Showing papers on "Bend radius published in 1985"

Some numerical experiments on developing laminar flow in circular-sectioned bends

Abstract: The paper reports numerical solutions to a semi-elliptic truncation of the Navier–Stokes equations for the case of developing laminar flow in circular-sectioned bends over a range of Dean numbers. The ratios of bend radius to pipe radius are 7:1 and 20:1, corresponding with the configurations examined experimentally by Talbot and his co-workers in recent years. The semi-elliptic treatment facilitates a much finer grid than has been possible in earlier studies. Numerical accuracy has been further improved by assuming radial equilibrium over a thin sublayer immediately adjacent to the wall and by re-formulating the boundary conditions at the pipe centre. Streamwise velocity profiles at Dean numbers of 183 and 565 are in excellent agreement with laser-Doppler measurements by Agrawal, Talbot & Gong (1978). Good, albeit less complete, accord is found with the secondary velocities, though the differences that exist may be mainly due to the difficulty of making these measurements. The paper provides new information on the behaviour of the streamwise shear stress around the inner line of symmetry. Upstream of the point of minimum shear stress, our numerical predictions display a progressive shift towards the result of Stewartson, Cebici & Chang (1980) as the Dean number is successively raised. Downstream of the minimum, however, in contrast with the monotonic approach to an asymptotic level reported by Stewartson, the numerical solutions display a damped oscillatory behaviour reminiscent of those from Hawthorne's (1951) inviscid-flow calculations. The amplitude of the oscillation grows as the Dean number is raised.

Attenuator for optical fiber

Abstract: An attenuator for an optical fiber has a tapered screw around which the fiber is looped, the fiber engaging within the screw thread. The fiber is held fixed in position by a spring so that as the screw is rotated the radius of curvature of that part of the fiber held against the screw is altered. Light propagating along the fiber is radiated out at the fiber bend, the level of radiation loss depending on the bend radius of curvature. The attentuator elements are mounted within a light-tight box with the fiber terminating at optical connector components mounted within a wall of the housing. The connector components enable rapid insertion of the attenuator into an optical transmission line to provide an accurate reproducible level of attenuation.

Polarization mode dispersion in a coil of single-mode fiber

Abstract: Polarization mode dispersion resulting from lateral stress by bending is measured as a function of bending curvature. The magnitude of the modal dispersion is found to be 286 psec/km for a bending radius of 2.8 mm. The experimental result is in good agreement with that predicted theoretically for bulk material.

Optical fiber cable

Abstract: PURPOSE: To provide a strong and highly flexible optical fiber cable by using a bundle formed by bundling inorg. insulating long fibers having specific tensile strength and modulus of elasticity of extension as a tension member, twisting optical fibers onto the member and coating the same with a sheath consisting of a synthetic resin. CONSTITUTION: The bundles 10 each formed by bundling the inorg. insulating long fibers having ≥250kg/mm 2 tensile strength and ≥20,000kg/mm 2 modulus of elasticity of extension are used for the tension member 6 and sub-tension members 8, 8 and therefore, these members have an electrical insulating characteristic, do not generate an induced voltage and does not damage the terminal apparatus for optical communication. The flexibility is extremely high and the permissible bending radius of the cable 5 can be eventually made smaller. Smooth pulling is made possible with an overhead earth wire, etc. by which the tensile force in the stage of drawing is made smaller and the need for exerting extra power to the cable 5 is eliminated. COPYRIGHT: (C)1987,JPO&Japio

Push-bending type cold pipe bending device

Abstract: PURPOSE:To execute cold bending to a thin pipe without thinning the thickness of a bend forming part by a small bending radius, by using a bending device provided with two arms having a roller on the tip, and a roller-shaped die. CONSTITUTION:A thin metallic pipe 1 to be bent is placed on a grooved bending die 2 having a desired radius of curvature. A V-shape is formed by arms 4, 5 supported so as to be freely oscillatable in a center shaft 3 of this bending die 2, and also a cylinder is attached by brackets 4a, 5a so that a V-shaped angle formed by the arms 4, 5 is made large by an operation of the cylinder 6. Rollers 7, 8 are installed to a suitable position of the arms 4, 5, and placed on the metallic pipe to be worked 1. By driving the cylinder 6 functioning as a pressing device, the arm 4 is turned around the shaft 3 of the bending die 2, pushed and turned so that an angle of the V-shape becomes large without changing the distance between the center of the roller 7 and the axial core 3, and the metallic pipe 1 is bent in accordance with a curvature of the bending die 2.

Tube bending device

Abstract: PURPOSE:To bend a tube without generating bending wrinkles on the tube even when the tube is thin by constituting a tube bending device of a bending die, a pusher die having rack teeth on the back and its pushing device. CONSTITUTION:A thin tube 14 is set to the fixed bending die 11 having specified bending radius, and set by a clamping die 13. Then, a hydraulic cylinder 16 is driven and its piston rod 20 is retreated. The pushing device 15 pushes the tube 16 through the pusher die 12 to the bending die 11 side to complete preparation for bending. Then, the pushing device 15 is rotated clockwise by a hydraulic motor 23. Downward force is applied to the pusher die 12, and the tube 14 is pressed in the direction in which tensile stress generated at the inside is reduced. On the other hand, the pushing device 15 moves engaging with the rack teeth 12a of the pusher die 12, and turns around a shaft 17. The pusher die 12 and pushing device 15 move to positions 12' and 15' respectively, and bend the tube 14 along the bending die 11.

