Cutting by use of rotating axially moving tool – Tool-support with means to move tool relative to tool-support – To move radially
Patent
1989-07-07
1990-11-20
Howell, Daniel W.
Cutting by use of rotating axially moving tool
Tool-support with means to move tool relative to tool-support
To move radially
279 16, 408127, 408147, B23B 4100, B23B 5108
Patent
active
049714864
DESCRIPTION:
BRIEF SUMMARY
The invention concerns an undercut drill bit with a mounting arbor, a deflection plate which bears on the borehole rim and on which a shaft with a cutter part is fastened at a slant relative to the plumb on the stop face of the deflection plate.
Such an undercut bit for creating undercuts in predrilled lightweight construction materials is known from the German patent disclosure No. 30 22 464 and serves the preparation of an anchoring of fasteners by form fit in the undercut part of the bore. On the prior device, the cutting part is slanted at a fixed angle relative to the longitudinal axis of the mounting arbor and, thus, the longitudinal axis of the impact drill or drilling machine used. The cutting part is introduced in a previously produced cylindrical bore and the drilling machine or impact drill is turned on with the cutting part stirring about in the cylindrical bore, causing in the case of lightweight construction material a removal of the cylindrical sidewalls. Pivoting the longitudinal axis of the drilling machine or impact drill along the longitudinal axis of the cylindrical bore accomplishes the gradual formation of the conic undercut. In the process, lateral forces are exerted on the shaft of the impact drill and the drilling machine, and on the corresponding bearings of the drilling equipment, which usually do not occur in drilling equipment.
Described in the German patent disclosure No. 30 27 408 is a drilling device for the production of undercut bore holes where the drill bit shaft is mounted fixed and aligned on the longitudinal axis of the drilling apparatus, installed together with the drilling apparatus in a ball joint which permits the pivoting of the drill shaft in a predrilled cylindrical bore hole. In this device, too, the bearings are heavily stressed. Additionally, a longer lever arm involves the risk that the drill shaft will be bent. Finally, the pivoting of the drilling apparatus requires room for maneuvering, which is not always available, so that with the prior device it is not possible, for instance, to drill undercut bore holes in the vicinity of corners and edges.
The problem underlying the invention is to provide an undercut drill bit of the initially mentioned type that makes it possible to produce a conically undercut borehole both in lightweight construction materials and concrete, in a single operation without circular pivoting of the drilling machine or impact drill.
This problem is intentionally solved in that the mounting arbor is connected with the deflection plate through a cardan joint and the drill shaft features on its front end a radially protruding cutting plate as cutting component.
The cardan joint transmits both rotary and axial forces, and a pivoting of the drilling machine or impact drill is no longer necessary because the stop surface of the deflection plate transmits upon contact with the borehole rim a tilting moment to the drill shaft which on account of the cardan joint is not transmitted to the mounting arbor because the cardan joint allows a transmission of force from the mounting arbor to the drill shaft while variable angles can be assumed between the mounting arbor and the drill shaft.
On a suitable embodiment of the invention, the cardan joint is provided in a housing which on its end facing toward the drill shaft is covered with a circular deflection plate which in the form of a wedge tapers in one direction. What is accomplished by this design is that the longitudinal axes of the drill shaft and the mounting arbor are in mutual alignment while the cylindrical part of the borehole is being made.
To avoid damage to the surface around the borehole rim the stop face of the deflection plate may be covered with a plastic plate.
On the end away from the deflection plate, the housing has an opening through which protrudes an entrainment screw which is pivotable in any direction and is permanently connected with the mounting arbor. The entrainment screw features a hex head with a ball-shaped front which is installed in a hex recess in the housing i
REFERENCES:
patent: 2381102 (1945-08-01), Boyd
patent: 2392039 (1946-01-01), Gideon
patent: 4545706 (1985-10-01), Hiroyasu et al.
Frischmann Albert
Rinklake Manfred
Steurer Paul
Howell Daniel W.
Upat GmbH & Co.
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