Boring or penetrating the earth – Bit or bit element – Impact or percussion type
Reexamination Certificate
1999-05-11
2001-07-17
Neuder, William (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Impact or percussion type
C175S427000
Reexamination Certificate
active
06260637
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a rock drill having a shank and a drill head with a cutting tip on its front end.
Conventional rock drills consist of a drill shank and a drill head, into which a carbide cutting element, which is roof-shaped in side view, is inserted (see FIG. 1 of EP 0 452 255 B1). The cutting element has lips or rake faces which are ground in a wedge shape on either side of the roof-shaped front end and in each case have a top cutting edge. In this case, the cutting edges are arranged so as to be laterally offset from a vertical center plane of symmetry, so that so-called chisel edges are produced (see FIG. 2 of EP 0 452 255 B1).
As a rule, the flanks arranged behind the end cutting edge in the direction of rotation have a flank angle of about 20°-30° compared with a conventional cutting edge angle or rake-face angle of 60°, the angles being measured being measured relative to a vertical plane to the longitudinal axis of the drill.
With regard to the design of such cutting tips, reference is additionally made to DE 81 04 116 U1, FIGS. 2 to 4 , and DE 29 12 394 A1, FIG. 1. Some of these drilling tools have secondary cutting tips or corresponding pins which are intended to serve the drilling advance.
The roof-shaped cutting tip made of carbide can pass completely through the drill head over its entire diameter and as a rule forms an additional lateral projecting length for forming the nominal diameter. Provided there are no secondary cutting tips or corresponding pins, the transition region from the drill helix to the drill head is designed as a supporting region for the cutting tip. In this case, to prevent dislodgement, the carbide cutting tip is supported laterally in the drill head by an appropriate, voluminous supporting body, retaining surfaces for the removal of the drillings being formed at the front end as a rule.
A drilling tool having a cemented-carbide insert has been disclosed by EP-A 0353 214, this drilling tool serving to cut rock. In order to produce a better brazed connection between the tool body and the sintered-carbide insert, additional side tips of sintered carbide, which embed the main sintered-carbide insert, are provided. In this case, the sintered-carbide insert is of symmetrical construction relative to its longitudinal center plane, side sections having a different point angle being provided, and these side sections lead to an improved brazed connection. A distinction between different rake faces and flanks is not provided in this tool.
SUMMARY OF THE INVENTION
The object of the invention is to improve a drilling tool of the type described above to the effect that drilling capacity in concrete is improved. At the same time, a lower loading of the carbide cutting tip is to be achieved.
Starting from a drilling tool having a shank and a drill head with at least one cutting tip on its front end pointing in a direction of feed of the drilling tool, this object is achieved by the at least tip having at least one cutting edge, a rake face with a negative rake-face angle (&agr;) and a flank located behind the at least one cutting edge where the flank is subdivided into a first flank section adjoining the at least one cutting edge and a second flank section wherein the rake-face angle (&agr;) is constant and is greater than a first flank angle (&bgr;
1
) of the first flank section.
Advantageous and expedient developments of the design according to the main claim are specified in the subclaims.
Compared with known tools, the drill according to the invention has the advantage that markedly improved penetration into concrete is effected by lips which are not so “obtuse”.
This results directly in a quicker drilling advance. The percussion power acting on the drilling tool is not transmitted to a conventional obtuse carbide cutting tip; on the contrary, the percussion power is converted on the whole, even more effectively, into drilling capacity by a markedly slimmer embodiment of the drill head. As a result, smaller tool dimensions may also be used in larger hammer drills without these smaller tools being damaged. Due to the design according to the invention of the front end of the carbide cutting insert, a lower loading of the carbide cutting tip itself takes place.
An essential basic idea of the invention is to modify the flank of the carbide cutting tip so that the flank is arranged on the back of a respective rake face, without involving the risk of fracture of the cutting edge. This is done according to the invention by each flank being subdivided into at least two flank sections, which, for example, may have the same widths, in which case the flank section pointing toward the side wall of the carbide cutting tip may have, for example, a flank angle which is approximately twice as large as the first flank section pointing toward the cutting edge. In this way, the flank is made to taper, so that the carbide cutting tip is of a tapered design, as seen in a side view, toward its narrow side. As a result, the carbide cutting tip, in a tool additionally shaped so as to be more acute overall, penetrates with low resistance into the material to be drilled, so that the percussion power leads to a quicker drilling advance.
In a special refinement of the invention, a conventional carbide cutting element, for example, is provided with a flank section at its respective flank, the flank section at its respective flank, the flank sections being divided approximately in half, for example, in their projected length directed upward. However, the flank sections may be designed to differ in their projected lengths and their flank angles.
A development of the invention provides for the rake face to be designed with an increased rake-face angle of >60°, in particular about 70°, compared with a conventional embodiment. In this case, depending on the optimization of the drilling tool, the rake face may be designed to be flat or concave or convex. Here, the tangential or aligned transition to the supporting surface for the carbide cutting tip is important. If it was previously assumed that a further increased in the rake-face angle and thus an even more acute design of the carbide cutting tip leads to an increased risk of fracture of the point of the carbide cutting tip, then extensive tests have shown that the improved disposal of the drillings from such a lip increases the loading capacity.
The widening of the rake face in the direction of the center axis of the drill is also to be seen in this connection, since the width of the chisel edge is thereby reduced.
In an independently patentable development of the invention, the carbide cutting tip designed according to the invention with a second flank angle is integrated in a drill head whose lateral supporting body for the carbide cutting tip is designed to be very slim and likewise tapered. Compared with a conventional drilling tool having voluminous end supporting surfaces, the lateral supporting surfaces, according to the invention, are therefore designed as lateral surfaces which are tapered as far as possible and, for example, are concave or arched or even flat in their outer contour. This design results in a sharply tapered, arrow-shaped side view of the drill head with a carbide cutting tip. In this case, it is especially expedient if the outer contour is designed to be flat, convex or concave, the supporting surfaces for the carbide cutting tip and thus the outer contour of the drill head merging virtually tangentially or completely tangentially or asymptotically into the rake face and respectively the flank of the carbide cutting element. This results in a flat or an inwardly arched surface in a view of the narrow side of the carbide cutting element, and this surface, in its upper region, runs in an at least partly tapered manner into the rake face or respectively the flank or respectively the side wall of the carbide cutting element. End retaining surfaces are thereby avoided. This measure at the drill head can also lead to the desired effect with a conventionally designed cuttin
Fuss Mathias
Haussmann August
Moser Bernhard
Wagegg Thomas
Hawera Probst GmbH
Kinberg Robert
Neuder William
Venable
Voorhees Catherine M.
LandOfFree
Rock drill does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rock drill, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rock drill will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2488178