Patent Application
20110240169
This application claims priority of German Patent Application No. 10 2010 014 384.7, filed on Apr. 6, 2010, the subject matter of which is incorporated herein by reference.
This disclosure relates to straightening and cutting-off machines for the production of straightened elements of predeterminable length from a wire-shaped material, in particular for the production of straightened bars from reinforced-concrete wire.
Straightening and cutting-off machines, which are also occasionally designated as straightening and cutting-to-length machines or simply as straightening machines, are designed to straighten wires and other materials processable by straightening and having different cross-sectional sizes and shapes and cut them off to a desired length. Thus, for example, ribbed wires consisting of reinforced-concrete steel can be processed into straightened bars which are subsequently welded together in a net-like manner to form reinforced-concrete steel mats for reinforcing concrete structures. Unribbed smooth wires can also be processed, for example, to obtain straightened wire bars for the construction of cages, shopping trolleys, fences, baskets or the like.
A known straightening machine has a feed device for drawing in the material to be straightened from a material stock, a straightening device for straightening the material conveyed by the drawing-in device into a working range of the straightening device, and a cutting device, following the straightening device, for separating a portion of predeterminable length from the straightened material to produce the straightened element. The material is usually present on a wire spindle (coil), is unwound from the wire stock by push rollers of the feed device and is led into the straightening device where the wire, still having stresses and bends, is straightened. Thereafter, the then straightened material is drawn out of the straightening device by draw rollers on the feed device and conveyed in the direction of what may be referred to as an “add-on.” When the desired length is reached in the straightened material portion, the portion is cut off with the aid of the cutting device and falls into a collecting trough. Straightened elements having a great length of several meters or several tens of meters and having low length tolerances can be produced.
The cut by which the straightened element is separated from the material must take place at the correct time point or at the correct location of the conveyed material to obtain the desired length with the desired accuracy. For this purpose, a straightening and cutting-off machine has a length measurement system that measures the length of the moved material and generates a measurement signal which represents the length and which is then processed by a control device to activate the cutting device. Various measurement methods are employed nowadays for length measurement.
A known method works with the aid of a measuring wheel, the circumference of which is pressed onto the material running through such that the measuring wheel is driven by the material and co-rotates with it. The shaft of the measuring wheel transmits the rotational movement to a rotary encoder, the encoder signals of which are processed for indirect length measurement. To prevent slip between the measuring wheel and the moved material, a running wheel is pressed against the material from the opposite side, with the result that the material is tensioned between the measuring wheel and the running wheel. The configuration of the measuring wheel may vary, depending on the material to be straightened. In the straightening of ribbed structural steel, for example, a measuring wheel having teeth on the circumference is normally employed to achieve the best possible take-up. Where smooth material surfaces are concerned, measuring wheels having a smooth circumferential face are occasionally used, especially when the surface of the material running through should not be damaged. In some configurations, to enlarge the pressure area, a continuous groove is introduced into the circumference of the measuring wheel, with the result that slip between the measuring wheel and material can be reduced.
Length measurement with the aid of a measuring wheel is a structurally simple and robust measurement method. When measuring wheels are used, however, it must be remembered that, after a certain period of use, measurement accuracy may gradually become lower due to wear on the measuring-wheel circumference. Relatively frequent calibration or exchange of measuring wheels is therefore recommended. Further inaccuracies or measurement errors may arise due to insufficient friction between the material and measuring wheel, that is to say due to slip. Although it is possible to mitigate this problem by increasing the pressure force, this usually has an adverse effect upon the wear which may lead, in turn, to measurement inaccuracies after lengthy use.
Another possibility of length measurement is to use a manually adjustable trigger head in the add-on. In this method, triggering of the cut takes place via the trigger head which is fixed in a suitable position on a carrying rail of the add-on, depending on the desired length of the straightened element. For this purpose, as a rule, a scale fastened to a guide element of the add-on is used. When the free front end face of the straightened material impinges onto a trigger lever during feeding, the latter pivots out of the path of movement of the material and triggers the cut via a signal. The trigger head may also contain a stop which is mounted at a short distance behind the contact face of the trigger lever. In these instances, during triggering of the cut, the element impinges onto the stop to achieve as exact a length as possible. Since, in length measurement by a manually adjustable trigger head, length measurement takes place only very shortly before the cut, the distance over which measurement errors can still arise is very short and, therefore, very high measurement accuracies can be achieved. Length tolerances when a stop is used may lie in the range of a few tenths of a millimeter and, without a stop, tolerances of the order of one to two millimeters are usually achieved. Although the measurement method with a trigger head is accurate, setting up a new desired length is relatively complicated and requires operator experience. Variants with a stop should not be used in machines with a rotating cut since material is otherwise pushed onto the stop during cutting.
