Programmable pressure controlled mandrel extractor for tube bending machine

Abstract

A tube bending machine is provided which includes a rotatable bend die about which the tube is bent, a mandrel insertable into the tube adjacent the bend, and a mandrel rod fixed to a rear end of the mandrel. A mandrel extractor system is also included which linearly advances and retracts the mandrel. The mandrel extractor system includes a linear actuator connected to the mandrel rod and an electro-hydraulic control system which automatically drives the linear actuator at variable pressures. The linear actuator includes a hydraulic cylinder with a piston connected to the mandrel rod. The electro-hydraulic control system includes a hydraulic pump which provides hydraulic fluid to the cylinder, a directional valve which selectively feeds the hydraulic fluid to opposite sides of the piston, a proportional pressure control valve which varies pressure of the hydraulic fluid, and a microprocessor based controller in electrical communication with the valves which provides control signals to vary the pressure of the hydraulic fluid. The controller is pre-programmed with several preselected pressure levels for the mandrel extractor. The tube is loaded over the mandrel while the mandrel is at a system pressure. The mandrel is moved within the tube at a very low pressure, below that of the system pressure, to the tangent point of the tube and the bend die. After reaching the tangent point, the mandrel pressure is increased back to the system pressure. During the bending operation, the mandrel pressure can be maintained at the system pressure or varied. At the end of the bend operation, the pressure is increased to a level above the system pressure to pull the mandrel out of the tube.

Dependencies are inferred from the claim text.