Die Cushion Device Complete Locking Mechanism
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Solution Overview
Problem
Conventional die cushion devices may cause scratches or cracks in molded products due to the cushion pad rising slightly when system pressure is released, especially when handling thin plates, as they lack complete locking below the slide's bottom dead center.
Innovation Solution
A die cushion device design that includes a fluid-pressure cylinder and a fluid-pressure closed circuit with accumulators for first and second system pressures, a pilot drive type logic valve, and a pilot relief valve, allowing for complete locking below the slide's bottom dead center without a fluid-pressure pump, using differential pressure to prevent the cushion pad from rising.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the system pressure is released to enable the cushion pad to rise from the bottom dead center, then the cushion pad can be moved upward, but the cushion pad rises by around 2 mm causing scratches and cracks in molded products
Solution Approach 1:
The invention applies preliminary counter-action by introducing a lowering pressure generation line connected to the cushion pad lowering pressure generation chamber. This line applies a downward force on the cushion pad during the locking period at the bottom dead center, counteracting the upward rise that would otherwise occur when system pressure is released. The downward force prevents the cushion pad from rising above the bottom dead center position, thereby preventing scratches and cracks in molded products while still allowing the cushion pad to be moved upward when needed.
2Reliability
If a hydraulic pump is provided to pressurize and supply hydraulic oil continuously, then the die cushion process can be maintained, but the device becomes complex and power cost increases
Solution Approach 1:
The invention implements self-service by using the die cushion force itself to pressurize the hydraulic oil in the closed circuit. During the die cushion process, the hydraulic oil is pressurized only by the die cushion force applied from the cushion pad via the hydraulic cylinder, and is accumulated in an accumulator as low-pressure system pressure capable of the knockout process. This eliminates the need for a separate hydraulic pump and power supply, making the device simpler and reducing power costs while maintaining process reliability.
3Device complexity
If the cushion pad is locked at the bottom dead center without downward pressure, then the device structure remains simple, but the cushion pad cannot be held below the bottom dead center for complete locking
Solution Approach 1:
The invention uses hydraulic pressure differentials to achieve complete locking below the bottom dead center. The lowering pressure generation line introduces hydraulic pressure to the cushion pad lowering pressure generation chamber, creating a downward force that holds the cushion pad below the bottom dead center position. This hydraulic approach maintains relative structural simplicity while achieving high locking position accuracy, as the downward pressure is generated through the existing hydraulic circuit rather than requiring additional mechanical locking components.
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
The solution enables complete locking of the cushion pad below the slide's bottom dead center, preventing scratches and cracks in molded products while eliminating the need for a fluid-pressure pump, thus saving power costs and maintaining device simplicity.
Implementation Method 1
a first system pressure line connected to a first accumulator which is configured to accumulate hydraulic fluid having first system pressure capable of lowering process of the fluid-pressure cylinder
Implementation Method 2
a second system pressure line connected to a second accumulator which is configured to accumulate hydraulic fluid having second system pressure lower than the first system pressure, the second system pressure line capable of knockout process
Implementation Method 3
a pilot relief valve provided between the die cushion pressure generation line and the first system pressure line, and configured to generate pilot pressure for controlling the logic valve
Implementation Method 4
In the first system pressure line and the second system pressure line in the fluid-pressure closed circuit, the hydraulic fluid can be pressurized by using only die cushion force applied from the cushion pad through the fluid-pressure cylinder, in one cycle period of the cushion pad
Data Source
AI summary
To provide a die cushion device which is inexpensive, functional, and capable of locking completely (at or below the slide bottom dead center). The die cushion device includes a cushion pad, a hydraulic cylinder that moves the cushion pad up and down, and a hydraulic closed circuit connected to a die cushion pressure generation chamber of the hydraulic cylinder. The hydraulic closed circuit includes a cushion pad lowering pressure generation line and a second system pressure line in addition to a die cushion pressure generation line and a first system pressure line. When the cushion pad is locked at the bottom dead center, the cushion pad lowering pressure generation chamber is connected to the first system pressure line, and the die cushion pressure generation chamber is connected to the second system pressure line such that the cushion pad is held at or below the slide bottom dead center.