US20060006002A1

US20060006002A1 - Working tool for machining mineral constructional components

Info

Publication number: US20060006002A1
Application number: US11/170,672
Authority: US
Inventors: Peter Mugg; Till Cramer; Stefanie Tschegg; Herwig Mayer; Bernd Zettl
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2004-06-30
Filing date: 2005-06-29
Publication date: 2006-01-12
Also published as: JP2006015481A; DE102004031600B4; EP1612018B1; EP1612018A1; DE102004031600A1

Abstract

A working tool for machining mineral constructional components, in particular, for machining mineral constructional components, mineral foundations, and the like with an ultrasonic tool, has a carrier body which is formed of an unalloyed hardened steel having a carbon content from 0.2% to 0.8% and which is provided with at least one cutting element.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a working tool for machining mineral constructional components, mineral foundations, and the like, in particular, for machining with an ultrasonic tool, and having a carrier body provided with at least one cutting element.
2. Description of the Prior Art
Mineral constructional components, mineral foundations, and the like and foundations, and the like are subjected to drilling, cutting, grinding with suitable power tools such as, e.g., drilling tools, cutting or grinding tools, etc. Both hand-held tools and column-guided tools are used.
In particular, with hand-held systems, the pressure forces, which are applied by a user during the operational process, are limited and rarely exceed 200 N. In order to increase an operational efficiency of hand-held systems, it is known to superimpose a rotational movement of a working tool with an auxiliary or additional kinematics. E.g., German application DE4444853A1 of the assignee herein discloses superimposition of a rotational movement of a core drilling bit with ultrasonic oscillations in the direction of a bore longitudinal axis. The proposed system achieves good results. However, the improvement of the machining efficiency is diminished because of economical considerations, e.g., the performance capability of the core drilling bit is reduced in comparison with systems without additional kinematics.
German Publication DE 44 26 238 A1 discloses forming a carrier body for a working tool, e.g., a bit body for a core drilling bit of an unalloyed constructional steel with a carbon content less than 0.2% (e.g., of S235JR, material No. 1.0037 (European standard EN 10025, corresponds to steel A252-02 (ASTM)). This material provides for an economical manufacturing of core drilling bit and has good welding characteristics. However, these core drilling bits are not suitable for an ultrasonic drilling because the produced ultrasonic oscillations are strongly attenuated by an unalloyed constructional steel, which leads to an inefficient machining process and excessive heating of the core drilling bit, resulting in a reduced fatigue strength of the core drilling bit.
In order to eliminate the foregoing drawbacks upon the use of an ultrasonic machining, German Patent DE 42 07031 C2 suggests to use a chromium-nickel steel. This material has very good characteristics, which makes it suitable for ultrasonic machining. However, this material is in 3-5 times more expensive than an unalloyed constructional steel. Another material that has very good characteristics for an ultrasonic machining is a titanium alloy which, however, is also much more expensive than an unalloyed constructional steel. Therefore, from an economical point of view, neither chromium-nickel steel nor titanium alloy is suitable for manufacturing of single-use working tools.
Accordingly, an object of the present invention is to provide a tool for machining mineral constructional components, mineral foundations, and the like that can be used with conventional power tools and, at the same time, has good characteristics for use with an ultrasonic tool, and that can be economically produced.

