DE19735433A1 - Measuring probe for measuring thin layers e.g. paint, varnish, galvanised layer - Google Patents

Abstract

The measuring probe has a stop (9) at the guide unit (3) working with an abutment (9a) at the probe housing (5), and a push element (2) provided above the abutment for a measuring sensor (12), is guide movable limited by a stop at the probe housing. Two coil springs (4, 10) of different spring force, working together with each other, are arranged between the push element and the measuring sensor in the force path. The different spring forces are so measured, that in the starting position of the measuring sensor, the spring force of one of the coil springs (4) is less than the spring force of the other spring (10). Such that with the operation of the push element, first the coil spring (4) is loaded so much, until its spring force overpowers the counter force of the other spring, so that guide unit (3) is moved with the measuring sensor only against the working of the other spring from the drawn back rest condition into the measuring position. After reaching this, further pressure on push element is elastically absorbed by first coil spring.

Description

The invention relates to a measuring probe for measuring thinner Layers on a base material after a magnetic one or eddy current process.

In the non-destructive measurement of the thickness of solid Layers, such as lacquers, galvanic layers and the like, on generally metallic base materials or at Thickness measurement of films, such as plastic films, on a metallic base material are attached, used Layer thickness gauges according to a magnetic or the we belstromstrom. In such measuring devices, the measuring pole is the Measuring sensor spherical with a radius of curvature of typically 1 to 10 mm. The measuring sensor with the spherical measuring pole is either applied directly to the surface of the hand measuring layer set, or the measuring pole is below the Effect of a preloaded spring in the holder of the Meßsen sors is arranged with a defined contact force  of the layer to be measured. With the immediate touchdown the measuring probe is the contact force by the weight of the hand dependent and can range from a few tenths of Newtons to a few 10 Newtons.

When measuring solid layers, the difference is different Tracking force of the measuring pole of minor importance. At the measurement of powdery or soft layers on solid Base material or from layers on yielding base structure However, there are various disadvantages to materials.

When placing the measuring pole with a pre-tensioned spring in the The probe is held by the contact force of the measuring pole constant and is typically 0.5 to 1 Newton.

The disadvantage of this type of probe for the measurement of powdery or soft layers but also from thin layers into the however, there is a special focus on yielding base materials in that the contact force when using the typical Radii of curvature from 1 to 10 mm of the spherical measuring pole so exerts great pressure on the surface that z. Legs powdery or soft layer is pierced or the measuring pole at least strong and different depths in the layering fabric penetrates.

In the case of yielding base materials, deformation of the Measurement object are caused by the pressure effect. Incorrect measured values are the result.

This danger also exists when the measuring sensor is lowered from Hand. The inertia of the measuring sensor leads to Place the measuring pole on the surface - even if it is weighs only a few grams - due to the abrupt delay in the Movement speed of the hand from about 10 to 20 cm / s 0 cm / s within a path length of only a few µm to one  considerable force on the layer, so that the measuring pole, especially for powdery or soft layers can penetrate the base material or the layer at least to a considerable extent. The mass forces te are between 0.2 to 20 Newtons.

The mass forces act in a similar way during measurements yielding materials of the measurement object.

A reproducible measurement when using typical used known probes on powdery or soft layer or on test objects with compliant materials this high and different forces is therefore not possible. Practice confirms this statement. Depending on the type of When the probe is attached, the measured values are reduced by a few Percent or to zero percent of the original shift thickness ke. The measurement statement is therefore practically unusable. From the For this reason, contacting layer thickness measuring probes are particularly important for the measurement of powdery and soft layers not used.

The same applies analogously for measurements on objects with compliant materials.

In practice, there is also an urgent need, the thickness of powdery or soft layers before the on burn or cure to determine before the next one Processing as quickly as possible to be able to lead.

At the moment the correction can only be made after measuring the fixed Layer, i.e. after baking or curing, because the commercial measuring instruments are only able to fix Measure layers. The waiting time, e.g. B. in the powder  layering, between the application of the powder layer and the earliest possibility of measuring the layer thickness of the burned shift is about an hour; this is a Time period that is very uneconomical if the Deviations in layer thickness must be corrected.

As an example of layers to be measured, thin acetylene should also be used marked layers on metal foils, e.g. B. Alumi painted inside called nium tubes for toothpastes and similar mixtures of substances. Conventional hand probes bend the thin base material when attaching the measuring pole and therefore do not deliver reproducible measured values.

From DE 36 22 708 A1 a measuring probe is known for testing is used for the final painting of motor vehicle bodies. This Measuring probe is kept gimbal and by means of handling machines along a body. It is through the handling machine with a certain pressure placed vertically on the surface to be measured. By the pretension of a compression spring supporting the measuring probe becomes immediately after touching the probe pole with the measuring surface the full prestressing force of this Compression spring effective. During the measurement, the measuring probe held onto the body by a suction cup.

To lift the probe system off the body, the Air can be let back into the suction cup. This causes the vacuum to be applied to the suction cup loosens, causing the suction cup from the surface of the body takes off. Precise replacement of the measuring probe on the same measuring point for repeating and checking the first Measurement is not possible.

