GB1566919A

GB1566919A - Anchors for fasteners

Info

Publication number: GB1566919A
Application number: GB1144977A
Authority: GB
Original assignee: ITW Ateco GmbH
Current assignee: ITW Ateco GmbH
Priority date: 1976-03-20
Filing date: 1977-03-17
Publication date: 1980-05-08
Also published as: ES226767Y; JPS52125669U; IT1077362B; ES226767U; JPS5819367Y2; CA1066177A; AU2119377A; FR2344739A1

Description

(54) ANCHORS FOR FASTENERS (71) We, ITW-ATECO GMBH, a Germany Body Corporate, of Stormarnstrasse 43-49, 2000 Norderstedt 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to anchors for fasteners, consisting of elastically deformable material having an outer contour serving to anchor the element in a workpiece opening and a reception opening co-operating with a fastener, preferably a screw.

Anchors in the form of push-fitting nuts, dowels or the like are known from many instances. They are normally inserted in a rough-bored opening of a workpiece and serve to receive a fastening element, preferably a screw, which is received in the reception opening of the anchor. Known plug-in type anchors are normally formed in one piece, and normally consist of a head and a shank portion, wherein the shank portion may comprise two or more legs which are urged apart against the wall of the opening when the fastener is driven into the anchor, and thereby the legs grip the wall of the opening to fasten the anchor securely in the workpiece.

The most frequently used anchor normally comprises two legs formed integrally with a head plate. When driving-in the fastening means such as a screw, the legs are urged outwards against the wall of the opening, with the screw being encompassed by the flexible legs only at segments of its circumference, the legs being urged against the screw through their own resilience only. The main disadvantage of known anchors, however, resides in that the axis of the screw hole has to coincide with the axis of the screw. It is only possible to insert a fastener obliquely with respect to the anchor shank if the axis of the screw hole is inclined to the anchor shank, but in this case problems arise, as the axis of the screw hole and the axis of the fastening means must coincide.

This requires careful angular positioning of the anchor to align the screw hole to the fastener.

The invention is based upon the problem of providing an anchor for fasteners, in which the fastener may be inserted obliquely into the anchor without the need for positive alignment between the anchor and the fastener.

According to the present invention, an anchor for a fastener includes a workpiece engaging outer part and a fastener engaging inner part, the inner part comprising a resilient thin-walled frusto-conical portion and a cylindrical tubular portion formed coaxially therewith and extending from the smaller diameter end thereof, the inner part being joined to the outer part at its end remote from the tubular portion.

With the anchor according to the invention, the fastener engages in the tubular portion of the inner part, the direction of introduction of the fastener, which, for example, may be a self-tapping screw, being from the wider to the narrower end of the conical portion of the inner part. As the conical portion is elastically deformable, there will result upon the screw being driven in the tubular portion a deformation of the conical portion which will be drawn in a direction towards the screw head and thereby will guarantee an encompassing of the fastening element depending upon the tightening force of the screw.To obtain the ability to introduce a fastening element at an oblique angle relative to the axis of the conical part, it is essential that the elastic deformability of the conical portion is sufficient that the tubular portion may, and preferably will, become aligned with the axis of the fastener positively upon the fastener being driven in. In connection with this there results a relatively great radial deflection of the narrow end of the conical portion which, however, will be possible only if there is nothing to obstruct the radial deflection.

An anchor has thus been provided which is capable of adapting itself to the respective oblique position of a fastener, for example a screw, while simultaneously well encompassing the screw. From this there results also a technical advantage, as a plug-in type anchor according to the invention no longer has to be exactly oriented with respect to the axis of the screw, as is the case with the previously used plug-in type anchors.

Provision is made in one further development of the invention for one outer part to be connected with the conical portion of the inner part through an axially limited connection, in such a manner that the inner part may be pivoted with respect to the outer part about axes perpendicular to the axis of the inner part. The outer and inner parts may be of different axial lengths depending on the workpiece with which the anchor is to be used, but with thinner workpiece panels, however, the outer part must extend a distance at least slightly in excess of the workpiece thickness.The conical portion, which may be either longer or shorter than the outer part, depending upon the purpose for which it is used, will be situtated radially within the outer part and will be connected with the latter through a pivotal connection only so as to guarantee deformability of the conical portion to receive an obliquely applied fastening element. The connection preferably is disposed at the wider end of the conical portion, because the strongest radial deviation of the conical portion takes place at the narrower end.

