DE102006030824A1 - measuring cell - Google Patents

Abstract

The present invention relates to a measuring cell for detecting a force to be expected from a predetermined direction.

Description

The The present invention relates to a measuring cell for detecting a predetermined direction expected force.

such measuring cells are known.

In The following documents assume that a measuring cell a pair of for measuring purposes with strain gauges to be equipped Double bending beam exists between a mounting flange and a yoke of connection.

At the connection yoke should attack the expected force.

This leads to, that the Double bending beam, each for is deformed to form an S-shock.

The Reversal points of every single S-beat are covered by the present Documents also referred to as joints, although it is not technically a joint.

Everyone Double bending beam makes this way at each of its ends, both on the mounting flange as well as on the yoke each an S-beat, so that Yoke under the influence of attacking force is shifted parallel to itself.

Further It is assumed that under the High direction or height H is understood that direction in which the main component the force to be measured, i. Double bending beams are in the Measuring level one above the other arranged.

Accordingly, results for the transverse direction or the width B of the measuring cell in perpendicular to the measuring plane Direction, e.g. in front view on the yoke, where then still the longitudinal direction or the longitudinal distance L with regard to the longitudinal dimensions the double bending beam is to be understood.

such measuring cells have proven themselves in practice outstanding.

One fundamental The problem, however, is the influence of parasitic forces, that forces in transverse or longitudinal direction be that generally on the measuring cell act and in the conventional Systems lead to unpredictable voltage conditions, which the measurement result distort.

It is therefore an object of the present invention, the known measuring cell so to develop that the Influence of parasitic forces especially forces in the transverse direction an increasingly smaller influence on the measurement result will have.

These Task solves the invention with the features of the main claim.

Essential is the use of guide bars, which also work on the double bending beam principle, in addition to the double bending beam, which is used for measuring purposes with strain gauges stocked become.

The guide beams Therefore have the function of individual links, and contribute to the stability of the measuring cell in particular against the influence of forces at that with the measuring function the measuring cell have nothing to do.

there is the length of the sensor, so the center distance of the joints of the Meßbalkenpaares always in the relationship to see the width dimension and should be less than 1.0 better even less than 0.4 and even better less than 0.2.

Furthermore is also the height the measuring cell, that is, parallel to the measurement plane certain distance of the involved double bending beam relevant, because he offers a measure of how stable the measuring cell against personnel is designed, which ultimately leads to a buckling load in the measuring direction seen behind lying double bending beam lead.

Becomes the height distance H is chosen large accordingly, is this is a reliable one Assessment factor for the kink resistance of the above-mentioned underlying double bending beams, in a particular embodiment the invention is sought, the width B and the height H of the measuring cell about the same size too choose.

It arises in this way a very short measuring cell, with in relation to Length very large latitude and height dimensions.

In an embodiment like the length L are at 20mm to 25mm.

The Width B can then be in the range of about 80mm to 100mm. Especially this also applies to the height H.

It arises in this way a very short-built sensor whose Base, with which it is finally attached to the machine frame, cuddly is thick, in this way the forces and consequent Moments unwanted parasitic influences ablate.

there it always depends on the ratio of Length L to the height H or B width.

This relationship should preferably be less than 0.4, more preferably less than 0.2, be.

In same size this applies to the ratio of Length L to the height H or width B, which should be of the same order of magnitude.

The However, the principle of the invention is not necessarily in addition to the for the Measuring task designed double bending beam ahead of additional guide beam.

The guide beams can in principle also directly and in one piece with those for the measuring task be designed designed double bending beam.

This then leads ultimately to a pair of very broadly executed leaf springs, whose width is over everything at least that big like the length, So the distance between the joints, preferably even something two up to three times as big.

For this will be embodiments specified.

Conveniently, however, the measuring cell is completely symmetrical constructed, i. to each pair of measuring beams is in each case right and left next to a pair of guide bar arranged.

there can the Meßbalkenpaar at the joints where the strain gauges are placed, very thin accomplished be while the guide bar pair then at these locations for the purpose of high resistance moments accordingly has thick material.

in this respect it is useful if the neutral fibers of both Meßbalkenpaares, and the associated guide bar always in one and the same plane, in addition to occurring internal tensions preferably to avoid or even to keep low.

