile

2

light alloy profile

3

end area

4

end area

5

cuts (recesses)

6

cuts (recesses)

7

coil circuit board

8th

circuit board

9

plug

10

linear position measuring device

11

wall area

12

bottom section

13

end cap

14

end cap

15

screw (wood screw)

16

actuator

17

fasteners

18

lanyard

f

spring range

Claims (22)

Measuring device based on an internal linear displacement sensor for determining the position of an actuator that can be moved in a straight line and in the direction of the longitudinal axis of the measuring device: i) with a main housing, formed by a light metal profile (2) open on one longitudinal side and the two end faces and a closed plastic profile (1) but open on the two end faces with almost identical linear dimensions and different thermal expansion coefficients, wherein j) the thermal expansion coefficient of the plastic profile (1) is greater than that of the light metal profile (2) k) the plastic profile (1) and the light metal profile (2) have parallel or identical longitudinal axes, l) the plastic profile (1) is fixed in the light metal profile (2), in particular latched, preferably via an integrated outer profile and a Corresponding inner profile, but longitudinal axial mobility with regard to of the light metal profile (2), so that m) the profiles (1, 2), viewed in the longitudinal direction, are longitudinally axially movable in the event of changes in the ambient and/or material temperatures and are therefore friction-based relative to one another, n) each having an end cap (13) which closes the corresponding end face of the plastic profile (1), is mechanically fixed thereto and which is larger than the cross-sectional area of the plastic profile (1), wherein o) the respective end cap (13) is designed in such a way that the light metal profile (2) presses, at least at a certain ambient or device temperature, directly or indirectly via a seal, in particular a flat seal, onto correspondingly protruding areas of the cap (13), p) the light metal profile (2) has at least one spring integrated into it, which is designed in one piece with the light metal profile (2) and is formed by at least two contrary, in particular parallel slots (5, 6) with an overlapping area, the angle of which to the longitudinal axis of the Light metal profile (2) are greater than 45 degrees, in particular approximately or exactly 90 degrees, so that q) when the temperature drops, the spring can compensate for part of the increase in length of the light metal profile (2) due to the different thermal expansion coefficients. measuring device claim 1 , characterized in that the end cap (13) is designed in such a way that, in the assembled state and at least at a temperature of approx. 2) presses, but is not fixed to it. measuring device claim 1 or 2 , characterized in that an overlap length of at least 20-50% of the slot length of each slot (5, 6) is given. Inductively or magnetically working linear path measuring device, containing a metallic housing serving to directly or indirectly accommodate at least one actuator, formed by a light metal profile (2) and a plastic profile (1), the profiles (1, 2) being viewed in the longitudinal direction relative to one another are movable, in particular when the device is functional and/or operating, also containing end caps (13, 14) which are in particular detachably connected to the plastic profile (1), measuring and transmission means (7, 8, 9) are provided and recesses (5, 6) are made in the light metal profile (2) to compensate for different expansion coefficients of the profiles (1, 2) used. linear path measuring device claim 4 , characterized in that the recesses (5, 6) are formed by incisions. linear path measuring device claim 4 or 5 , characterized in that the recesses (5, 6) are formed by a plurality of spaced incisions. Linear position measuring device according to one of Claims 4 - 6 , characterized in that the incisions (5, 6) are provided in the bottom area (12) of the light metal profile (2) and in particular completely sever a wall section (11). Linear position measuring device according to one of Claims 4 - 7 , characterized in that the incisions (5, 6) run approximately parallel to one another. Linear position measuring device according to one of Claims 4 - 8th , characterized in that the incisions (5, 6) run alternately, starting from the respective wall section (11) adjoining the base section (12). Linear position measuring device according to one of Claims 4 - 9 , characterized in that the light metal profile (2) consists of aluminum, magnesium or an aluminum or magnesium alloy. Linear position measuring device according to one of Claims 4 - 10 , characterized in that the plastic profile (1) is completely closed except for the end faces, is in particular designed and manufactured in one piece and/or consists of a plastic material which is permeable to magnetic and/or electromagnetic and/or optical fields. Linear position measuring device according to one of Claims 4 - 11 , characterized in that the plastic material is formed by a glass fiber reinforced polyamide (PA), in particular with a glass fiber content of 15-50%, preferably 15-25%, is provided. Linear position measuring device according to one of Claims 4 - 12 , characterized in that the end caps (13, 14) are made of plastic, in particular of polybutene (PB). Linear position measuring device according to one of Claims 4 - 13 , characterized in that the end caps (13, 14) are provided with a flat seal and are connected to the plastic profile (1) in particular by wood screws (15). Linear position measuring device according to one of Claims 4 - 14 , characterized in that measuring means (7) which are operatively connected to the sensor are formed by a coil printed circuit board which corresponds approximately to the length of the plastic profile (1). Linear position measuring device according to one of Claims 4 - 15 , characterized in that the sensor interacts directly with the light metal profile (2) and is designed in particular as a resonator provided with a transmission coil. Linear position measuring device according to one of Claims 4 - 16 with a length of ≥ 1000 mm, in particular 1200 to 4500 mm. Linear position measuring device according to one of Claims 4 - 17 , characterized in that the linear path measuring device (10) works inductively and has at least one inductive flat coil, preferably two or three flat coils, which are preferably all mounted on a rigid printed circuit board (7) which is connected via inner double profiles integrated into the interior of the plastic profile (1). is inserted over an end face (3.4). Unit consisting at least of a (mechanical, electrical, pneumatic, hydraulic or electronic) machine, such as a lathe, and at least one measuring device, in particular a linear path measuring device, according to one of the preceding claims. unit after claim 19 , characterized in that the actuator (16) is attached to a part of the machine, in particular a movable part, the measuring device (10), in particular the length measuring device, being positioned rigidly with respect to the basic structure and/or housing of the machine. unit after claim 19 , characterized in that the actuator (16) is part of the measuring device (10), in particular the length measuring device, wherein the measuring device, in particular the length measuring device, is arranged rigidly with respect to the basic structure and/or housing of the machine, the actuator (16) being movable in the longitudinal direction of the measuring device (10), in particular the length measuring device. unit after one of claims 19 until 21 , characterized in that the actuator (16) is in operative connection with the measuring device (10), in particular the length measuring device, in a non-contact or touching manner.

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