EP0252952B1 - Device for measuring the thickness of slivers - Google Patents

Abstract

The device comprises a compression unit (T) and a unit for measuring the thickness of a sliver passing through a measurement channel (4). The measurement unit consists of a blade-spring (BF) provided with a string gauge. The measurement channel (4) is arranged in an exchangeable measurement head (MT) arranged on a funnel (T). The measurement head is provided with a connector (19) for compressed air. This design provides on one hand easy adaptation of the device to the various sliver numbers and on the other hand allows easy cleaning of the measurement head.

Description

The invention relates to a device for measuring the sliver thickness and the non-uniformity of fiber slivers, preferably on spinning preparation machines, with a compression member compacting the fiber sliver and with a measuring member arranged thereon, mechanically scanning the compressed sliver in a measuring channel and formed by a leaf spring provided with a strain gauge for the thickness and the unevenness of the sliver.

In a device of this type described in DE-PS 15 10487, the measuring channel is provided in a wall which integrally connects to the outlet opening of the compression member formed by a band funnel, and the leaf spring is fastened to the band funnel and extends along a generatrix of the band funnel.

The latter results in a certain inertia of the measuring element; in addition, the entire band funnel must always be replaced to adapt to changing band numbers.

This known device is now to be improved by the invention in such a way that even very short non-uniformities can be measured at high belt speed and that a simple range adaptation to changing belt numbers can be carried out.

This object is achieved according to the invention in that the measuring channel is provided in a measuring part which is arranged interchangeably on the compression member and is equipped with a compressed air connection, and in that the leaf spring is arranged transversely to the running direction of the fiber sliver.

The arrangement of the measuring channel in a measuring part that can be replaced on the compression element has the advantage that it is no longer necessary to replace the entire compression element, but only the named component or even only a part of it, in order to adapt to changing band numbers. The compressed air connection offers the possibility of blowing out dust and / or cooling the measuring point. Due to the arrangement of the leaf spring according to the invention, it can be designed such that it has a very high natural frequency. This makes it possible to measure even very short irregularities at higher belt speeds than before.

• Fig. 1 einen Längsschnitt durch ein erstes Ausführungsbeispiels eines Bandtrichters mit einem Messorgan,
• Fig. 2 eine Ansicht in Richtung des Pfeils 11 von Fig. 1,
• Fig. 3 eine Ansicht in Richtung des Pfeils 111 von Fig. 2,
• Fig. 4-6 Details des Messteils der Fig. 1 bis 3,
• Fig. 6a eine schematische Darstellung zur Funktionserläuterung,
• Fig. 7 einen Längsschnitt durch ein zweites Ausführungsbeispiels eines Bandtrichters,
• Fig. 8 eine Ansicht in Richtung des Pfeiles A von Fig. 7,
• Fig. 9 eine Draufsicht auf den Anschlagteil eines für den Bandtrichter von Fig. 7 geeigneten Messteils,
• Fig. 10 einen Schnitt nach der Linie B-B von Fig. 9,
• Fig. 11 eine Draufsicht auf eine Blattfeder mit ihrem Träger,
• Fig. 12 einen Schnitt nach der Linie C-C von Fig. 11, und
• Fig. 13 einen Schnitt nach der Linie E-E von Fig. 12.

An embodiment of the invention is explained below with reference to the drawings. It shows:

• 1 shows a longitudinal section through a first embodiment of a belt funnel with a measuring element,
• 2 is a view in the direction of arrow 11 of FIG. 1,
• 3 is a view in the direction of arrow 111 of FIG. 2,
• 4-6 details of the measuring part of FIGS. 1 to 3,
• 6a is a schematic representation to explain the function,
• 7 shows a longitudinal section through a second exemplary embodiment of a band funnel,
• 8 is a view in the direction of arrow A of FIG. 7,
• 9 is a plan view of the stop part of a measuring part suitable for the band funnel of FIG. 7,
• 10 shows a section along line BB of FIG. 9,
• 11 is a plan view of a leaf spring with its support,
• Fig. 12 is a section along the line CC of Fig. 11, and
• 13 shows a section along the line EE of FIG. 12.