A quantitative statement for the realization of the invention we in the dependent claims formally recorded.

Out This formula shows that all below the triangular area in the first quadrant, which up through a falling straight line is delimited, lying width dimensions of the measuring cell certain circumstances the L to B, which are beneficial to the invention.

Further It has been found that this triangular area is additionally reduced can be through another formulaic context, which for width B, which are smaller than about 25mm.

These formulaic relationships apply however, only with regard to certain limitations of the invention, such as For example, Measuring tasks of less than 1000 N and measuring cell lengths L less as 20mm to 25mm.

From particular advantage is a development in which both the flange as well as the yoke each equipped with a central thread are.

About the Central thread can be namely the measuring cell on the one hand very easy to attach to the machine frame, while the Central thread in the yoke of simple attachment of a force application point serves, e.g. may consist of a pulley over which a running continuous material, e.g. a filament, a train or the like led under redirection becomes.

The the inherent longitudinal stress of the material gets in this way from the measuring cell detected.

By the central arrangement of the threads is beyond a largely symmetrical introduction of the residual stresses in the Material of the measuring cell, from the attachment of the measuring cell and the point of application of the force.

Also For this reason, the sensor should be as symmetrical as possible be.

Furthermore is proposed, the measuring cell to produce a uniform material.

Here offers the wire EDM technology.

These Technology offers about it addition, the advantage that by appropriate wire guide between the Anschraubflansch and the yoke in a simple way, an overload stop can be produced.

This Advantage is achieved in that a step-shaped wire guide is selected, so that the yoke then with a step simply on a complementary formed Countershaft on the mounting flange can interpret as soon as the overload case entry.

Furthermore can be over the Wire eroding technique can very easily achieve that due to residual stresses Anschraubbefestigung tipping Anschraubflansche tension of the Meßbalkenpaar can be decoupled.

For this are embodiments specified.

In addition, can through a guide the erosion wire, which is substantially parallel to the Meßbalkenpaar runs, and laterally next to it, a further decoupling of Meßbalkenpaares from possibly additional Residual stresses can be achieved.

These measure therefore serves to improve or optimize the linear path-elongation behavior of the measuring beam pair.

in the Following, the invention will be explained in more detail with reference to embodiments.

It demonstrate:

1a -C: possible arrangements of measuring bar or guide bar pairs;

2 : formal capture of the invention in graphical representation;

3 : the invention in 3-D view;

4 : the invention gem. 3 in front view;

5 : the invention gem. 3 in top view;

6 : the invention in the installed position on the machine frame;

7 : shows a further embodiment Unless otherwise stated below, the following description applies to all figures.

1a - 1c show different arrangements of Meßbalkenpaaren 1 or guide bar pairs 2 ,

The Representations correspond to a plan view in the longitudinal direction of the respective Double bending beam.

The longitudinal dimension L is thus to be seen here perpendicular to the paper plane.

The Cross sections are only qualitative.

1a shows a Meßbalkenpaar 1 of relatively small cross section, which is on only one side of a pair of guide bars 2 flanked.

Out give each resulting centers of the joints then the width dimensions B and height dimensions H, in relation to the - here - vertical standing on the paper plane longitudinal dimensions L are larger by about a factor of 2 to 4 or more.

In that regard corresponds 1b an alternative embodiment, wherein the Meßbalkenpaar 1 , which also has very short longitudinal dimensions L, is formed by two very wide leaf springs whose width is considerably greater than the longitudinal distance between the centers of the joints between the connecting flange and yoke of each double bending beam.

In addition is this longitudinal distance L but also significantly smaller than the largest midpoint distance between the joints of the double bending beam in the vertical direction H.

1c shows the ideal case of a symmetrical arrangement of Meßbalkenpaar 1 or guide bar pairs 2 ,

One pair of guide bars each 2 is right and another pair of guide bars 2 left of the measuring beam pair 1 arranged.

you recognizes that the Cross sections of the guide bar pair considerably larger than that of the Meßbalkenpaares are.

In addition, it is satisfied that all neutral fibers 21 each lie in a single plane, which is determined by the respective measuring bar.

Before now on the actual core of the invention, namely the skillful integration of the cross-sectional dimensioning and position dimensioning in a per se known measuring system, the invention is based on 3 be described a little closer.