Another layer thickness measuring probe is from GB 637 471 knows. This probe works on the electromagnetic  Principle of adhesive force. The adhesive force of the pole pin that is on the Surface of the coated soft magnetic steel base material works, results from the interaction of one Armature spring with low spring force and the electromagnetic force of the coil system by the direct current is powered by a battery. The adhesive force becomes indirect measured by the excitation current flowing through the coil. The current measured on an ammeter serves as the measured variable, the - by steadily reducing a maximum current outgoing - just no longer enough to the pole pin against the pressure force of the anchor spring on the layer surface to keep. When tearing off the pole pin from the one to be measured A contact is made on the surface after the on switching a switch causes a lamp to light up. At this moment, the further reduction of the current must be done Using two resistors can be stopped because of this current value is a measure of the layer thickness.

Another measure of the layer thickness is the spring force of the Anchor spring, which acts as a measuring spring together with the electromagnetic force of the pole pin acts. A decrease in the Fe derkraft, e.g. B. by aging, changes the rash of the Am peremeters and thus also the layer thickness display. At the This measuring device would decrease the anchor spring lead to a smaller layer thickness display than that of the deed neuter layer thickness.

In the known device there is also a second one larger spring available, but not on the pole pin acts and therefore no effect on the tracking power of the Has pole pin on the layer surface. Besides, that is electromagnetic force is very strong with this probe depending on the layer thickness, so that from the measuring principle strong different contact forces must arise. A constant contact force or almost zero  Tracking force is due to the electromagnetic adhesive force zips not possible with this known measuring probe. If the both contacts for the indicator light are closed, can by pressing on the measuring probe to different degrees the pole whoever presses the pole pin firmly onto the surface the. This known measuring probe therefore enables in particular none with thin, powdery or soft layer materials usable measurement results.

DE 39 02 095 A1 is yet another measuring probe for measuring thin layers on electrically conductive base materials known.

When the probe is attached, a sliding sleeve touches it Measurement object. Since the probe is on an outer grip sleeve is held by hand, this grip sleeve slides in one Movement downwards in the direction of the measurement object. The probe body is against the Effect of a coil spring moved down. This Wendelfe however, it only has the task of closing the probe body at rest stood to push back into the sliding sleeve or after opening put the sliding sleeve into the probe body with one in sheet spring-loaded sensor part for so long until the spherical surface of a measuring pole Pot core sits on the surface of the measuring object.

A soft placement of the spherical surface of the measuring sensor is with this known probe only in the context of the vorege low travel of the fixed two blades springs and therefore only possible within narrow limits.

This known measuring probe is also due to the short Travel not possible to relax the spring system where thanks to a precise re-installation of the sensor system for a new measurement at the same place  is closed. When relaxing the grip sleeve is also a brief lifting of the entire measuring probe from the measuring head unavoidable area with manual control, unless the Probe would be carried in a tripod. When you resume setting the probe by hand will be different in any case re measuring point touched.

In this known measuring probe, the contact force is due to the Design features of the probe and the sheetfeed used fixed. The setting of a maximum force by the operator of the probe is not possible. Ande re contact forces require probes with a different design features.

The contact force of the measuring sensor is also from the Direction of measurement depends in so far as it is used for measurements from above downwards differently than overhead measurements from bottom to bottom is up. These differential support forces are unchangeable. An adjustment of the spring system depending on the measurement direction is not possible.

In the known measuring probe, the measuring system has two sheets springs are also freely suspended and can therefore be axially free commute. When the probe moves between individuals Measurements and the entire handling, however, arise Acceleration and deceleration forces that the measuring system constantly knock on the contact surfaces inside the probe to let. Such shocks are disadvantageous for the measuring properties and the measuring accuracy of such precision measuring devices.

Since the placement of the sliding sleeve on the object to be measured and the measuring system with the spherical contact surface of the pot core on the surface to be measured not in separate Steps can be carried out with this known measuring probe also other disadvantages. The touchdown  Operation of the entire probe with its mass and with the mass the operator's hand and arm can be the landing speed is not carried out in a controlled manner.

This allows the time of touching the face of the The operator does not see the sliding sleeve with the measuring object be recorded. A gentle placement of the pot core with minimal impulse transmission requires the first touch the sliding sleeve immediately brakes the attachment process ges, so that the measuring system be very slowly the surface stirs. But this is because of the known measuring probe uncontrolled touchdown speed caused by under different masses of probe, hand and arm of the operator is not possible.

The invention has for its object in the measurement thin layers with a measuring probe of the aforementioned Type the static contact pressures and the dynamic forces to reduce that despite a touching measurement solution, if possible also of powdery or soft layers as well as for measurements on objects with yielding Materials, a reproducible measurement result is achieved, that delivers meaningful good values for the assessor.

