IL39893A

IL39893A - Fixing element

Info

Publication number: IL39893A
Application number: IL39893A
Authority: IL
Original assignee: Fischer Artur
Priority date: 1971-08-17
Filing date: 1972-07-12
Publication date: 1974-11-29
Also published as: NO130549C; IL39893A0; DD98556A5; RO61294A; GB1376524A; DK133312C; PL82680B1; YU195372A; CA958263A; DK133312B; NO130549B; NL7211205A; IE36869L; AT315446B; US3837257A; CS161058B2; NL157086B; IE36869B1; JPS4831358A; AU4469372A

Description

Fixing element ARTUR FISCHER Artur Fischer 27 April 1972 7241 Tumlingen Zn/Ik PM 1226 The invention concerns a fixing element for fastening in a drill hole in concrete construction components, comprising a fixing screw, a wire spring as expandable sleeve, and a conical expansion body that can be inserted into the spring by means of the fixing screw.

When testing a known fixing element of this kind, it has been found that fastening which resists large extraction forces could not be achieved. Surprisingly* spring c Consequently, the fastening action was restricted to two, but in most cases to only one coil. Moreover, when an extraction force was applied, the coil that was pushed against the wall of the drill hole slid over the expansion body, so that the expansion body was inserted into the spring past the tensioned coil. No tensionin of the spring coils could be achieved in the zone of the mouth of the drill hole which, as is known, is often larger than the desired diameter, and not circular.

It is the object of the invention to provide a fixing element of the kind described above, that can be manufactured very simply and inexpensively and permits the application of large extraction forces in concrete construction elements without damage to the wall and which achieves, using only one spring, effective fastening over that region of the : sprin which is acted upon by the expansion body.

This is achieved according to the invention by winding the spring as a block spring, providing the expansion body at its insertion end with a collar, the outside diameter of which corresponds to the diameter of the drill hole, and arranging at the end of the spring opposite the insertion end a cap having two sections, one section protruding into the spring and the other section covering the front face of the spring.

To fasten the fixing element according to the invention, a bore is first produced, the diameter of which corresponds to the outside diameter of the spring. The fixing element is now inserted into the drill hole together with the expansion body and with the fixing screw, a few threads of which have been screwed into the expansion body. In hard concrete it is hardly possible to produce a perfectly cylindrical hole. Due to its elasticity, the spring, however, adapts itself to the wall of the drill hole and thus achieves, before the expansion body has been inserted, a bracing action which is sufficient to prevent the twisting of the fixing element in the drill hole when the expansion body is inserted. At the same time, the lower coils of the spring also exert a bracing action upon the expansion body, so that the latter cannot twist in relation to the sprin when the fixing screw is screwed in. -"'or fastening, the expansion body is now inserted with the fixing screw into the spring. aome coils are thus pushed radially outwards onto the wall of the drill hole by the cone of the expansion body. At the same time, the fixing element is shortened so that the remaining coils of the spring overlap and are thus clamped into the space between fixing screw and drill hole wall.

Only radial expansion forces are effective in the fastening of the fixing element according to the invention, and the expansion action and the pressure are uniformly distributed over a great length and circumference, independent of uneven and irregular zones of the wall of the drill hole. Through this so-called "soft fixing", locally increased surface pressures, which destroy the concrete structure, are avoided, and chipping is eliminated, so that break-out cones are not formed.

It is a further advantageous effect of the spring, that the expansion action increases with increasing extraction force t Tests even proved that after applying a first high extraction force, which was followed by a short wandering and renewed clutching of the fixing element, the load could be increased over the initial load. This factor, which is essential for the safet of the fastening, thus meets a demand repeatedly made for considerations of statics.

• Due to the uniform pressure distribution of the fixing element and due to the absence of a chipping action, a drill hole of small depth suffices for effective fastening, for example for supporting suspended ceilings, tubes etc In the case of the fixing element according to the invention, the spring is the dowel- sleeve and the expansion sleeve, that is the dowel body. Without impairing the function of the dowel, it is thus possible to shorten the length of the dowel by cutting the spring wire. It is thus possible for the first time, to adapt, by cutting its expansion sleeve, a metal dowel to any drill hole depth and to any purpose.

