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(11) | EP 0 016 267 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Material tensioning method and apparatus |
| (57) For subjecting a continuous strip of metallic-material or stock to an applied high
tension for a drawing, straightening or stretching process, apparatus is disclosed
which comprises a pair of elastic ring-equipped roll assemblies for holding the material
there-between under a high tension applied by the roll assemblies. The elastic ring
(5,6) of each roll assembly is capable of elastic deformation which elongates the
area of the ring in contact with the material (13) along the circumference of the
ring as applied tension increases, thus increasing the contact area over which the
applied force is distributed evenly. This results in a reduction of the force per
unit area. Each elastic ring is mounted on a shaft (1,2), at least one of the shafts
being drivable, byway of atleastthree rollers (3,3a 3b; 4, 4a, 4b) which are interposed
between the ring (5,6) and shaft (1,2) for axial rotation and two of which (3, 3a;
4, 4b) are arranged to bridge the ring overthe ring contacting area ofthe material. |
[0001] The present invention relates generally to processing a strip of metallic material or stock under an applied high tension, and more particularly to method and apparatus which provides a high tensioning force for a material or stock drawing, straightening or stretching process.
[0002] In the art of drawing, straightening or stretching a strip of metal such as a bar or coil stock of round, square or other cross section, there is known no method or apparatus of the type which can provide a high tension for processing the stock without causing damage to the stock material. According to a known method or apparatus, if a high tension should be applied to the material, it would be very likely to be damaged by the rollers or similar means which hold and pull it therebetween. The damage would more frequently tend to occur and become more significant as the tensioning force is increased. For this reason, it is the practice to provide additional means to prevent such damage. For example, when a material is subjected to different tensile forces supplied by one tensioning apparatus, preliminary provision should disadvantageously be made-so as not to damage the material under the maximum applied tensile force.
[0003] It is an object of the present invention to provide a new and improved material tensioning method and apparatus for use in drawing, straightening or stretching a strip of material.
[0004] The invention provides in one aspect a material tensioning method for placing a continuous strip of metallic material or stock under an applied high tension for a drawing, straightening or stretching process, comprising:-
holding the material between a pair of elastic ring-equipped tensioning roll means;
increasing a tensile force provided by said tensioning roll means to place the material under the increased tension; and
enlarging that area of the elastic ring in each of the roll means which contacts the material as the tensile force provided by the roll means increases, whereby the enlarged contact area of the ring can evenly distribute the amount of the applied pressure upon the material, resulting in a reduction in the applied pressure per unit area.
[0005] Preferably, the contact area of the elastic ring is elongated in a circumferential direction of the ring by elastically deforming the ring.
[0006] The invention provides in another aspect material tensioning apparatus for placing a continuous strip of metallic material or stock under an applied high tension for a drawing, straightening or stretching process, comprising:-
a pair of parallel spaced shafts at least one of which is drivable and a pair of tensiohing elastic ring-equipped roll means mounted on the corresponding shafts for holding therebetween the material under a high tension, in use, applied by said roll means, the elastic ring of each of said roll means being capable of elastic deformation which elongates the area of the ring in contact with the material along the circumference of the ring as said applied tension increases.
[0007] Preferably, each of said roll means includes a plurality of regularly-spaced rollers interposed for axial rotation between said shaft and said ring.
[0008] Preferably, two of said rollers are arranged to bridge the ring over the ring contacting area of the material.
[0009] Desirably the outer peripheries of said rings together define a shape in cross section which corresponds to that of a material to be processed.
[0011] The invention will now be more particularly described with reference to the accompanying drawings, wherein:
FIG. 1 is a graph illustrating the relationship between the applied pressure and resulting longitudinal elastic deformation of the elastic ring shown in Fig. 2;
FIG. 2 is a side view of one embodiment of material tensioning apparatus according to the present invention;
FIG. 3 is an end view of the pair of elastic rings shown in Fig. 2;
FIG. 4 is a plan view of a straightening machine incorporating the apparatus shown in Fig. 2;
FIG. 5 is an end view of the mechanism shown in Fig. 4;
FIG. 6 is a perspective view of part of the machine shown in Fig 4, shown on an enlarged scale; and
FIGS. 7 to 12 are schematic diagrams illustrating examples in which the apparatus shown in Fig. 2 can be employed, FIG. 7 being for a continuous stretching machine; FIG. 8, for a straightening machine, FIG. 9, for a drawing machine; FIG. 10, for a wire flattening machine; FIG. 11, for a rolling machine; and FIG. 12 for a drawing machine in which material is back- tensioned.