1 to 3 show a first exemplary embodiment of a band funnel T serving for the compression of a sliver with a funnel wall 1 and an inlet and an outlet opening 2 and 3 respectively. Such band funnels are known and are used in particular on draw frames or cards; on lines, for example, in the direction of flow after the drafting system and / or in front of a pair of calender rollers. In the case of cards, the band funnel can be assigned to the can stock, for example, or it can be provided to combine the card fleece.

Following the outlet opening 3, the band funnel T has a gradation into which a measuring part MT having a measuring channel 4 is inserted. This consists of two parts, namely a channel part 5 and a stop part 6, between which a leaf spring BF is clamped. The leaf spring BF serves as a measuring element for the thickness of a sliver running through the band funnel 1 and the measuring channel 4.

4 shows a view of the leaf spring BF and FIGS. 5 and 6 each show a view of the clamping surface of the channel part 5 or the stop part 6 facing the leaf spring BF. The structure of the measuring part MT is now explained with reference to FIGS. 1 to 6, wherein the scale is 4: 1 in each case.

The channel part 5 is approximately plate-shaped and has on its clamping surface the measuring channel 4 provided with a conical inlet part, which is formed by a groove in the channel part 5. On the opposite surface, the channel part 5 is provided with a centering rib 7 which runs transversely to the measuring channel 4 and which is latched into a corresponding groove in the graduation of the band funnel T. As a result, the channel part 5 and with it the entire measuring part MT are fixed relative to the band funnel T in two coordinate directions. The fixation in the third coordinate direction, that is the direction perpendicular to the plane of the drawing in FIG. 1, is carried out by means of two screws 8, which are pushed through corresponding bores 9 of the stop part 6 and slots 10 and 11 in the leaf spring BF or in the channel part 5 and in Threaded bores 12 of the band funnel T are screwed in.

Since the screws 8 at the same time for attachment serve of the measuring part MT on the belt funnel T, the measuring part can be replaced by simply loosening and tightening the screws 8 and thus the device consisting of the belt funnel T and the measuring part MT can be easily adapted to changing belt numbers.

The leaf spring BF as shown (see in particular FIG. 4) consists of a measuring beam 13 and two torsion bars 14, by means of which the measuring beam 13 is fastened to a connecting part 15. The leaf spring BF consisting of the parts mentioned is made in one piece and is clamped at the two points 16 marked by hatching in FIG. 4 in the transition region between the connecting part 15 and torsion bars 14 between the channel part 5 and the stop part 6. The measuring bar 13 of the leaf spring BF lies across the measuring channel 4 and is prevented at its ends by two bearing surfaces 17 of the stop part 6 from pivoting away from the measuring channel 4.

A sliver coming from the sliver funnel 1 and running through the measuring channel 4 is compressed by the measuring bar 13 in the measuring channel 4 and generates a pressure on the measuring bar 13, the absolute value of which increases reproducibly with increasing sliver thickness. Each change in the strip thickness causes a corresponding change in this pressure and the force acting on the measuring bar 13. As a result of the abutment surface 17, the measuring bar 13 cannot pivot away from the measuring channel 4, but instead undergoes deflection, and in the measuring bar 13 there is a positive elongation on one surface and a negative elongation on its other surface, which is proportional to the force acting and thus a measure of the strip thickness is. The mechanical quantity strain is converted into an electrical quantity by means of strain gauges arranged on the measuring bar 13 (see FIG. 6a).

As can be seen in particular in FIG. 2, the support surfaces 17 are less than 1 mm in front of the web of the stop part 6 connecting them. The maximum possible deflection of the measuring beam 13 is thus limited to this distance and the web between the two stop surfaces 17 acts as Stop against overstretching or overstressing.

As can be seen from FIGS. 2 and 3, a tube or nipple 18 is attached to the stop part 6 on both side walls transversely to the measuring channel 4 of the channel part 5. The tubes are each fastened in a bore 19 penetrating the corresponding side wall. One of the tubes 18 is used for supplying the electrical connections, the other enables simple cleaning and cooling of the measuring part MT by means of compressed air. The cleaning is carried out by intermittent and the cooling by constant supply of compressed air.