This object is achieved according to the invention by means of a measuring probe for measuring thin layers on a base material a magnetic or eddy current process with a tube shaped probe housing with a lower front opening voltage for a measuring sensor with a measuring pole, which is at the bottom End of a guide device is arranged in the Stop the longitudinal axis of the probe housing against spring action is guided displaceably, being in the starting position tion or rest position of the measuring sensor a stop on the Guide device with an abutment on the probe housing cooperates, solved in that above the abutment  a sliding element for the measuring sensor on the probe housing is slidably guided, and that in the force path two between the sliding element and the measuring sensor other cooperating coil springs of different Fe derkraft are arranged, which are dimensioned so that in the Starting position of the measuring sensor, the spring force of one Coil spring so lower than the spring force of the others Coil spring is that when you operate the sliding element first the one coil spring is stretched until their spring force is the counterforce of the other coil spring overcomes and thus the guide device with the measuring only against the action of the other coil spring from the retracted rest position is moved into the measuring position, after they have been reached, another pressure on the sliding lever element is elastically caught by the first coil spring becomes.

Further features of such a probe are in the claims Chen 2 to 29 marked.

Due to the resilient arrangement of the guide device with the Measuring sensor in the probe housing between two together Menus acting coil springs of different spring force becomes a very low contact force of the measuring pole on the measuring layer reached with the measuring sensor lowered.

When measuring with the measuring probe according to the invention, first the probe body with its probe foot on the one to be measured Layer put on. Only then is the measuring sensor actuated term of the sliding element, such as a grip cap or one Push pin, slowly and springily placed on the surface. The measuring pole first touches the measuring counter without force stood, and the contact force increases by pressing the Actuator linear from zero to one preselect barely low final contact force.  

In the relaxed, unused state of the probe, the measurement retracted sensor retracted inside the probe body and does not stand over the contact surface of the probe foot forth.

The possibility of a front is particularly advantageous selectable or adjustable contact force of the measuring sensor by changing the clamping length of one of the two or at the springs of the spring system by z. B. the screwed annular stop either in the longitudinal direction of the guide device is adjusted up or down or distance rings of different thickness at the ends of the screw be used.

The twist on the outside of the probe broke The ring nuts also allow a preselectable adjustment end bearing force. Especially when used of coil springs their spring forces and thus the Final contact force of the probe system easily by adjusting screws be changed at one end of the spring.

The probe base with its flange-like level is used for measuring NEN placement surface on the layer to be measured sets and looks like a small tripod. It can therefore precise repeat measurements by repeated absences ken of the measuring sensor from the raised rest position in the Measurement position can be carried out at the same place.

The following procedure results when measuring with the probe:

• - By actuating the designed as a sliding element First, the first weaker screws are used spring until its spring force equals that Biasing force of the second stronger coil spring is;  
• - When depressed further, the measuring sensor moves with its guide device against the one to be measured Layer, while the spring force of the two screw fe who constantly work against each other and are practical cancel (except for the negligible mass and Frictional forces). As a result, the measuring sensor moves close too "floating" against the layer.
• - At the time when the measuring pole touches the layer the measuring sensor places no force on the layer. A further movement of the sliding element is then from the first coil spring added.

In the measuring probe according to the invention, the measuring sensor is thus after attaching the probe body with the probe foot a defined larger distance from the one to be measured Layer led, and the contact force of the measuring pole increases touching the layer from zero to the preselectable final force set.

A particularly precise mass balance when putting on the Measuring probe on the object to be measured is according to a training the invention achieved in that both coil springs as Tension spring are formed, the weaker tension spring between the sliding element and the guide device with the measuring sensor and the other stronger tension spring between the Guide device and the housing head is arranged. The Both tension springs can be particularly space-saving Way in the interior of the guide device parallel to it Axis can be arranged side by side, the weaker Tension spring at its upper end with an upper cross bar connected to the guide device and with its lower end on one of them, the full length of the spring is pushed through from above zenden adjustment pin is attached. At the top of the Ju the sliding element sits on the top of the housing  te. The other stronger tension spring is between a retaining eye in the interior of the guide device above the measuring sensor and an adjustable retaining eyelet clamped on the housing head. The smoothness and thus the measuring accuracy the probe can also be improved in that the Füh tion device with a ball guide in the probe housing leads is.

It has also surprisingly been found that through an elastically flexible film from a metrologically suitable ten material, e.g. B. made of plastic or bronze, the zwi rule the measuring pole of the measuring sensor and the layer material is arranged, the surface pressure on the powdery or soft Layer is reduced so that the penetration of the Meßsy stems in the layer can be neglected and reprodu measurable measured values can be achieved. The pressure reduction film is integrated on the measuring probe or on the measuring device Measuring sensor attached and is therefore part of the measuring probe or Measuring device.

It is arranged between the measuring pole and the layer and enlarged ßters the radius of curvature of the contact surface of the measuring pole. This reduces the specific contact pressure, what especially with very soft and powdery layer material fen leads to a higher measuring accuracy.

To the favorable initial characteristics of the measuring sensor at The probe foot can make better use of measurement of thin layers with the film also from the probe body, for example Screws are removed and against another probe foot can be replaced without foil with flat contact points. Of the Thickness value of the film is used in the evaluation of the measurement results deductions, so that only the thickness of the Layer on the base material is measured.  

It does not matter, which is absolutely absolute to determine the highest thickness value. For predestination that layer thickness, which is after baking or curing ten results, it is sufficient to have a typical thickness value of the powder hard or soft layer. This typical one Thickness value, even if it is slightly smaller than the absolute highest value, is in a fixed and be by trial knew connection to the fixed layer, which after the Burning in or curing results.