Performance of Four 4.5 M Two-in-One Superconducting R & D Dipoles for the SSC

Abstract: Four 4.5 m long superconducting dipoles built to specifications similar to those for SSC Reference Design A have been successfully tested. They were wound with NbTi cable in two-layer cos? coils of 3.2 cm inner diameter. The coil ends were flared to increase thie minimum bending radius, anticipating coils wound from prereacted Nb3Sn. The coils were mounted in a reusable "two-in-one" iron yoke prestressed by means of a bolted stainless steel shell. The first two magnets as well as the fourth one, a special magnet designed to study cross-talk between the bores, used CBA/Tevatron cable. The third utilized cable with improved ("high homogeneity") NbTi conductor. All four reached central fields corresponding to their short sample limits at 4.5K without training, nearly 6. OT for the first two magnets, 6.5T for the third, and 5.4T for the fourth. At 2.5K modest training was required to reach short sample limits of 7.2T, 7.1T, 7.8T, and 6.6T respectively. The measured values of the allowed harmonics were within several × 10-4 of the calculated ones.

Method and device for straightening end bend of long-sized tube

Abstract: PURPOSE: To straighten an end bend of a long-sized tube by moving a pressure ram and a pressure receiving base and pressing and straightening the tube, without moving the long-sized pipe in the axial direction, at a straightening position of the long-sized tube. CONSTITUTION: A tube 10 is transferred to a press position II from a holding position I. The tube 10 is inserted and held by rotary rollers 11, 12 and rotated, its bend is measured by a measuring member 14, and the rotation of the tube 10 is stopped with the maximum bend part up. A pressure ram 18 is moved to the upper part of a position of the maximum bend part by a cylinder 19. In accordance with a state of the bend of the pipe 10, a selection of pressure bases 23, 24 is executed, the rotary rollers 11, 12 descend and the tube 10 is placed on the pressure receiving bases 23, 24. The pressure ram 18 descends by a prescribed quantity by a hydraulic servo-control, and the tube 10 is straightened. When the straightening is executed once, the rotary rollers 11, 12 ascend, and when the bend of the tube is within an allowable value or not is measured by the measuring member 14. In case when restraightening is required, said straightening operation is repeated. COPYRIGHT: (C)1987,JPO&Japio

Device for reequipping cable, line and hose screw unions with bending protection

Abstract: Particularly in the case of apparatuses whose position is variable and which have flexible connecting lines, the cable insertion or bushing screw union must be provided with bending protection which prevents sharp kinking or the minimum bending radius of the connecting line being undershot. Helical bending protection consisting of thermoplastic material can be subsequently installed in the compression screw of commercially-available PG screw unions as a result of the special design of the mounting nipple (annular thickening on the start and longitudinal slot or slots).

Bending radius control method in high frequency bender

Abstract: PURPOSE:To prevent a wrinkle-like bulge from being generated in a bending start part of a pipe material by using a length detecting rod of a specified structure, when bending a locally heated pipe material by using a bending roller and a length detecting rod for controlling bending. CONSTITUTION:A pipe material 1 to be bent is supported by supporting point rollers 2, 3, heated locally by a high frequency heating coil 4, the pipe material 1 is pushed in the direction P, and simultaneously, a bending force is given in the direction as indicated with an arrow C by a bending roller 5. In this case, a length detecting rod 14 which is supported by a bending center 8 in order to control a radius, and fixed to the tip of the pipe material 1 by a fitting tool 9 is installed in advance. This length detecting rod 14 is a slide type and expandable, and in the beginning of bending by a pressure of the bending roller 5, a length of this length detecting rod 14 is varied by sliding it. When a prescribed bending angle is obtained, thereafter, the pipe material 1 is bent by keeping a length of the length detecting rod 14 constant, by which it is prevented that a wrinkle-like bulge 12 is generated in a bending start part of the pipe material.

Bending method of superconductive lead

Abstract: PURPOSE:To bend a metallic pipe inserted tightly with plural pieces of conductors to a small radius without buckling the pipe by using a pair of jigs each having a semicircular groove of a prescribed bending radius and pressing the metallic pipe by said jigs thereby forming the bent part thereof. CONSTITUTION:The pressing jigs 2, 3 having the semicircular grooves 1 which face each other, have the bending radius equal to the bending radius R of the metallic pipe 51 inserted tightly with plural pieces of the conductors 52 therein and allowing passage of a cooling gas 53 and have the section of the same diameter as the outside diameter (d) of the pipe 51 are used. A straight lead 42 is sandwiched by the grooves 1 of such jigs and the jigs 2, 3 are pressed to form the bend to the lead 42. The pipe 51 is thus restrained by the jigs 2, 3 even if the radius R of the pipe 51 is smaller than the diameter (d) of the pipe 51 and therefore the lead 42 is formed to the small size without buckling the pipe.

