Adjustable Stop Cam Pivot Hinge for Refrigerator Door Dwell Positioning
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Solution Overview
Problem
Pivot hinges for commercial reach-in refrigerator doors face issues such as wear due to metal-to-metal contact, misalignment, and inability to adjust door open positions, as well as problems with spring mounting and dirt intrusion.
Innovation Solution
A pivot hinge design featuring a tubular housing with a stop cam and cam follower assembly, allowing multiple fixed rotational positions and adjustable dwell points, eliminating metal-to-metal contact through a plastic bearing surface and enabling easy repositioning of the stop cam for varying door open positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a metal pivot pin is mounted within a central tube with metal-to-metal contact, then the hinge provides structural support and rotation, but wear occurs over time causing misalignment
Solution Approach 1:
A plastic bearing surface is introduced as an intermediary material between the metal pivot pin and the central tube. This plastic layer prevents direct metal-to-metal contact, reducing wear and maintaining alignment over time while still providing the necessary structural support for rotation.
2Reliability
If a flange is added to provide more bearing surface, then wear resistance improves, but the flange wears or breaks causing misalignment
Solution Approach 1:
The bearing surface is created using a composite structure where a plastic material is applied to the central tube. This plastic bearing surface combines the wear resistance needed for durability with the flexibility to prevent catastrophic failure, eliminating the need for a separate metal flange that could wear or break.
3Ease of manufacture
If a small hole is drilled in the central tube for spring mounting, then the spring can be installed, but the hole is difficult to manufacture and cannot be created during molding
Solution Approach 1:
The spring mounting feature is integrated into the central tube design before the final assembly. The plastic bearing surface incorporation creates a pre-formed mounting structure that allows spring installation without requiring post-molding hole drilling, simplifying the manufacturing process.
4Ease of manufacture
If the spring end extends through a small hole in the central tube, then the spring can be mounted, but the spring may move downward out of the hole causing release
Solution Approach 1:
The plastic bearing surface acts as an intermediary structure that provides a retained mounting feature for the spring. This plastic structure can be designed with integrated retention features such as ribs or grooves that prevent the spring from moving downward out of the mounting hole, ensuring reliable spring retention.
5Ease of manufacture
If a gap is created between the pivot pin and central tube, then the spring can be installed, but dirt or insulating foam can intrude into the central tube
Solution Approach 1:
The plastic bearing surface serves as an intermediary seal between the pivot pin and central tube. It fills and seals the gap that would otherwise allow dirt or insulating foam to intrude, while still permitting the necessary spring installation and pivot movement.
6Reliability
If the stop cam is fixed to the tubular housing, then the door can be held at a fixed position, but the door open position cannot be adjusted
Solution Approach 1:
The stop cam is designed with a selective configuration that allows it to be positioned at different fixed rotational positions relative to the tubular housing. This dynamic positioning capability enables the door to be held at various fixed positions (such as 90 degrees or 120 degrees open) while maintaining stability at each selected position.
7Reliability
If the stop cam has a detent for dwelling, then the door can be held open temporarily, but the door must rise slightly causing wear on door components
Solution Approach 1:
The cam follower assembly with its bearing surface acts as an intermediary mechanism between the stop cam detent and the door. It provides a smooth transition for engaging and disengaging the detent, eliminating the need for the door to rise slightly and thereby preventing wear on door components while maintaining the door holding capability.
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 design reduces wear, prevents door misalignment, and allows for customizable door positions without the need for a flange, enhancing durability and functionality.
Implementation Method 1
a spring assembly rotatably mounted to the tubular housing and coupled to the second mount. The spring assembly includes a pivot pin and a torsion spring coupled to the pivot pin
Implementation Method 2
The stop cam also has an exterior surface including a round portion and a detent portion. A cam follower assembly is mounted to the second mount. The cam follower assembly has a cam follower riding upon the stop cam exterior surface and set to mate with the detent portion to resist rotary movement
Data Source
AI summary
A pivot hinge includes a spring housing with a central tube, a spring assembly, an upper mounting plate, and a lower mounting plate. The bottom end includes a knurled outer surface. A stop cam is positioned about the knurled outer surface and has an inner surface that conform to the knurled outer surface so that it may be positioned in a plurality of rotatable positions relative to the central tube. The stop cam also has an exterior surface which includes a detent. The different rotational positions of the stop cam upon the knurled outer surface changes the relative position of the detent in relationship to the central tube. A cam follower assembly is coupled to the lower mounting plate and has a cam follower plate with a cam follower that rides upon the stop cam and engages the detent recess to hold the door in an open position.