Due to the additional pressure valve attached to the measuring probes rungs film with an insignificant additional effort So far not covered scope of such Layer thickness measuring devices detected. The application of the measuring probes is also by hand when using the "pressure reduction film" have known measuring probes and devices very similar, so that the operator does not have to learn new handling rules.

When using the measuring probe with pressure reducing foil and on The tips of the probe foot have pierced pulv or soft layers with the tips not as proved disadvantageous, since soft layers after the Ab lift the probe again or close the powder layer burn-in itself by melting the powder closes again. The probe foot acts like a small tripod. The measurements are therefore with the probe body attached repeatable by releasing and pressing again of the actuator.

When measuring with the measuring probe, the measuring sensor is after the Attaching the probe body with the probe foot from a defi nated distance against the layer to be measured, and the contact force of the measuring pole increases after touching the Pressure reduction film or the layer to be measured from zero off to the preselected final force.  

The pressure reduction film also has the advantage that no or very little powder dust in the movement mechanism of the Layer thickness probe penetrates. If powder penetrates, he there is an uncontrolled friction on the movable Share and leads to different investment forces that do not allow reproducible measurements. That is through counteracted the pressure reduction film.

The unscrewable probe base also allows in a simple manner a possibly necessary cleaning of the inside Guide surfaces for the measuring sensor of penetrated powder dust from blowing out or compressed air.

The unscrewable probe foot can also be replaced by a probe foot with an inverted V-shaped notch or groove for measurement longitudinally arched or cylindrical, also tubular counter stands to be replaced.  

Preferred embodiments of the invention are in the Drawing shown schematically. Show it

Fig. 1 shows a section through a first embodiment of a measuring probe in the idle state of the measuring sensor, wherein the measuring sensor is located at a distance above the measuring position,

Fig. 2 shows a section through the probe of Fig. 1 in the measuring position, in which the measuring sensor with the pole tip on a pressure reduction film rests for measuring a powdery or soft layer on a solid base material,

Fig. 3 shows a detail III of Fig. 1 in an enlarged partial view,

Fig. 4 shows a longitudinal section through a modified second embodiment of a measuring probe, wherein the Meßsen sor is brought by pressure on an end-side pressure pin according to the mechanical pencil principle in the measuring position,

Fig. 5 is an external view of this second probe,

Fig. 6 a longitudinal section through yet a further embodiment of such a measuring probe verbes serte,

FIG. 7 shows a first section through this probe according to section line VII - VII of Figure 6.

Fig. 8 shows a second section along section line VIII-VIII and

Fig. 9 shows a section through the probe base with an inverted V-shaped notch or groove for measuring on longitudinally arched objects.

In the first exemplary embodiment of a measuring probe 1 shown in FIGS. 1 and 2, a grip cap 2a as a sliding element 2 is guided on a multi-part cylindrical probe housing 5 as a sliding element 2 against the pressure of two differently dimensioned coil springs 4 and 10 . Both coil springs 4 and 10 are arranged coaxially to one another on a guide tube as a guide device 3 , which carries a measuring sensor 12 with a crowned measuring pole 13 at its lower end. From the grip cap 2 a, two driving pins 6 , 6 a are directed radially inward, with which the grip cap 2 a is guided on the probe housing 5 in guide slots 8 , 8 a so as to be longitudinally displaceable. The driving pins 6 , 6 a lie on a support ring 7 at the upper end of the coil spring 4 to lower the measuring sensor 12 with the measuring pole 13 from the rest position shown in FIG. 1, in which the measuring pole is in a lifted position in one larger defined distance from the layer 19 to be measured, in the measuring position of FIG. 2. The layer 19 is located on a base material 20 .

As can be seen in FIGS. 1 and 2 in detail, the measuring probe 1 has a tubular probe housing 5 with an end-side lower opening 5 a for the measuring sensor 12 with the measuring pole 13 .

The measuring sensor 12 arranged at the lower end of the guide device 3 is guided with the guide tube in the longitudinal axis of the probe housing 5 so as to be limited against the action of spring.

An annular stop 9 on the guide tube interacts with an annular abutment 9 a on the probe housing 5 .

On the probe housing 5 above the abutment 9 a for the stop 9 of the guide device 3, a pusher 2 for the measuring sensor 12 is also guided in the longitudinal axis of the probe housing 5 so that it can be displaced in a stop-limited manner. The handle 2, a handle cap 2 a (Fig. 1 and 2) or a pressure pin 2 b (FIG. 4 and 5).

Between the pusher or sliding element 2 and the stop 9 on the guide device 3 , the first coil spring 4 is arranged, which is designed as a compression spring and by which the pusher is resiliently supported relative to the measuring sensor 12 .

Between the stop 9 on the guide tube and a lower annular abutment 30 on the probe housing 5 , the second coil spring 10 is also arranged, which is also designed as a compression spring and counteracts the first coil spring 4 . The measuring sensor 12 is supported in the idle state of FIG. 1 at a distance above the opening 5 a for the measuring pole 13 in the probe housing 5 .