SUMMARY OF THE INVENTION

This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a working tool the carrier body of which is formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%.
The costs of an unalloyed hardened steel with a carbon content from 0.2% to 0.8% are only slightly higher than the costs of a conventional unalloyed constructional steel. However, a working tool the carrier body of which is formed of an alloyed hardened steel with a carbon content from 0.2% to 0.8%, has a small material-dependent attenuation of the ultrasonic oscillations and, as a result, an increased fatigue strength. In addition, the unalloyed hardened steel with a carbon content from 0.2% to 0.8% has good welding properties and machinability. Working tools, which have a carrier body formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%, can be used with both conventional power tools and ultrasonic tools.
Surprisingly, it was found out that the working tools, the carrier body of which is formed of an un alloyed hardened steel with a carbon content from 0.2% to 0.8%, not only have a smaller attenuation of ultrasonic oscillations and an increased fatigue strength in comparison with tools from un alloyed constructional steel, but also require less power for generation of the ultrasonic oscillations. Furthermore, the working tools, which have a carrier body formed of an un alloyed hardened steel with a carbon content from 0.2% to 0.8%, have, because of a reduced material fatigue, a reduced probability of failure, so that with a probability of fracture the same as with the tools the carrier body of which is formed of an alloyed constructional steel, the inventive working tools can operate with an elongation (expansion) amplitude greater by up to 80% than the tool the carrier body of which is formed of an unalloyed constructional steel. It has also been found that by using an unalloyed hardened steel with a carbon content from 0.2% to 0.8% instead of an unalloyed constructional steel for forming carrier bodies of working tools for use with ultrasonic tools, it became possible to obtain greater ultrasonic amplitude at the same ultrasonic power. As a result, due to an increased fatigue strength of the unalloyed hardened steel with a carbon content from 0.2% to 0.8%, the material-dependent probability of failure of the incentive working tools remained the same as of the tools formed of an unalloyed constructional steel even at a greater ultrasonic amplitude.
Preferably, the carrier body is formed of an unalloyed hardened steel with a carbon content in a range from 0.5% to 0.7%, advantageously 0.6%. A suitable unalloyed hardened steel can be, e.g., steel “C60E” (material No. 1.1221, European standard EN 10297-1 corresponding to AISI 1060), which has a carbon content from 0.57% to 0.65%.
According to one embodiment of the present invention, the working tool is formed as a core drilling bit having a hollow cylindrical bit body that forms the carrier member. Such core drilling bits are used, in particular, for drilling holes in a reinforced concrete. At the first end of the bit body, there is provided a shank for connecting the core drilling bit with a power drilling tool. At the second, opposite end of the bit body, there are provided cutting elements such as, e.g., sintered diamond segments or cutters of hard metal, and which serve as machining elements. The machining process is effected by rotation of the core drilling bit with a power drilling tool. These core drilling bits form so-called single-use consumer goods, when the bit body is provided with new cutting elements for a new application of the core cutting bit.
Instead of an entire hollow cylindrical bit body, often, section of the hollow cylindrical bit body, so-called exchange modules are used, which are provided with cutting elements. An exchange module has a hollow cylindrical bit body section that forms the carrier body and is provided at its first end with a connection surface for connection the bit body section with the hollow cylindrical bit body, and at its second, opposite end is equipped with cutting elements. In order to insure that the core drilling bit retains the advantageous characteristics of the inventive core drilling bit also when the bit is used with an ultrasonic tool, the hollow cylindrical bit body section is also formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%.
According to a further embodiment of the present invention, the inventive working tool is formed as a drill the stem of which forms the carrier body. Such drills are used for drilling bores, with the stem being provided with a shank at its first end for connecting the drill with a power drilling tool, and having, at its other opposite end, at least one cutting element that forms the machining element. The at least one cutting element can be formed of a hard metal plate or as a drilling head, with the hard metal plate or drilling head being fixedly secured at the second end. The stem is provided on its outer circumference with at least one helical groove for removing the drilling cuttings, so that the drillings or drilling dust, which are produced during a drilling process, are removed. According to an alternative embodiment of the drill, the stem is provided with a longitudinal bore through which a rinsing fluid is fed to the at least one cutting element during the drilling process, or through which drillings or drilling dust, which are produced during a drilling process, can be aspirated from the drilling bore.
According to a still further embodiment of the present invention, the inventive working tool is formed as a cutting disc with a disc-shaped carrier body. Such cutting discs are used for cutting the constructional components, mineral foundations, and the likeand foundations, and the likeor for forming slots therein. The cutting disc has a through-opening for mounting the cutting disc on a drive shaft of a power tool. On the outer circumference of the cutting disc, there are provided cutting elements such as, e.g., as sintered diamond segments or cutters having a predetermined shape and formed of a hard metal. The diamond segments or cutters form machining elements.
According to another embodiment of the present invention, the inventive working tool is formed as a grinding disc having a substantially disc-shaped carrier body. Such grinding discs are used for machining, grinding, flat surfaces of constructional components. The substantially disc-shaped carrier body has a through-opening for mounting of the grinding disc on a drive shaft of a power tool, and is provided on its bottom with grinding elements, e.g., sintered diamond segments which form the grinding elements.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:
FIG. 1 a longitudinal cross-sectional view of a working tool according to the present invention formed as a core drilling bit;
FIG. 2 a longitudinal cross-sectional view of another embodiment of a working tool according to the present invention also formed as a core drilling bit;
FIG. 3 a longitudinal cross-sectional view of a working tool according to the present invention formed as a drill;
FIG. 4 a plan view of a working tool according to the present invention formed as a cutting disc;
