EP4095349A1

EP4095349A1 - Tool for mechanical drilling, in particular for the construction of tunnels, and its creation method

Info

Publication number: EP4095349A1
Application number: EP22161389.6A
Authority: EP
Inventors: Andrea BERTOLI; Stefano Lupi
Original assignee: Tunnelling AB Srl
Current assignee: Tunnelling AB Srl
Priority date: 2021-05-25
Filing date: 2022-03-10
Publication date: 2022-11-30
Anticipated expiration: 2042-03-10
Also published as: EP4095349B1; EP4095349C0

Abstract

Described is a mechanical boring tool, in particular for excavating tunnels, which comprises, on a substantially cylindrical base body (5), extending along a central axis (X) and which is designed to be removably connected to the drive head of a machine for excavating tunnels, a series of cutting elements, wherein at least one (1) of the cutting elements has a connecting portion (3) with the base body (5), a tooth (2) protruding from the base body (5) and extending along a vertical direction (Y) substantially normal relative to the central axis (X) and a cutting edge (6) defined on an end portion of the tooth (2).The tooth (2) has at least one lateral profile (2a) which defines an upper angle (B) with the limiting line (Z) of the cutting edge (6)A particular feature of the invention is due to the fact that the upper angle (B) is substantially between 70° and 85°, inclusive, preferably between 73° and 84°, inclusive, more preferably between 75° and 81°, inclusive, even more preferably between 77° and 79°.