It could therefore be helpful to provide a straightening and cutting-off machine which is capable of producing, in continuous operation, and at a high production rate, straightened elements having very low deviations from the desired length. It could also be helpful to enable a changeover to other desired lengths with only little effort and provide that precision in length setting depends as little as possible on the operator's experience.
We provide straightening and cutting-off machines that produce straightened elements of predeterminable length from a wire-shaped material including a feed device that draws in material from a material stock, a straightening device that straightens the material conveyed into a working range of the straightening device by the feed device, a cutting device, following the straightening device, that separates a portion of a predeterminable length from the straightened material to produce the straightened element, a contactlessly operating length measurement system that measures length of the material and generates a measurement signal representing the length, and a control device that activates the cutting device on the basis of the measurement signal.
We also provide straightening and cutting-off machines that produce straightened elements of predeterminable length from a wire-shaped material including a feed device that draws in material from a material stock, a straightening device that straightens the material conveyed into a working range of the straightening device by the feed device, a cutting device, following the straightening device, that separates a portion of predeterminable length from the straightened material to produce the straightened element, a length measurement system that measures length of the material and generates a measurement signal representing the length and includes a laser measurement system having a device that generates at least one laser beam directed onto the material and devices that detect interaction between the laser beam and a surface of the material, wherein the laser beam impinges onto the surface of the material from above such that an angle between a radial direction to a run-through direction of the material and a radiation direction is less than about 30°, and a control device that activates the cutting device based on the measurement signal.
It will be appreciated that the following description is intended to refer to specific examples of structure selected for illustration in the drawings and is not intended to define or limit the disclosure, other than in the appended claims.
We provide straightening and cutting-off machines for the production of straightened elements of predeterminable length from a wire-shaped material comprising: a feed device for drawing in material from a material stock; a straightening device for straightening the material conveyed into a working range of the straightening device by the feed device; a cutting device, following the straightening device, for separating a portion of predeterminable length from the straightened material to produce the straightened element; a length measurement system for measuring the length of the material and for generating a measurement signal representing the length; and a control device for activating the cutting device on the basis of the measurement signal; wherein the measurement system is a contactlessly operating measurement system.
In our straightening and cutting-off machines, the measurement system is a contactlessly operating measurement system. A contactlessly operating measurement system is capable of ensuring length measurement or speed measurement of the material running through in a run-through direction without touch contact occurring between an element of the measurement system and the material running through. As a result, inter alia, wear of measuring elements and possible slip between the moved material and a measuring element may be avoided. A contactless measurement system can operate continuously, free of wear, so that measurement accuracy does not depend on the period of use. Wear-induced maintenance or repair work is also avoided. The measured material is protected.
Preferably, the measurement system is an optical measurement system, that is to say a measurement system in which light from a suitable wavelength range of the electromagnetic spectrum is used for the measurement and evaluation of the movement of the material. In this case, the interaction of light from the visible wavelength range or from adjacent wavelength ranges of the spectrum with the moved material is detected and evaluated with the aid of optical systems and optical effects. Contactless measurements of high accuracy are possible here even in the case of high speeds of movement of the moved material.
Comprehensive investigations have shown that, in light of the various boundary conditions in straightening and cutting-off machines, it is usually especially advantageous if the measurement system is a laser measurement system which has a device for generating at least one laser beam directed onto the material and devices for detecting the interaction between the laser beam and a surface of the material. For example, laser distance measurement may be employed in which a laser beam is directed essentially coaxially to the moved material, onto an end face of the material. The orientation of the measuring beam involves a relatively high outlay and measures for reducing the sensitivity of the measurement system to dust and dirt should be taken.
