Abstract:
This invention relates to a fixing element ( 1 ) for fixing insulating strips ( 5 ) and optionally, additional sealing strips ( 6 ) on a solid substructure ( 7 ). A screw ( 4 ) and a large-surface washer ( 2 ) with a tubular extension ( 3 ) are used. A rib ( 15 ) that projects radially inward into the displacement area is provided in a partial section of the tubular extension ( 3 ), which accommodates a screw bead ( 11 ) in such a way that it is axially displaceable. After passing the rib ( 15 ) in the direction of the free end of the tubular extension ( 3 ), the screw head ( 11 ) can rest on the rib in the direction opposite to the screwing-in direction.

Description:
BACKGROUND 
     The invention relates to a fixing element for fixing insulating strips or plates and optionally additional sealing strips on a solid substructure. 
     Such fixing elements, as well as their availability in a preassembled state, are already known in many varied configurations. In a preassembly of the fixing elements, the screws are inserted in the fixing elements. Then, the fixing elements are processed by means of automatic setting machines, in which a screwdriver bit directly provides the axial advance of the screw as well as the insertion of the fixing element into a roofing strip. 
     BRIEF SUMMARY OF THE INVENTION 
     In relatively small roofing structures or during the fixing of insulation strips or plates, it is desirable that the fixing elements be pre-inserted by hand in a preassembled state, i.e. pushed by hand into the insulating strips or plates and optionally into additional sealing strips. Such pushing-in can also be advantageous when it is followed by processing with a setting machine. 
     One embodiment of the fixing element of the present invention is adapted for use with a screw which is provided with a thread over at least a portion of the length of its shaft and which has a screw head. The fixing element preferably includes a large-surface area washer having a tubular extension that defines a passage for receiving the screw. The tubular extension includes at least one rib to preferably allow the fixing element and screw to be pushed into insulation. 
     The object of the present invention is to substantially improve the handling potential during pre-insertion of a fixing element of the previously described kind. 
     In accordance with the invention, this is achieved by providing, in the segment of the tubular extension for axially displaceable reception of the screw head, at least one rib which protrudes radially inward into the displacement region, or one or more burls or the like, against which the screw head can abut after surmounting the ribs, burls or the like in a direction which is opposite to that of the screwing-in direction toward the free end of the tubular extension. 
     The screws are preassembled in a tubular extension of the large-area washer by pushing-in the screw head past an appropriate obstacle (rib, burl or the like), whereby the rib, burl or the like forms an abutment for pushing the completed fixing element into insulating strips or plates and potentially also into sealing strips. Due to the large-area washer, there is available a relatively large hand-hold for mounting the fixing element, and that is so independently of whether insertion is by hand or by means of a setting tool, so that the force transfer, during pushing into the insulating strips or plates and optionally additionally into sealing strips, can be carried out without any problem. Nevertheless, there is the assurance that the screw cannot move all the way into the tubular extension, but rather encounters a limiting member in the form of a rib, a burl or the like. Even with relatively forceful pushing-in of the preassembled fixing element, the force exerted upon the large-area washer is transmitted by the rib, burl or the like to the screw head and thereby to the inserted screw. This also ensures that the boring or penetrating tip formed at the free end of the screw always lies at the most forward point of the preassembled fixing element, whereby the pre-insertion of the fixing elements is facilitated. 
     One kind of embodiment contemplates that the rib, burl or the like is formed near the mid-range of the length of the tubular extension. By so doing, the screw can slide axially inside the tubular extension over a relatively wide range, which creates a telescopic effect. A telescopic effect is especially appropriate for use of the fixing element in the roof area, i.e. when walk-on surfaces are to be provided with such fixing elements. When stepping on such a fixing element, the large-area washer with the tubular extension can move downwardly in the axial direction and then back again into the initial position, through the elastic action of the insulating strips or plates. 
