Boring or penetrating the earth – Below-ground impact members – Telescoping members relatively rotatable
Reexamination Certificate
2001-07-11
2003-05-06
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Below-ground impact members
Telescoping members relatively rotatable
C175S414000, C173S128000
Reexamination Certificate
active
06557653
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a working tool, such as trepan or chisel, for use with a percussion power tool, such as a hammer drill or a chisel hammer, for treating, preferably, stone, concrete, and brickwork.
2. Description of the Prior Art
A trepan or a boring bit, which is used, e.g., with a hammer drill, is subjected to mechanical impacts applied to its end surface by an anvil and/or percussion piston of e.g., electropneumatic percussion mechanism of the hammer drill. The impact or shock energy propagates, substantially in form of longitudinal pulses, which assume the form of shock pulses, toward the opposite end surface of the bit which transmits the shock energy to the treated material. The removal of the treated material results from the work produced by the transmitted shock energy. The opposite end surface is usually formed as a tool or bit head formed of hard metal or including hard metal work elements.
The physics of pulse transmission discloses how a pulse, upon being transmitted between two abutting each other bodies, is distributed therebetween, i.e., is transmitted from one body to another or is reflected from the other body. A portion of the excited energy, which is transmitted from the working tool to the treated material, depends on the cushioning properties of the bodies located in the pulse transmission chain in accordance with the pulse ratio for bar-shaped bodies determined by the bar theory. The excited energy causes, in the working took, a translational movement of the gravity center, on one hand, and a pivotal movement about the gravity center, on the other hand. However, essentially, only the translational movement of the gravity center is used in the operational process.
U.S. Pat. No. 4,165,790 discloses dividing a working tool in several components connected with each other for joint rotation with each other and for a limited axial movement relative to each other. The tool disclosed in U.S. Pat. No. 4,165,790 consists of a short tool head, a substantially elongate tool stem, and a shank, with the head, stem, and shank being connected by using a hexagonal connection secured with a transverse pin. Such a connection insures a connection that provides for joint rotation of the connected components and for their limited axial displacement relative to each other. U.S. Pat. No. 4,605,079 discloses a tool with a very short tool head having an inner hexagon for a formlocking connection that insures joint rotation of the connected components and their limited axial movement relative to each other. The known tool heads do not have optimal characteristics for pulse transmission.
International publication WO97/08421 discloses a working tool formed of a boring tube or a boring bar at the free end of which a drilling insert is provided, with the tool head itself being formed of arranged along its axial length, head portion and stem portion. The connection, which insures the joint rotation of the two parts, is formed by elements having polygonal cross-sections or by a nose receivable in a recess formed in another part. The tool head is secured to the boring tube or the boring bar for a limited axial displacement relative thereto with a light metal pin or a ring. The transmission of the impact or shock pulses, from the boring tube or bar to the tool head, is effected over substantially flat, pulse transmitting surfaces extending transverse to the tool axis. The pulse transmitting surfaces can be provided between a boring tube and radially outer, inwardly located end surface regions of the tool head, and between the boring bar and radial, axially inwardly located, regions of the sleeve-shaped tool head.
As disclosed in WO97/08421, the ratio of the length of the stem portion to the head portion is selected to be as large as possible, in particular, larger than five, in order to transmit a maximum amount of the pulse energy accumulated in the tool head for treating the processed material. Generally, a certain resistance ratio between the stem portion and the head portion should be provided, though some constructively necessary, small axial variations of absolute values are allowable. A shock pulse, which is transmitted to a head side end surface of the boring tube or bar located in the transitional region between the stem and head portions, and which has a double length of the head, is partially transmitted over the short head portion in the treated material, with another portion of the shock pulse being transmitted as a thrust pulse into the axially movable stem portion in which the pulse energy is stored. With this solution, a thrust shock is transmitted to the treated material. According to the teachings of WO97/08421, with the transmission of a pulse energy of a shock pulse having a pulse length double of the length of the tool head, essentially no recoil pulse is excited in the boring tube or bar. Thus, the pulse energy is almost completely transmitted to the tool head and, thereby, into the treated material. With this solution, the pulse transmission of a thrust pulse into a tool head, which is provided with a stem portion, is optimized, with the tool head being formed as an independent or separate working tool with stem and head portion and suitable for treating a material.
The object of the present invention is to provide a constructively simple and easily produced working tool that would permit to optimize the transmission of pulse energy generated in a percussion power tool with which the working tool is used.
SUMMARY OF THE INVENTION
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a working tool including a cushioning elongate stem and a head connected with the stem for joint rotation therewith and for a limited axial displacement relative thereto, with the tool head being adapted, with respect to its resistance associated with its cushioning properties, to characteristics of the percussion piston, and with the tool stem and the tool head having mutually abutting each other end surfaces which form at least a partially flat contact upon abutting each other.
With such an adaptation of the working tool head to the characteristics of the percussion piston and/or the anvil, the shock pulse, which is excited by the percussion piston and/or the anvil and has a pulse length double of the tool head length, is transmitted to the tool head almost completely, without any noticeable backward reflection and, thus, without the loss of pulse energy.
As a result of at least partial substantially flat contact of respective shock-transmitting components, a substantially rectangular shock pulse, which is produced by the percussion piston, is not noticeably widens upon being transmitted to the tool head. As a result, the shock pulse is transmitted, with maintaining its shape to a most possible extent, through the tool stem almost completely to the tool head which is adapted with respect to its cushioning characteristics to the percussion piston.
This almost complete transmission of the pulse energy of the percussion piston and/or the anvil to the tool head, which transmits this pulse energy at least partially to the treated material, leads, with relatively large and heavy, with respect to the percussion piston, working tool, to an increase of the operational capacity in comparison with standard systems from about 25% to about 80%.
It should be noted, however, that a limited axial movement of the tool head, even with a geometry adapted, with respect to its cushioning characteristic to the characteristics of at least the percussion piston, is not sufficient for implementing the teachings of the present invention. This is because for using the teachings and advantages of the present invention, an adequate flat contact is necessary for transmitting a substantially non-deformed rectangular pulse of a certain length. Only under these conditions, an almost complete transmission of the pulse is achieved. According to the teachings of the present invention, under
Artmann Konrad
Bauer Josef
Fünfer Josef
Hauptmann Udo
Popp Franz
Hilti Aktiengesellschaft
Sidley Austin Brown & Wood LLP
Tsay Frank
LandOfFree
Working tool for a percussion power tool does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Working tool for a percussion power tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Working tool for a percussion power tool will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3060501