Reciprocating Mowing Sickle with Frequency-Tuned Spring Stiffness
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Solution Overview
Problem
Conventional mowing sickle drive systems are inefficient due to large space requirements and non-optimum speed adjustments, leading to increased wear and energy consumption, especially at low speeds, and they struggle with compensating for rapid changes in inertia.
Innovation Solution
A mowing sickle drive system with a knife bar driven by a linear motor and equipped with a spring having a variable modulus of elasticity, controlled by a flow control valve, to adjust restoring forces based on drive frequency, reducing wear and energy consumption by minimizing restoring force at low speeds and maximizing stiffness at high speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mechanical sickle drive systems with flywheels are used to compensate for rapid changes in inertia, then inertia compensation is achieved, but the device occupies large space and extends laterally outside the cutterbar width
Solution Approach 1:
The patent extracts the inertia compensation function from the mechanical drive system and relocates it to a separate spring mechanism. The spring is connected to the knife bar to provide restoring force, while the drive system itself is simplified to only perform driving function, thereby reducing the space occupied by the drive system while maintaining inertia compensation capability
Solution Approach 2:
The spring acts as an intermediary element between the knife bar and the frame, providing inertia compensation through its elastic restoring force. This intermediary mechanism compensates for rapid inertia changes without requiring the knife bar or drive system to occupy additional space
2Productivity
If the cutterbar is driven at constant speed proportional to other crop processing systems, then synchronization with threshing and separating systems is maintained, but the cutterbar operates at non-optimum speed for encountered crop conditions and ground speed
Solution Approach 1:
The patent applies dynamics by making the drive frequency variable rather than fixed. The linear motor can operate at different frequencies to adjust the cutterbar speed dynamically, allowing optimization for different crop conditions and ground speeds while maintaining synchronization capability through controlled frequency adjustment
3Reliability
If coil springs are used to compensate for rapid changes in inertia in linear electric motor systems, then inertia compensation is achieved, but unnecessary opposing forces are encountered by the motor at low speeds where inertia is low
Solution Approach 1:
The spring constant is made variable rather than fixed, allowing the spring to provide appropriate restoring force at different operating speeds. At low speeds where inertia is low, the spring constant is reduced to minimize opposing forces and energy consumption, while at high speeds the spring constant increases to provide adequate inertia compensation
Solution Approach 2:
The patent changes the parameter of spring constant from a fixed value to a variable value that can be adjusted based on operating conditions. This parameter change allows the spring to adapt its stiffness to match the inertia requirements at different speeds, reducing unnecessary energy consumption at low speeds while maintaining effective inertia compensation at high speeds
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 system allows for a compact and efficient operation of the mowing sickle, reducing wear and energy consumption by dynamically adjusting the spring's stiffness in response to changing inertia, enabling optimal speed adjustments and minimizing damage to crops.
Implementation Method 1
a spring connected to the knife bar for applying a restoring force to the knife bar toward a neutral position when in motion
Implementation Method 2
the knife bar carries inertia when driven in a reciprocating motion
Implementation Method 3
a linear electric motor configured for driving the knife bar in a reciprocating linear motion
Data Source
Figure 1
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Figure 4
AI summary
A mowing sickle drive system comprises a knife bar (56) supported by a frame (66) and drive apparatus (64) operable to drive the knife bar (56) in a reciprocating linear motion at a variable drive frequency. A spring (72) is coupled to the knife bar (56) for applying a restoring force to the knife bar (56) toward a neutral position when in motion. The spring (72) has a variable modulus of elasticity that is controlled in dependence upon the drive frequency.