Patent GB-1075331-A (GB)
Title: Method and apparatus utilizing vibratory energy
IPC: B21C1/18
Filed: 1964-06-22
Abstract: 1,075,331. Drawing. AEROPROJECTS Inc. June 22, 1964 [June 21, 1963 (2); Aug. 19, 1963], No. 25807/64. Heading B3P. A die and mandrel tube draw-bench has means for applying to both the die and the mandrel vibratory energy at an optimum frequency between 14,000 and 35,000 c.p.s. The direction of vibration is parallel to the axis of the die and examples are given of drawing operations on aluminium, copper and stainless steel tubes in which reductions of crosssectional area of up to 55% were achieved with reduced drawing tension as compared to drawing without vibration. The apparatus comprises a base 36 on which is mounted a pulling device 62 operated by an hydraulic cylinder, a cable, or a rack-and-pinion device, a die 12 and a mandrel 16. Means for vibrating the mandrel.-The rear end of the mandrel screws or is brazed into an acoustical coupler element 20 made of steel, aluminium-bronze or a copper-nickel alloy. The length of the element is a whole number multiple of a half-wavelength and the combined length of the mandrel and coupler is such that an anti-node appears at the die orifice. The opposite end of the coupler is screwed into a mechanical transformer 22, and locked by a nut 51. The effective length of the coupler can be varied to ensure resonance at the operating frequency. The transformer 22 is brazed to a magnetostrictive, electrostrictive or piezo-electric transducer 26 which has a power coil 72, connected to an amplifier 86 and an oscillator 80, and also has a polarizing coil 74. The transformer 22 is supported on the bench by a force insensitive mount 30 which comprises a sleeve 32 one half wavelength long. One end 48 of the sleeve is bonded to the transformer at an anti-node region, the other end of the sleeve is free and at a quarter wavelength from the attached end 48 is a flange 34 which is clamped to the support 35 by a ring 37. The support 35 is adjustable along the bench 36 in the direction of the arrows 100. Means for vibrating the die.-An extension 42 of the die 12 screws into a coupler 40 which has four horns 44a, 44b, 44c, 44d, each of which is fixed to a transducer 50a, 50b, 50c, 50d. Each of the transducers has a polarizing coil and a power coil. The power coils are connected to an oscillator through an amplifier and a phaseshifting device 88. The die is supported by a force insensitive mount 52 similar to the mount 30. Operation.-A pointed tube 18 is fed over the mandrel 16 and coupler 20 and the pointed end passed through the die 12 to the pulling device 62, which then pulls the tube to seat the mandrel and look the tube between the mandrel and die. Power is then supplied to the coils of the transducers and the oscillator is set to the resonant frequency of the transducers. The phase-shifting device 88 is adjusted so that the vibrations of the die and mandrel are in phase. The waveform of the oscillator is sinusoidal and the frequency range is 59- 300,000 c.p.s. The preferred range is 3,000 to 50,000 c.p.s. The transducers are designed to have a resonant frequency of 15,000 c.p.s. In the examples given electrical power input to the mandrel varied between 100-450 watts and the input to the die was between 1200- 2000 watts. In some of the examples only the mandrel was vibrated. Drawing tension was reduced by approximately 30% by using vibration. When the length of tubing which has been drawn is i wavelength there is a drop in the drawing tension necessary and thereafter the required drawing tension decreases momentarily as the length increases by half-wavelengths. To take advantage of this effect and thereby maintain the required drawing tension at a minimum a second fixed die is positioned at a “-wavelength distance from the first die so that a permanent condition of resonance obtains in the section of tubing between the two dies. Further dies may be positioned at half-wavelength intervals beyond the second die. The second and further dies are dimensioned so that they produce a slight sinking effect on the tube.