The spring force of the first compression coil spring 4 is gear position to off, in which the stopper 9 abuts against the abutment 9 a, so less than the spring force of the second compression coil spring 10 so that first the first coil spring 4 is so far compressed upon depression of the push button 2 until their spring force overcomes the counterforce of the second screw benfeder 10 and thus the guide device 3 with the measuring sensor 12 against the action of the second helical spring 10 is moved from the retracted rest position into the measuring position of FIG. 2. After reaching the measuring position, further pressure on the pusher 2 is elastically absorbed by the first helical compression spring.

The stop 9 for the two helical compression springs 4 , 10 is axially adjustable on the guide device 3 . It is functional as a ver on the guide tube in a thread 3 a adjustable ring nut.

One or more spacer rings 31 , 32 for adjusting the end bearing force of the measuring pole 13 on the layer 19 to be measured can be arranged on the guide tube at the ends of the coil springs 4 , 10 .

The probe housing 5 has a probe base 33 widened flange-like around the opening 5 a for the measuring sensor 12 .

This probe foot 33 is detachably attached to the lower part of the probe housing 5 by means of a screw thread 34 or a bayonet connection. The probe foot 33 is made of clear acrylic glass.

In the first embodiment shown in FIGS. 1 and 2, the sliding element 2 for the measuring sensor 12 is designed as a cylindrical handle cap 2 a which overlaps the upper end of the probe housing 5 and has two driving pins 6 , 6 a which are directed radially inward and are located opposite one another in parallel the longitudinal slots 8 , 8 a on the probe housing 5 on both sides of the guide device 3 are guided with limited stops and rest with their free ends on a support ring 7 as an upper abutment for the first coil spring 4 .

On the probe housing 5 , an axially adjustable ring nut 35 is arranged as a lower end stop for the handle cap 2 a. This ring nut 35 can be adjusted in a thread 36 as required.

In the second exemplary embodiment of such a measuring probe 1 shown in FIGS. 4 and 5, the sliding element 2 for the measuring sensor 12 is designed as a tubular pressure pin 2 b. This pressure pin 2 b is on the upper end of the guide device 3 and also arranged in a concentric opening 37 at the upper end of the probe housing 5 telescopically and at limited impact. With its lower annular end, it serves as an abutment for the upper coil spring 4 , a spacer ring 31 for changing the spring force being arranged at the upper end of the coil spring 4 in FIG. 4.

The pressure pin 2 b has an annular flange 38 at the lower end, with which it is axially supported on an inner recess 39 at the upper end of the probe housing 5 . In addition, the pressure pin 2 b has a longitudinal slot 40 and the guide tube has a longitudinal slot 40 a for a pin 41 protruding inwards from the probe housing 5 as an anti-rotation device.

On the push pin 2 b is also a ver on a thread 42 adjustable ring nut 43 with a scale 44 for preselectable adjustment of the end contact force on the object to be measured by limiting the path when depressing the actuation of the or pusher 2 .

In this second exemplary embodiment, spacer rings 31 , 32 are located at the ends of the two coil springs 4 , 10 for adjusting the spring forces of the two coil springs acting against one another.

In both of the exemplary embodiments shown, a probe cable 18 extends from the handle cap 2 a or the pressure pin 2 b at the upper end of the measuring probe 1 , which can be seen with a kink protection 17 and inside the measuring probe 1 by means of flexible connecting wires 11 with an inside of the guide device device 3 for the measuring sensor 12 arranged circuit board 45 ( Fig. 4), which is connected to the measuring sensor 12 , is the verbun.

Both measuring probes 1 can be used in the embodiment described above for the measurement of solid layers 19 on solid base materials 20 . The probe foot 33 rests with its flat, flat underside 33 a on the layer to be measured, the measuring sensor 12 in the probe housing 5 initially having the rest position shown in FIGS . 1 and 4 at a more or less large distance from the layer 19 to be measured occupies from which it is lowered for each measuring process by means of the sliding element 2 , the handle cap 2 a or the Druckstif tes 2 b, in the measuring position of FIG. 2.

In order to be able to use the measuring probe 1 also for measuring powdery or soft layers 19 on solid or possibly also flexible base materials 20 , screw-in openings for at least three attachment tips 16 are arranged on the probe foot 33 around the opening 5 a for the measuring sensor 12 .

In addition, in the opening 5 a for the measuring sensor 12 on the son denfuß 33 a film 15 is attached to reduce pressure. This consists of an elastic, dimensionally stable material, such as plastic or bronze, which is designed in such a way that powdery layer materials do not adhere to it as far as possible. It is inserted in the manner of a membrane on its circumference in an annular groove 14 on the probe foot 33 and expediently has a wavy outer area similar to a loudspeaker membrane.

As indicated by dashed lines in Fig. 5, in both embodiments between the sliding element 2 and the measuring sensor 12, a pneumatic or hydraulic damping system 50 can be arranged, the measuring sensor 12 largely independent of the actuation speed by hand, with a uniform but slow speed can be lowered against the film 15 or onto the layer 19 to be measured.