[0012] Referring to FIG. 2, the apparatus shown therein comprises a pair of upper and lower horizontal driving shafts 1 and 2 arranged in parallel, each of the driving shafts having a set of idle rollers spaced at equal intervals thereon, as designated by 3, 3a and 3b, or 4, 4a and'4b, and an elastic ring 5 or 6 fitted over the idle rollers. The two rollers 3 and 3a, or 4 and 4b in each set have a different function from the rest i.e. rollers 3b or 4a, which function will later be described in more detail. The driving shafts 1 and 2 are powered by an external power source (not shown) for causing a rotation of the shafts in opposite directions, and at least one of the shafts is constructed to be moved down in the direction of an arrow 7 in FIG. 2 to apply pressure to a material.
[0013] In accordance with the embodiment described above, the operation is performed in the following manner. The driving shaft 1 is driven so as to rotate in the direction of arrow 8, causing axial rotation of the idle rollers 3, 3a and 3b in the directions of arrows 9, 10 and 11, respectively. The rotation of the rollers 9, 10 and 11 causes rotation of the elastic ring 5 in the direction of an arrow 12. As may be understood, the driving shaft 2 is driven concurrently with the shaft 1 and rotates in the opposite direction, and all the associated elements rotate in like manner to elements associated with the shafts 1, as indicated by arrows 16, 17, 18 and 19. Thus, a strip of material 13, as shown a bar, can be moved in the direction of arrow 14. As described above both shafts 1 and 2 are powered for rotation, but alternatively, only the shaft 1 may be driven with the other shaft 2 mounted for free rotation.
[0014] , As shown in FIG. 3, the elastic rings 5 and 6 are V-grooved at 20 and 21, respectively, around the outer peripheries thereof, which peripheries as shown are adapted for a bar 13 of square cross-section. These elastic rings may be replaced by other elastic rings which are provided with any peripheral shape in cross-section depending upon the shape in cross-section of the material to be processed, such as round, flat, etc. Three idle rollers are shown and described, but the number of the rollers is not limited to the described embodiment and may be varied, such as four. The two rollers 3 and 3a, or 4 and 4b are arranged such that an isosceles triangle is formed by imaginary lines connecting the centers of the rollers and the mid-position of that area of the ring which contacts the material. In other words, the two rollers'are located at equal distances from said mid-position, or viewed from the contact area of the ring, said mid-position is located exactly between the two rollers. Functionally, the two rollers bridge the ring over the ring contacting . area of the material. The other roller 3b or 4a is functionally different from the above-mentioned rollers, in that this roller prevents the ring from being slipped out of position.
[0015] The graph shown in FIG. 1 represents the results of an experiment with a pair of elastic rings 5 and 6 in the above apparatus. The experiment was carried out with the following parameters:
Elastic ring material: bearing steel; Young's modulus of 21,000 kg/mm2; outer diameter of 321 mm; inner diameter of 300 mm; thickness of 10.5 mm:
Material or stock to
be processed 12.3 mm wide and 1.7 mm thick; tensile strength of 55 kg/mm2.
Applied pressure : 2.5 tons
[0016] The stock held between the elastic rings was placed under the above pressure, and the experiment shows that that area of the elastic ring in contact with the stock was elongated along the longitudinal direction of the stock due to the elastic deformation of the ring, the resulting length ℓ being equal to approximately 7.0 mm. When the areas in contact between the rings and the stock were lubricated, a tension of up to 450 kg could be applied to the material with no accompanying effect of the rings upon the material. That is to say, the experiment shows there is no danger of the rings causing damage to the stock under that applied tension or affecting the thickness of the stock which would usually change if rolled.
