Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D7/00—Bending rods, profiles, or tubes
  • B21D7/02—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment
  • B21D7/022—Bending rods, profiles, or tubes over a stationary forming member; by use of a swinging forming member or abutment over a stationary forming member only
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D7/00—Bending rods, profiles, or tubes
  • B21D7/16—Auxiliary equipment, e.g. for heating or cooling of bends

Definitions

• the present invention relates to a tool for shaping tubes which are made of a polar or dielectric plastic material, to a machine for bending tubes provided with the shaping tool and to a process for bending tubes.
• the technique currently used consists in shaping a plastic tube on a template machined to the shape which it is desired to give to the tube and this over its entire length.
• the template plus tube assembly is heated and then cooled.
• the tube and the template are heated by means of a conduction system (hot water, steam, hot air) or radiation (infrared).
• This technique of raising the temperature implies that the whole of the tube and the template is brought to the deformation temperature of the tube, which is generally long because of its large mass. It can be seen that the geometry of the part or of the tube depends on the geometry of the template, which implies making one template per piece according to the shape which it must obtain.
• the object of the shaping tool according to the present invention is to place a tube of dielectric plastic material in an electric field of high frequency and voltage so as to agitate the molecules of the material, in order to cause heating on inside the tube.
• the tool for shaping a tube comprises means for heating by dielectric loss using frequencies which are adapted to the polar materials constituting the tube, in order to conform it.
• the shaping tool according to the present invention is isolated from the outside by means of a shielding cage retaining the external radiation of the electromagnetic waves coming from the heating means.
• the shaping tool is made of an insulating material.
• the shaping tool comprises heating means which consist of two electrodes each formed by a metal plate arranged in two parallel planes and on either side of the shaping tool, said first plate being connected to an alternating voltage source, while the other is connected to ground.
• the bending machine according to the present invention comprises an elongated frame integral with a carriage provided with a mandrel for holding a tube of dielectric plastic material so as to be able to move said tube in a longitudinal direction towards a bending head located at one end of said frame, said bending head comprising at least one shaping tool is means for heating by dielectric loss using frequencies which are adapted to the polar materials constituting said tube in order to conform it.
• the bending machine according to the invention has a bending head which comprises means for cooling the tube which are arranged along the same longitudinal axis as that carrying said tube.
• the bending machine according to the present invention comprises a bending head which is isolated from the frame of the machine by means of a shielding cage retaining the external radiation of the electromagnetic waves coming from the heating means.
• the bending machine according to the invention comprises a tool for shaping the tubes which is made of an insulating material.
• the bending machine according to the invention has heating means which consist of two electrodes in the form of metal plates arranged in two parallel planes and on either side the shaping tool, said first plate being connected to an alternating voltage source while said second is connected to ground.
• the process for bending a plastic tube according to the present invention consists of:
• Figures 1 and 2 are perspective views illustrating the bending machine according to the present invention.
• Figure 3 is a perspective view showing the bending machine provided at one of its ends with its bending head.
• Figure 4 is a perspective view showing the bending head of the bending machine according to the present invention.
• Figure 5 is a perspective view illustrating the bending head before the establishment of the plastic tube to be formed.
• Figure 6 is a front view showing the placement of the plastic tube inside the shaping tool of the bending head.
• Figure 7 is a perspective view showing the plastic tube before its bending around the shaping tool.
• Figure 8 is a view similar to that of Figure 7, but illustrating the plastic tube bent around the shaping tool.
• FIGS. 1 to 3 show a machine for bending 1 of the tubes 2 made of plastic and more particularly in dielectric or polar materials.
• the bending machine 1 comprises a fixed elongated frame 3 and carrying at one of its ends a bending head 4.
• the latter comprises a first 5 guide devices 5 making it possible to ensure the horizontal movements of said bending head 4 by relation to the main axes of the fixed frame 3.
• the fixed frame 3 is integral on one of its sides and parallel to its longitudinal axis with a guide rail 6 on which slides a carriage 7 which approaches and moves away from the bending head 4.
• the guide rail 6 is offset laterally and in height relative to the longitudinal axis of the frame 3 to present the carriage 7 along a longitudinal axis parallel to that of the bending head 4.
• the carriage 7 has a mandrel 8 for receiving of the tube 2 to be bent which is brought via a loading station 9 provided with pivoting arms 10 and 11. The latter come to pick up the tubes 2 to be bent in a magazine 12 arranged next to the loading station 9.
• the bending head 4 of the machine 1 is placed in a shielding cage 32 so as to isolate it from the outside during the shaping of the tube 2.
• the cage 32 consists of walls 13 joined together by a ceiling 14 and a floor 15, while doors 16 allow access to the interior of said cage in order to be able to intervene on the bending head 4.
• the cage 32 is made of an insulating material to avoid any risk of danger during the shaping of the tube 2.
• the bending machine 1 is controlled by different programming and control units 17, 18, 19 to obtain the bending of the tube 2 made of dielectric plastic.
• the bending head 4 which comprises a horizontal arm 20 secured at one of its ends to a plate 21 which cooperates with the guide device 5 ensuring the horizontal movements of said head relative to the main axes of the frame 3.