Figs. 1 and 2 allow the operation of Schichtdickenmeß detect probe 1. In Fig. 1, the measuring device 12 attached to the guide device 3 is still inserted into the probe housing 5 and is held by the coil spring 10 in the stop position shown. The measuring pole 13 does not touch the film 15 . The film 15 is therefore relaxed and loosely arranged in the annular groove 14 .

In FIG. 2, the measurement probe is shown in the measuring position. For measurement, the probe housing 5 with the three attachment tips 16 is placed on the base material 20 with the layer 19 to be measured, which is still powdery or soft. Then the handle cap 2 a is pushed slowly against the pressure of the coil spring 4 by hand. The BEFE in the handle cap 2 Stigt driving pins 6 and 6 a press the spring 4 over the support or driving ring 7 together until the biasing force of the guide tube with the measuring sensor 12 surrounding second coil spring 10 has been overcome and the measuring sensor 12th with the measuring pole 13 comes to a delay on the film 15 and presses it against the layer 19 with a defined low force.

The measuring pole 13 bends the film 15 until it touches the surface of the layer 19 .

The spring forces of the two coil springs 4 and 10 are dimensioned such that they just overcome the internal stress of the film 15 in total and only a small amount of force acts on the layer 19 to be measured.

Due to the significantly larger radius of curvature of the bent sheet 15 , with which it rests on the layer 19 , compared to the typical radius of curvature of the measuring pole 13 , and the lower contact force of the film 15 on the layer 19 compared to the contact force of conventional probes results in a significant overall Pressure reduction.

For the rest, the measuring probe of FIGS. 4 and 5 also works as described using the exemplary embodiment of FIGS. 1 to 3 before. The same parts are provided with the same reference numerals as there. Instead of as compression springs, the coil springs 4 , 10 can optionally also be used in the form of tension springs.

The latter is the case in the third embodiment of FIGS. 6 to 8 or 9. In this measuring probe, both screws are designed as spring springs. The weaker tension spring 104 is arranged between the sliding element 2 and the guide device 3 with the measuring sensor 12 and the other stronger tension spring 110 between the guide device 3 and the housing head 5 b.

Both tension springs 104 , 110 are arranged in the interior of the guide tube 3 serving as a guide tube parallel to the axis thereof side by side. The weaker tension spring 104 is connected at its upper end to a form-fitting and non-positively inserted upper crossbar 3 b and is fastened at its lower end to an adjusting pin 111 penetrating the spring 104 over its entire length, at its upper end the sliding element 2 or the pusher sits on the top of the housing. The other, stronger tension spring 110 is clamped between a retaining eye 112 in the guide tube 3 above the measuring sensor 12 and an adjustable retaining eye 113 on the housing head 5 b.

The tubular guide means 3 is particularly smoothly guided by a ball guide 114 in the probe housing. 5 As a result, the two tension springs 104 , 110 can be precisely matched to one another in order to achieve particularly low contact forces.

The adjustment pin 111 for the weaker tension spring 104 is attached to the sliding element 2 or pusher by means of an upper threaded head 115 adjustable in length from the outside. The upper spring end 104 a of this tension spring 104 is, as shown in FIG. 8, opened laterally and fastened to the crossbar 3 b by means of a retaining screw 118 .

The upper eyelet 113 for the stronger tension spring 110 is part of an adjusting screw 116 , which is introduced in the housing head 5 b above the guide device 3 adjustable in length.

In addition, the sliding element 2 is supported in the housing head 5 b by means of an additional weak compression spring 117 , which generates only a slight finger pressure when the measuring sensor 12 is actuated, but has no effect on the function of the two tension springs.

As with the other two embodiments, too with this measuring probe the measuring pole, if it is the upper to be measured touches the surface, first the zero contact force, and this then increases linearly to the adjustable limit on. The limit is from zero Newton to z. B. some Hun The newton can be set by the operator.

By holding the probe in the measuring position on the Surface of the measuring object and by pressing the Sliding element is due to the precise guidance of the Sen sorsystems in the housing arrangement a precise re  place the measuring sensor on the surface of the measuring object guaranteed.

Depending on the design, the tension springs are almost equally strong thereby together so that only the differential force as Contact force of the measuring pole comes into effect, regardless of how hard the probe housing is pressed onto the surface and how firmly the sliding element or the pusher in the son the housing is pushed in. The differential force can In extreme cases also be zero. The tracking force is independent on the layer thickness.

The guide device 3 can be designed as a tube, plunger, rod, ball guide or in another suitable shape without leaving the scope of the invention. Likewise, all shown versions of the measuring probe can also be provided with a screw-off probe foot 33 , which, as shown in FIG. 9, has an inverted V-shaped notch or groove 119 for measuring on longitudinally curved objects.