The two torsion bars 14, which position the measuring bar 13 and determine its pivot point, additionally fulfill the further important task of preventing the cracking effect when the measuring bar 13 is locally heated by the continuous fiber sliver and thus prevent the occurrence of mechanical stresses as a result of temperature fluctuations. So that the measuring bar 13 is not worn out by the sliver, it is provided on its side contacting the sliver with a pressure plate 20 made of hard metal or ceramic, which is applied to the measuring bar 13. In addition to the strain gauges, a temperature sensor can also be provided on the measuring bar 13 or in its area to take account of any temperature fluctuations.

6a shows the basic arrangement of the strain gauges on the measuring bar 13 and the evaluation of their signals. The figure schematically shows the measuring bar 13 supported against the abutment surfaces 17, on the pressure plate 20 of which a force F would act through a sliver. In order to evaluate the resulting strain on the two surfaces of the measuring beam 13, two strain gauges D1 and D3 or D2 and D4 are arranged on each of these.

The strain gauges lie symmetrically to the imaginary point of application of the force F in the middle of the measuring channel 4 (FIG. 5). This ensures that interfering effects caused by friction of the fiber sliver are fully compensated for by the ambient temperature or by local heating of the measuring beam 13.

Each strain gauge D1 to D4 has a certain electrical resistance R1 to R4, which resistances are all the same. Since the relative change in resistance when the measuring beam 13 bends is known to be proportional to the elongation of the strain gauges, the determination of the elongation can be carried out by measuring this change in resistance. This is done with the aid of a Wheatstone bridge circuit, which consists of four branches, which are formed by the ring-shaped interconnected resistors R1 to R4. If one now applies a supply voltage UE to the connection points between the resistors R4 and R1 on the one hand and R2 and R3 on the other hand, then an output voltage UA proportional to the bridge detuning can be tapped, which in turn is the sum of the strain of the individual strain gauges D1 to D4 is proportional.

• - Einfache Bereichsanpassung des Bandtrichters 1 durch Auswechseln der Bandführung (Kanalteil 5).
• - Möglichkeit der Anordnung des Messorgans sehr nahe an der Abzugsvorrichtung.
• - Einfache Möglichkeit der Reinigung des Messorgans.
• - Schutz des Messorgans gegen externe mechanische Einwirkungen.
• - Schutz des Messbalkens 13 gegen Ueberdehnung durch mechanischen Anschlag.
• - Praktische Unabhängigkeit des Messorgans von Temperaturschwankungen.
• - Weitgehende Unabhängigkeit des Messorgans von Schwankungen der Faserfeinheit des Faserbandes.

Since the measuring bar 13 is relatively short and has a high spring constant and small mass, it has a very high natural frequency and enables the measurement of very short unevenness in the strip thickness at a high throughput speed of the fiber strip. Further advantages of the described device are the following:

• - Easy range adjustment of the band screed ters 1 by changing the tape guide (channel part 5).
• - Possibility of arranging the measuring element very close to the trigger device.
• - Easy way of cleaning the measuring element.
• - Protection of the measuring element against external mechanical influences.
• - Protection of the measuring bar 13 against overexpansion by mechanical stop.
• - Practical independence of the measuring element from temperature fluctuations.
• - The measuring element is largely independent of fluctuations in the fiber fineness of the sliver.

FIGS. 7 to 13 show a second exemplary embodiment of a band funnel T '(FIGS. 7, 8), one suitable for use with this stop part 6' (FIGS. 9, 10) and a suitable leaf spring BF '(FIGS. 11-13 ). The scale in FIGS. 7 and 8 is 2: 1 and in FIGS. 9-13 5: 1.

The band funnel T 'is basically the same as the band funnel T shown in FIGS. 1 to 3 and has an outlet opening 3' of approximately oval or elongated cross-section as the main difference compared to this. This shape leads to a corresponding deformation of the cross section of the fiber sliver, so that the leaf spring no longer lies tangentially thereon but along a side surface.

The band funnel T 'also has a step following the outlet opening 3', in which a measuring part is inserted and fixed by screws (not shown). While in the measuring part MT of the first exemplary embodiment (FIGS. 1-6), with reference to FIG. 1, the channel part 5 is at the bottom and the stop part 6 is at the top, this is the reverse in the second exemplary embodiment of FIGS. 7 to 13. The stop part 6 '(FIGS. 9, 10) thus lies directly on the graduation of the band funnel T' and the channel part is arranged above this. The leaf spring BF '(Fig. 11-13) is clamped between these two parts. Which of the two parts, channel part or stop part, lies directly on the gradation of the band funnel T or T 'is not essential to the invention.