It has proven substantially more beneficial if the measurement system is set up in such a way that the laser beam impinges onto the surface of the material in a radiation direction running transversely with respect to a run-through direction of the material. The radiation direction can then, for example, be in the radial direction to the run-through direction or at an acute angle thereto. An essentially radial radiation of the laser beam may be advantageous because, as a rule, only little axial construction space is then required for those components which are needed directly for generating the laser and guiding its beam and detecting the laser radiation after interaction with the material so that integration into straightening and cutting-off machines is possible in a simple way. As exact a radial radiation as possible may be beneficial in some examples to obtain high measurement accuracy. If deviations from radial radiation are present, these should be low. Preferably, an angle between a radial direction to the run-through direction and the radiation direction amounts to less than about 30°, or less than about 20°, or less than about 10°, or less than about 5°.
As an alternative to a laser measurement system, optical measurement systems can also be used which, for example, operate according to the CCD spatial-filter method or according to the grid transmitted-light method.
It has proven especially advantageous if a laser measurement system is used which operates according to the laser Doppler principle. With a suitable design, maximum measurement accuracies for a multiplicity of diameters of the material of, for example, approximately 0.5 mm to 30 mm or more and for most movement speeds typically occurring in straightening and cutting-off machines (typically of between about 3 m/min and about 400 m/min) can be achieved. The laser beam emanating from a laser is in this case broken down with the aid of a beam splitter into two coherent part-beams which are projected obliquely to one another onto a region of the measurement object, are superposed there and generate in the superposition region a system of interference fringes. Particles or structures on the surface of the measurement material scatter the light when it passes through the bright fringes. A detector receives this scattered light which is modulated with a Doppler frequency from which the speed of the scatter centers and, therefore, also the speed of the irradiated surface can be determined. The length that has run through can be determined by integrating the speed.
A frequency shift may be generated between the two transmission beams of the laser Doppler measurement system so that a moving interference-fringe system is obtained. It is thereby possible, inter alia, to measure with high precision even up to the standstill of the measurement object.
When a contactless measurement system is integrated into a straightening and cutting-off machine, numerous boundary conditions must be taken into account, operator safety also playing a major part in the use of a laser measurement system. Typically, the straightening and cutting-off machine has an operator side and an operator-remote side, while critical components of the machine should be accessible from the operator side for maintenance, repair and setting-up work, and the drives are normally arranged on the operator-remote side. Preferably, the measurement system is set up in such a way that the laser beam impinges onto the material from the operator side, thus ensuring that the eyes of operators are safe. To ensure that the operation of the machine is not impaired by components of the measurement system, the operator side should, at least in the region of the material run-through, be free of components of the measurement system. Preferably, the run-through direction of the material lies in a vertical plane, and the measurement system is set up in such a way that a radiation direction of the laser beam forms with the vertical plane an angle of less than about 45°, in particular of less than about 20°, the laser beam preferably impinging onto the material from above.
In a laser-based measurement system, the laser beam should impinge onto the moved material continuously as far as possible without interruptions so that measurement signals can be generated constantly or at very high frequency. Special conditions prevail in this respect in straightening and cutting-off machines. In the straightening device, the material running through is formed mechanically in a plurality of directions running obliquely with respect to one another to achieve the desired straightening action. Preferably, the straightening device has a straightening mechanism which rotates during operation and by means of which it is possible to straighten the material in all planes. The mechanical engagement of the straightening device on the material may give rise in the latter to stresses, in particular also torsional stresses, which are occasionally discharged in a jolt-like manner during further transport of the material. This may lead to an unsteady run of material and to associated measurement errors if no countermeasures are taken.
Preferably, the feed device has a pair of draw rollers arranged downstream of the straightening device and rotatable contradirectionally about parallel axes of rotation, and a measuring head of the measurement system is arranged between the draw rollers and the cutting device. The draw rollers preferably have a concave circumferential contour or a continuous groove, so that, in the region of their greatest approach to one another, they provide a guide orifice for the straightened material with certain lateral guidance. If torsional stresses within the wire are to be reduced, the wire can rotate slightly within the guide orifice, with the result that the material is relaxed by slip in the circumferential direction. Since lateral movement of the material is greatly limited directly downstream of the draw rollers, it is especially beneficial to direct the measurement radiation onto the material in this region, since the material cannot shift away laterally there.