3ff , shows a measuring cell 10 which serves to detect a force to be expected from a predetermined direction.

One can imagine that the expected force is approximately vertical in the measuring cell 10 should be initiated.

The measuring cell 10 has a connection flange 11 on, which for attaching the measuring cell to a machine frame 12 serves.

From this connection flange 11 extend in the direction of the connection flange 11 away, two measuring bars, the Meßbalkenpaar 1 ,

Just the upper measuring beam can be seen.

The lower measuring bar and the upper measuring Bars sit between connection flange 11 and a yoke 13 and are attached there in the manner of bending springs.

The measuring beam pair 1 is at the respective inflection points of the bend, each measuring beam has two pieces, with strain gauges 3 stocked.

in this respect however, reference is made to the prior art.

If the expected force acts essentially, ie with a main component, in the vertical direction, the measuring cell is 10 oriented correctly, because the Meßbalkenpaar 1 lies practically in the measurement plane and the individual measuring beams are arranged one above the other in the vertical direction H.

Each measuring beam is in principle ungelenkig both with flange 11 as well as with yoke 13 connected.

Nevertheless, by a parallel displacement of the yoke 13 As a result of the attacking force, a deformation of the Meßbalkenpaares done, which on the strain gauges 3 is detected.

In addition, guide bar pairs 2 provided in the same way as the Meßbalkenpaar 1 between the connecting flange 11 and the yoke 13 extend.

Each guide beam pair is therefore formed by a pair of double bending beams, each double bending beam sits in the same way between connecting flange 11 and yoke 13 like every single measuring bar.

The guide bar pairs 2 lie on the one hand right and on the other hand left of Meßbalkenpaares and have a pure handlebar function.

At They are not provided with strain gauges.

The neutral fibers 21 of the guide bar pair 2 however, lie in a single plane with the neutral fibers 21 of the measuring beam pair 1 ,

It is essential that the longitudinal distance L between the centers of the joints 30 each double bending beam, so both those double bending beam, which the Meßbalkenpaar 1 form as well as those double bending beam, wel che the guide beam pair 2 form, is significantly smaller than the largest center distances between the joints of the double bending beam in the transverse direction, here referred to as width B, and in the vertical direction, here referred to as height H.

The representations of the 3 to 5 in this respect correspond to an approximately quantitative representation of the geometric relationships, but this without limiting the invention to the actual dimensions.

It can now be easily imagined that instead of a Meßbalkenpaar and two pairs of guide bars with symmetrical arrangement according to 1 also an arrangement gem. 1b can be selected, in which the Meßbalkenpaar 1 is formed by two such wide-shaped leaf springs that the width B is considerably larger than the longitudinal distance L between the centers of the joints 30 each double bending beam is, the joints between the flange and the yoke sit and in turn, this longitudinal distance is considerably smaller than the largest center distance between the joints of the double bending beam in the vertical direction H.

1ff In this respect shows a special case in which to each measuring beam of Meßbalkenpaares 1 on both sides in each case a guide bar of a guide bar pair 2 is provided.

Due to the quasi-quantitative representation can be easily understood that the longitudinal distance L between the centers of the joints between the flange 11 and yoke 13 The double bending beam should be less than 30mm, preferably less than 20mm.

Have proven such measuring cells 10 in which this distance is about 1/2 inch.

In addition, the show 3 - 5 Embodiments in which the center distances in the transverse and in the vertical direction are approximately equal.

Here applies: B to H approximately equal to 1.

In addition to this shows 2 a preferred development in quantitative representation.

Shown is the first quadrant.

On the abscissa is the width dimension B applied.

The Coordinate carries The relationship L / B.

The Triangle A / B / D describes a ratio L: B of less than or equal to -0.8: 100 · B + 1.

All measuring cells lying below the B / D line and within the first quadrant this condition and are beneficial to the invention.

This Triangle is bounded on the left in a training by the line A / C.

For this Limit that for Widths of less than 25mm meaning, L to B is less than or equal 0.8: 25 · D.

It would therefore all measuring cells fulfill both conditions, which lie within the triangle A / C / D.

In addition to this but also a safe distance to the above two triangles, i.e. especially recommended to the respective boundary lines be.

