Cam-Based Jack Assembly Resilient Push Block Locking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional jack assemblies in materials testing machines tend to loosen during mechanical testing, causing unwanted specimen movement and artifacts in test results, as they require external forces to be transmitted through the jack assembly and maintained without loosening throughout the test program, which is challenging with cam-based systems that need to be rotated over-center to lock the grip.
Innovation Solution
A cam-based jack assembly that incorporates a resilient push block with a progressive eccentric, which increases frictional force by deflecting and pinching the cam in place, eliminating the need for over-center rotation and maintaining constant force on the specimen grip, utilizing a cam with an upper and lower circular cylinder and a push block with a high modulus of elasticity to securely lock the specimen in position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a cam is rotated over-center to lock the grip in place, then the grip is secured in position, but the mechanical force applied by the cam decreases from its peak value, reducing the lock force and potentially allowing specimen movement
Solution Approach 1:
A resilient push block is introduced as an intermediary component between the cam and the grip. The push block deflects elastically under cam pressure and maintains continuous contact with the grip, ensuring constant force transmission throughout the cam rotation cycle, including the over-center position where the cam alone would provide insufficient lock force.
Solution Approach 2:
The push block's elastic properties are utilized to change the force transmission parameter. By selecting a material with appropriate modulus of elasticity and designing the block's geometry, the system maintains constant force output despite the cam's varying force output during rotation, particularly during the over-center locking phase.
2Force
If a screw-type jack assembly is used to generate high mechanical force, then the force can be transmitted through the jack assembly, but the assembly becomes too large to comfortably fit within the jack assembly space
Solution Approach 1:
The screw-type mechanical advantage system is replaced with a cam-based mechanical system. The cam's rotational motion directly converts to linear force application through the resilient push block, achieving high force transmission without the bulky threaded components and nut assemblies required by screw-type jacks of comparable force capacity.
3Reliability
If conventional jack assemblies are used throughout the test program, then the grip can be initially secured, but the assemblies tend to loosen during testing, causing unwanted specimen movement and artifacts
Solution Approach 1:
The system transitions from a static screw-lock configuration to a dynamic cam-based system with continuous force application. The resilient push block continuously adapts to force variations during the test program, maintaining grip security through elastic deformation rather than relying on friction that degrades over time.
Solution Approach 2:
The cam-based system provides continuous force application throughout the entire test program, whereas screw-type assemblies rely on initial tightening and friction that may loosen. The resilient push block maintains constant contact and force transmission from the cam's continuous rotation, ensuring uninterrupted grip security.
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 cam-based jack assembly securely holds the specimen in place throughout the test program, eliminating artifacts from unwanted specimen movement and providing higher mechanical forces than comparable screw-type assemblies, ensuring accurate and reliable mechanical test results.
Implementation Method 1
a resilient push block with a progressive eccentric, which increases frictional force by deflecting and pinching the cam in place
Implementation Method 2
increases frictional force by deflecting and pinching the cam in place
Implementation Method 3
a cam-based jack assembly that incorporates a resilient push block with a progressive eccentric
Implementation Method 4
a cam-based jack assembly that incorporates a resilient push block with a progressive eccentric
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 4A~4B
AI summary
A jack assembly (30), for use in a materials testing system, utilizes both a cam (50) and a resilient push block (60). The cam, having an progressive eccentric (56), is situated between the push block and a jaw housing and located partially within a corresponding shallow channel in each such that both channels effectively straddle the cam. The channels accommodate axial rotation of the cam. The push block is formed of a material with an appropriate modulus of elasticity such that bending moments, particularly at ends of the push block and resulting from axial rotation of the eccentric to its top dead-center position, cause the channel in the push block to elastically deform and increasingly and sufficiently deflect against and around the eccentric, thus increasingly pinching the eccentric and securely locking the cam, push block and specimen grip in their proper positions.