DE29520128U1 - Traction measuring device - Google Patents

Description

Patent attorneys * : .* *: * : : :w ^on (0202)557040

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Dipi.-ing. Harald Ostriga* "" " "" "'

Dipi.-ing. Bernd Sonnet*

Dipi.-ing. Jochen-Peter Wirths "^address; ^t: _{6 g}

r ° Stresemannstr. 6-8

* Authorized by the European Patent Office 42275 Wuppertal-Barmen

Ostriga, Sonnet & Wirths · PO Box 20 16 53 ■ D-42216 Wuppertal

S/g

Applicant: Tensometric-Meßtechnik

Strohmann & Co. GmbH Ferdinand-Thun-Str. 44

42289 Wuppertal

Designation

of the invention: Tensile force measuring device

The invention relates to a tensile force measuring device according to the preamble of claim 1.

For electronic tensile force measurement, which is of great importance in the manufacture and processing of yarns, fibers, wires, cables, ropes, tapes or similar elongated or endless products, which are summarized under the uniform term 'thread' in the sense of the invention, measuring devices are used whose transducers directly measure the tensile force and convert it into an electrical signal. The signal is fed via a cable to a device which displays the measured values and makes them available for recording, evaluation or control.

To convert the force into an electrical signal, the thread is usually guided at a constant, defined angle by a measuring roller or a ceramic pin as a thread deflection device in its entirety or as a component.

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one such deflection. For the defined deflection, two guide rollers may be required, one of which is arranged in front of the measuring roller in the direction of the thread and the other behind it in such a way that the three rollers are partially wrapped around by the thread in an essentially W-shape, so that a resulting transverse or radial force is exerted on the measuring roller or its axis. The thread tension can be calculated from the measured radial force and the wrap angle (force parallelogram).

In most tensile force transducers, the measuring roller is mounted on or at a bending pin, namely at its freely movable, deflectable end section. Strain gauges are glued to the defined bending points on the bending pin, which may be designed as a double bending beam. These strain gauges are usually wired in a half-bridge or full-bridge circuit. The radially absorbed force of the measuring roller is converted into an electrical signal by a detuning of the bridge circuit caused by the stretching and/or compression of the strain gauges, which is proportional to the radial force with very high accuracy. The well-known and used double bending beam with glued-on strain gauges is particularly characterized by the fact that it can convert the force into an electrical signal over a wide range, independent of the lever arm.

A comparable state of the art is shown, for example, in DE 34 08 497 A1, in particular in its Fig. 1 . It also shows that the entire measuring device, viewed in the longitudinal direction of the bending pin (there referred to as 'fixed shaft 1'), has a very long design.

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which cannot be installed at many measuring points on a machine due to limited space. Consequently, tensile force measurements cannot be carried out at key points on many machines.
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This is where the invention comes in. It is based on DE 34 08 497 A1 with the features specified in the preamble of the independent claim. Its task is to cleverly design such a tensile force measuring device in a particularly small construction so that its use is less restricted than before and is even possible in areas of the machine that are difficult to access.

The invention solves this problem with the features of the independent claim and consequently in particular through a novel and particularly clever geometry and arrangement of the double bending beam or assignment of the force action axis to the double bending beam.

While in known double bending beams the force is absorbed at the front end of an elongated bending pin, the force absorption location in the force measuring device according to the invention is in the double bending beam area insofar as the force introduction into the double bending beam is shifted to a plane between the two bending beams. A zone is thus used for the force application which, from the point of view of the present invention, has previously been wasted in favor of the supposed functional necessity of a bending pin arrangement with a measuring wheel axis.