FIG. 5 a plan view of a working tool according to the present invention formed as a grinding disc; and
FIG. 6 a diagram illustrating attenuation behavior of different materials at two different characteristics of ultra-sound.
In the drawings, the same elements are basically shown with the same reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A working tool according to the present invention, which is formed as a core drilling bit 11 and is shown in FIG. 1, has a hollow cylindrical bit body 12 that serves as a carrier body and is formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%, e.g., of C60 E. The core drilling bit 11 has a first end 13 with a shank 15 for connecting the core drilling bit 11 with a drilling tool (not shown), and a second opposite end 14 provided with cutting elements 16 which serve as machining elements.
In a core drilling bit 21, which is shown in FIG. 2, at the second end 24 of the hollow cylindrical bit body 22, there is provided a replaceable exchange module 30 having a hollow cylindrical bit body section 27 that serves as a carrier body and is formed of an alloyed hardened steel with a carbon content from 0.2% to 0.8%. The bit body section 27 has a first end 28 that is formed as a connection surface for connecting the bit body section 27 to the bit body 22 of the core drilling bit 21, and a second, opposite end 29 provided with cutting elements 26 which serve as machining elements. The exchange module 30 is connected with the hollow cylindrical bit body 22 by a weld seam 31 or, alternatively, can be connected by a solder seam. The exchange module 30 can be separated from the bit body 20 upon wear of the cutting elements 26 and be replaced with a new exchange module with new cutting elements 26.
A working tool according to the present invention, which is shown in FIG. 3, is formed as a drill 36 having a stem 37 which serves as a carrier body and is formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%, e.g., of C60E steel. The stem 37 is provided at its first end 38 with a shank 40 for connecting the drill 36 with a drilling tool (not shown). At its second, opposite end, the stem 37 is provided with a cutting element 41 that is formed a hard metal plate and serves as a machining element. The stem 37 is provided with helical grooves 42 on its circumference.
A working tool according to the present invention, which is shown in FIG. 4, is formed as a cutting disc 46 having a disc-shaped carrier body 47 formed of unalloyed hardened steel with a carbon content from 0.2% to 0.8%. The disc-shaped carrier body 47 has a through-opening 48 for mounting the cutting disc 46 on a drive shaft of a power tool (not shown). A plurality of cutting elements 49, which serve as machining elements, is provided on the outer circumference of the disc-shaped carrier body 47.
A working tool according to the present invention, which is shown in FIG. 5, is formed as a grinding disc 56 having a substantially disc-shaped carrier body 57 formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%. The disc-shaped carrier body 57 has a through-opening 58 for mounting the grinding disc 56 on a drive shaft of a power tool (not shown). On the bottom 60 of the disc-shaped carrier body 57, there are provided a plurality of grinding elements 59.
Advantageous characteristics of working tools having a carrier body formed of an alloyed hardened steel with a carbon content from 0.2% to 0.8%, in particular, of C60E and unexpected properties obtained by their use with ultrasonic tools were confirmed by numerous tests. Thus, diagram of FIG. 6 shows temperature rise of different materials at two different amplitudes. The left column of each column pair shows the temperature rise when the material sample is loaded for 2 min at elongation (ε) of 0.3×10⁻³at an amplitude of 12 μm. The right column of each column pair shows the temperature rise when the material sample is loaded during 1 min at elongation (E) of 0.5×10⁻³at an amplitude of 20 μm. The first column pair show results for a material sample of a titanium alloy (Ti₆Al₄V) which is used as a reference material and has a very small temperature under a respective ultrasonic load. The small temperature rise of the titanium alloy corresponds to a small material-dependent attenuation of ultrasonic waves. The second column pair shows, in comparison, the results for a material sample form an unalloyed constructional steel (S235JR) which is conventionally used for manufacturing of carrier bodies of the working tools and which has a high temperature rise at a respective ultrasonic load. The very high temperature rise corresponds to a large material-dependent attenuation of the ultrasonic waves. The third column pair shows results for a material sample of an unalloyed hardened steel (C60E) which is used for manufacturing of the carrier body of a working tool according to the present invention. The temperature rise of this material sample under the respective ultrasonic load is only slightly greater than of the titanium alloy (first column pair) but is substantially smaller than of the unalloyed constructional steel (second column pair).
Further tests confirmed these results and showed that the efficiency of the fed power with regard to the produced ultrasonic amplitude with working tools having a carrier body formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%, in particular of C60E, is noticeably increased in comparison to the tools having a carrier body formed of an unalloyed constructional steel (S235JR). In addition, with tools having a carrier body formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%, in particular of C60E, higher elongation amplitudes are obtained in comparison with an unalloyed constructional steel at the same probability of fracture.
Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof, and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A machining working tool, comprising a carrier body formed of an unalloyed hardened steel having a carbon content from 0.2% to 0.8%; and at least one machining element provided on the carrier body.

2. A working tool according to claim 1, wherein the carrier body is formed of an unalloyed hardened steel having a carbon content of about 0.6% (±0.1%).

3. A working tool according to claim 1, wherein the working tool is formed as a core drilling, bit (11;21) having a bit body (12;22) that forms the carrier body.

4. A working tool according to claim 1, wherein the working tool is formed as a drill (36) having a stem (37) that forms the carrier body.

5. A working tool according to claim 1, wherein the working tool is formed as a cutting disc (46) having a disc-shaped carrier body (47).

6. A working tool according to claim 1, wherein the working tool is formed as a grinding disc (56) having a substantially disc-shaped carrier body (57).

7. A method of machining mineral constructional components and mineral foundations, with an ultrasonic tool, comprising the steps of providing a machining working tool for use with the ultrasonic tool and having a carrier body formed of an unalloyed hardened steel with a carbon content from 0.2% to 0.8%, and at least one machining element provided on the carrier body; and effecting a machining operation with the ultrasonic tool.