Description

This invention relates to a mechanical boring tool, in particular for excavating tunnels.
The machines used for mechanically boring tunnels are known as "tunnel boring machines" (TBM).
They have a rotary head, on which are mounted the tools for excavating the material which must be removed from the excavation front.
These tools ("cutters") have a wearable part consisting of a steel ring, called a cutter ring, in direct contact with the rock or the ground at the front of the tunnel.
Obviously, with use the cutters wear and they must be periodically replaced.
Replacing a cutter involves maintenance costs and the relative stoppage time for the worn part to be changed.
Cutting rings are currently available on the market with an external diameter variable from 15 to 20 inches and cutting profiles varying from 1/2 to 1 inches, as shown in Figure 1.
According to the prior art, the "heavy duty" cutting rings are made of hot work tool steels, belonging to the family chrome molybdenum-vanadium family of steels (CrMoV).
Such steels have good balancing in terms of temperability, resistance to tempering, hardness, wear resistance, impact and compression.
The manufacturers of cutters have therefore chosen a type of raw material which is suitable for dealing with the majority of conditions at the excavation face, in such a way as not to deal with specific problems, but in a way such as to have a generalised and balanced product.
However, the observation and analysis of cutters reaching the end of their service life suggests that the wear mechanisms are mostly attributable to the effect of wear of the fine particles, of a silicon nature, of the soil, together with shock stresses or sporadic overload.
Consequently, the cutters currently on the market have a low efficiency profile and due to the high degree of wear they must be changed very often, forcing the stoppage of the TBM in order to remove the worn tool to replace it with a new one.
The aim of the invention is to overcome the above-mentioned drawbacks of known types of mechanical boring tools, in particular for excavating tunnels which allow a cutting edge to be made with higher performance levels.
In the context of the above-mentioned purpose, an aim of the invention is to provide a tool for mechanical boring, in particular for excavating tunnels, which is less deteriorated by wear and can therefore minimise the laborious and difficult operations for disassembling and reassembling the tools on the head of the TBM.
Another aim of the invention is to allow operations for excavating tunnels which are faster, more efficient and safer.
Yet another aim of the invention is to provide a mechanical boring tool, in particular for excavating tunnels, with means which guarantee an economic advantage.
This purpose, as well as these and other aims which are described in more detail below, are achieved by a mechanical boring tool, in particular for excavating tunnels, according to the invention, more particularly for excavating tunnels with a mechanised method, comprising the technical features described in one or more of the appended claims. The dependent claims correspond to possible different embodiments of the invention. More specifically, according to a first aspect, the invention relates to a tool for mechanical boring, in particular for excavating tunnels, used for excavating tunnels with a mechanised method with the use of mechanical cutters known as TBMs (Tunnel Boring Machines).
More in detail, the tool is used to excavate the rock face, whether it is hard and/or abrasive and/or fractured, and has been developed to optimise and speed up the forward movement of the mechanical cutter, minimising maintenance operations.
The tool has a substantially cylindrical base body extending along a central axis and is designed to be removably keyed hot on the drive head of a machine for excavating tunnels. The tool comprises a series of cutting elements, wherein at least one of them has a portion for connecting with the base body; a tooth projecting from the base body and extending along a vertical direction substantially normal to the central axis; and a cutting edge defined on an end portion of the tooth.
A fundamental feature of the invention is its geometrical configuration.
Advantageously, the tool consists of a single type of steel, which, following heat treatment, is particularly resistant to compression and wear. The geometrical design of the tool has been specifically designed to improve the strength of the profile and prevent its failure in the case of lateral blows.
In particular, the tooth has at least one lateral profile which defines an upper angle with the limiting line of the cutting edge, substantially between 70° and 85°, inclusive, preferably between 73° and 84°, inclusive, more preferably between 75° and 81°, inclusive, even more preferably between 77° and 79°.
Other geometrical parameters are given by the lower connecting radius between the connecting portion and the lateral profile: the lower connecting radius is substantially between 25 and 35 mm, inclusive, preferably between 27 and 33 mm, inclusive, more preferably between 28 and 32 mm, inclusive, even more preferably equal to approximately 30 mm.
Moreover, the connecting portion defines, with the vertical direction, a lower angle substantially between 40° and 50°, inclusive, preferably between 42° and 48°, inclusive, more preferably between 44° and 46°, inclusive, even more preferably 45°.
In this specification, the terms "upper" and "lower" mean, respectively, that part or component which, relative to the base body is further away (nearer geometrically) or closer.
A fourth geometrical parameter is given by the upper connecting radius between the lateral profile of the tooth and the cutting edge. The upper connecting radius is substantially between 2 and 6 mm, inclusive, preferably between 3 and 5 mm, inclusive, more preferably equal to approximately 4 mm.
Another aspect of the invention is in the method for making the mechanical boring tool, in particular for excavating tunnels, made of chrome molybdenum-vanadium steel and which has a content of chromium of between 7.00 and 8.00 by weight, inclusive, preferably between 7.10 and 7.95, inclusive, more preferably between 7.20 and 7.90, inclusive, even more preferably between 7.30 and 7.80, inclusive, and which comprises a heat treatment which consists a treatment prior to the heat treatment, so as to eliminate all the micro-porosities/micro-fractures inherent in the material and increase the density, a vacuum hardening and then cooling with inert gases.
Further features and advantages of the invention are more apparent in the detailed description below, with reference to a preferred, non-limiting embodiment of the tool for mechanical boring, in particular for excavating tunnels, illustrated by way of example and without limiting the scope of the invention, with the aid of the accompanying drawings, in which:

Figure 1 shows the profiles of the tools for mechanical boring, in particular for excavating tunnels, according to the prior art;
Figure 2 shows the profile of an annular tool for mechanical boring, according to the invention, cross-sectioned with a plane passing through the central axis X.