As a rule, one of the draw rollers is mounted fixedly with respect to the machine, whereas the other draw roller can be displaced in a lifting-off direction running perpendicularly with respect to the axis of rotation, counter to the force of a press-down device which, for example, operates pneumatically. This maneuvrability of one axis of rotation makes it possible that the movably mounted draw roller can shift away in the lifting-off direction when thickenings, ribs, dirt and/or other irregularities run through the guide orifice of the draw rollers. Since, in such instances, there is a certain latitude parallel to the lifting-off direction for the material, preferably the measurement system is set up in such a way that a radiation direction of the at least one laser beam forms with the lifting-off direction an angle of less than about 45°, in particular of less than about 20°, the laser beam preferably impinging onto the material from above. What can be achieved thereby is that the laser beam remains on the material even when the latter lifts off in the lifting-off direction. Measurement errors on account of irregularities of the material can thereby be avoided. By a measuring head of the measurement system being arranged above the run-through direction, the situation can also be prevented where optical components and/or sensors of the measurement system quickly become soiled, so that low-maintenance continuous operation is possible.
This and further features may also be gathered from the description and the drawings, as well as from the appended claims, while the individual features can in each case be implemented individually or severally in the form of subcombinations in selected examples and in other fields and can constitute advantageous structures. Representative examples are illustrated in the drawings and are explained in more detail below.
The straightening machine is capable, in the case of high material throughput and run-through speeds of up to about 160 m/min or more, where appropriate even of up to about 360 m/min or about 400 m/min, of producing large quantities of such straightened elements with a length of, where appropriate, several meters, and with a very low length error in the per-thousand range or below.
The wire-shaped material is initially present on a large wire coil and is drawn off from the material stock with the aid of a feed device and conveyed into the straightening machine. The feed device has, on the entry side of the straightening machine, two pairs, arranged one behind the other, of push rollers 112, 114 which draw off the wire from the material stock and convey it in the direction of the straightening device 120 following in the run-through direction 102. The straightening device serves for straightening the material conveyed into the working range of the straightening device by the push rollers and for this purpose has a rotary-driveable straightening wing 122 with a plurality of lead-through orifices for the material which are arranged at an axial distance one behind the other and are offset radially with respect to one another. Such rotating straightening systems are known per se and are therefore not explained in any more detail here.
Directly downstream of the straightening device is arranged a pair of draw rollers 116 which belong to the feed device of the straightening machine and draw the straightened material out of the straightening device. Mounted at a distance downstream of the draw rollers is a cutting device 130 which follows the straightening device and which is intended for separating portions of predeterminable length from the straightened material to produce the straightened elements of predeterminable length.
The cutting device 130, which can be seen especially well in
The cutting tools are then moved into their initial position again so that the rotating cutting-tool carriers execute one revolution per cut. In cutting without wire standstill, the rib abrasion in the region of the draw rollers can be minimized. Moreover, no non-uniform structural variations occur in the material in the region of the straightening device since each portion of the material experiences the same forming action in the region of the straightening device.
On the exit side of the straightening machine is located what is known as the add-on 140 with a guide chute into which the straightened elements are pushed. When the set length is reached, the wire is cut off and falls into a collecting trough 150. This basic construction may be used for different lengths.
Straightened elements consisting of reinforced-concrete steel wire typically have a length of several meters and may, for example, be up to about 25 m long. However, shorter elements can also be produced by the same principle.
To achieve the desired length of the straightened elements with high accuracy, a length measurement system is provided for measuring the length of the material and generating a measurement signal representing the length. The measurement signal is processed by a computer-based control device, not illustrated in any more detail, of the straightening machine for the purpose of activating the cutting device 130 to generate a correctly positioned cut.
A contactlessly operating measurement system in the form of a laser measurement system which operates according to the laser Doppler principle may be provided. Mounting details are illustrated in
A measuring head 182 of the laser measurement system is mounted above the run-through direction of the wire directly downstream of the draw rollers 116 between the draw rollers 116 and the cutting device 130. The measuring head is fastened to the front side, facing the draw rollers, of a vertical intermediate wall 189 mounted fixedly with respect to the machine approximately centrally between the draw rollers 116A, 116B and the cutting device 130, that is to say nearer to the draw rollers than to the cutting device. The intermediate wall serving as a carrier for the measuring head has a passage orifice for the material 105. The position of the measuring head on the intermediate wall 189 can be set via adjusting screws.
