Metal Extrusion Press Hydraulic Circuit With Pilot-Line Speed Control
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Solution Overview
Problem
Existing metal extrusion presses face challenges with high costs, complexity, and maintenance requirements due to the use of variable displacement pumps and electric motors with low moment of inertia, which are expensive and difficult to manage.
Innovation Solution
A hydraulic circuit with a fixed displacement pump driven by a three-phase asynchronous electric motor, incorporating a hydraulic control unit with a pilot line and valves that allow gradual pressure increase to control piston acceleration, decoupling piston acceleration from motor acceleration, thereby using conventional motors and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a variable displacement pump is used to control piston speed, then the extrusion speed can be adjusted according to material type and die complexity, but the pump cost and complexity increase significantly requiring frequent and accurate maintenance
Solution Approach 1:
A pilot line is introduced as an intermediary hydraulic circuit between the main pump and the cylinder. The pilot line receives a portion of the pump's output and uses it to control the main piston's movement. This mediator allows the simple fixed-displacement pump to achieve variable speed control through the pilot line's pressure regulation, avoiding the need for complex variable displacement pumps while maintaining adjustable piston speeds.
2Use of energy by moving object
If a fixed displacement pump with variable frequency motor is used to adjust oil flow by varying motor speed, then energy saving is achieved and pump cost is reduced, but motors with low moment of inertia are required which are expensive and require complicated liquid cooling systems
Solution Approach 1:
The pilot line is pre-filled with hydraulic fluid and maintains a reservoir of pressurized oil ready for immediate use. When the main piston needs to move, the pilot line already has the necessary fluid pressure and volume prepared, allowing the main piston to accelerate without requiring the motor to rapidly change speed. This preliminary preparation of hydraulic pressure enables the use of standard high-inertia motors that can accelerate gradually.
Solution Approach 2:
The pilot line acts as a buffer and mediator between the motor's rotational speed and the piston's linear motion. Even if the motor accelerates slowly, the pilot line can build up pressure and deliver the necessary oil flow to the piston independently. This decoupling allows the use of conventional motors with high moment of inertia without compromising the piston's ability to reach required speeds.
3Loss of time
If motors with low moment of inertia are used for rapid speed variation, then fast response time is achieved, but the motors are very expensive and require various ancillary systems including complicated liquid cooling systems
Solution Approach 1:
The invention uses hydraulic pressure in the pilot line to control the main piston's movement rather than relying solely on motor speed variation. By using hydraulic pressure buildup and fluid dynamics in the pilot line, the system achieves rapid piston response without requiring the motor to accelerate quickly. This hydraulic mediation allows standard motors to produce fast piston response times through pressure-driven fluid flow rather than direct mechanical coupling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for controlled and efficient piston acceleration, reducing peak current demand and extending acceleration times to match conventional motor capabilities, enhancing reliability and cost-effectiveness while minimizing the need for complex ancillary systems.
Implementation Method 1
a hydraulic circuit (10) for controlling the movement of the piston (3), comprising a pump (11) for circulating a hydraulic fluid driven by an electric motor (12)
Implementation Method 2
a pilot line (60) provided with an inlet (60A) connected to said pump (11) and an outlet (60B), and a control element (51) connected to said pilot line (60) and determining a gradual increase of the pressure in said pilot line (60)
Data Source
Figure 1
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AI summary
The invention relates to a press for extruding metal material. The press comprises a hydraulic oil circuit for controlling one or more extrusion pistons movable within corresponding cylinders. Such a circuit comprises a fixed displacement, circulation pump (11) operated by an electric motor (12) with variable rotation speed. The hydraulic circuit comprises a main line (20) and a branch line (30), along which a shutoff element (25) is arranged. The hydraulic circuit (10) comprises a hydraulic control unit (50) comprising a pilot valve (65) arranged along a pilot line (60) provided with a first segment (60C) communicating with the main line (20) and a second discharging segment (60D). Said hydraulic unit (50) is provided to move the shutoff element (25) between an opening position and a closing position of the branch line (30) according to the difference between the oil pressure upstream of the shutoff element (25) and that in the first segment (60C) of said pilot line (60). The hydraulic circuit (10) further comprises a control element (51A, 51B) which, in an activation condition, and as a result of the activation of said pilot valve (65), determines a gradual increase of the pressure in the first segment (60C) of said pilot line (60) and a corresponding gradual closing movement of said shutoff element (25) causing a consequent gradual increase of the thrust on the piston until the reference speed is reached.