Abstract:
A fastening element having a stem provided, at its opposite ends, with a head and a tip, respectively, and a separate cover element releasably arrangeable on the head.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a fastening element for use in setting tools and having a stem provided at its opposite ends with a tip and a head, respectively, with the head being covered by a cover element. 
     2. Description of the Prior Art 
     Setting tools for driving fastening elements in a substrate include a drive piston that impacts a fastening element for driving the fastening element in. The problem with the drive piston consists in that metallic impacts of the piston on the to-be-set fastening elements, e.g., bolts or nails lead to a high wear of the piston. In setting tools having a small power, e.g., in combustion-engined setting tools, the wear of the piston tip or end is a primary reason of the piston failure. As a result, because of a rapid wear of the piston, the setting tools should be designed so as to insure an easy replacement of the drive piston. This results in high costs of the setting tools and in high maintenance costs as the drive piston should be replaced often. 
     U.S. Pat. No. 2,140,749 disclose a manually driven-in nail the head of which is covered with a coating. The coating remains dry at a normal room temperature. However, under higher temperatures, the coating becomes sticky. Such nails are used, e.g., in roof covering when, simultaneously with driving-in of a nail, sealing of the entry opening of the nail against the nail head should take place in order to prevent penetration of moisture. In the known fastening elements, the cover or the coating is removed, after the setting of a fastening element, only with much difficulty. However, in many applications, in which the fastening elements are driven in with a setting tool, it is required that no soft or sticky coating remains on the head of a fastening element. Accordingly, an object of the present invention is to provide a fastening element in which the above-discussed drawbacks of conventional fastening elements are eliminated and which can easily be used in a setting tool. 
     SUMMARY OF THE INVENTION 
     This and other objects of the present invention, which will become apparent hereinafter are achieved by providing a separate cover element that is detachably arranged on the head of a fastening element. 
     A separate cover element, which, during a setting process, absorbs the setting energy by being deformed, noticeably reduces the wear of the drive piston. Likewise, by forming the cover element as a detachable element, it is easily removed from the head after the setting process, without leaving any residue. 
     Advantageously, the cover element is provided with stud or a clip element for being releasably secured to the head of a fastening element. The provision of the stud or clip element insures that the cover element does not become lost during transportation, while still being easily removable from the head after the setting process. 
     Advantageously, the fastening elements can be assembled into a magazine by connecting separate cover elements with each other. In this case, additional elements for forming the magazine of fastening elements are not needed. 
     According to a further advantageous development of the present invention, the cover element is provided with a holding element that permits to releasably secure the cover element to the head of a fastening element. This holding element can be formed as a stud engageable in a groove formed in the fastening element head. 
     According to another advantageous development of the present invention, the holding element can be formed as a collar provided at the edge of the cover element and with which the cover element can be clipped on the head of a fastening element. 
     Advantageously, a strip of cover elements with the cover elements is secured not to the fastening elements but rather is provided with braces or/and webs with which the cover element strip is mounted on another magazine strip that encompasses the stems of the fastening elements. During the setting process, the webs are automatically teared off, whereby the separation of the cover element from the second magazine strip takes place automatically. 
     Advantageously, cover elements are formed of a plastic material, which substantially reduces the wear of the setting direction end of the drive piston. Instead of the plastic material, other deformable materials, e.g., light metals, can be used. 
     According to the present invention, between the cover elements of a cover element strip, there are provided weakness arears or break-off points, which insure an easy separation of the cover elements from the cover element strip during a setting process. 