The above-mentioned drawings show a preferred embodiment of a tool for mechanical boring, in particular for excavating tunnels, according to the invention, which is denoted in its entirety with the numeral 1 and which comprises a series of cutting elements, with an annular shape, on a substantially cylindrical base body 5. The body 5 extends along a central axis X which coincides with its axis of symmetry and is keyed hot, removably, on an element for supporting the drive head of a machine for excavating a tunnel.
Each of the cutting elements has a connecting portion 3 for each side of the tooth, between the base body 5 and a tooth 2 protruding from the body 5 and extending along a vertical direction Y substantially normal relative to the central axis X (Figure 2).
The tooth 2 has a cutting edge 6 formed on its end portion and, moreover, a lateral profile 2a on each side defining an upper angle B with the limiting line Z of the cutting edge 6.
The upper angle B is approximately 78°, substantially between 77° and 79°, inclusive, in such a way as to reinforce the flanks of the tooth and its profile, widening the width.
Advantageously, on each side, the lower connecting radius R between the connecting portion 3 and the lateral profile 2a of the tooth 2 is equal to approximately 30 mm. This makes the tooth 2 even more solid, highlighting the mechanical characteristics of the tool.
On each of the sides of the tooth 2, the connecting portion 3 forms a lower angle A with the vertical direction Y; the lower angle A is approximately 45° (Figure 2). This feature makes the profile of the tooth more robust, thus increasing the resistant section of the tooth and thus improving the performance of the tool.
Advantageously, the upper connecting radius T between each lateral profile 2a of the tooth 2 and the cutting edge 6 is substantially equal to approximately 4 mm, so as to allow a longer life of the tool which in this way attacks the piece to be worked in an optimum manner.
With regard to the material for making the teeth of the tool, a more specialised steel has been advantageously used, with which the entire tooth is solidly made, in such a way that it has the same physical-chemical form also in the layers below the surface one (which is obviously worn firstly), saving maintenance costs and increasing the efficiency of the excavator.
This steel is of the chrome molybdenum-vanadium type with a high content of chromium, in particular, the content of chromium is between 7.30% and 7.80% by weight, inclusive.
Preferably, the steel has a carbon content of between 0.45% and 0.50% by weight, inclusive, a molybdenum content of between 1.30% and 1.50% by weight, inclusive, and a vanadium content of between 0.6% and 1.50% by weight, inclusive.
In effect, increasing the carbon/chromium content gives primary carbides with optimum dimensions for excellent wear resistance and, moreover, a hardness/tempering temperature curve after hardening is reached.
A material of this kind is therefore able to reach the hardness of 60 Hrc over the entire resistant section of the cutting edge which will therefore be able to provide excellent compressive strength.
Moreover, a steel of this type is also suitable for being transformed hot by means of a lamination and/or moulding process for the production of tools with various geometries.
The HIP treatment modifies the micro-structure of the steel and makes it possible to improve and enhance its properties, further increasing its mechanical properties and resistance to wear.
In practice, the hardness of the tool has been enhanced in a chemical manner, selecting a steel with a high content of chromium, as described above, whilst the strength has been improved geometrically, strengthening the profile of the tooth to make it, as mentioned above, more able to absorb impact without breaking.
The method for making a mechanical boring tool as described comprises a thermal treatment which consists in:

carrying out a treatment prior to the heat treatment, so as to eliminate all the micro-porosities/micro-fractures inherent in the material and increase the density,
performing a vacuum hardening,
performing at least one tempering,
cooling with inert gases.

More specifically, according to the embodiment described here, the thermal treatment comprises a double tempering.
In effect, the thermal treatment is an operation which has a fundamental role in establishing the final quality of the cutting edge. "Traditional" thermal treatment cycles often result in a marked variability of the mechanical characteristics of the finished product.
In order to optimise the characteristics of the steel and make the quality of the product as uniform as possible, the treatment prior to the heat treatment which consists of "hipping" (from the acronym HIP, that is, "Hot Isostatic Pressing") is performed, so as to eliminate all the micro-porosities and/or the micro-fractures inherent in the material and thus increase its density.
From the above description it may be seen how the invention achieves the preset purpose and aims and in particular it should be noted that a mechanical boring tool is made, in particular for excavating tunnels, which allows the production of a cutting edge with higher performance levels. More specifically, the combination of a chemical alternative and a different geometrical solution allows a tool to be made which deteriorates less due to wear and is therefore able to minimise the operations for disassembling and reassembling the tools on the head of the TBM.
Another advantage of the invention is that it allows faster, more efficient and safer excavation operations thanks to the improved mechanical properties of the tools.
Lastly, the greater efficiency of the tool, together with an improved service life, makes it possible to obtain an economically competitive tool.
The invention can be modified and adapted in several ways without thereby departing from the scope of the inventive concept.
Moreover, all the details of the invention may be substituted by other technically equivalent elements.
In practice, the materials used, as well as the dimensions, may be of any type, depending on requirements, provided that they are consistent with their production purposes.