[0017] The apparatus may have a variety of uses as shown by way of example in FIGS. 7 to 12. FIG. 7 shows a continuous stretching machine in which two sets each of two pairs of elastic ring-equipped rolls A and B, and C and Dare arranged in series along the travelling path of a strip material 28. A high-tension straightening machine shown in Figure 8 incorporates two spaced apart pairs of elastic ring-equipped rolls A and B, and a number of leveler rollers 22 and 23 interposed between the two pairs, pairs for removing strains from a strip material 29. FIG. 9 shows a drawing machine including a die 24 with two pairs of elastic ring-equipped rolls A and B disposed at the outlet of the die for obtaining a desired diameter of a strip material 30. In FIG. 10, one pair of elastic ring-equipped rolls is employed for producing a flattened wire material 27. In connection with the application in FIG. 10, it is known that by increasing the diameter of rolls or by increasing the number of passes, the resulting product can be provided with better width precision. However, in practice this is not economical. Then, the use of the ring rolls as shown in FIG. 10 can provide the same result as increasing the diameter of the rolls or increasing the number of passes. FIG. 11 shows a high-tension rolling mill including multi-staged rolls 25 with two pairs of elastic ring-equipped rolls A and B, each pair installed on the opposite sides of the multi-staged rolls 25. This structure permits reciprocating movement of a strip material 27. In the arrangement of FIG. 11, the part of the material located between the pairs of ring rolls A and B is tensioned so that it is possible to reduce the compressive force that the material exerts on the winding drums'when being wound in layers, thereby avoiding breakage of the drums due to. the compressive force. FIG. 12 shows an arrangement in which each of the two pairs of elastic ring-equipped rolls A and B is installed on opposite sides of a die 33. The pair of rolls A is given a braking torque placing the part of the material 27 between the pair A and the die 33 under a back tension. Thus, the overall compressive force exerted on the die can be reduced.
[0018] The construction shown in FIGS. 4 to 6 is a realized form according to the principle of FIG. 8. A material to be processed is a stainless steel flat bar 13 mm wide and 3 mm thick having a tensile strength of 80 kg/mm2. It is shown from the measuring results that a curve in the direction of width over 1 m length of the material can be straightened to within 0.3 mm as measured by a scale, and a curve in the direction of thickness can be so straightened as to make a 0.15 mm thickness gauge insertable. A material previously twisted through an angle of 180 DEG over a length of 3 m is passed through the machine, and the result is that the twisted material can be untwisted to a straight line through a single pass, this being satisfactory as measured by a scale.
[0019] In the machine shown in FIGS. 4 to 6, two pairs of the elastic ring-equipped rolls A and B described heretofore are mounted each pair on opposite sides of the machine, and two sets, each comprising a plurality of leveler rollers, 22 and 23 are mounted between the pairs A and B, one set having rollers disposed in a horizontal position for specifically correcting a lateral curve of a material 29, and the other set having rollers disposed in a vertical position for correcting a vertical curve. The ring-equipped roll pairs A and B are set to rotate at a proper number of revolutions which provide a proper amount of tension for the part of the material between the two roll pairs A and B. Driving the ring roll pairs at the speed as set causes a strip material to be fed into the machine and through the first pair A and the leveler rollers 22 and 23 into the second pair B. Then, the strip is placed under the set high tension, and is drawn out of the second pair B as indicated by arrow 32.. The thus obtained material is a straightened product.
[0020] As can be readily-understood from the foregoing description, the present invention is advantageous in that the material to be processed can be subjected to a maximum tension without causing damage such as permanent. strain or deformation, to the portion thereof held between the elastic ring rolls since the areas of the rings in contact with the material increase with the increasing amount of the tensile force, and the total applied force can, therefore, be distributed over the increased areas and this results in a reduced force per unit area.
holding the material between a pair of elastic ring-equipped tensioning roll means;
increasing a tensile force provided by said tensioning roll means to place the material under the increased tension; and
enlarging that area of the elastic ring in each of the roll means which contacts the material as the tensile force provided by the roll means increases, whereby the enlarged contact area of the ring can evenly distribute the amount of the applied pressure upon the material, resulting in a reduction in the applied pressure per unit area.
a pair of parallel spaced-shafts at least one of which is drivable and a pair of tensioning elastic ring-equipped roll means mounted on the corresponding shafts for holding therebetween the material under a high tension, in use, applied by said roll means, the elastic ring of each of said roll means being capable of elastic deformation which elongates the area of the ring in contact with the material along the circumference of the ring as said applied tension increases.