Patent GB-744041-A (GB)
Title: Improvements in or relating to the damping of vibrations in machine tool parts
IPC: F16F7/104
Filed: 1950-09-27
Abstract: 744,041. Vibration dampers and dashpots. PRODUCTION ENGINEERING RESEARCH ASSOCIATION OF GREAT BRITAIN, and LEWIS, F. A. Sept. 24, 1951 [Sept. 27, 1950; Sept. 27, 1950; Sept. 27, 1950], Nos. 23698/50, 23699/50 and 23700/50. Class 108 (3). [Also in Groups XXII and XXIII] An absorbing or damping system for a machine tool part liable to self-induced vibration comprises a substantial mass, a spring and a viscous damper, the natural frequency of the absorbing or damping system being slightly less than that of the vibrations to be damped, the mass being coupled, or adapted to be coupled to the machine part in such a way that the mass has freedom of oscillation in the direction or directions of the vibrations to be damped, the entire absorbing or damping system being grouped in the vicinity of the point of maximum amplitude of the vibrations to be damped and the value of the viscous damping of the combined vibrating system constituted by the machine part and the absorbing or damping system is sufficient for the combined system to be stable. One embodiment of the invention suitable for application to the arm of a radial drill or to lathe headstocks or tailstocks, planing machines and grinding machines comprises a pair of parallel leaf-springs 1, 2, Figs. 2 and 3a, joined at their ends by hinged sprung pieces 3, the lower spring being adapted to be attached by its centre to the machine part through a bracket 4. The upper spring 2 carries the mass 5 and a dashpot 6 is connected centrally between the springs. The dashpot, Fig. 3a, comprises a cylinder 8 bolted to the lower spring 1 and piston having its rod attached by a screwthreaded end 20 to the upper spring. The piston is in two parts with adjustable means for varying the effective openings of passages 17, 18, connecting the two sides of the piston. A variation of this embodiment with the mass supported by spiral springs and the dashpot arranged within the mass may be built into the end of the arm 22, Fig. 4, of a radial drilling machine. In the application to a boring bar 71, Fig. 12, a mass 76 is supported by a rod 77 and has clearance in the hollow end 72 of the bar. A cap 73 closes the chamber so formed which is filled with a damping liquid. A cross-slot 74 in the cap serves to receive a cutter bit which is clamped by screws 75. In an application to shaping machines the mass may be arranged for movement in the direction of movement of the ram by supporting it for sliding movement along a rod. Another form of damper has the mass in the form of a cylinder supported by spiral springs at its ends and adapted for movement in any radial direction, the mass being enclosed in a cylinder filled with a damping fluid. In order to save weight, in a further modification applied to a radial drilling machine, the electric driving motor 81, Fig. 13, for the drill is used as the absorbing mass and is supported by springs 86, Fig. 14, and guided in its vertical movements by rods 83 which terminate in pistons 87 forming part of dashpot devices 88. The drive passes through a flexible coupling 89 to permit movement of the motor. A vibration absorber for rotating parts of machine tools such as lathe chucks is also described.