The cap serves for guiding the spring and, moreover, prevents jamming and tilting of the first coil in the bore of the object to be fixed.

According to one embodiment of the invention, the spring may be wound from soft wire, in particular from copper wire.

This method/facilitates the insertion of the expansion body into the spring, because a soft wire can be easier widened by the expansion body.

Advantageously, the spring may be wound right-handed. Due to its elasticity, the spring pushes against the cone of the expansion body in such a manner that in normal conditions the expansion body cannot twist in relation to the spring. If, however, this should happen, for example when the thread of the fixing screw is damaged, the spring with the coils in contact with the expansion body is also twisted. In the case of right-handed winding, however, the spring would then contract and increase the pressure upon the expansion body to such an extent, that the action which prevents twisting is again fully effective.

Further, the end of the wire at the insertion end of the spring may be bent outwards, When the fixing screw is screwed in, this wire end engages with the wall "of the drill hole and thus also contributes to the prevention of spring twist in relation to the drill hole.

According to another advantageous enitodiirent of the invention,., the expansion body may contain at the end opposite its insertion end a cylindrical attachment, the outside diameter of which corresponds to the inside width of the spring. This attachment serves fo centering the expansion body in the spring.

According to a further development of the invention, a collar that engages in the coils of the spring may be arranged at the attachment. This collar advantageously contains a thread.

The expansion body can thus be screwed into the spring without the possibility of being lost, so easily possible to unscrew the fixing screw from the expansion body after the fixing element according to the invention has been fastened.

Finally, at least part of the attachment may be roughened by knurling. This construction increases the friction between the spring and the expansion bod still further, so that twisting of the expansion body in relation, to the spring is excluded.

Without departing from the idea underlying the invention, it is also possible to set off the thread section of the fixing screws in such a manner that the outside diameter of the spring corresponds to the shaft diameter of the fixing screw.

This construction permits. push-through assembly, which saves time and expense. In order to increase the expansion effect, the end of the shaft of the fixing screw may in addition be conically tapered in the direction of the thread section, so that the spring is braced between the cones of the expansion body and the fixing screw opposite one another.

In the same manner, the section of the cap that protrudes into the bore of the spring may be tapered in the direction of the insertion end.

The fixing element thus consists of a spring and two opposed cones as expansion bodies bracing the spring in the drill hole. The spring itself forms a dowel body that can be widened. By screwing in the fixing screw, the expansion bod i is drawn in the direction of the cap provided with a cone, which is supported by the object to be fixed. The reduction of the gap between the two opposite cones effects a shortening of the spring, the coils of which are thus pushed against the wall of the drill hole. Moreover, the two cones penetrate into the bore of the spring and further widen the spring. Two factors are thus essential for the fastening of the fixing element, which by their cooperation contribute to the achievement of retention values by means of the fixing element according to the invention, far surpassing those of known fixing elements 0 According to another advantageous embodiment of the invention, a cylindrical attachment may be connected to the oone of the cap, the outside diameter of which attachment corresponds to the inside width of the spring. This attachment serves for centering and guiding the spring.

According to a further embodiment, a collar which engages in the coils of the spring may be arranged at the attachment.

\ By means of this collar, the cap is connected with the spring without the possibility of being lost.

As a rule, the fixing element is mounted flush with the wall. Since the outside diameter of the fixing screw to be screwed into the expansion body is smaller than the outside diameter of the fixing element, this means, that the fixing screw is free in the object to be fixed.

Besides the fact that the object to be fixed has thus no support, the fixing element also lacks a counter bearing when the expansion body is drawn in by means of the fixing screw, due to the equality :: of the drill hole diamters in the wall and in the object to be fixed, which counter bearing should prevent the withdrawal of the fixing element from the drill hole.

These drawbacks are obviated in an advantageous embodiment of the invention by extending the section of the cover sleeve which covers the spring.

Before the fixing element according to the invention is fastened, a hole is drilled into the wall through the object to be fixed, the diameter of which hole corresponds to the outside diameter of the fixing element. Without having to remove the object to be fixed from the wall, the fixing element may be inserted to such an extent that its upper end is flush with the outer surface of the object to be fixed. By drawing in tfte expansion body by means of a stay bolt and a nut, or, respectively, a cap screw, the fixin 'element is fastened in the drill hole and the object is strained to the wall.

