Replaceable Valve Pin Bushing for Hot Runner Maintenance
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Solution Overview
Problem
Valve gated injection molding systems using a valve pin bushing suffer from leakage due to wear and require complex disassembly for maintenance, making replacement of worn components difficult without disassembling the mold.
Innovation Solution
A replaceable bushing design in the nozzle base with access ports on the second plate allows for removal and replacement of the valve pin actuator and bushing without disassembling the hot runner assembly, including a bushing access port and actuator access port, enabling maintenance without disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the valve pin bushing is secured in the nozzle base with a tight fit to guide the valve pin and prevent melt leakage, then sealing reliability is improved, but maintenance complexity increases and bushing replacement requires complete mold disassembly
Solution Approach 1:
The nozzle base is segmented into removable components: the nozzle body, nozzle tip, and nozzle base plate. The bushing is accessible by removing only the nozzle base plate through a access port, rather than requiring complete mold disassembly. This segmentation allows maintenance of the bushing while keeping the rest of the mold assembled.
Solution Approach 2:
A access port is introduced as an intermediary feature in the nozzle base plate, allowing tools and hands to reach the bushing for removal and installation. This access port enables maintenance operations without requiring complete disassembly of the mold assembly.
2Reliability
If the valve pin bushing is made tightly fitted to prevent melt leakage upstream of the gate, then sealing performance is improved, but wear creates gaps that enable leakage and affect valve pin movement
Solution Approach 1:
The bushing is designed as a replaceable wear component with a relatively short service life. When wear creates gaps that compromise sealing, the bushing is removed and replaced rather than attempting to repair or restore it. This approach maintains reliable sealing performance throughout the bushing's service life and simplifies maintenance by making the bushing a disposable component.
Solution Approach 2:
The worn bushing is discarded and replaced with a new one to restore proper sealing. The old bushing is removed through the access port and discarded, while the new bushing is installed in its place, recovering the sealing function without requiring complex repair procedures.
3Ease of repair
If the nozzle housing is completely disassembled to access and replace the bushing, then bushing replacement is possible, but maintenance time and operational downtime increase
Solution Approach 1:
The nozzle assembly is segmented into removable components, with the nozzle base plate being separable from the nozzle body. This segmentation creates a maintenance access path that requires removing only the nozzle base plate rather than the entire nozzle housing, significantly reducing maintenance time and operational downtime.
Solution Approach 2:
The access port is pre-designed and pre-positioned in the nozzle base plate to facilitate quick bushing removal. This preliminary design feature eliminates the need for complex disassembly procedures during maintenance, allowing operators to quickly access and replace the bushing with minimal downtime.
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
Facilitates easy maintenance and replacement of the valve pin bushing without disassembling the mold, reducing downtime and improving operational efficiency by allowing access to the bushing through the rear plate, thus preventing melt leakage and extending the system's lifespan.
Implementation Method 1
as the valve pin rubs against the bushing, wear will occur
Implementation Method 2
The bushing supports the valve pin for its slidable movement and furthermore provides a seal to prevent melt from flowing out of the nozzle housing along the valve pin
Implementation Method 3
The valve stem moves slidably within a tight fitting bushing secured to a rear face of a nozzle housing
Implementation Method 4
A valve pin actuator is mounted to the second plate and connected to the valve pin activator end for moving the valve pin along the passage for the opening and closing of the melt outlet
Data Source
AI summary
The invention provides a replaceable bushing in the base of a nozzle of a hot runner assembly and provides access through a manifold and a rear plate for removal and replacement of the bushing without having to disassemble the hot runner assembly. According to one embodiment of the invention, an actuator access port is provided for removing the valve pin actuator and a bushing access port is provided for accessing the bushing upon removal of the valve pin actuator, both of which may be removed from a second or rear plate of the injection molding assembly.