In order to achieve the invention-specific, almost idiosyncratic seeming shift in the axis alignment from a

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When the longitudinal extension of conventional bending pins in an identical direction in a direction transverse or perpendicular to the bending body was found to be suitable, the fear that torsions that would distort the measurement values could occur due to the new direction of force introduction into the bending beam arrangement had to be put aside. In fact, it was surprisingly found that these disruptive forces are negligible and that it is sufficient to anchor the fixed end of the bending beam arrangement, referred to as the foot area, firmly in or on the housing. The favorable properties of the double bending beam for lever arm-independent measurement are also fully retained.

A tensile force measuring device according to the invention can be designed in such a small size that it can be installed in a mounting plate which could previously only be used to hold the guide rollers.

The invention also offers the advantage that only small holes or threads are required to attach the force measuring device to the machine frame, which can be easily installed even on existing machines using hand tools. The device according to the invention can be installed at practically any point on the machine frame where the thread runs past, since it requires very little space.

Due to its space-saving design, the

Application also in hand-held thread tension measuring devices. Hand-held thread tension measuring devices have a tension measuring head and a display device in one housing, whereby a small construction

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form makes handling the device much easier when measuring tensile force.

A particularly compact design can be achieved according to a further development of the basic idea if the deflectable head section of the bending body is arranged between the bending beams, i.e. not only in a plane between their planes, but spatially in their interior and thus in their overlap. This is the first time that the space between the bending beams of a double bending beam is used for technical purposes, apart from possibly attaching strain gauges or balancing resistors.

Other developments and additional advantageous and expedient embodiments of the invention are the subject of the other subclaims. In addition, the invention is particularly clear from the following detailed description based on some embodiments shown in the drawings. In the drawings:

Fig. 1 is a schematic plan view of an opened housing containing a double bending beam with strain gauges and their connecting wires,

Fig. 2 is a schematic cross-section through the arrangement according to Fig. 1 along the cutting direction indicated therein with II&mdash;II,
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Fig. 3 shows a schematic cross-section through the arrangement according to Fig. 1 along the cutting direction indicated therein as III-III,

Fig. 4a to 4c a schematic representation of a complete thread deflection and tension measuring device in top view (Fig. 4a), side view (Fig. 4b) and front view (Fig. 4c),

Fig. 5 is a schematic view of a tensile force measuring device, which uses a quadruple bending beam and which also has a circular housing,

Fig. 6 a schematic representation of a double bending beam according to the state of the art, in rough qualitative relation to

Fig. 7 a comparable schematic view of the double bending beam concept according to the invention in

Top view (Fig. 7a) and side view (Fig. 7b) in the direction of the view arrow VIIb of Fig. 7a.

A tensile force measuring device is essentially designated by 10. 11 is a housing which is to be attached to the machine and which accommodates a bending body 13 in a chamber-like receiving space 12 which, in contrast to the prior art, no longer has a tenon shape, as described in detail below.
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The housing 11 can be imagined, for example, as a plate-like light metal block from which the receiving chamber 12

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milled out or in which it is removed (e.g. during casting production). The bending body 13 comprises two bending beams 14 and 15 that are spaced apart from one another and arranged parallel to one another. The bending beams 14, 15 define planes that (more precisely: their tracks) are designated 16 and 17 and that are also parallel to one another. In principle, the bending beams 14, 15 each have a flat, rectangular cross-section and do not differ from conventional bending beams in this respect.

One end of each bending beam 14, 15 ends in a common foot section 18, while the two opposite bending beam ends in the longitudinal direction of the bending beam merge into a common head section 19, which has a fastening point designated 20 for an axle 21 supporting a measuring roller 22. The bending body 13 is firmly connected at one end to the housing 11, in the embodiment by means of two screws 24 that tighten the block-shaped foot section against the chamber floor 23.

Washers 25 (Fig. 3) distance the bending body 13 from the floor surface and create a certain gap-like clearance 26 so that when the bending beams 14 and 15 and their head section 19 are deflected under the action of force in the direction of arrow 30', no obstructive sliding contact with the chamber floor 23 occurs.