In an advantageous embodiment, the extended section of the cover sleeve may be provided with a surrounding incision in the shape of saw teeth which has a distance from the front end of the fixing element that preferably corresponds to the thickness of an object to be fixed. The reduction of the cross-section caused by this incision has the result that an upset occurs , when the fixing screw is screwed in further or the nut is tightened further after the fastening of the fixing element, in the zone of the change of the cross-section, which upset 1 enables the object to be fixed to be braced particularly rigidly to the wall.

The incision has the further advantage that the section which is separated by this incision from the cover sleeve can be knocked off when not used. This is desirable when, for example, the thickness of the object to be fixed is very small* In mass production it is expedient to restrict the distance of the incision from the upper end of the fixing element to a few sizes. As a rule, it will nevertheless be possible to find the appropriate dowel for each object to be fixed. Variations of the thickness of the object to be fixed from the selected distances of the recess may be compensated by lowering the fixing element.

The necessity of tightening the contac of the construction part to be fixed with the surface of the concrete construction by. corresponding tightening of the -nut or screw after the fixing element has been fastened in the depth of the drill hole, pre-supposes a further penetration of the extended cover sleeve into the drill hole, because in the case of a push-through assembly, as is known, the cover sleeve is in contact with the nut or the head of a fixing screw.

By further developing the invention, this can be achieved by providing that the major part of the coils forming the spring are in the non-expanded state in immediate contact with one another in the manner of a block spring, while the remaining part of the coils, which faces away from the expansion body, has coils at a distance from one another.

In this embodiment, the part of the spring wound in the manner of a block spring is first widened by drawing in the cone by means of the fixing screw and is thus braced against the wall of the drill hole.

The block spring-type part of the spring is stationary fastened in .the drill hole even through this bracing. When the expansion body is drawn in further, the fastening is further reinforced, on the one hand, while on the other hand the cover sleeve is now drawn into the drill hole to such an extent that the coils previously not in contact are now in contact.

When this state has been reached, the fastening of the fixing element in the depth of the drill hole, as well as the bracing of the constructional part to be fixed between the head of a screw or the nut of a screw bolt and the surface of the constructional part are completed. . " Accordin to a different embodiment of the invention, the bracing of the constructional part to be fixed can be achieved by providing the extended cover sleeve with a short widening of the bore, beginning at its free end face.

Through this widening of the bore, the extended cover sleeve acquires in the zone of its free end face a region of reduced wall thickness which can give way after the fastening of the fixing element in the drill hole and when the fixing screw or the fixing nut are further tightened, so that in this embodiment too, a bracing of the constructional component to be fixed to the surface of the construction is made possible. The region of reduced wall thickness carries the further advantage that when a stay bolt with fixing nuts is used and the drill hole has inadvertently been drilled oblique, complete contact of the fixing nut and the surface of the constructional part to be fixed can nevertheless be achieved. The region of the reduced wall thickness has then partially given way so that he- ".··.... nut can take up a position perpendicular to the axis of the bore, the stay bolt being given a slight deflection in that its end protruding from the bore hole is bent in the direction of the. axis of the bore.

The retention values of the fixing elements could be increased still further if a better pressure distribution in the zone of the expansion body can be achieved and, moreover, sliding over expansion body of the coils is prevented when the expansion body is drawn in.

This is achieved by arranging between the cone and the collar of the expansion body a cylindrical section with a diameter corresponding to the largest diameter of the cone, the length of which suffices for taking up at least one coil of the spring.

By means of the cylindrical section, the outside diameter of which corresponds to the largest diameter of the cone, several coils are widened to the same outside diameter, so that several coils are pressed with maximum pressure against the wall of the drill hole. This results in further, improvement of the pressure distribution, which increases the retention values. The collar at the insertion end of the expansion body, corresponding to the outside diameter of the drill hole, prevents a further sliding back of the spring, so that the other coils too contribute to the fastening of the fixing element by the shortening of the spring. Two factors are thus essential for the fastening, the cooperation of which makes the achievement of high extraction values possible.