     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 preferred embodiments, when read with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings show: 
     FIG. 1 a side view of a section of a magazine with fastening elements according to the present invention; 
     FIG. 2 a top view of the magazine section shown in FIG. 1; 
     FIG. 3 a cross-sectional view along III—III in FIG. 2; 
     FIG. 4 a top view on several fastening elements according to a second embodiment; 
     FIG. 5 a side view of a section of a magazine with fastening elements according to a third embodiment of the present invention; 
     FIG. 6 a top view of the magazine section shown in FIG. 5; 
     FIG. 7 a cross-sectional view along line VII—VII in FIG. 6 at an increased scale; and 
     FIG. 8 a cross-sectional view of a section of a magazine with a fastening element according to a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of a fastening element  10  according to the present invention is shown in FIGS. 1-3. The fastening element  10  has a stem  12  at one end of which, there is provide a tip  13  and at another opposite end of which, there is provided a head  11 . The head  11  of the fastening element  10  is provided with a cover element  20  that is secured to the head  11  by clip sections  35 . The cover element  20  is formed e.g., of a plastic material. A plurality of cover elements  20  are connect with each other by material webs, whereby a magazine strip  22  of fastening elements  10  is formed. The material webs form weakness areas  26  which define break-off points. In the embodiment shown in FIGS. 1-3, the stems  12  of the fastening elements  10  extend through separate segments  27  of a magazine strip  40 . The separate segments  27  are connected with each other by webs  46  having each a break-off point. 
     When a fastening element  10  is brought into a bolt guide of a setting tool and is advanced through the bolt guide by a setting direction end of a drive piston, a respective web  46  is teared off at its break-off point, and a respective cover element  20  is teared Doff from the strip  22  at the break-off point of the respective weakness area  26 , which insures displacement of the fastening element  10  through the bolt guide (not shown). 
     The clip section  35  of the cover element  20 , which is provided on the head  10 , is formed, in the embodiment shown in FIGS. 1-3, by a holding element  25  provided at an edge of the cover element  20 . The holding element  25  is formed as a concave collar. After setting of a fastening element  10 , the clip section  35  can be easily released, providing for removal of the cover element  20  from the fastening element  10 . It should be pointed out that the magazine strip  40  is not absolutely necessary as arranging the fastening elements in the magazine strip  22  suffices. However, in spite of this, it makes sense to provide separate elements on the stems which serve for guiding the fastening elements in the bolt guide of the setting tool. 
     The embodiment of the fastening element  10 , which is shown in FIG. 4, differs from that shown in FIGS. 1-3 in that the cover element  20  has a square shape. 
     In the embodiment of fastening elements  10  shown in FIGS. 5-7, the fastening elements  10  are hoisted on the magazine strip  40  which is formed, as in the embodiment of fastening element  10  shown in FIGS. 1-3, of separate segments  27  connected with each other by webs  46 . The separate segments  27  serve, as it has been discussed above, for guiding the fastening elements  10  in the bolt guide of a setting tool. However, in the embodiment of fastening elements  10  shown in FIGS. 5-7, contrary to that of FIGS. 1-3, the magazine strip  40  extends immediately beneath the heads  11  of the fastening elements  10 . Above the heads  11 , there is provided, as in the embodiment of FIGS. 1-3, a strip  22  of separate cover elements  20  which cover the heads  11  of respective fastening elements  10 . The strip  22  is connected with the located below, magazine strip  40  by web-shaped elements  23  which extends into the space between adjacent separate segments  27 . The strip  22  and the web-shaped elements  23  can be glued to the magazine strip or be welded thereto. 
     The strip  22  is provided with weakness areas  26  that circumscribe the cover elements  20 . When the fastening element  10  of the embodiment shown in FIGS. 5-7, is brought or advanced into the bolt guide of a setting tool and is advanced in the setting direction by the drive piston (not shown), the cover element  20  is teared off of the strip  22  at the weakness area  26 , and the separate segment  27  of the strip  40  is teared off at a web  23 . Because the cover element  20  is not connected directly with the head  11  of the fastening element, the cover element  20  falls off the head  11  immediately after the setting process, or the cover element  20  can be easily removed, without extending much force, from the head  11  of a set fastening element  10 . 
     In the embodiment of a fastening element  10  shown in FIG. 8, the cover element  20  is secured to the head  11  with a web-shaped element  24  with a, possibility of easy removal therefrom. The head  11  is provided, to this end, with a groove  14  into which a web-shaped holding element  24  can engage. The web-shaped holding element  24  extends from the bottom  21  of the cover element  20 . As in the previous embodiments the adjacent cover elements  20  are connected with each other by weakness areas  26 , forming the strip  22 . 
     It should be pointed out that the shape of a cover element should be adapted to the geometry of a head of a fastening element. 
     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.