Reference list

1 measuring probe
2 sliding element or pusher
2 a handle cap
2 b push pin
3 guide device
3 a thread
3 b crossbar
4 coil spring
5 probe housing
5 b housing head
5 a opening
6 drive pin
6 a Driving pin
7 support ring
8 longitudinal slot
8 a longitudinal slot
9 stop
9 a abutment
10 coil spring
11 connecting wires
12 measuring sensor
13 measuring pole
14 ring groove
15 foil for pressure reduction
16 attachment tip
17 Kink protection
18 probe cables
19 layer
20 base material
30 abutments
31 spacer ring
32 spacer ring
33 probe base
33 a bottom
34 screw thread
35 ring nut
36 threads
37 opening
38 ring flange
39 return
40 longitudinal slot
40 a longitudinal slot
41 bolts
42 threads
43 ring nut
44 scale
45 printed circuit board
50 damping system
104 tension spring
104 a upper spring end
110 tension spring
111 alignment pin
112 eyelet
113 retaining eye
114 ball guide
115 threaded head
116 set screw
117 compression spring
118 retaining screw
119 notch or V-groove

Claims (29)

1. Measuring probe for measuring thin layers on a base material according to a magnetic or eddy current drive with a tubular probe housing ( 5 ) with a front lower opening ( 5 a) for a measuring sensor ( 12 ) with a measuring pole ( 13 ) at the bottom The end of a guide device ( 3 ) is arranged, which is guided in the longitudinal axis of the probe housing ( 5 ) so as to be displaceable against the action of a spring, whereby in the starting position or rest position of the measuring sensor ( 12 ) a stop ( 9 ) on the guide device ( 3 ) with a Abutment ( 9 a) cooperates on the probe housing, characterized in that above the abutment ( 9 a) a sliding element ( 2 ) for the measuring sensor ( 12 ) on the probe housing ( 5 ) is slidably guided,
and that in the force path between the sliding element ( 2 ) and the measuring sensor ( 12 ) two co-operating coil springs ( 4 , 10 ) of different spring force are arranged, which are dimensioned so
that in the starting position of the measuring sensor ( 12 ) the spring force of one helical spring ( 4 ) is so low than the spring force of the other helical spring ( 10 ) that when the sliding element ( 2 ) is actuated the one helical spring ( 4 ) is first tensioned so far, until their spring force overcomes the counterforce of the other coil spring ( 10 ) and thus the guide device ( 3 ) with the measuring sensor ( 12 ) is only moved against the action of the other coil spring ( 10 ) from the retracted rest position into the measuring position after it has been reached a further pressure on the sliding element ( 2 ) is elastically absorbed by the first coil spring ( 4 ). 2. Measuring probe according to claim 1, characterized in that the coil springs ( 4 , 10 ) are designed as compression springs and are arranged coaxially one behind the other on the guide device ( 3 ). 3. Measuring probe according to claim 1 and 2, characterized in that the first helical compression spring ( 4 ) is arranged between the sliding element ( 2 ) and an adjustable stop ( 9 ) on the guide device ( 3 ),
and that the second helical compression spring ( 10 ) is clamped between the adjustable stop ( 9 ) on the guide device ( 3 ) and a lower abutment ( 30 ) on the probe housing ( 5 ) and the guide device ( 3 ) with the measuring sensor ( 12 ) in the idle state an abutment ( 9 a) on the probe housing ( 5 ) presses, the measuring sensor ( 12 ) occupies such a distance from the opening ( 5 a) on the son dengehäuse ( 5 ), the travel of the second helical compression spring ( 10 ) when operating the slide mentes ( 2 ) for a measurement process. 4. Measuring probe according to claims 1 to 3, characterized in that the stop ( 9 ) for the coil springs ( 4 , 10 ) on the guide device ( 3 ) is axially adjustable. 5. Measuring probe according to claims 1 to 4, characterized in that the stop ( 9 ) for the two coil springs ( 4 , 10 ) is an at the Füh approximately device ( 3 ) in a thread ( 3 a) adjustable ring nut. 6. Measuring probe according to one of claims 1 to 5, characterized in that on the guide device ( 3 ) at the end of the coil springs ( 4 , 10 ) one or more spacer rings ( 31 , 32 ) for setting the end bearing force of the measuring pole ( 13 ) are arranged on the layer ( 19 ) to be measured. 7. Measuring probe according to one of claims 1 to 6, characterized in that the probe housing ( 5 ) has a flange-like widened probe foot ( 33 ) around the opening ( 5 a) for the measuring sensor ( 12 ). 8. Measuring probe according to claim 7, characterized in that the probe foot ( 33 ) on the lower part of the probe housing ( 5 ) by means of a screw thread ( 34 ) or a bayonet connection is releasably attached. 9. Measuring probe according to claim 7 or 8, characterized in that the probe base ( 33 ) consists of clear acrylic glass. 10. Measuring probe according to one of claims 1 to 9, characterized in that the sliding element ( 2 ) for the measuring sensor ( 12 ) as a the upper end of the probe housing ( 5 ) overlapping cylin drical handle cap ( 2 a) is formed with two of the grip cap ( 2 a) radially inward driving pins ( 6 , 6 a), which are guided in a parallel manner in the opposite longitudinal slots ( 8 , 8 a) on the probe housing ( 5 ) on the other side of the guide device ( 3 ) and with their Free ends rest on a low support ( 7 ) as the upper abutment for the first coil spring ( 4 ). 11. Measuring probe according to claim 10, characterized in that an axially adjustable ring nut ( 35 ) is arranged as a lower end stop for the handle cap ( 2 a) on the probe housing ( 5 ). 