     A preferred embodiment is one in which there is provided an annular rib extending around the entire inside wall. In a preassembly, this rib can not be easily surmounted, because the preassembly of large-area washers having tubular extensions and screws is usually performed with appropriate assembly tools which provide the required force. If the fixing elements are then pre-inserted by hand, there exists the assurance that the screw head can no longer surmount the complete annularly closed rib, i.e. a firm abutment exists. 
     It is preferable that the spacing of the rib, burl or the like from the free end of the tubular extension is less than the overall length of the screw including a boring portion formed at its free end. This provides assurance that, in the condition in which the screw head abuts against the rib, burl or the like, the free end of the screw and especially its boring portion still always protrudes beyond the free end of the tubular extension. This substantially facilitates penetration by the fixing element during pre-insertion. 
     It also contributes to simple mounting capability and optimal abutting during pre-insertion, if the screw head is lens-shaped and its transition to the shaft has a truncated cone shape. In such a case, it is possible during preassembly to easily push the screw head over the projecting rib, burl or the like. Nevertheless, the lens-shaped configuration of the top of the screw head assures an optimal abutment. 
     The configuration of the preassembled fixing elements, in accordance with the invention, creates the additional possibility that several washers having a tubular extension which are contiguous to each other, or which follow each other closely, are connected to each other by webs or tapes into a kind of screw strip. This makes it substantially easier for transportation and pre-insertion at the construction site. In this connection, the joined-together washers can also be made so as to be relatively easy to separate from each other. 
     In theory, it is conceivable that the respective screws can be mounted in the tubular extension of the washers just before pre-insertion. Preferably, however, the screws are already preassembled in the tubular extensions of the large-area washers, i.e. each screw head is already pushed in past the rib, burl or the like at the internal limit of the tubular extension, so that the rib, burl or the like serves as abutment for the screw head. By such preassembly, loss prevention is additionally provided, because both during transportation and during their use at the construction site, the screws can not fall out of the tubular extensions of the large-area washers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional inventive characteristics and special advantages are further explained in the following description with reference to the drawings wherein: 
     FIG. 1 shows a section through a washer with tubular extension along the line  1 — 1  in FIG. 2; 
     FIG. 2 shows a top view of a large-area washer; 
     FIG. 3 shows a section along line  3 — 3  in FIG. 2; 
     FIG. 4 shows a longitudinal section through a large-area washer with tubular extension, in which the large-area washer is of substantially circular form; 
     FIG. 5 shows a section through several fixing elements in which screws are preassembled in the tubular extension of the large-area washers, with the fixing elements connected to each other in the manner of an screw strip; 
     FIG. 6 shows a top view of the screw strip according to FIG. 5; 
     FIG. 7 shows a section through a fixing element upon pre-insertion in an insulating strip or plate with an additional sealing strip. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The drawings show two different embodiments of large-area washers, namely washers of elongated shape on the one hand, and washers of circular shape on the other hand. However, the configuration of the washers  2  has no bearing on the present invention, so that the description also does not differentiate between them in this regard. Basically, all possible shapes are available. Thus, it is also possible to manufacture the large-area washer  2  and an extension  3  connected to it as separate components, which are subsequently joined firmly together or else are interlocked by interlocking shapes or friction. The washers  2  as well as their tubular extension  3  are usually made of plastic. It is also possible to make the tubular extension  3  of plastic and the large-area washer  2 , of metal, for example. 
     The fixing element  1  consists of a large-area washer  2  having a tubular extension  3  and a screw  4 . By means of such a fixing element  1 , insulating strips  5  or plates and potentially additional sealing strips  6  are to be fixed on a solid substructure. The screw  4  is provided with a thread  9  over at least a portion of the length of its shaft  8 , a boring portion  10  being formed at the free end of the screw  4  for penetration into the substructure  7 . At the other end, the screw  4  has a screw head  11 , whose top side  12  is lens-shaped. The underside  13  of the screw head is shaped like a truncated cone. 
     The tubular extension  3  has, at least over a large segment of its length, an inner cross-section sufficiently large for the rotational reception and axial displacement of the screw head  11 , i.e. an appropriately large diameter D. At the end of the tubular extension  3  facing away from the washer  2  there is formed an end segment  14  with a pass-through opening, which permits passage of the shaft  8  of screw  4  or of the thread  9  on shaft  8 . 