The channel part of the second embodiment practically corresponds to the channel part 5 (FIG. 1) of the first embodiment and is therefore not shown. In contrast, there are a number of differences in the stop part and the leaf spring between the two exemplary embodiments, which are now to be explained with reference to FIGS. 9-13. Since the leaf springs in particular are different, the leaf spring will be described first.

As can be seen in FIGS. 11-13, the leaf spring BF 'essentially consists of a thicker support part 21 forming the edge part thereof and a measuring bar 13', which has one end face directly and a torsion bar 14 'at its other end the carrier part 21 is connected. Since the leaf spring BF 'is also made from one piece, "connected" in this context naturally does not refer to a connection between two different parts but the boundary of two regions of one and the same part. The leaf spring BF 'has two holes 22 for the screws 8 (FIG. 1) corresponding fastening screws for rough adjustment in the measuring part. The fine adjustment is carried out by screws (not shown) which are guided in a second pair of bores 23 and screwed into corresponding threads 24 of the stop part 6 '(FIG. 9).

The measuring bar 13 'has a thickening 25 with the pressure plate 20 on its area contacting the fiber sliver which is passing through and is to be measured. The four strain gauges are arranged on the surface of the measuring bar 13 ′ facing away from the pressure plate 20, preferably in the area between the thickening 25 and the end of the measuring bar 13 merging into the carrier part 21.

The stop part 6 '(FIGS. 9, 10) is correspondingly adapted to the leaf spring BF' and has at its edge an approximately U-shaped bearing surface 26 for the leaf spring BF 'and in the area of the measuring bar 13' a gradation set back against the bearing surface 26 27 on. The gradation 27 is divided in two by a web 28 arranged in the area of the pressure plate 20 (FIG. 11). The web 28 projects beyond the step 27, but is lower than the support surface 26 and forms a stop limiting the deflection of the measuring beam 13 '.

As can also be seen from FIGS. 9 and 10, the stop part 6 'also has two chamber-like cutouts 29 and 30. In each of the chambers 29 and 30 a bore 19 penetrates the corresponding side wall of the stop part 6 'and at least one tube 18 is fastened in one of the bores 19. The electrical connections of the strain gauges are guided through this tube 18 via chamber 30 and gradation 27 to the outside. In the bore 19 opening into the chamber 29, a nipple is fastened (not shown), through which compressed air is blown from the outside into the stop part 6 'for cleaning and cooling the measuring point, which passes through chamber 29 and web 28 via the measuring beam 13' .

9 and 11, it can be seen that the leaf spring BF 'has larger dimensions than the corresponding surface of the stop part 6'. This stems from the fact that the leaf spring BF 'matching the illustrated stop part 6' only extends up to the line G shown in broken lines at its upper and left edge in FIG. 11. The leaf spring BF 'in this case has an approximately L-shaped support part 21 and the bore 23 on the left in FIG. 11 is located between the torsion bar 14' and the adjacent bore 22.

The variant of the leaf spring BF 'shown in FIGS. 11-13, when used the stop part 6' and of course the channel part 5 (FIG. 1) to be modified accordingly would be distinguished by the fact that the measuring bar 13 'and the torsion bar 14' are surrounded on all sides by the carrier part 21 and are thus optimally protected against external influences. If the leaf spring BF 'has the smaller dimensions indicated by the border G, then both the measuring bar 13' and the torsion bar 14 'lie on the outer edge of the measuring part MT (FIG. 1) and can thereby be damaged by external action. In the leaf spring BF 'shown in FIGS. 11 to 13, this is precluded by the part 21' of the carrier part 21 lying outside the border G, which forms a shield for the measuring bar 13 'and the torsion bar 14'.

Claims (20)

1. An apparatus for measuring the thickness and irregularity of fibre slivers, preferably on machinery used in preparation for spinning, with a compression member which compresses the fibre sliver, and a measuring device which is arranged thereon, mechanically scans the compressed fibre sliver in a measuring duct and is formed by a leaf spring provided with a resistance strain gauge, for measuring the thickness and irregularity of the fibre sliver, characterized in that the measuring duct (4) is provided in a measuring member (MT) arranged removably on the compression member (T, T') and equipped with a compressed air connection (19), and in thatthe leaf spring (BF, BF') is arranged transversely to the direction of travel of the fibre sliver.