In accordance with another further development of the invention, provision is made for the conical portion to be of approximately equal wall thickness over its length. It is also possible, however, to vary the wall thickness over the length to obtain a sufficient degree of axial deformability of the conical portion, while ensuring a sufficient force of retention against withdrawal of the fastening element from the conical portion and also preventing the conical portion from turning inside out.

As already mentioned above, the conical portion is designed in such a manner that on the one hand it has a sufficient degree of inherent flexibility to adapt itself to the respective oblique position of a screw and that on the other hand it ensures a good grip on the screw threads. In this connection.

provision is made in the invention for the tubular portion to join the conical portion, the diameter of the tubular portion being preferably equal to the smallest diameter of the conical portion. A particularly effective encompassing of the screw, accordingly, takes place in the tubular portion.

It may indeed be imagined that the conical portion might be formed of several separate, elastically deformable branches or legs. In order to secure, however, a sufficient degree of strength, provision is made in accordance with another embodiment of the invention for the conical portion to be formed of a closed circumferentially extending conical wall which is weakened at circumferentially spaced intervals. In this manner there will be obtained an effective fastening of a screw while, however, the weakenings take care to avoid any tearing which might occur in the narrower portion caused by too high a tangential stress. In accordance with another further development of the invention the weakenings may be in the form of longitudinally extending grooves, said grooves preferably forming membrane-like elongation portions.In this arrangement the weakenings of the conical portion have a shorter peripheral length than the portions disposed therebetween.

The anchor according to the invention may be employed in workpieces of different materials, for example for an interconnecting construction for panels of wood, chip board or the like. In this connection, the invention in one embodiment thereof provides for the outer part to include an external wall formed with barbs. The barbs ensure an effective anchoring in a bore, for example, a blind bore in a wood panel. Such an anchoring, however, is important because the driving-in of the fastening element into the anchor does not contribute anything towards a reinforcement of this anchoring.

In order to secure the insert element against rotation, provision is made in another further development of the invention for the outer part to include a number of rows of barbs, the rows separated by flattened areas extending in parallel with the axis of the bore.

The last-described type of anchor is particularly suited for connections in furniture parts or the like. But there are quite a few cases of application where the anchor is to be inserted into an opening in a relatively thin workpiece such as a thin metal sheet. In this connection, provision is made in another further development of the invention for the outer part to comprise a head having a contact surface lying closely against the workpiece surface, and for locking means to be provided in addition which are adapted to be brought into engagement with the underside of the workpiece. Such a further development of the insert element according to the invention makes it possible to use self-tapping screws even in cases of application where they are not normally employed.

So that sufficient coverage of the fastening screw may be obtained, the axial length of the conical portion in case of insertion in an opening in a thin metal sheet or the like exceeds the thickness of the sheet in which the element is to be anchored. The interlocking of the anchor in the sheet in this case may again be effected in different ways. In one further embodiment of the invention provision is made for the locking means to comprise two or more spring legs having a shoulder facing the contact surface to engage the opening edge remote from the head. The spring legs in this arrangement secure the anchor to the sheet, in that the workpiece "is clamped in" by engaging both sides of the sheet.With another further development of the invention provision is made for the head to include two or more spring legs which are bent outwards and back again at the lower end thereof, and which by their free ends engage the opening edge remote from the head. With this embodiment, so-called expansion feet ensure a secure positioning of the anchor in the opening, with extraordinarily high clamping forces being obtained.

In all the cases where snapping feet or expansion feet are utilised to secure the anchor according to the invention, it is advantageous to provide radially extending arresting cams formed on the conical portion and/or on the head between the spring legs to permit a better positioning of the anchor in the opening.

A third method of securing the anchor in a panel is to provide a square embossment on the contact surface, the embossment being formed with another four projections forming a second square, the same size as the embossment but angularly offset by 45" with respect to the embossment and axially spaced therefrom. This embodiment in the first place is for square fastening apertures, with the anchor when inserted being positively interlocked in the aperture by rotation thereof through 45".