Claims

A mechanical boring tool, in particular for excavating tunnels, comprising, on a substantially cylindrical base body (5), extending along a central axis (X) and designed to be removably connected to the drive head of a machine for excavating tunnels, a series of cutting elements, wherein at least one (1) of said cutting elements comprises:
a portion (3) connecting with said base body (5);

a tooth (2) protruding from said base body (5) extending along a vertical direction (Y) substantially normal relative to the central axis (X); and

a cutting edge (6) defined on an end portion of said tooth (2);

at least one lateral profile (2a) of a side of said tooth (2) defining an upper angle (B) with the limiting line (Z) of said cutting edge (6)

characterised in that the upper angle (B) is substantially between 70° and 85°, inclusive, preferably between 73° and 84°, inclusive, more preferably between 75° and 81°, inclusive, even more preferably between 77° and 79°.
The tool according to the preceding claim, wherein the lower connecting radius (R) between said connecting portion (3) and said lateral profile (2a) is substantially between 25 and 35 mm, inclusive, preferably between 27 and 33 mm, inclusive, more preferably between 28 and 32 mm, inclusive, even more preferably equal to approximately 30 mm.
The tool according to claim 1 or 2, wherein said connecting portion (3) defines with said vertical direction (Y) a lower angle (A) substantially between 40° and 50°, inclusive, preferably between 42° and 48°, inclusive, more preferably between 44° and 46°, inclusive, even more preferably 45°.
The tool according to any one of the preceding claims, wherein the upper connecting radius (T) between said lateral profile (2a) of said tooth (2) and said cutting edge (6) is substantially between 2 and 6 mm, inclusive, preferably between 3 and 5 mm, inclusive, more preferably equal to approximately 4 mm.
The tool according to any one of the preceding claims, wherein both sides of said tooth (2) comprise:
both the connecting portions (3) defining with said vertical direction (Y) a pair of angles (A) substantially between 40 and 50°, inclusive, preferably between 42 and 48°, inclusive, more preferably between 44 and 46°, inclusive, even more preferably 45°;

wherein preferably the connecting radiuses (R) between said connecting portions (3) and the lateral profiles (2a) of said tooth (2) are substantially between 25 and 35 mm, inclusive, preferably between 27 and 33 mm, inclusive, more preferably between 28 and 32 mm, inclusive, even more preferably equal to approximately 30 mm;

wherein preferably the connecting radiuses (T) between said lateral profiles (2a) of said tooth (2) and said cutting edge (6) are substantially between 2 and 6 mm, inclusive, preferably between 3 and 5 mm, inclusive, more preferably equal to approximately 4 mm; and

wherein said lateral profiles (2a) of said tooth (2) define with the limiting line (Z) of said cutting edge (6) angles (B) substantially between 70 and 85°, inclusive, preferably between 73 and 84°, inclusive, more preferably between 75 and 81°, inclusive, even more preferably between 77 and 79°.
The tool according to any one of the preceding claims, made of chrome molybdenum-vanadium steel with a content of chromium of between 7.00 and 8.00 by weight, inclusive, preferably between 7.10 and 7.95, inclusive, more preferably between 7.20 and 7.90, inclusive, even more preferably between 7.30 and 7.80, inclusive.
The tool according to the preceding claim, wherein the content, expressed as a percentage weight
of carbon is between 0.40 and 0.60, inclusive, preferably between 0.45 and 0.50, inclusive,

of molybdenum is between 1.10 and 1.70, inclusive, preferably between 1.30 and 1.50, inclusive, and

of vanadium is between 0.6 and 1.50, inclusive, preferably between 1.30 and 1.50, inclusive.
A method for making a mechanical boring tool, in particular for excavating tunnels, comprising a thermal treatment which consists in:
- carrying out a treatment prior to the heat treatment, so as to eliminate all the micro-porosities/micro-fractures inherent in the material and increase the density,

- cooling with inert gases.
The method according to the preceding claim, wherein said tool is made of chrome molybdenum-vanadium steel and has a content of chromium of between 7.00 and 8.00 by weight, inclusive, preferably between 7.10 and 7.95, inclusive, more preferably between 7.20 and 7.90, inclusive, even more preferably between 7.30 and 7.80, inclusive.
The method according to claim 8, wherein said tool has a carbon content of between 0.40 and 0.60 in percentage by weight, inclusive, preferably between 0.45 and 0.50, inclusive; a molybdenum content of between 1.10 and 1.70 in percentage by weight, inclusive, preferably between 1.30 and 1.50, inclusive; and a vanadium content of between 0.6 and 1.50 in percentage by weight, inclusive, preferably between 1.30 and 1.50, inclusive.