Core Drill Bit Holder Geometry for Quick Changes Without Jamming
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Solution Overview
Problem
Existing electric hand-held core drilling devices face challenges with quick core bit changes and high-wear operation due to inadequate torque transmission and jamming issues during high-torque operations.
Innovation Solution
The design enhances torque transmission by using journal surfaces with a spring force of approximately 1600 N, decoupling torque transmission from the spring force along the axis of rotation, and incorporating flat stop surfaces for sliding contact, which allows for rotational freedom and prevents sticking, along with a compression spring arrangement and a sealing ring to reduce preload losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the compression spring arrangement exerts high spring force to secure the insertion end in the tool holder, then the torque transmission is improved, but the insertion end may jam in the tool holder during high-torque operations
Solution Approach 1:
The contact interface is segmented into multiple pin surfaces (at least three) distributed around the circumference, each providing independent torque transmission paths. This segmentation distributes the mechanical stress and prevents concentrated loading that could cause jamming, while maintaining high overall torque transmission capability through the combined effect of multiple contact points.
Solution Approach 2:
The pin surfaces are designed with specific geometric features including inclined surfaces and flat surfaces that allow dynamic adaptation during operation. The inclined pin surfaces enable self-adjustment under load, while the flat surfaces provide sliding contact that accommodates rotational movement, preventing jamming while maintaining secure torque transmission during high-torque operations.
2Strength
If the stop surfaces are designed for secure locking, then the insertion end is firmly held, but rotational freedom is restricted causing sticking and dust buildup
Solution Approach 1:
Instead of designing stop surfaces that completely constrain rotation, the invention inverts the approach by providing flat pin surfaces that allow controlled sliding contact. This inverted design maintains locking security through the compression spring force while permitting minimal rotational movement, preventing dust accumulation and sticking issues that would result from complete rotational constraint.
3Strength
If the pin surfaces extend fully across the stop surfaces, then maximum torque transmission is achieved, but the insertion end jams in the tool holder
Solution Approach 1:
The pin surfaces are designed with non-uniform geometry, featuring inclined surfaces in some regions and flat surfaces in others. This local quality variation optimizes torque transmission in specific contact zones while providing sliding contact in other zones to prevent jamming. The selective application of different surface characteristics resolves the contradiction between maximum torque transmission and ease of operation.
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
This solution enables quick and low-wear core bit changes, reduces jamming, and maintains effective torque transmission, ensuring efficient operation during high-torque conditions while preventing adhesion and construction dust buildup.
Implementation Method 1
a compression spring arrangement which is arranged inside the receiving sleeve and which resiliently supports the receiving sleeve and the tool holder against each other
Implementation Method 2
the stop surfaces are designed as flat surfaces, so that they form a sliding contact with the corresponding contact surfaces at the insertion end
Data Source
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AI summary
An electrical hand-held core drilling device having a tool receiving piece (70) on which precisely three regularly spaced-apart bearing surfaces (71), which each face the stop surfaces (57), are provided, wherein the bearing surfaces (71) for their part form an axial stop, oriented in the opposite direction with respect to the stop surfaces (57), for an insertion end (210), located in a locking rotary position (SL), of a diamond core bit (200) by means of mating bearing surfaces (71') formed on the insertion end (210), wherein precisely three regularly spaced-apart studs (73) project from the bearing surfaces (71), delimiting the bearing surfaces (71) in each case on one side, a respective stud surface (75) being formed on said studs, the respective surface normal of said stud surfaces being oriented perpendicularly to the axis of rotation (R) and tangentially to the circumference (UW) such that transmission of torque takes place in the operating direction of rotation (BR) from the tool receiving piece (70) to the insertion end (210), when the latter is in the locking rotary position (SL) and the compression spring arrangement (60) is comparatively less pressurized, only by way of a form fit between the three stud surfaces (75) and the stud mating surfaces (75'), corresponding thereto, on the insertion end (210), wherein each of the three stud surfaces (75) extends at most half as widely in the radial direction (RR) as a respective bearing surface (71) in the radial direction (RR).