     In the segment of the tubular extension  3  in which the screw head  11  is axially displaceable, there is provided a rib  15  which extends radially inward into the slidable region, and which limits the range of movement of the screw head  11 . During preassembly of screw  4  in the tubular extension  3 , the screw head  11  is pushed downwardly across rib  15  in the direction toward the free end of the tubular extension  3 . As soon as the screw head  11  has surmounted the obstacle formed by rib  15 , rib  15  forms an abutment for the screw head  11  oriented against the screwing-in direction. In other words, the screw is restrained inside the tubular extension  3  oppositely to the screwing-in direction. 
     The preassembly is performed by appropriate tools or instruments such that the force required to overcome the projecting rib  15  presents no problem. Since the tubular extension  3  customarily consists of plastic, the rib  15  is elastically depressed during pushing-past of the screw head  11 . This is also promoted by shaping the underside of the screw head as a truncated cone transition. Thus it is quite possible that rib  15  extends in continuous circumferentially closed form around the entire portion of the interior wall. 
     Rib  15  is formed approximately in the middle of the length of the tubular extension. Depending on the length of screw  4 , or depending on the desired telescoping capability between the tubular extension  3  and the screw  4 , rib  15  can be formed either nearer to the free end of tubular extension  3 , or nearer to the large-area washer  2 . However, care must be taken that the distance A of rib  15  from the free end of tubular extension  3  is smaller than the overall length L of the screw including the boring portion  10  formed at its free end. This ensures that at least the boring portion  10 , but also portions of shaft  8  bearing thread  9 , will protrude beyond the free end of tubular extension  3 . 
     If a fixing element  1  of the preassembled type shown in FIG. 7 is available, the large-area washer  2  can be grasped by hand, for example, and then the boring portion  10  and with it also an appropriate corresponding segment of shaft  8  of screw  4 , can be pushed into the sealing strip  6  and the insulating strip  5  by pressing downwardly in the direction of arrow  16 . This enables pre-insertion of the fixing element  1  and its ultimate setting thereof by means of a driving-in tool. During pushing-in, rib  15  forms an abutment for screw head  11 , so that the force exerted during pushing down on the large-area washer  2  is transmitted to the screw head  11  and with it also to the free end of screw  4 . A preassembled fixing element  1  can also be processed advantageously in a setting machine. In that case, the projecting screw can sometimes be pushed into the substructure even before the screwdriver bit is operatively connected to the screw. 
     Such fixing elements  1  are preferably already preassembled during their manufacture, by inserting screws  4  into the tubular extension  3  of the large-area washers  2 . By the application of appropriate force, the screw head  11  can be pushed past the constriction formed by rib  15 , whereupon rib  15  serves as abutment for the screw head in one direction of movement. Nevertheless, a telescope-like movement is possible between screw  4  and the tubular extension  3 . By virtue of this, handling during pre-insertion is substantially improved, and loss prevention for the screw is also provided. 
     From FIGS. 5 and 6 it can be seen that several fixing elements can be connected to each other either contiguously or following each other at a small distance, into a kind of screw strip. In the example shown, mutual connections in the regions of large-area washers  2  are provided by webs  17  or tapes. 
     The foregoing description always referred to a rib  15  extending radially inward. However, it is also entirely possible to provide more than one rib  15 . In such a case, the screw head can be preassembled, for example between two ribs  15 , with the spacing of the ribs determining the range of axial movement between screw and tubular extension. Within the scope of the invention, there also exists the possibility of utilizing, instead of ribs, merely one or more burls, which can perhaps be surmounted more easily during preassembly of the screws but which provide nevertheless an adequate abutment during pre-insertion of the completed fixing element. To facilitate pushing-in of the screw head and nevertheless make an appropriately strong abutment against reverse movement, one possible adaptation is to provide the ribs, burls or the like with special cross-sectional shapes.