The increase in the retention values of the fixing element depends substantially upon the. length of the cylindrical section. An increase may be achieved by a length of the section which suffices for taking up one coil. Tests have proved, however, that an optimum value is achieved when the cylindrical section permits two to four coils to be taken up..

The drawings show embodiments of -the invention by way of example Fig. 1 shows the fixing element according to the invention, inserted into a concrete construction component, Fig. 2 a special construction of the expansion body, Fig. 3 a fixing element according to the invention of differen construction, inserted into a concrete construction component, 1 Fig. 4 an embodiment permitting push-through assembly, Fig. 5 a special construction of the cap, Fig. 6 an embodiment of the fixing element having an ' extended cap, ' Fig. 7 a special construction of the free end of the cap, Fig. 8 a special construction of the spring and Fig. 9 a special construction of the expansion body.

The fixing element according to the invention shown in Fig. 1 consists of a spring 1 wound from wire as block spring and a fixing screw 3 engaging in an expansion body 2. By screwing the fixing screw 3 into the conical expansion body 2, the latter is drawn into the spring 1. The lower coils of the spring 1 are thus widened and pushed onto the wall o the drill hole.

The expansion body 2 further contains at its insertion end a collar 4, the outside diameter of which corresponds to the diameter, of the drill hole. A cap 5 is set upon the rear end of the spring 1, one section of which protrudes into the bore of the spring 1, and the other section of which covers the front face of the spring 1. This prevents the first coil of the spring from jamming or tilting in the drill hole of an object 6 to be fixed. The coils of the spring 1 adapt themselves to the irregular form of a drill hole 7 in the concrete construction component 8 and thus prevent by their intrinsic tension force a twisting of the spring 1 when the fixing element is fastened.

The expansion body 2 shown in Fig. 2 contains at its end opposite the insertion end an additional cylindrical attachment 9, the outside diameter of which corresponds to the inside width of the spring 1. A collar 10 is arranged at the front end of the attachment, which collar engages in the coils of the spring.

This collar 10 is advantageously formed as a thread.

In the embodiment according to Pig. 3f the cap 5 contains two sections 5a, 5b, the section 5a protruding into the bore of the spring 1 and the section 5b covering the frontface of the spring 1. The section 5a which protrudes into the bore of the spring 1 is conically tapered in the direction of the expansion body 2. When the expansion body 2 is drawn in, the spring 1 is thus braced between the two opposite cones of the expansion body 2 and the cap 5 by means of the fixing screw 3· The cap 5 is supported by the object 6 to be fixed and thus prevents a withdrawal of the spring 1.

Pig. 4 shows an embodiment, in which the section 3a of the fixing screw,which section engages in the expansion body 2, in the spring 1 and in the cap 5, is set off. The outside diameter of the shaft 3b of the fixing screw 3 corresponds to the outside diameter of the spring 1. When the expansion body 2 is drawn in, the cap 5 is in this embodiment supported by the front face 11 of the shaft 3b of the fixing screw 3» It is also possible to manufacture in this case the cap and the fixing screw in one piece.

The cap 5 shown in Fig. 5 contains as extension of the cone an additional cylindrical attachment 12, the outside diameter of which corresponds to the inside width of the spring 1. A collar 13 is arranged at the front end of the attachment, which collar engages in the coils of the spring 1. This collar is advantageously formed as a thread.

According to Pig. 6, the section 5b of the' cover sleeve 5 is extended and serves for the support of the object 6 to be fixed. The fact that the outside diameter is uniform over the entire length of the fixing element: makes push-through assembly possible, in which the same drill hole diameter is required in the object to be fixed and in the wall 8.

The surrounding saw tooth-shaped recess 20 sub-divides the extended section 5b of the cover sleeve 5 into two parts, the length of the upper part 5c corresponding approximately to the thickness of the object 6 to be fixed. The saw tooth-shaped recess 20 serves on the one hand as knock-off notch for the other · upper part 5c and on the/hand as upsetting zone which should render it possible, that the fixing screw 3 can be drawn, after the fastening of the fixing element, in the direction of the wall for bracing the object 6 to be fixed.

