Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Thread or shank structure
Reexamination Certificate
2000-01-07
2001-07-24
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Thread or shank structure
C411S916000, C411S392000
Reexamination Certificate
active
06264414
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of co-pending German Patent Application No. 199 00 791.8 entitled “Verbindungselement für zwei Maschinen- oder Bauteile, insbesondere Pa&bgr;-Dehnschraube, Pa&bgr;-Gewindebolzen o. dgl.”, filed on Jan. 12, 1999.
FIELD OF THE INVENTION
The present invention generally relates to a fastener for connecting at least two components. More particularly, the present invention relates to a fastener, for example a fitting elongation screw or a fitting threaded bolt, having a shank including at least one threaded portion, one elongation portion and one fitting portion. The elongation portion and the fitting portion are spaced apart along the longitudinal axis of the shank.
BACKGROUND OF THE INVENTION
For example, the fastener or the connecting element may be designed in the form of a fitting elongation screw including a head. The fastener may also be designed in the form of a fitting threaded bolt additionally including a fastening thread.
Fasteners and connecting elements, especially fitting elongation screws and fitting threaded bolts, are generally used to connect two or more components or structures. The fasteners are tightened with relatively great preload forces to prevent an opening of the two components in their common contact area under operational conditions. To attain the necessary preload force, such fitting elongation screws are deformed beyond the elastic region of the material into the plastic region. The elastic region is the region of the material in which the material is exclusively deformed elastically. The plastic region is the region in which the material is deformed both elastically and plastically. This elastic/plastic region is entered by tightening the fitting elongation screw. The tightening process usually is either angle-controlled or yield-controlled.
A fastener for connecting two components in the form of a fitting elongation screw is known from European Patent Application No. 0 313 927 A1. The fitting elongation screw includes a head for transmitting torque and a shank including a threaded portion, at least one elongation portion and at least one fitting portion including protrusions and channels. The threaded portion, the elongation portion and the fitting portion are axially spaced apart along the shank. The elongation portion includes protrusions and channels. The protrusions and channels of the fitting portion and of the elongation portion are different, but they all have the design of a thread. The root diameter of the channels of the fitting portion is more than the root diameter of the channels of the elongation portion, preferably at least by 10 percent. In this way, a plastic transverse contraction, meaning a reduction of the diameter, is prevented in the fitting portion during a deformation of the fitting elongation screw into the transelastic region, meaning a tightening of the fitting elongation screw beyond the elastic region into the plastic region. The outer diameter of the fitting portion is more than the outer diameter of the elongation portion, and it is also more than the outer diameter of the threaded portion. This fitting elongation screw may be produced from a shank having a constant diameter along its length by axial displacement of material, and an enlargement of the outer diameter of the protrusions resulting therefrom. The axial width at the outer diameter of the protrusions is relatively small. Additionally, it is even smaller in the fitting portion than in the elongation portion. Consequently, the bearing portion of the fitting portion is very small. Thus, a minimum surface is usable to receive transverse forces in the fitting portion. The design of the elongation portion including spaced apart protrusions and channels reduces the fatigue strength and the dynamic properties of the fastener.
Another fitting elongation screw is known from German Patent Application No. 2 143 784. The function of the fitting portion and the function of the elongation portion are fulfilled by a common portion of the shank of the screw. The shank includes a fitting thread, meaning an inclined arrangement of protrusions and channels in the fitting elongation portion. The root diameter of the fitting elongation portion is less than the root diameter of the connecting portion by 2 to 10 percent. In this way, the elastic elongation and the fatigue strength of the fitting elongation screw is improved. An axial elongation occurs in the region of the fitting elongation portion in combination with a permanent reduction of the outer diameter when the fitting elongation screw is tightened beyond the elastic region. The fitting elongation portion loses the functionality of the fitting portion and the fitting elongation screw is not reusable as desired.
Another fitting elongation screw is known from European Patent No. 0 144 503 B1. The fitting elongation screw includes a shank including a threaded portion and a fitting elongation portion. The fitting elongation portion includes non-inclined protrusions and channels. The outer diameter of the protrusions in the fitting elongation portion is more than the outer diameter in the threaded portion by 0.1 to 0.5 mm. The stressed cross section corresponding to the root diameter of the channels in the fitting elongation portion has the same dimensions as the stressed cross section of the threaded portion. In this way, a fitting elongation screw only being used in the region of an elastic elongation is provided.
SUMMARY OF THE INVENTION
Briefly described, the present invention provides an a fastener for connecting at least two components. The fastener includes a shank having an axis. At least one threaded portion is arranged at the shank, and it has a stressed cross section. At least one elongation portion is arranged at the shank, and it has a stressed cross section. The stressed cross section of the at least one elongation portion is less than the stressed cross section of the at least one threaded portion. At least one fitting portion is arranged at the shank. It has a stressed cross section, and it includes a plurality of protrusions and channels. The at least one elongation portion and the at least one fitting portion are spaced apart along the axis of the shank. The channels have a root diameter determining the stressed cross section of the at least one fitting portion. The stressed cross section of the at least one fitting portion is at least 20 percent more than the stressed cross section of the at least one elongation portion.
The present invention is based on the idea to arrange the fitting portion and the elongation portion of the fastener axially spaced apart at the shank of the fastener, and to separate the functions of the fitting portion and the elongation portion. For this reason, the threaded portion, the elongation portion and the fitting portion are arranged at the shank of the fastener or the connecting element with a special design and special dimensions. The three portions are designed and arranged to be coordinated with each other. The elongation properties or the extensibility of the fastener, especially in case of dynamic loads, are substantially determined by the elongation portion. The stressed cross section of the elongation portion is designed to be less than the stressed cross section of the threaded portion. On the other hand, it is important that the fitting portion does not fulfill a substantial elongation function, but instead it permanently maintains its properties being important to its fitting properties. Consequently, the fitting properties of the fastener are also maintained beyond the elastic region of the material such that the fastener or the connecting element, for example a screw or a bolt, is reusable. For this purpose, the stressed cross section of the fitting portion is at least 20 percent more than the stressed cross section of the elongation portion. The stressed cross section of the fitting portion A
R
is calculated according to the equation
(
X
)
A
R
=&pgr;/4
*d
3R
2
,
the stressed cross
Hartmann Gunther
Sommer Wolfgang
Kamax-Werke Rudolf Kellermann GmbH & Co.
Saether Flemming
Thomas Kayden Horstemeyer & Risley
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