Abstract:
A screw with a threaded shaft which has a slot running lengthwise dividing the threaded shaft into two shaft halves. A deformable mass is provided in the slot and fills the slot. This mass prevents the screw threaded into a threaded hole or application-related cored hole from loosening by itself.

Description:
This application claims the priority of German patent application number 199 30 905.1, filed Jul. 6, 1999, the disclosure of which is expressly incorporated by reference herein. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to a screw with a threaded shaft which has a slot running longitudinally which divides the threaded shaft into two halves. 
     A screw is known from DE 38 12 111 C2 corresponding to U.S. Pat. No. 4,822,225 which can be inserted especially quickly into a threaded hole or application-related cored hole because it does not have to be threaded into it at the beginning, but needs merely to be pushed into it axially at first, letting the threads of the screw slip over the threads of the hole. When screws of the above kind are used at places where vibration and oscillation occur there is the danger of accidental loosening of the screws in the course of time. It is, therefore, necessary to secure the screws against unintended loosening. 
     Very different means are known for securing screws. It is common, for example, to slip a spring or lock washer onto the threaded shaft to produce a bias force on the screw head when the screw is tightened. Another common method of screw locking consists in binding the screw head to the surface with a lacquer against which it presses when the screw is tightened. The known screw locks involve relatively great additional work, so that for cost reasons such screw locks are not applied and instead the risk of unintentional loosening of the screws is accepted. 
     This invention is addressed to the problem of designing a screw of the kind described above such that it can be secured against unintentional loosening with as little work as possible. This problem is solved by the invention by the fact that a plastic mass filling the slot partially or entirely is provided in the slot. 
     Such a screw is only slightly more expensive than a screw unsecured against unintentional loosening. Therefore one can use such screws with locking means at basically little additional cost and thus prevent unintentional loosening of the screws. Since the mass according to the invention is plastic it does not interfere with the drawing together of the shaft halves when the threaded shaft is pressed axially into a threaded hole. The screw according to the invention can therefore be inserted at first axially into a threaded hole while the mass is compressed in its slot. 
     It is especially desirable if, according to an advantageous embodiment of the invention, the mass is an elastic polymer. Such a mass is especially cheap and brings about an effective screw lock. 
     To further increase the holding power of the screw lock it is helpful if, according to another embodiment of the invention, the mass is a fiber material or synthetic material mixed with fibers or a composite material of synthetic material and metal. 
     The force involved in inserting the screw is especially low if the mass is a synthetic material mass, such as a lacquer, which hardens under pressure. 
     Since when the screw is inserted into a threaded hole the shaft halves are forced together from both sides of the slot, the mass in the slot can pass out of it upon insertion so as to exercise the locking function, so that it does not interfere with insertion if the mass reaches no further than the outer contour of the threaded shaft. 
     If especially great locking forces are required, however, provision can be made for the mass to protrude on both sides of the slot beyond the contour of the outside diameter of the threaded shaft. 
     The mass can be reliably anchored in the slot if the screw shaft has at least one transverse bore leading into the slot and the mass reaches into this transverse bore. 
     It contributes to a further increase of the holding power if the mass at the same time coats at least a portion of the circumferential surface of the threaded shaft. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front end view of a screw according to the present invention; 
     FIG. 2 is a side elevational view of the screw according to the present invention; 
     FIG. 3 is a side view of the screw rotated 90° from that of FIG. 2; 
     FIG. 4 is a side view of a second embodiment of a screw of the present invention; 
     FIG. 5 is a section through the threaded shaft of FIG. 2 showing one embodiment of the invention; 
     FIG. 6 is a section through the threaded shaft of FIG. 9; 
     FIG. 7 is a section through the threaded shaft of FIG. 2 showing another embodiment of the invention; 
     FIG. 8 is a section through the threaded shaft of FIG. 2 showing another embodiment of the invention; and 
     FIG. 9 is a side view showing another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1,  2 , and  3  show a screw  1  which is configured as an oval-headed screw. It will be appreciated that the shape or configuration of the head does not affect the novel inventive characteristics of the instant invention. The invention is not, therefore, limited to any particular shape or configuration of screw head. The screw has a threaded shaft  2  which has a centrally disposed slot  3  running lengthwise, which divides the front portion of the threaded shaft  2  into two halves  4  and  5 . On the two longitudinal sides of the threaded shaft  2 , two free surfaces  6  and  7  perpendicular to the slot  3  are provided, which are arranged at an acute angle to one another. The front part of the threaded shaft  2  is provided with a conical taper  8 . 
     The screw  1  shown in FIG. 4 differs from the screw  1  previously described, especially by having a broad-surface screw head  9 . Such screws are used especially for covering dowel fasteners and as screws for holding the backs of shelving. In the case of the illustrated screw  1 , due to the use to which the screw will be put, the two shaft halves  4  and  5  of the threaded shaft  2  are made resiliently yielding and spread apart from one another. For this purpose the threaded shaft  2  and the broad-surfaced screw head  9  are made preferably from an elastic plastic or an aluminum-magnesium alloy by the pressing or injection molding method. If the screw  1  is made of steel, the springing action of the shaft halves  4  and  5  can be produced by appropriate material selection and shaping methods or after manufacture by hardening and tempering methods. 
     Important for the invention is a moldable mass  10  which is provided in the slot  3 . This mass serves to lock the screw. It can be provided over the entire length of the slot  3  or only over a portion of its length. 
     FIG. 5 shows that the mass can finish flush with the outside contour of the threaded shaft  2 . It is also possible, however, for the mass  10  to protrude slightly beyond the outer contour of the threaded shaft  2 , which is shown in FIG.  6 . FIG. 6 likewise shows two transverse bores  11  and  12  which pass through the shaft halves  4  and  5  into the slot  3  and are likewise filled with the mass  10 . Thus the mass  10  is reliably anchored in the slot  3 . The mass  10  can also protrude slightly from the transverse bores  11  and  12  in order to increase the holding power of the screw  11  in a threaded hole. 
     In the embodiment according to FIG. 7, the mass  10  in slot  3  does not reach as far as the outer contour of the threaded shaft  2 . If the shaft halves  4  and  5  approach one another when the screw  1  is inserted into a threaded hole, the mass  10  is then compressed and thus runs against the threads. 
     In the embodiment according to FIG. 8, the mass  10  simultaneously forms a covering  13  which blankets at least a portion of the threaded shaft  2 . 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.