Fig. 7 shows another construction of the recess 20, which is easier to manufacture. In this case, the free front end of the cover sleeve is provided with a widened bore 23 which ensures a lower wall thickness of the cover sleeve in the zone of the front end. In the zone of the reduced wall thickness, the cover sleeve may give way in axial direction when an axial force is applied by crumpling.

Fig. 8 shows a special embodiment of the spring. In the non-expanded state, the major part of the spring contains coils which are in immediate contact with one another in the manner of block spring, while the remaining part 21 of the coils, which faces away from the expansion body 2, shows a distance between the coils « The cover sleeve 5 can be mo ed in the direction of the expansion body 2 by the total amount of the distances between the coils of the smaller part 21.

In Pig. 9, the expansion body 2 contains a cone 30 and at its insertion end a collar 4, the outside diameter of which corresponds to the diameter of the drill hole 7. A cylindrical section 31 for taking up at least one coil of the spring 1 is arranged between the cone 30 and the collar 4, the diameter of which section 31 corresponds to the largest diameter of the cone. A head screw or a stay bolt with nut may selectively be used as fixing screw 3.

Claims

1. A fixing element for fastening in a drill hole in concrete construction components, consisting of a fixing screw, a wire spring as expandable sleeve, and a conical expansion hpdy^which can be drawn into the spring by the rfixing sorew, wherei ■the spring is wound as block spring, the expansion body \ oontains at its insertion end a 'collar,J;. i! the ■:out-side ' * diameter of which corresponds to the diameter of the drill hole a cap ! containing two sections being arranged at the -end of the sprin ! opposite the insertion end, one section" υ· protruding into the springj ϊ and the other section covering the front, face of t e spring,, *■· -

2. A fixing element as claimed in claim 1, wherein the spring is wound from soft wire, in particular copper wire. ^ . „■

3. A fixing element as oiaimed in claim 1, wherein the expansion body j contains at the end opposite its insertion end a cylindrical attachment, ; . the outside diameter of . .which corresponds to the inside width of the spring.

4. A fixing element as claimed in claims 1 and.3, wherein a collar 1 is arranged at the . attachment, | _ which cellar engages in the coils of the spring. ~ ~ "■■ ■ ·

5. A fixing element as claimed in claims 1 and' 3i wherein at least a part of the attachment ,) is roughened, in particular, roughened by knurling,

6. A. fixing element as claimed in claim 1,, wherein that part of the fixing screw < '/which engages in the springv ; and the expansion body . is set off, and the outside diameter of that part of the^ fixing screw;, . ' which remains outsider the sleeve equals the outside diameter · of the non-expanded spring^ .; . - ' .. ·.'.

7. » A fixing element a,s claimed in claims 1 and.6, wherein the end of the par of the fixing screwL which remains outside the spring, positioned opposite the head^of :*iihe fixing screw ' ,; !is conically tapered in .the direction of the expansion body,

8. A fixing element as claimed in olaim 1, wherein the sectio ! of the cap that protrudes into the bore of the spring jis tapered in the direction of the insertion end. . - ■■' ...'

9. A fixing element as claimed in ci'aira 8, wherein a cylindrical attachment is connected to the cone,, the-, outside diameter of which attachment corresponds to the inside ■ width of the spring^ ~ '~ '

10. A fixing element as claimed in claims 8 and 9i wherein ,. a collar · I which engages in the coils of the spring;' is arranged at the attachment/ .

11. A fixing element as claimed in claim 1, wherein the section · of the' cover sleeve which covers the spring . is extended . .' . · I I · . . ·-»··»

12. A fixin element as claimed in claim 11, wherein* the ' extended section I of the cover sleeve : is provided with a surrounding, in particular, saw tooth-shaped, recess,, which has a' distance from the upper end of the fixing element ; that preferably correspond to the thickness of an object' · to be fixed. . .. · .

13. A fixing element as claimed in claim 1, wherein the major part j of the coils forming the spring- are in the non-expanded state in immediate contact in the manner of a, block spring, whereas the remaining part of the coils, facin away .from the expansion body ' are at a distance from one another.