Welding torch used for welding robot

Abstract: PURPOSE:To simplify a work in case of leading in a wire, and also to straighten a bend of the wire by coupling a welding wire straightening device to a welding torch nozzle, and providing a wire guide of a prescribed bend radius on a wire leading-in port of the straightening device. CONSTITUTION:A leading-in work of a welding wire fed to a welding torch nozzle 10 passing through a cable 12 can be executed easily even if a welding torch is linear, by providing a curved wire guide 8. Also, a bend generated in the welding wire 11 is straightened by a welding wire straightening device 1 coupled directly to the welding torch nozzle 10. The welding wire straightening device 1 displaces a position of an adjusting roller 6 in the direction vertical to a line for connecting shaft centers of rollers 3, 4 by operating an adjusting screw 5, and gives a suitable curve to the wire 11 between the rollers 3, 4.

Flow Patterns and Hydraulic Losses in Quasi-coil Pipes : The effects of configuration of bend cross section, curvature ratio and bend angle

Abstract: Pipes with bend combinations are much used in the heat exchangers, since the curved path in the bends promotes the mixing in flow for active heat transfer. In the present paper, one of the pipes with bend combinations, namely, quasi-coiled pipes composed of many bend elements are investigated, and the relationships between the hydraulic loss and the secondary flow are studied experimentally. The configurations of the cross sections, the bent angles and the curvature ratios of the bend elements of the quasi-coiled pipes are changed in the experiment. The effects of these factors are investigated in detail. As the result, it is found that the secondary flow becomes the type of a one-directional swirling flow in the quasi-coiled pipes if the bend cross sections are changed from circular to rectangular. Moreover, many interesting results are described.

Bending device of three piece roll

Abstract: PURPOSE:To save the trouble of an operator to see the result with fitting to a gage one by one and to perform efficiently a bending work by providing a measuring mechanism of a bending radius accuracy to a bending device of a three piece roll. CONSTITUTION:Linear scales 5, 6 and fixed probe 7 are moved together by operating a motor cylinder 9 with the input of an electrical signal, etc. and by extending a ram 9a to the direction of a work 4. The scales 5 and 6 are first brought into contact with the work 4 and retreated by compressing an incorporated spring. When the fixed probe 7 is brought into contact with the work 4, then, a pin 9b is projected from a supporting tool 8 and brought into contact with a microswitch 12 to operate and stops the operation of the motor cylinder 9. The displacements of the scales 5, 6 are taken out as an electrical signal and inputted into an arithmetic and display device and the radius of curvature of the work 4 is calculated and displayed. The target value and measured value of the radius of curvature are compared, and by increasing, etc. the stroke of a bending roll 1, the bending work of the 2nd time is performed and the measurement of the radius of curvature is performed. The target value of the radius of curvature is obtd. with repeating the above measurement.

Optical u-link

Abstract: PURPOSE:To set a ferrule pitch to a diameter of an optical fiber critical bend or below by inserting and fixing each one end of two optical fibers into ferrules, respectively, in a housing, and inverting and connecting to each other end through one light deflecting element. CONSTITUTION:Two optical fibers 25, 26 are contained in a housing 20, and each one end is inserted and fixed into ferrules 21, 22. Also, each other end of the optical fibers 25, 26 is connected in a connecting part C. Moreover, each end face of the optical fibers 25, 26 is chamfered in the opposite direction to each other at an angle of 45 degrees to the optical axis, and these inclined end faces are coated with light total reflecting films 28, 29, respectively. In this way, light O sent to an optical fiber 25a is reflected and polarized by the light reflecting films 28, 29, and made incident to an incident end face of an optical fiber core 26a. In this way, it is unnecessary to bend the optical fibers 25, 26 by a small bending radius, and a pitch between the ferrules can be set to a diameter of an optical fiber critical bend or below.

Device for bending plate material

Abstract: PURPOSE:To reduce the sort of metal dies and to shorten the time for replacement work by dividing in longitudinal direction the upper die having several sorts of projected dies for bending radius and also by performing a bending work of different bending radius and bending length with the rotary combination of upper die and lower die. CONSTITUTION:An upper die 2 is divided into plural pieces in longitudinal direction and fitted to upper die fitting seat by a fitting bolt 9. The upper die 2 also has upper face and lower face having a different curvature and is fitted by a bolt 9, so the working of steel materials having different bending radii can be performed with the same upper die 2. The lower die 3 has both faces of a recessed face 3B having larger bending radius and a recessed face 3S with smaller one. The upper die 2 can be fixed with half turn respectively and also the lower die can be replaced with half turn as well in the working of steel material having different bending radii. The metal dies sorts can be reduced and also the time for replacement work can be shortened by the combination of the upper die 2 and lower die 3.