This is for the triangle A / B '/ D' realized by the formula L to B less than or equal to -0.8: 100 * B * 0.95.

It So there is an approximately 5% safety distance to the boundary line B / D through the new boundary line B '/ D'.

In this also applies to the left boundary line A / D, which passes through the new boundary line A '/ C' takes place.

Also here is the safe distance to the absolute limit is about 5% and is through the formula L to B less than or equal to 0.8: 25 · B - 0.05 realized.

These Quantitative statements apply in particular to measuring cells used for forces of less than 1000 N are designed.

practicable Widths B are therefore preferably in the range between about 20mm up to about 120mm.

It But it must not be forgotten that widths are less detected as 20mm from the invention should be.

In addition to this show the 3 - 6 a development in which the connecting flange 11 with a central thread 14a is provided.

A comparable central thread 14b also shows the yoke 13 on.

Each central thread serves for the attachment of the measuring cell 10 on a machine frame 12 and on the other hand, for example, a deflection device 15 at the yoke 13 ,

In addition to this shows 7 a development in which at least the central thread of the yoke in a box 25 is arranged.

The rifle 25 is in a corresponding hole in the yoke 13 plugged in.

There is the rifle 25 taped.

The bore itself also goes a bit into the connecting flange 11 into it.

In addition, the rifle 25 turned off at the end to a slightly smaller diameter, so that they with a ring distance to the bore in the connection flange 11 sitting.

In this way, not only a further stress decoupling between the load-bearing member and the yoke 13 achieved, but also also provided an acting in all directions overload stop.

In addition to this show the 3 - 6 one out of a single piece of material worked out sensor.

The Sections that pass through the sensor are in the diameter range an erosion wire.

In particular, it can be seen that between the mutually facing surfaces of the connecting flange 11 and the yoke 13 a step-shaped separation plane in two directions 16 taken out, which acts as an overload stop.

In addition to this, it may be advantageous to use the erosion wire in the area of the steps 17 . 18 either to choose thinner or supply so that the distances of the surfaces facing each other at the level are less than the wall distances in the region of the remaining parting planes 16 ,

The Dimensioning is based on the desired nominal force.

So is e.g. the upper stage as an overload stop towards the bottom and the lower stage as an overload stop in the direction be usable upwards.

In addition to this could also on Meßbalkenpaar 1 laterally arranged decoupling cuts 19 be provided to the Meßbalkenpaar 1 as tension-free as possible to the remaining measuring cell 10 to keep.

In addition, the figures show further cuts 20 which are substantially horizontal and immediately adjacent to those components of the measuring cell 10 are arranged, which is the central thread 14a respectively. 14b wear.

Through these cuts cuts a radiation of stresses in the yoke 13 at least reduced, which by the attachment of the deflection 15 arise or by attaching the measuring cell 10 on the machine frame 12 ,

This will be particularly advantageous if the assembly to be attached, with which the introduction of force is to be realized, in the technical sense flying on the measuring cell 10 is attached, for example, as a cantilevered roller or the like.

1

Meßbalkenpaar, leaf spring

2

Guide bar pair

3

strain

10

measuring cell

11

flange

12

machine frame

13

yoke

14a

Central thread of 11

14b

Central thread of 13

15

deflecting

16

parting plane

17

step

18

step

19

Decoupling section of 1

20

Separating cut of 14

21

neutral fiber

25

rifle

26

annular gaps

30

articulation point

H

height

B

width

L

length

Claims (19)

