Boring Apparatus Feed Control via Planetary Gear Differential
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Solution Overview
Problem
Existing large-scale industrial drilling apparatuses face challenges in achieving continuously variable and consistent feed rates for cutting heads, particularly in hot-tap drilling, requiring precise control of rotational velocities between the cutting head and feed screw, and often necessitate complex electro-hydraulic or computerized systems, which are cumbersome and prone to errors.
Innovation Solution
The implementation of a boring apparatus with a primary and secondary feed motor system utilizing planetary gear assemblies allows for direct gearing of the primary feed motor to one planetary gear assembly and the secondary feed motor to another, enabling continuous variable feed rates without the need for sophisticated control systems, by adjusting the gear ratios to control the relative rotational velocities between the feed screw and boring bar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a feed gearbox with multiple selectable gear ratios is used, then discrete feed rates can be achieved, but the feed rate cannot be continuously variable and the system becomes more complex
Solution Approach 1:
The patent applies dynamics by making the feed rate continuously variable through a differential mechanism that combines rotational movements. Instead of fixed gear ratios, the system dynamically adjusts feed rate by controlling the rotational speed difference between the cutting head and feed screw, enabling continuous adjustment rather than discrete steps.
Solution Approach 2:
The differential mechanism acts as an intermediary between the cutting head rotation and the feed screw rotation. It mediates the relationship between these two movements, allowing the feed rate to be derived from the difference in rotational velocities rather than direct mechanical gearing, thus simplifying the transmission system.
2Adaptability or versatility
If separate drive motors for cutting head and feed screw are used, then continuous variability of feed rate is achieved, but sophisticated electro-hydraulic control systems are required
Solution Approach 1:
The patent replaces complex electro-hydraulic control systems with a purely mechanical differential mechanism. The feed rate control is achieved through mechanical means by controlling the rotational speed difference between the cutting head and feed screw, eliminating the need for sophisticated electronic or hydraulic control systems while maintaining continuous variability.
Solution Approach 2:
The differential mechanism is self-regulating in that the feed rate automatically corresponds to the rotational speed difference between the cutting head and feed screw. The system inherently maintains the relationship between cutting rotation and feed rate without requiring external monitoring or adjustment, making the control system self-sufficient.
3Measurement precision
If hydraulic motors with close speed control are used, then feed rate can be controlled, but constant monitoring and adjustment are required to maintain uniform speed difference
Solution Approach 1:
The differential mechanism automatically maintains the correct relationship between cutting head rotation and feed screw rotation. The feed rate inherently corresponds to the rotational speed difference, eliminating the need for constant monitoring or manual adjustment of speed ratios. The system self-regulates the feed rate based on the mechanical relationship between the rotating components.
4Device complexity
If a single feed rate ratio is used, then the system is simple, but only one feed rate per revolution is available
Solution Approach 1:
The system transitions from static fixed gear ratios to dynamic continuous adjustability. By controlling the rotational speed of the feed screw relative to the cutting head through a differential mechanism, the feed rate can be continuously varied without changing physical gear ratios, providing infinite feed rate options while maintaining mechanical simplicity.
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 provides reliable, accurate, and continuously variable feed rates over a wide range, allowing for both slow and rapid axial movement of the cutting head, enhancing operational efficiency and reducing the complexity of control systems, while maintaining precise control without the need for constant monitoring or electronic adjustments.
Implementation Method 1
A first planetary gear assembly is provided at the proximal end of the feed screw. A tubular drive shaft is coaxially mounted around the boring bar and has a second planetary gear assembly at its proximal end
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A boring apparatus, such as a drilling apparatus for forming holes in pressurised pipes, comprises a cutting head (5) mounted to a distal end of a boring bar (2) which is itself connected to a feed screw (3) by a feed nut so that relative rotation between the boring bar (2) and the feed screw (3) cause the cutting head (5) and boring bar (2) to traverse axially along the feed screw (3) whilst the cutting head (5) is rotated for cutting. The apparatus has a main drive motor arranged to drive the cutting head (5), boring bar (2) and a main drive shaft (4). The main drive shaft (4) and the feed screw (3) are operably connected at the proximal end through a pair of adjacent coaxial planetary gear assemblie (6) whose planetary gear carriers are liked to rotate in unison about the axis. An independent, primary feed drive motor is geared to a planetary gear ring (20) and is operable to provide a difference in rotation velocities between the feed screw (3) and boring bar (2) whereby the movement of the cutting head (5) and boring bar (2) to and from along the axis may be controlled.