Hilti Aktiengesellschaft

Stumpp & Kurz Gmbh & Co.

Jurgen Kessler

Postive-locking dowel for concrete

A drilling tool for drilling a cylindrical borehole of relatively great depth in a soft material and then forming a conical enlargement adjacent the bottom of the borehole includes an axially elongated tool shank with a first drill at one end for cutting the cylindrical borehole and a second drill adjacent the first drill for cutting the conical enlargement. The second drill is formed of bit holders pivotally connected to a flattened part of the tool shank. An adjustable stop is provided on the tool shank for determining the depth of the borehole. A connecting link guide located within the tool shank interengages the bit holders and the tool shank. When the desired depth is reached, due to relative axial displacement between the tool shank and the connecting link guide, the bit holders are pivoted outwardly so that the second drill can cut the conical enlargement.

Drilling tool

An anchor bolt is arranged to be secured in a relatively deeply drilled hole having a conical enlargement adjacent the base or inner end of the hole. The anchor bolt is formed of an axially elongated tie rod and an anchor located on the end of the tie rod which is inserted into the base of the drilled hole. The anchor is made up of a number of radially expandable sleeve segments. The anchor also includes a cone element for expanding the sleeve segments radially outwardly into the conical enlargement in the hole. The sleeve segments have an outside radius variable in the axial direction of the segments. The radially outer surface of the segments is substantially smooth for their axial length. At the smaller diameter end of the sleeve, the segments are held together by an annular elastic disc. The radial outer periphery of the disc projects at least partly beyond the diameter of the smaller diameter end of the sleeve and is arranged to have a larger diameter than the smaller diameter end of the conical enlargement in the hole.

Anchor bolt

A tool which makes an undercut in the surface surrounding a drill hole in a layer of coal has a head plate which abuts against the surface at the inner end of the hole when the tool is inserted and which is installed at the front end of a rotary tubular guide for two bit holders constituting one-armed levers and having front portions provided with bits and being movable radially outwardly through windows in the guide. The rear portions of the holders are coupled to the front part of a reciprocable rotary shank which can be moved forwardly to expel the bits from the guide while moving the holders forwardly. When the shank is retracted, the bits are withdrawn into the guide. Such movements of the bits are caused by a transverse pin mounted in the guide and extending through elongated cam grooves in the median portions of the holders. The configuration of surfaces flanking the cam grooves is such that the bits move outwardly during a first stage of forward movement of the shank relative to the guide and the bits thereupon remain in extended positions and make a cylindrical portion of the undercut in the surface surrounding the hole during the last stage of axial movement of the shank into the guide. The tool is thereupon withdrawn and replaced with an anchor bolt which can be expanded against the surface portion surrounding the undercut and serves as a supporting or holding device.

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Stuttgart, Germany

Jurgen Kessler