Measuring cell ( 10 ) for detecting a force to be expected from a predetermined direction, wherein the measuring cell is connected to a connecting flange ( 11 ) for attachment to a machine frame ( 12 ), from which connecting flange extends a Meßbalkenpaar, which of measuring purposes for use with strain gauges ( 3 ) is formed to be assembled double bending beam, which are arranged in the direction of at least one component of the force to be measured in the measurement plane with a distance (H) in the vertical direction one above the other and at the connecting flange and with their ends facing away from the connecting flange to a yoke ( 13 ) are connected each ungelenkig, as well as with at least a single pair of guide bars, also in the form of double bending beam, of which in each case a guide beam between flange and yoke in the same way but laterally next to each one of the strain gauges to be equipped with measuring beam extends and wherein the longitudinal distance (L ) between the centers of the joints between the connecting flange and the yoke of each double bending beam are considerably smaller than the largest center distances between the joints of the double bending beam in the transverse direction (= width (B)) and in the vertical direction (= height (H)). Measuring cell ( 10 ) for detecting a force to be expected from a predetermined direction, wherein the measuring cell is connected to a connecting flange ( 11 ) for attachment to a machine frame ( 12 ), from which connecting flange extends a Meßbalkenpaar, which of measuring purposes for use with strain gauges ( 3 ) is formed to populating Dop pelbiegebalken which are arranged one above the other in the direction of at least one component of the force to be measured in the measuring plane and at the connecting flange and with their ends facing away from the connecting flange to a yoke ( 13 ) are each connected ungelenkig, the Meßbalkenpaar is formed by two such wide-shaped leaf springs that the width (B) is considerably greater than the longitudinal distance (L) between the centers of the joints between the connecting flange and the yoke ( 13 ) of each double bending beam, and wherein this longitudinal distance (L), in turn, is considerably smaller than the maximum center distance between the articulation points of the double bending beams in the vertical direction (= height (H)). Measuring cell ( 10 ) according to claim 1 or 2, characterized in that for each measuring beam of the Meßbalkenpaares ( 1 ) is provided on both sides in each case a guide bar. Measuring cell according to one of claims 1 to 3, characterized in that the longitudinal distance (L) between the centers of the articulation points between the connecting flange ( 11 ) and the yoke ( 13 ) of the double bending beam is less than 30mm, preferably less than or equal to 20mm. measuring cell according to one of the claims 1 to 4, characterized in that the center distances in transverse or in the vertical direction are about the same size. Measuring cell according to one of claims 1 to 5, characterized in that the ratio L to B L: B <= -0.8: 100 · B + 1 is. Measuring cell according to Claim 6, characterized in that, in addition, for widths B which are smaller than 25 mm, the following applies: L: B <= 0.8: 25 · B Measuring cell according to claim 6 or 7, characterized in that the ratio L to B L: B <= -0.8: 100 B + 0.95 is. Measuring cell according to claim 8, characterized in that the ratio L to B L: B <= 0.8: 25 B - 0.05 is. measuring cell according to one of the preceding claims, characterized that the Design for personnel of F <= 1000 N he follows. Measuring cell according to one of claims 1 to 10, characterized in that the connecting flange ( 11 ) with a central thread ( 14a ), over which the measuring cell ( 10 ) on a machine frame ( 12 ) can be screwed. Measuring cell according to one of claims 1 to 11, characterized in that the yoke ( 13 ) with a central thread ( 14b ), which attaches a deflection device ( 15 ) is used for a running thread, a web or the like, whose force present at the deflection point is to be measured. Measuring cell according to one of claims 1 to 12, characterized in that the connecting flange ( 11 ), Yoke ( 13 ), Meßbalkenpaar ( 1 ) and possibly guide bar pair ( 2 ) are made of the same material from a single piece of material. measuring cell according to claim 13, characterized in that the recesses in the piece of material Drahterrosionstechnik are generated. Measuring cell according to claim 13, characterized in that between the mutually facing surfaces of the connecting flange ( 11 ) and the yoke ( 13 ) at least one step-shaped parting plane ( 16 ), which in the area of the stage ( 17 . 18 ) for the measuring cell ( 10 ) provides an overload stop. Measuring cell according to Claims 1 to 15, characterized in that the measuring beam pair ( 1 ) by laterally arranged separating cuts ( 20 ) inherent voltage from the connection flange ( 11 ) or yoke ( 13 ) is decoupled. Measuring cell according to Claims 1 to 16, characterized in that the connection points of the connecting flange ( 11 ) on the machine frame ( 12 ) or yoke ( 13 ) at the deflection device ( 15 ) by transverse to the measuring direction separating cuts ( 20 ) voltage from the remaining material of the measuring cell ( 10 ) are decoupled. Measuring cell according to Claims 1 to 17, characterized in that the neutral fibers ( 21 ) the measuring bars lie in the same plane as the neutral fibers ( 21 ) of the guide bar. Measuring cell according to Claims 1 to 18, characterized in that the yoke ( 13 ) a flying assembly is mounted.