Down-the-hole Drilling Device with Radially Movable Bits
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Solution Overview
Problem
Existing down-the-hole drilling devices face issues such as high torsion stress leading to breakage risks, unreliable guiding pins under demanding conditions, uneven wear of drill bits, and difficulty in removing the drilling head from drilled holes due to eccentric reaming drills and asymmetrical bit arrangements.
Innovation Solution
A drilling device with a second drill bit arrangement featuring radially movable bit pieces in symmetrical slide grooves, controlled by a rotation mechanism and a movement mechanism, allowing for efficient expansion and reduction to optimize drilling efficiency and facilitate complete removal from the hole without leaving extra parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an eccentric reaming drill is used to ream the drilled hole, then the drilling device can effectively enlarge the hole, but high torsion stress is generated causing breakage risk of the drill rod unit
Solution Approach 1:
The drilling device is divided into separate functional components: a center drill for initial hole creation and an eccentric reaming drill for hole enlargement. This segmentation allows each component to be optimized for its specific function while reducing overall stress on the drill rod unit, as the center drill prepares the path and the reaming drill operates on a pre-formed hole.
Solution Approach 2:
The eccentric reaming drill is designed to move dynamically between a drilling position (where it enlarges the hole) and a return position (where it retracts inside the core pipe). This dynamic positioning allows the device to adapt its configuration during operation, reducing stress by retracting when not actively drilling and positioning optimally when hole enlargement is needed.
2Productivity
If the eccentric reaming drill is used for reaming, then hole enlargement is achieved, but the return of the reaming drill to its return position becomes unreliable due to ground substance collection
Solution Approach 1:
The harmful factor (ground substance accumulation) is addressed by designing the return mechanism to actively overcome resistance rather than relying on passive retraction. The movement mechanism extracts the reaming drill from the problematic zone by providing controlled force to overcome ground substance interference, ensuring reliable return to the start position.
Solution Approach 2:
A movement mechanism acts as an intermediary between the control system and the eccentric reaming drill. This intermediary component provides controlled movement and positioning, mediating the interaction between the drill and ground substances, and ensuring reliable return motion even when ground substances are present.
3Reliability
If high operating power is used to ensure the reaming drill returns to position, then return reliability improves, but breakage risk of the drill rod unit increases
Solution Approach 1:
The drilling operation uses periodic reciprocating motion where the eccentric reaming drill alternates between drilling/enlarging position and return position. This periodic action allows the system to build up controlled forces over multiple cycles, ensuring reliable return motion without requiring excessive instantaneous power that would risk drill rod breakage.
Solution Approach 2:
The movement mechanism changes operational parameters (speed, force, position) to optimize the return process. By adjusting these parameters dynamically, the system achieves reliable return motion at lower power levels, avoiding the need for high operating power that would increase breakage risk.
4Productivity
If bit pieces are arranged in asymmetrical configuration, then drilling efficiency is improved, but removal of the drilling head from drilled holes becomes difficult
Solution Approach 1:
The bit pieces are arranged in a symmetrical configuration that allows dynamic movement between drilling and removal positions. This symmetrical arrangement ensures that during removal, all bit pieces can be retracted equally and simultaneously, preventing binding or interference that would occur with asymmetrical arrangements, thus enabling easy extraction of the drilling head.
Solution Approach 2:
While the overall bit piece arrangement is symmetrical for removal purposes, the drilling operation itself creates asymmetric cutting action through the eccentric motion of the reaming drill. This allows asymmetric drilling efficiency (through eccentric reaming) while maintaining symmetric geometry for easy removal, resolving the contradiction between drilling performance and extraction ease.
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to a drilling device that is meant to be used in a down-the-hole drilling apparatus for drilling a hole by using the drilling device (1) and a casing part (2) as well as a hammering device when needed. The drilling device (1) comprises in a drilling head (I) thereof a guide (4), drilling means (5) and as well as advantageosly flushing means for flushing of drilling waste being generated. The drilling means (4) comprise a first drill bit arrangement (5a) and a second drilling bit arrangement (5b) that is movable with respect to the above and that is arranged on the one hand to be expanded for drilling a greater (t) hole than the free cross-sectional surface area of an end (Ι') of the casing part (2) and on the other hand to be reduced to a smaller size than the free end (Ι') of the casing part. The bit pieces (5bl) of the second drill bit arrangement (5b) are arranged, for expanding/reducing of the second drill bit arrangement (5b) by means of the guide (4), movable in slide grooves (U) that pass wide open in the radial direction (r) on a drilling surface (P) of the drilling means (5) for expanding the second drill bit arrangement (5b) by moving its bit pieces (5bl) in the radial direction (r) outwards in the slide grooves (U), by rotating (w) the guide (4) in a drilling direction, and for reducing the second drill bit arrangement (5b) by moving its bit pieces (5bl) in the radial direction inwards in the slide grooves (U), by rotating the guide (4) in an opposite direction.