SE432996B - DEVICE FOR DETECTING VARIATIONS IN Grease Film Thickness - Google Patents

Description

15 20 30 40 ßšüiliiri “å inte.

The minimum detectable resistance measured with the known construction corresponds to the resistance in the trees between the traction sheaves, ie approximately 10 milliohm.

Thus, using the arrangement according to the known Japanese patent, it is not possible to register uneven product quality with good time / longitudinal resolution. It is also not possible to calculate the accumulated resistance distribution with good accuracy in order to assess disc wear therefrom.

Furthermore, the integrity of demolition can be recorded, as it requires resolution at a resistance value below one milliohm.

The above-mentioned disadvantages are eliminated according to the invention by means of a detection device of the type mentioned in the introductory paragraph, which is mainly characterized in that a transformer driven by alternating current is arranged to transfer current without contact to the wire included in the circuit and that a capacitive probe is arranged in a housing galvanically connected to the draw plate for measuring the voltage across the lubricating film, wherein an evaluation means electrically connected to the probe is arranged to determine the lubricating film resistance according to the formula RX = k - H 1 where i is the current through the measuring wire, U is the via the probe measured the voltage and k is a constant. Preferably, the trees themselves are included in the secondary winding of the transformer. I A detection device of this kind can be designed for use at reaction times down to the range of 1 millisecond, which allows the detection of point-shaped defects at traction speeds of fh flfl meters per second.

The invention will now be described in more detail below in the form of a preferred embodiment with reference to the accompanying drawing.

Figure 1 shows an example of the main parts of a wire drawing bench, in which the electrical resistances and capacitances which become relevant when utilizing electrical circuits according to the principles of the invention are plotted.

Figure 2 shows a tree tractor with a detection device which is designed and installed according to the invention. 40 8301441-5 principles.

Figure 3 shows in more detail the new device according to the invention for providing current in the pull wire and measuring the electrical contact resistance between the wire and the pull plate.

In the various figures, like parts are provided with the same reference numerals.

The towbar arrangement generally shown in Figure 1 comprises a fixed support 10, on which a reel 12 or a reel 14 are rotatably mounted. In the drawing, said reels 12, 14 are shown only partially. Between the reels 12,14 there is the so-called drawer 16, which is heated by a lubricant container 18 and a drawer 22 arranged in a special space 20, which is well sealed against the drawer itself by means of seals 24. The drawer ZZ is cooled during work by cooling water 26, which make contact with the draw plate 22 around its periphery.

During wire drawing, the wire 28 is forced in a known manner through the opening 30 of the draw plate 22, the lubricant film applied around the wires - not shown - being continuous and uniform in order to obtain the best possible results.

Figure 2 shows the wire drawing bench schematically together with the connected detection device according to the invention, the current and corresponding circuits according to the construction according to Figure 1 being indicated.

RX denotes the electrical resistance across the lubricating film, R1 the resistance in the pull plate 32, the seal Z4 and the drawbar support 10, RZ the resistance across the bearing of the spool 12, the RS contact resistance between the spool 12 and the wire 28, C1 being the corresponding capacitance between the contact resistance 14 and the wire 28, where Ck is the corresponding capacitance, and RS the resistance across the bearing of the paddle 14.

As the power source for the detection device shown, in the example given, an oscillator 32 is used, which drives a current transformer 34. The primary winding of the transformer 34 consists of a toroidal coil So, which encloses the wire 28, which will thus be none in the secondary winding of the transformer 34. The current paths are shown in the directions of the arrows in figure Z. The alternating current of the nut circuit is thus obtained without contact.

In the drawing, ip 34 indicates primary and secondary windings. A capacitive measuring probe 58, and the currents through the transformer J 10 15 20 25 35 40 öšüílït fi øßlrš L, which comprises a tube electrode 40 together with an associated amplifier 4Z, capacitively connected to the wire via the tube electrode 40, are anoiwhiad in a housing 44, which is galvanically connected to the draw plate 22 for measuring the voltage Uk across the lubricating film. The housing 44 shields the measuring probe 38 from external electric interference fields. The galvanic coupling to the traction sheave 22 is arranged so that undesired voltage drops are eliminated. The housing 44 is thus directly connected to the draw plate 22 via an intermediate piece 46, which has a good abutment against a bearing flange 4 projecting from the draw plate ZZ. The tubular intermediate piece 46 is provided with through-going slots 50, which make undesirable lubrication flakes which detaches from the lubricating film, can easily pass out.

An electrical insulation 52 is arranged between the pull plate 22 and the pull plate 16 itself on the side facing the measuring probe 38.

On the opposite side, on the other hand, a good galvanic connection is achieved. This is shown in the drawing by means of a ground wire 54. the position R] is low, which is thus ensured by pure metallic contact.

