This invention relates to a hydraulic pipe bender of large dimension, particularly a device through which a pipe is guided, fed by a guiding mechanism, a feeding mechanism, wherein slipping or staggering phenomena will be prevented during the bending process. Besides, the speeds of the top, right or left roller can be adjusted automatically according to the load variation during the operation to bend a smooth metal pipe ring.
When a standard sheet metal plate is rolled into a cylindrical shape, the most popular method is to use three rollers with identical diameters, as shown in FIG. 1 which shows the working principle of bending a plate on conventional rollers. The positions of the two lower rollers are fixed first, then the height of the top roller can be adjusted. Therefore, cylinders of various diameters can be produced therefrom. The closer the distances are among the three rollers, the smaller the diameter of a metal cylinder will be produced, i.e. a circle is obtained by the three points where the metal plate contacts the three rollers.
In a metal cylinder, due to the thickness of the metal plate itself, there is a difference between the inner ring (I.D.) and outer ring (O.D.), however it will not effect the speed of the rollers seriously. When a rolling machine is used to bend a metal pipe into a circular ring, due to the diameter of the metal pipe itself, the inner (I.D.) and outer (O.D.) ring circumferences will result in a great difference. However, the speeds of the three rollers are completely identical, so they will not be effected by the difference between inner and outer circumference. Thus to comply with the load variation of the inner circumference and load variation of the metal pipe, intermedient staggering will occur in the top roller. It will not produce a smooth circular metal pipe ring, besides the universal joint of the top roller breaks frequently.
Accordingly, usually an electric motor is used in the manufacturing field to rotate the top roller, and the two bottom rollers are moved by another motor, so that the top roller, to comply with the inner circumference and load variation, will reduce the speed automatically. However, the effect of the technical means may not be perfect. Further, such troubles as damage to the motor, difficult starting and slow braking may occur. They create problems to the manufacturer.
Furthermore, by adjusting the height of the center of the top roller, the diameter of a circular metal pipe ring can be determined. However, during the bending process, the front and the rear portion of the metal pipe ring will curve upwards, which causes difficulty to manufacture a totally smooth circular metal pipe ring of large dimension. Besides, during the bending process of a metal pipe, no suitable feeding mechanism and guiding .mechanism cooperate. Usually it will stag or stop easily, and it becomes difficult to manufacture a smooth circular metal pipe ring with a large dimension. Besides, during the process of bending a metal pipe, neither the feeding mechanism nor guiding mechanism is synchronized, therefore, the staggering and slipping phenomena will occur easily, causing difficulty to manufacture a smooth circular metal pipe ring with a large dimension.
Due to this shortcoming of operation in bending a pipe as mentioned above, the inventor has tried to overcome this manufacturing problem. Through numerous trials, analysis and tests, finally this invention "A hydraulic pipe bender of large dimension" is achieved.