Hydraulic Clamp Force Equalization for Free Lift Masts
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Solution Overview
Problem
Existing hydraulic control systems for free lift masts in material handling equipment fail to achieve automatic weight-responsive force control for load-clamping members, leading to undesirable telescoping in overhead constrained environments and requiring complex electronic solutions or higher unit costs.
Innovation Solution
A hydraulic valve circuitry system that equalizes load weight sensing independently of the lifting device's position, using pressure-differential regulating valves and accumulators to provide full-time automatic weight-responsive force control for load-clamping members, avoiding telescoping and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If free lift masts are used to lift loads without telescoping, then the mast assembly height remains constant and overhead constraints are satisfied, but automatic weight-responsive force control for load-clamping members cannot be achieved using hoist line pressures
Solution Approach 1:
A T-valve is introduced as an intermediary component to redirect hoist line pressure to a sensing line that connects to the load-clamping member control system. This allows weight information to be transmitted from the hoist mechanism to the clamping system without requiring direct pressure connection, enabling automatic force control while maintaining free lift mast operation
Solution Approach 2:
The patent replaces complex electronic weight sensing and control systems with a purely hydraulic solution. By using the T-valve to tap hoist line pressure and transmit it through hydraulic lines to control the load-clamping members, the system achieves automatic weight-responsive force control using only hydraulic components, avoiding electronics and sensors
2Extent of automation
If electronic controllers are used for gripping force regulation, then automatic weight-responsive force control can be achieved, but system complexity increases and unit cost increases
Solution Approach 1:
The patent substitutes electronic controllers, sensors, and conductors with a purely hydraulic control system. The T-valve redirects hydraulic pressure to a sensing line that automatically regulates load-clamping member force based on hoist line pressure, eliminating the need for electronics while maintaining automatic control functionality
Solution Approach 2:
The system uses hydraulic pressure from the hoist line as the sensing mechanism. The T-valve directs this pressure to control the load-clamping members, using fluid power principles to achieve automatic force regulation without electronic components, thereby reducing system complexity and cost
3Extent of automation
If electronic controllers with movable conductors are used, then gripping force control is achieved, but electrical conductors must be movable in response to mast extension
Solution Approach 1:
The patent replaces the entire electronic control system including movable conductors with a hydraulic system. The T-valve and hydraulic lines provide a fixed, non-movable connection that transmits pressure signals from the hoist mechanism to the load-clamping members, eliminating the need for flexible electrical conductors during mast extension
Solution Approach 2:
The invention extracts and removes the electronic control components and their associated movable conductors from the system. By using only hydraulic components with fixed connections, the patent eliminates the problematic requirement for movable electrical conductors while maintaining automatic gripping force control
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
Enables efficient, automatic weight-responsive force control for load-clamping members, preventing telescoping and reducing system complexity while maintaining consistent gripping forces across varying lift stages.
Implementation Method 1
A hydraulic valve circuitry system that equalizes load weight sensing independently of the lifting device's position, using pressure-differential regulating valves
Implementation Method 2
using pressure-differential regulating valves and accumulators to provide full-time automatic weight-responsive force control
Implementation Method 3
Equalized hydraulic clamp force control
Data Source
AI summary
Hydraulic valve circuitry adapted for hydraulic connection to a lift truck having a mast and at least one lift cylinder for alternately raising and lowering the mast. The hydraulic assembly is also adapted for hydraulic connection to an attachment to the lift truck, the attachment having opposed clamps actuated by respective clamp cylinders. The hydraulic assembly preferably comprises a valve circuit capable of causing the at least one lift cylinder to be an accumulator.