An additional toroidal coil S6 is arranged around the wire 28 in immediate connection with the housing 44 in order to eliminate undesired voltage drops along the wires by the blocking inductance. To achieve good function, it is very important to counteract a shunting of the contact resistor RX, which would otherwise be achieved. via wire 28, across resistor R4, capacitor CZ and resistor RS.

In the embodiment illustrated in the drawing, a special current measuring transformer 58 is also connected. This includes a toroidal coil 60 which encloses the wire 28 in the same manner as the toroidal coil 36. The two transformers 34, S8 are arranged in close proximity to each other. The purpose of the toroidal coil 60 is to enable accurate current measurement in cases where large impedance variations are to be expected. The contact resistance RX can then be calculated by dividing the measured voltage UX by the measuring current im passing through the current conductor 62 connected to the toroidal coil 60.

Both the oscillator 32, the measuring probe 38 and the toroidal coil 60 of the transformer 58 are connected to a signal processor 64, which makes it possible to evaluate the measured values obtained. The current circuit from the oscillator also has a current root doctor 66. The AC voltage signal obtained from the measuring probe 38 is demodulated in a demodulator 68 and then passes on to the signal processor 64. The signal processor 04 can issue alarms via the output 70 for criteria , which is input via the setting means 72.

Depending on the use of the detector device, it is possible to also take out alarm signals ~ at 74 - for unsatisfactory detector function and to analyze data - at 76 - with information on calculated quality or on traction plate wear. For connection of external data recording equipment, values regarding current, voltage and any calculated resistance can be obtained via an output 78.

In the embodiment shown, the signal processor consists of a microcomputer, but in its simplest form it may consist of an analog level discriminator. With the help of the described equipment, a signal processing adapted to the primary purpose takes place after signal conversion. In the simplest case, alarms are triggered when a predetermined resisunßgràn is exceeded; evanmelh: after a certain temporal duration. In more advanced use, signal analysis is performed to obtain a fast and safe response to changes or to correlate the result with experience regarding disc wear and production quality.

Modifications of the detector device described above can, of course, be made within the scope of the invention. Thus, the transformer shown in the drawing can be designed in many different ways. This also applies to the measuring probe itself. However, the constructive details are within the knowledge of those skilled in the art.

Furthermore, it is also possible to use the inventive idea when measuring lubricating film resistance, whereby a rotating shaft is used instead of the usual one used. The traction sheave is in this case replaced by a bearing.

Claims (10)

öšüiiælr fi- š Patcntkrav I. I. Apparatus for detecting, by measuring electrical contact resistance, variations in lubricating film thickness of wire (28) during wire drawing in a drawbench, in which the wire runs between stripping and pulleys (12 and 14, respectively) or lens discs via one with Lubricant and pulling disc (22) provided with pull box (16) located between the reels / discs, a piece of the wire (28), the lubricating film, the pulling disc (22) and further parts belonging to the pulling bench forming a closed circuit, characterized in that an AC transformer (34) is arranged to transmit current to the wire (28) included in the circuit and a capacitive measuring probe (38) is arranged in a housing (44) galvanically connected to the draw plate (22) for measuring the voltage across the lubricating film, an evaluation means (64) electrically connected to the measuring probe (38) being arranged to determine the lubricating film resistance according to the formula _ U Rx - k ï where i is the current through the measuring wire (28), U is measured via the measuring probe (38) take the voltage and k is a constant. Device according to claim 1, characterized in that the wire (28) is included in the secondary winding of the transformer (34). Device according to claim 1, characterized in that the primary winding of the transformer (34) consists of a toroidal coil (36) enclosing a wire (28). Device according to one of Claims 1 to 3, characterized in that a signal amplifier (42) is connected in series with the measuring probe (38). 5. A device according to claim 3 or 4, characterized in that a second toroidal coil (56) is arranged around the wire (28) in connection with said housing (44) in order to eliminate undesired voltage drops through the blocking inductance. Device according to one of Claims 3 to 5, characterized in that a second toroidal coil (60) is arranged around the wire (28) for measuring the current passing therethrough. Device according to one of Claims 1 to 6, characterized in that the measuring probe (38) is electric: connected to a signal processor (04) 8301f + f + 1-5, which acts as an evaluation means, preferably; via en (iexnodulntor (08). Device according to claim 7, characterized in that the signal processor is constituted by a nívádiscriminator. Device according to one of Claims 3 to 8, characterized in that the first signal, if any, also the third toroidal coil (36 and 40, respectively) are individually electrically connected to the signal processor (64). . Device according to one of Claims 7 to 9, characterized in that the signal processor consists of a microcomputer.