2. An apparatus according to Claim 1, characterized in that the measuring member (MT) is formed by a duct part (5) and a stop part (6, 6'), between which the leaf spring (BF, BF') is clamped.

3. An apparatus according to Claim 2, characterized in that the leaf spring (BF, BF') has a measuring beam (13,13')which is spring mounted on a support (15, 16; 21).

4. An apparatus according to Claim 3, characterized in that the measuring beam (13) is mounted at its ends via torsion rods (14).

5. An apparatus according to Claim 4, characterized in that the measuring beam (13) is provided on its side which rests on the fibre sliver and on the opposite side with in each case a plurality of resistance strain gauges, preferably with two resistance strain gauges (D1, D3; D2, D4).

6. An apparatus according to Claim 5, characterized in that the resistance strain gauges (D1, D3; D2, D4) are arranged on each side of the measuring beam (13) symmetrically to the longitudinal axis of the measuring duct (4).

7. An apparatus according to Claim 4, characterized in that the ends of the torsion rods (14) remote from the measuring beam (13) are connected via a connecting part (15).

8. An apparatus according to Claim 4, characterized in that the stop part (6) has, in the region of the measuring beam (13), two contact faces (17) for the ends thereof.

9. An apparatus according to Claim 8, characterized in that the stop part (6) has, between the two contact faces (17), a web which is set back from the measuring beam (13) for limiting the deflection of the measuring beam.

10. An apparatus according to Claim 9, characterized in that the stop part (6) has a U-shaped profile adjacent to its portion clamping the connecting part (15), the contact faces being provided on its lateral walls, and in that the compressed air connection (19) is provided in one of the lateral walls for cleaning and/or cooling the interior of the measuring member (MT) and of the measuring beam (13).

11. An apparatus according to Claim 3, characterized in that the measuring beam (13') is mounted on the support (21) directly at one end and via a torsion rod (14') at its other end.

12. An apparatus according to Claim 4 or 11, characterized in that, on its side lying on the fibre sliver, the measuring beam (13,13') is provided in the region of the longitudinal axis of the measuring duct (4) with a pressure plate (20) preferably composed of hard metal or ceramic material.

13. An apparatus according to Claim 12, characterized in that the leaf spring (BF, BF') is produced from one piece.

14. An apparatus according to Claims 11 and 13, characterized inthatthe part of the leaf spring (BF') forming the support (21) is thicker than the measuring beam (13').

15. An apparatus according to Claim 14, characterized in that the support (21) has an L-shaped configuration and inthatthe measuring beam (13') is mounted directly on one arm of the support and via the torsion rod (14') on the other arm of the support.

16. An apparatus according to Claim 15, characterized in that an additional member (21') for protecting the measuring beam (13') and the torsion rod (14') from external influences is provided on the support (21).

17. An apparatus according to Claim 16, characterized in thatthe additional member (21') also has an L-shaped configuration and is combined with the support (21) to form a rectangular one-piece plate, and in that the measuring beam (13') and torsion rod (14') are arranged in the internal portion of this plate.

18. An apparatus according to Claim 11, characterized in thatthe compression member (T') has an outlet opening (3') for the fibre sliver with an oval or oblong cross-section, and in thatthe measuring beam (13') is orientated parallel to one of the longer side edges of the outlet opening.

19. An apparatus according to Claims 11 and 12, characterized in that the stop member (6') has a contact face (26) for the leaf spring (BF') and, in the region of the measuring beam (13'), a stepped portion (27) which is set back towards the contact face and is divided by a web (28) which is arranged in the region of the pressure plate (20) and whose face turned towards the measuring beam lies at a level between the contact face and the stepped portion and forms a stop for the measuring beam.

20. An apparatus according to Claim 19, characterized in that two chambers (29, 30) are provided in the stop member (6'), of which the first (29) is connected to both parts and the second to one part of the stepped portion (27), in that a respective passage (19) in the stop member leads to the outside from each chamber, and in that the passage opening into the first chamber is provided as a compressed air connection and the passage opening into the second chamber is provided for guiding electric cables to resistance strain gauges arranged on the measuring beam (13').

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