• the arm 20 comprises, opposite the plate 21, an assembly 22 extending vertically above the said arm and carrying a winding roller 23, a tool 24 and heating means 25.
• the winding roller 23 is mounted free to rotate about a vertical axis 26 which is integral with an articulated arm 27.
• the arm 27 is controlled to pivot in rotation about the vertical axis of the assembly 22 and of the shaping tool 24 .
• the shaping tool 24 is fixed to the assembly 22 at the same level as the winding roller 23 and the horizontal axis carrying the carriage 7 secured to the mandrel 8 provided with the tube 2.
• cooling means 28 which consist, for example, of a nozzle 29 connected to a source of cold air pressure.
• the nozzle 29 comes to cooperate with the end of the tube 2 which is opposite to that which must be bent in the shaping tool 24.
• the mandrel 28 also allows the tube 2 to rotate around its longitudinal axis.
• the shaping tool 24 is adapted to the diameter of the tube 2, of the polar material constituting said tube and of the bending radius to which it must conform.
• the shaping tool 24 is made of an insulating plastic material insensitive to electric fields such as, for example, a material sold under the brand TEFLON.
• the tool could be made of ceramic without changing its characteristics.
• the heating means 25 of the tube 2 to be bent consist of two electrodes 30 and 31 each formed by a metal plate with a circular profile.
• the first electrode or plate 30 is arranged above and against the shaping tool 24, while the second electrode or plate 31 is located just below and against said tool.
• the electrode 30 is connected to the unit 19 which delivers an alternating voltage source, while the other electrode 31 is connected to a ground not shown.
• FIGS. 5 to 8 the various stages of bending the tube 2 are shown at the radius of curvature of the shaping tool 24.
• the tube 2 is brought by the carriage 7 so that the mandrel 8 integral with the cooling nozzle 29 cooperates with the end of the tube opposite to that which will be formed.
• the tube 2 is positioned near the shaping tool 24, while the roller 23 is moved laterally to block said tube so that it cooperates with the internal profile of each. Indeed, the roller 23 and the tool 24 has an internal profile which depends on the external diameter of the tube 2 (FIGS. 6 and 7).
• the arm 27 carrying the roller 23 pivots in rotation about the vertical axis of the assembly 22 which merges with that of the shaping tool 24 in order to cold deform the tube 2 at the bending radius (FIG. 8 ).
• an alternating voltage is applied by means of the unit 19 to the electrode 30, while the other electrode 31 is connected to ground.
• This voltage generates an electric field of frequency and high voltage so as to agitate the molecules of the dielectric material constituting the tube 2, so that the latter heats up.
• the heating means 25 emit when the temperature of the tube 2 rises external radiation from the electromagnetic waves. These radiations are recovered by the shielding cage 32 to avoid any risk of raising the temperature of the individuals in the vicinity of the machine 1.
• the heating means 25 make it possible to raise the temperature of the tube 2 in a few seconds.
• the cooling means 28 blows pressurized cold air through the nozzle 29 inside the tube 2 in order to cool it so that it retains its bending shape within the radius of the tool 24
• the arm 27 returns to its original position and the roller 23 moves laterally in order to release the tube 2.
• the tube 2 can be moved along its longitudinal axis and cause it to rotate around the latter to perform another bending said tube in a different plane. It is noted that, given the possibility of producing hangers by rapidly heating and cooling a tube 2 wound around a shaping tool 24, it becomes possible to produce different geometries by linking successive hangers.
• the length, rotation and bending movements of the tube 2 are carried out by numerically controlled axes managed by the control units 17 and 18.
• the shaping tool could comprise several bending radii, while the bending head would be provided with vertical guiding means in order to present the suitable shaping tool according to the bending radius to be obtained.
• the unit 19 comprises a high frequency assembly which consists of a transmitter capable of emitting a power whose level is adjustable, and of a processing structure of the capacitive type in which the area of material to be processed is placed. To meet the constraints of standard NE 55011, the generator is of the amplifier type controlled by quartz.
• the energy from the generator is transmitted to the processing structure via an impedance adapter by a coaxial cable of known impedance.
• the impedance adapter is equipped with two variable and motorized elements to transmit all the energy from the generator to the load. This function is automatically ensured by a double sensor, the output signals of which are amplified and processed by electronics which control each of the two motors coupled to the variable elements.
• the automatic tuning system makes it possible to optimize and manage the energy level transmitted to the product during the entire treatment, thereby ensuring good reproducibility of the treatment.
• the application structure of the field (capacity for example) is optimized so as to transmit the energy in an adequate and homogeneous manner in the areas to be treated.
• the shape of the electrodes is therefore optimized according to the diameter and thickness of the tube and the bending radius.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Shaping Of Tube Ends By Bending Or Straightening (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Machines For Laying And Maintaining Railways (AREA)
• Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
• General Induction Heating (AREA)

Applications Claiming Priority (3)

Publications (2)

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ID=9513348

Family Applications (1)

Country Status (6)

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Family Cites Families (3)

• 1997
  • 1997-11-07 FR FR9714259A patent/FR2770794B1/fr not_active Expired - Fee Related
• 1998
  • 1998-11-05 CA CA002309306A patent/CA2309306A1/fr not_active Abandoned
  • 1998-11-05 EP EP98954516A patent/EP1035930B1/de not_active Expired - Lifetime
  • 1998-11-05 AT AT98954516T patent/ATE213183T1/de not_active IP Right Cessation
  • 1998-11-05 DE DE69803879T patent/DE69803879T2/de not_active Expired - Fee Related
  • 1998-11-05 WO PCT/FR1998/002360 patent/WO1999024189A1/fr active IP Right Grant

Non-Patent Citations (1)

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