The largest part of the head section 19 and the fastening point 20 are, as can be clearly seen from Fig. 1, essentially in the area of a plane numbered 27 (which here also coincides with the longitudinal center plane of the system 10), which runs between the two bending beam planes 16 and 17. In addition, they are also

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between the bending beams 14 and 15 themselves, i.e. in the space covered by them. In comparison to the bending pin arrangement of the prior art, there is a sort of 'inverse arrangement'.
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Another important feature is that the axis 21 supporting the measuring roller 22 does not extend in or parallel to the longitudinal direction of the bending beams 14, 15, but rather transversely, in the embodiment exactly perpendicular to it. This is shown in Figures 2 and 3, in which the thread 28 running over the measuring roller 22 is also shown, the tensile force of which is to be measured and which therefore partially wraps around the measuring roller 22, forming an angle, in order to impart a radial force component designated 30, which is basically usual when measuring the tensile force of running threads and the like.

It can also be seen from Figures 2 and 3 that the force 30, which is introduced from the thread 28 via the measuring roller 22 at a significant frontal distance in front of the bending body 13 and is transmitted to the bending beams 14, 15 via the axis 21 and the bending body head piece, tends to exert a bending moment on them. Surprisingly, however, it has been shown that this bending moment is practically negligible, in particular due to the firm anchoring of the foot section 18 to the housing 11, the rectangular shape of the bending beam cross sections and also due to the grouping of the bending beam ends there on the head section side, and that the vertical component 30' of the force 30 is almost exclusively included in the measurement.

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A very narrow gap 32 is provided between the outside of the bending beam 15 and the inner surface of a housing wall 31 facing it, which forms a safety end stop in the simplest way to limit the maximum deflection of the bending beams 14, 15. The free space 33 between the opposite bending beam 14 and the adjacent housing wall 34 is wider and serves to accommodate strain gauges 35 glued to the outside of the bending beam 14 and their electrical connecting wires 36, which lead to a sheathed cable 37 emerging from the housing 11.

Finally, 38 designates a cover which covers and closes the side of the receiving chamber 12 open to the measuring roller 22 except for an outlet opening for the axle 21. This cover 38 can also serve as a bearing plate for the two guide rollers 39 and 40 used to deflect the thread for the tensile force measurement, which are arranged at a certain distance in front of and behind the measuring roller 22 and at a predetermined transverse offset from it in such a way that the thread 28 can exert a measurable transverse or radial force 30 due to its angle of wrap around the measuring roller. Figures 4a to 4c show such a complete device. In it, 41 designates through-holes in the housing 11 for screws with which the device can be attached to the machine, while reference number 42 designates cover closure screws.

Fig. 5 shows a force measuring device with a bending body 13, which has four bending beams 14, 15 and 14', 15', whereby the bending beams 14 and 15 on the one hand and the bending beams 14' and 15' on the other hand, i.e. in pairs

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Arrangement, each form a double bending beam with its own foot sections 18, 18'. In contrast, all four bending beams practically lead into a common, central head section 19, which in this embodiment essentially has the shape of a sleeve 43. The central bore 44 of the sleeve 43 serves to accommodate a bearing axis (not shown here) for a measuring roller (also no longer shown in this figure). Strain gauges 33 are glued to the surfaces of the two (upper ones with respect to Fig. 6) bending beams 14 and 14'.

The two foot sections 18, 18' of the four-fold bending beam arrangement are fastened with screws 24 to the base 23 of the circular and pot-shaped housing 11 (again with the previously described spacers 25). It goes without saying that the base 23 of the housing 11 has a central opening for the passage of the measuring roller axis, which is subject to deflection play. The receiving space 12 in the housing 11 can be closed by means of a cover plate (not shown), the fastening screws of which engage in the threads designated 45. 46 is a housing flange. This device could, for example, be fastened to a sheet metal of a thread processing machine by inserting its sleeve section 51 into a machine-side bore of an appropriate diameter, for example by pressing it in. The housing could also be glued, welded or screwed to it via its flange 46.