The measuring head 182 accommodates a laser which generates a laser beam. The laser beam is broken down with the aid of a beam splitter into two part-beams which are radiated onto the surface of the wire with the aid of transmission optics as transmission beams 183, 184 running obliquely with respect to one another. The bisector between the transmission beams defines the sensor longitudinal axis which should be oriented as perpendicularly as possible to the wire surface serving as a measurement surface and, consequently, as exactly as possible radially with respect to the central axis of the wire or to the run-through direction. The working distance between the beam exit face of the measuring head and the wire surface is approximately 200 mm. This short working distance is advantageous so that the split laser beam reliably impinges onto the wire surface even in the event of vibrations of the apparatus. The geometry of the arrangement is in this case such that the coherent transmission beams overlap one another in the region of the narrow curved surface of the monitored wire material 105 running through in an overlap region 185 (see the detail). In this region (measurement volume), a system of alternating light and dark interference fringes occurs, with a fringe spacing defined by the wavelength of the transmission beams (here, in the red part of the visible spectrum) and the angle between them. Scatter centers on the material surface, for example particles or certain surface roughness, run through this fringe system and scatter the light when it passes through the light fringes. A detector 186 receives this scattered light which is modulated with a Doppler frequency which is proportional to the speed component of the material in the run-through direction. The length that has run through can be determined by integrating the speed over time. This measurement method is not impaired by the ribs on the wire surface and is independent of the rib shape. In straightening machines with a rotating cut and with a material correspondingly running through continuously, simple and robust measurement systems of this type can advantageously be employed.
The laser light coming from a laser diode may be broken down into two part-beams by an optoacoustic modulator in the form of a Bragg cell. The Bragg cell not only splits the laser beam, but also generates in one of the two part-beams a frequency shift with respect to the other part-beam, thus giving rise in the overlap region to a system of running interference fringes. It is thereby possible both to determine the sign of the movement speed and measure it during a material standstill. Measurement accuracies for the run-through speed in the region of about 1 mm/min or below are regularly achievable. In particular, precise measurement is also possible in examples with a standing cut.
The two part-beams 183, 184 define a radiation plane 188 in which the sensor longitudinal axis (bisector between the part-beams) also lies. As can be seen clearly in
The geometric arrangement is such that the part-beams impinge onto the wire running through at any time in a superposition region, even if sudden relaxations of the torsional stresses generated in the rotating straightening wing and/or the passage of irregularities of material were to occur in the straightened material. A plurality of structural measures contribute to this.
It can be seen in
By contrast, minor upward shifting movements are permitted in structural terms to compensate for irregularities of the material and the like. For this purpose, there is provision for the lower draw roller 116A to be mounted in a rotary bearing fixed with respect to the machine, while the upper draw roller 116B is mounted movably such that slight displacement in a vertical lifting-off direction 117 is possible. As a result, the upper draw roller can be raised somewhat such that when the machines are being set up, a wire may be introduced between the guide rollers from the side. The upper draw roller is pressed in the direction of the lower draw roller with the aid of a pneumatically actuable press-down device 118, but can briefly be lifted off upwards, counter to the force of the press-down device, by the material running through. Even this lifting-off movement does not impair measurement, however, since the part-beams of the laser measurement system are directed onto the middle of the wire essentially from above and still impinge onto this middle even when the wire is raised upwards slightly.
This ensures continuous contactless optical length or speed measurement without measurement gaps, even under the special boundary conditions of a straightening machine with a rotating straightening system.
Some advantages are explained by an example of a straightening machine for the production of straightened bars from ribbed reinforced-concrete steel wire. By means of the same or other examples, unribbed structural steel and/or wires consisting of other materials from the smooth-wire sector can also be processed. However, straightening and cutting-off machines are not restricted for the processing of wire materials. Tubes or profiles can also be straightened and accurately cut to length. Depending on the diameter and cross-sectional profile of the material, correspondingly dimensioned components are to be provided for guidance and straightening.
Other examples with a contactless measurement system may be equipped with a standing cutting system, that is to say a cutting device with standing shears. These are often employed in the case of smooth wires and provide outstanding cutting quality, but normally require a brief wire standstill during cutting.
The above description is directed to preferred examples. From the disclosure given, those skilled in the art will not only understand our machines and their attendant advantages, but will also find apparent various changes and modifications to the structures and methods disclosed. It is sought, therefore, to cover all changes and modifications as fall within the spirit and scope of this disclosure, as defined by the appended claims, and equivalents thereof
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 014 384.7 | Apr 2010 | DE | national |