12. Measuring probe according to one of claims 1 to 9, characterized in that the sliding element ( 2 ) for the measuring sensor ( 12 ) is designed as a tubular pressure pin ( 2 b) which on the upper end of the guide device ( 3 ) and in a concentric opening ( 37 ) at the upper end of the probe housing ( 5 ) is arranged telescopically and with limited movement bar and with its lower annular end serves as an abutment for the upper coil spring ( 4 ). 13. Measuring probe according to claim 12, characterized in that the pressure pin ( 2 b) at the lower end has an annular flange ( 38 ) with which it is axially supported on an inner recess ( 39 ) at the upper end of the probe housing ( 5 ). 14. Measuring probe according to claim 12 or 13, characterized in that the pressure pin ( 2 b) has a longitudinal slot ( 40 ) and the guide device ( 3 ) has a longitudinal slot ( 40 a) for a protruding from the probe housing as an anti-rotation protruding bolt ( 41 ) . 15. Measuring probe according to claim 12 or 13, characterized in that on the pressure pin ( 2 b) a ring nut ( 43 ) with a scale ( 44 ) for pre-selectable adjustment of the end contact force on the measuring object was by limiting the path when depressing the actuator or pusher ( 2 ) is provided. 16. Measuring probe according to one of claims 1 to 15, characterized in that at the upper end of the measuring probe ( 1 ) from the handle cap ( 2 a) or the pressure pin ( 2 b), a probe cable ( 18 ) extends, which inside the measuring probe (1) by means of flexible te Anschlußdräh (11) having disposed in the interior of the guide means (3) for the measuring sensor (12) circuit board (45) which is connected to the measuring sensor (12) is connected ver. 17. Measuring probe according to one of claims 1 to 16, characterized in that on the son denfuß ( 33 ) around the opening ( 5 a) for the measuring sensor ( 5 ) at least three attachment tips ( 16 ) are arranged. 18. Measuring probe according to one of claims 1 to 17, characterized in that in the opening ( 5 a) for the measuring sensor ( 12 ) on the probe base ( 33 ) a film ( 15 ) is attached to reduce pressure. 19. Measuring probe according to claim 18, characterized in that the film ( 15 ) for reducing pressure from elastic dimensionally stable material, such as plastic or bronze, which is so created that powdery layer materials largely do not adhere to it. 20. Measuring probe according to claim 18, characterized in that the film ( 15 ) for reducing pressure on its circumference in an annular groove ( 14 ) on the son dengehäuse ( 5 ) or on the probe foot ( 33 ) is arranged in a membrane-like manner. 21. Measuring probe according to claim 18, characterized in that the film ( 15 ) has a wel len shaped outer region. 22. Measuring probe according to one of claims 1 to 21, characterized in that a pneumatic or hydraulic damping system ( 50 ) is arranged between the actuator ( 2 ) and the measuring sensor ( 12 ), the speed of the measuring sensor independently of the actuating speed ( 12 ) can be lowered against the film ( 15 ) and the layer ( 19 ) to be measured as far as possible at a uniform but slow speed. 23. Measuring probe according to claim 1, characterized in that at least one of the two coil springs ( 4 , 10 ) is designed as a tension spring. 24. Measuring probe according to claim 1, characterized in that both coil springs ( 4 , 10 ) are designed as tension springs, the weaker tension spring ( 104 ) between the sliding element ( 2 ) and the guide device ( 3 ) with the measuring sensor ( 12 ) and the other stronger tension spring ( 110 ) between the Füh approximately ( 3 ) and the housing head ( 5 b) is arranged. 25. Measuring probe according to claim 24, characterized in that the two tension springs ( 104 , 110 ) in the interior of the guide device ( 3 ) are arranged parallel to the axis thereof, the weaker tension spring ( 104 ) at its upper end with an upper crosspiece ( 3 b) connected to the guide device ( 3 ) and with its lower end to a spring ( 104 ) at full length from above penetrating Ju bull pin ( 111 ), at the upper end of the sliding element ( 2 ) or the pusher sits on the top of the housing, and that the other, stronger tension spring ( 110 ) is clamped between a retaining eye ( 112 ) in the interior of the guide device ( 3 ) above the measuring sensor ( 12 ) and an adjustable retaining eye ( 113 ) on the housing head ( 5 b). 26. A measuring probe according to claim 24 or 25, characterized in that the Führungseinrich device (3) with a ball guide (114) in the probe housing (5) is guided. 27. Measuring probe according to claim 24, 25 or 26, characterized in that the adjusting pin ( 111 ) for the weaker tension spring ( 104 ) on the sliding element ( 2 ) or pusher by means of an upper threaded head ( 115 ) is attached adjustable in length from the outside. 28. Measuring probe according to one of claims 24 to 27, characterized in that the upper retaining eyelet ( 113 ) for the stronger tension spring ( 110 ) is part of an adjusting screw ( 116 ) in the housing head ( 5 b) above the guide device ( 3 ) adjustable length is attached. 29. Measuring probe according to one or more of claims 24 to 28, characterized in that the sliding element ( 2 ) is supported in the housing head ( 5 b) by means of an additional weak compression spring ( 117 ), which only one when the measuring sensor ( 12 ) is actuated produces slight finger pressure, but has no effect on the function of the two tension springs.