Patent Application
20070297873
1. Field of the Invention
The present invention relates to a thread-tapping screw including a shaft having first and second ends, load application means provided at one of the first and second ends, and a thread extending at least regionwise along the shaft.
2. Description of the Prior Art
Screws with a self-tapping thread for different constructional components are well known. Thus, German Publication DE 33 01 414 A1 discloses a thread-tapping screw for a mineral constructional component, e.g., such as concrete and including a shaft having first and second ends, load application means provided at one of the first and second ends, and a thread extending at least regionwise along the shaft.
The thread-tapping screw is screwed in a pre-drilled hole in a constructional component with an appropriate tool such as, e.g., a screw-driver, hammer drill, spanner and the like, with a front portion of the screw tapping a counter-thread corresponding to the screw thread. A following thread engages the counter-thread, whereby a load is transmitted to the constructional component. In a soft constructional component such as, e.g., foam mortar, or plaster board, the thread-tapping screws can be screwed in without preliminarily forming a hole.
An essential advantage of a thread-tapping screw is a possibility to screw the thread-tapping screw out of the constructional component, without a portion of the produce attachment remaining in the constructional component. In particular, thread-tapping concrete screws, which can be set in mineral constructional components, proved themselves in practice for temporary attachments, e.g., during formwork, scaffolding or for securing of drilling and cutting power tools in diamond drilling and cutting technology. The thread-tapping screws not only can be withdrawn but, in principle, can be used for a new application.
The drawback of a conventional thread-tapping screw, in particular of that which is set in a mineral component, consist in that the screw is subjected to wear as it is being screwed in. The degree of wear and, thus, wear of the thread flanks of the thread depends on local conditions in the constructional component, and the possibility of a multiple use of the thread-tapping screw cannot be predicted. Therefore, with a conventional thread-tapping screw, the load bearing characteristics can be guaranteed only at a first use. Therefore, even at temporary attachments, for each new setting process, a new thread-tapping screw needs to be used, and a possible advantage of reuse is not used.
Accordingly, an object of the present invention is to provide a self-tapping screw, in particular, a concrete screw that is capable of multiple use.
Another object of the present invention is to provide a self-tapping screw that permits to determine its load bearing behavior.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing at least one wear indication element on the thread.
The at least one wear indication element shows degree of wear of the thread and, thereby, permits to determine load-carrying characteristics of a dismounted thread-tapping screw. The user can clearly and simply recognize if a load-bearing capacity of a dismounted thread-tapping screw fell below a predetermined threshold and whether the dismounted screw can be used anew or not. A multiple use of a thread-tapping screw permits to reduce costs and resources, e.g., associated with storage and logistics, in particular at temporary attachments.
Advantageously, the at least one wear indication element is formed by a discontinuity region formed by at least one side of a thread flank of the thread being discontinued from a rim of the thread toward a thread root. The discontinuity region of the thread flank defines a shoulder. Alternatively, the discontinuity region can define and form a step the adjacent flank portions of which form an obtuse or super obtuse angle. Further, the discontinuity region can be formed by a depression extending substantially parallel to the free rim of the thread, e.g., in form of a groove. A shoulder, a step and/or groove can be provided on both sides of the thread flanks. Moreover, a side of the thread flank can have more than one shoulder, step, or groove.
Advantageously, the at least one wear indication element is formed by a recess which is provided on the thread and is clearly seen to the use. The recess is so dimensioned and positioned that at an abrasive wear of the thread when the recess cannot be recognized any more, a lower threshold of the load-bearing capacity of the thread-tapping screw has been reached.
Advantageously, the recess is formed on a side of a thread flank of the thread. Advantageously, the recess extends from a rim of the thread flanks by a predetermined amount toward the thread root and is defined by a minimal load-carrying capacity that still must be reached by the thread-tapping screw with a worn thread. According to a further embodiment, the recess is formed by a circumferentially closed depression formed at a predetermined distance form the outer rim of the thread flank.
Advantageously, another wear indication element is arranged in the recess that forms visual advance warning means. Advantageously, the another wear indication element is formed of a material that visually distinguishes from the material for producing the thread-tapping screw, e.g., a temporary free-flowing wear means can be cast into the recess.
Advantageously, the at least one wear indication element is formed by a marking provided on a thread flank, e.g., in form of a color layer or by region having a particular surface structure. The region with a particular surface structure, e.g., a particular profile that is formed on the thread, advantageously, during the production of the thread-tapping screw.
Advantageously, the at least one wear indication element is formed by a separate wear indication element. The separate wear indication element can be formed by pins, balls, cubes, cones or the like which are embedded into the thread, e.g., during manufacturing of the thread-tapping screw. When a predetermined degree of wear is reached the wearable body is freed. The visually warning wearable body communicates to the user that the load-bearing capacity of the thread-tapping screw fell below its lower threshold.
According to an alternative embodiment of the present invention, the separate wearable body is frictionally or form lockingly set in the recess, whereby upon a complete wear of the wearable body, a visual signal is communicated to the user that the load-bearing capacity of the thread-tapping screw fell below its lower threshold.
Advantageously, more than one wear indication elements are provided on a thread. The wear indication elements are located at different locations at a distance from each other so that more than one region of the thread can predict further use of the dismounted thread-tapping screw. Alternatively, several wear indication means are arranged at different distances from the rim of the thread flank, whereby not only the lower threshold of the load-bearing capacity of the thread-tapping screw but also an intermediate threshold are visually communicated to the user. Further, different kinds of wear indication elements can be provided on the thread of a thread-tapping screw, which insures a high reliability of prediction of remaining load-bearing capacity of the thread-tapping screw.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of the preferred embodiments, when read with reference to the accompanying drawings.
In the Drawings:
In the drawings, the same elements are shown with the same reference numerals.
A thread-tapping screw 11 according to the present invention, which is shown in
A further wear indication element 56 is formed by a separate wearable body 57 embedded in a region between the shoulders 53 and the rim 17.
The side sections of the side 20 adjacent to the edge 68 form a super obtuse angle F. If upon dismounting of the thread-tapping screw 11, it is visualized that the flanks of the thread 16 wore off, as a result of the screw 11 being screwed in, up to the edges 63 and 68, the user recognizes that the load bearing capacity of the thread tapping screw 11 fell below its lower threshold, and the screw 11 cannot be used any more.
Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 000 269.5 | Jun 2006 | DE | national |