Fig. 6 and 7 show a qualitative comparison between the state of the art (Fig. 6) and the invention (Fig. 7a and 7b). The considerably long construction of a known bending body 13' is based on its

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Designed as a bending pin 47, all of whose functional parts or sections are arranged in the direction of the common longitudinal axis 48. This involves - from right to left in Fig. 6 - a base pin 18' to be firmly clamped in a device housing, a double bending beam 13' with the bending beams 14" and 15", furthermore a bending pin head piece 19' and a measuring roller bearing pin 21'.

In contrast, Fig. 7a shows in particular the nested arrangement between the bending beams 14 and 15 with regard to the head section 19 and, in conjunction with Fig. 7b, the transverse alignment of the bearing axis 21 for the measuring roller (not shown).

Imagine that conventional bending pins 13' require an installation space (measured in the direction of the measuring roller axis 21') which is designated 49 in Fig. 6. In the device designed according to the invention, this is only offset by the considerably smaller installation space 50 shown in Fig. 7b. Based on the principles of the invention, a force measuring device can be created which was previously unthinkable in terms of its compact design.

Claims (9)

Tensometric measuring technology Strohmann· &»Co. *?JmbH· - 12 - Expectations 1. Tension force measuring device for a running thread, with a sensor with double bending beams, the bending beams extending at one end from a common foot section fixed in a housing and at the other end being combined again in a head section which can be deflected under the influence of the tensile force to be measured and to which a thread deflection device is at least indirectly connected and the measured variable associated with the respective thread tensile force is the bend present on the double bending beam, characterized in that the axis (21) associated with the thread deflection device runs in a plane (27) between the two planes (16, 17) defined by the bending beams (14, 15) of the double bending beam and is arranged transversely to the longitudinal extension of the bending beams (14, 15). 2. Tensile force measuring device according to claim 1, characterized in that the deflectable head section (19) is arranged between the bending beams (14, 15). 3. Tensile force measuring device according to claim 1 or 2, characterized in that the foot section (18), head section (19) and bending beam (14, 15) each have at least approximately the same material thickness. 4. Tensile force measuring device according to one of claims 1 to 3, characterized in that the foot section (18) of the double bending beam (14/15) with a small clearance distance (26) is attached to a base surface (23) of the housing (11). Tensometric measuring technology Ströhmanj? &*.Cp. 5. Tensile force measuring device according to one of claims 1 to 4, characterized in that the bending beam (15) located at the front in the direction of force action (30') has such a small distance (32) from a housing wall (31) that the housing wall (31) itself forms a deflection limit stop for the double bending beam (14/15). 6. Tensile force measuring device with strain gauges as sensors according to claim 1 or one of the following, characterized in that all sensors (35), preferably four, are arranged on the same bending beam (14). 7. Tensile force measuring device according to one or more of the preceding claims, characterized in that two double bending beams (14, 15; 14 ¹ , 15 ') are present in a paired arrangement with two external, firmly anchored foot sections (18) and in the middle a common head section (19) which combines all four bending beams (14, 15; 14', 15') and on which the axis (21) of the thread deflection device (measuring roller 22) engages. 8. Tensile force measuring device according to claim 7, characterized in that all sensors (35), preferably four, are attached to the two bending beams (14, 14'), which each belong to a double bending beam (14, 15; 14', 15') and lie essentially in the same plane (16). 9. Tensile force measuring device according to one of the preceding claims, characterized in that the housing (11) or a housing cover (38) on the one hand has a passage opening for the axis (21) of a measuring roller (22) as a component of the thread deflection device and on the other hand Tensometric measuring technology Strohmann· &·£&sfgr;. gmbg· , ·..; - 14 - which also rotatably supports a guide roller (39, 40) arranged in the direction of thread travel in front of and behind the measuring roller (22) as further components of the machine-independent thread deflection device (22, 39, 40).