In the following, some examples of embodiment of the invention will be described in more detail with reference to the accompanying drawings, in which: - Figure 1 shows a sectional view of an anchor according to the invention in connection with a wooden panel; Figure 2 shows an end view of the arrangement according to Figure 1; Figure 3 shows a second panel connected with the panel shown in Figure 1; Figure 4 shows a sectional view of a second embodiment of the invention; Figure 5 shows a view taken in the direction of the arrow X in Figure 4; Figure 6 shows a sectional view of a third embodiment of the invention; Figure 7 shows a view of the anchor shown in Figure 6, taken in the direction of the arrow Y; Figure 8 shows a sectional view of a fourth embodiment of the invention; and Figure 9 shows a view of the anchor shown in Figure 8, taken in the direction of the arrow Z.

A wooden panel 10 according to Figure 1 is provided with a blind bore 11 having a plug-in anchor 12 inserted therein, with anchoring barbs 4 formed on a tubular outer part 13 securing the anchor in the bore 11.

Four flattened areas 5 (Figure 2) which are angularly offset from each other through 90" ensure a sufficient degree of resistance of the plug-in anchor 12 against rotation. An inner part 1, comprising a conical portion 15 having an opening angle a and a tubular portion 3 of constant diameter, is pivotally connected at its wider end to the outer part 13 through a connecting portion 14. The conical portion 15 defines a conical fasteneraccepting opening and joins at its narrower end a tubular portion 3, the diameter of the tubular portion being equal to the smallest diameter of the conical portion 15. The inner part 1 is composed of four segments 16 equally spaced from each other on the periphery and having about the same wall thickness in a longitudinal direction thereof.

Between the segments 16 there are membrane-like elongation portions which are formed by grooves 2.

Figure 3 shows second panel 17 likewise of wood, which possesses an oblique, stepped bore 18 with a screw 19 guided therethrough. The screw head 20 is received in the portion of the bore 18 of maximum diameter, while the lower region of the self-tapping shank 21 co-operates with the tubular portion 3 of the inner part 1, with the walls of the conical portion being strongly deformed because the screw strives to deform the elastic material in such a manner that the tubular portion is oriented parallel to the axis of the screw.

But there is yet obtained a high degree of coverage of thread due to the tubular portion 3, in particular, so that the workpieces 10 and 17 may be fixedly connected with each other.

Figure 4 and 5 show a sheet metal plate 22 with a square hole 23 to receive an anchor 24. The anchor includes an inner part 25 which is formed in a similar manner as the inner part 1 of the plug-in anchor shown in Figures 1 and 2. In the present case it is formed integrally with a substantially planar head 26, having a downwardly projecting square embossment 27 extending from a contacting surface on the underside thereof.

As will be seen from Figure 5, the head 26 further includes rectangular projections 28 defining another square, angularly offset by 45" with respect to the corners of the square embossment 27. Besides, the projections 28 are axially offset with respect to the square 27, so that by rotating the entire anchor 24 through 45 , the anchor may be positively interlocked in the square hole 23.

Figure 6 and 7 show an anchor 30 of a design similar to that according to Figures 4 and 5 as far as the inner part 31 and the head 32 are concerned. Resilient arms 7 extending from the undersurface of the head to secure the anchor in a sheet metal plate 33 having a square opening 34, the resilient arms 7 being each provided with a shoulder 35 facing the head to exert clamping forces from opposite sides of the sheet metal plate 33. As may be recognised from Figure 7, there are provided two diametrically opposed spring legs 7. Arresting cams 8 are provided at the two other sides of the anchor which come to lie closely against the walls of the opening 34 not abutted by the arms 7, so that the anchor 30 is effectively positioned.

Figures 8 and 9 show a sheet metal plate 36 provided with a square opening 37 having an anchor 38 inserted therein which again resembles the anchor shown in Figures 6 and 7. The inner part 39 too is of the same design as that shown in Figures 6 and 7, so that a more detailed description of this part may be omitted. Two diametrically opposed resilient arms 10 are provided to secure the anchor 38 in the opening 37, the arms each having a first part extending away from the head and a second part extending towards the head, arms 10 being positioned closely against the lower edge of the aperture. The resilient arms 10 permit of an extraordinarily easy assembly of the anchor to the panel, and are at the same time effective to bring about increased tightening forces due to the self-locking effect of the spring legs 10.

Arresting cams 9 on the two other sides of the anchor may be provided to ensure correct positioning in the square hole 37.

The material used for the anchor according to the invention must be sufficiently flexible and yet guarantee a high degree of strength. Therefore, synthetic plastics material is preferably used.

WHAT WE CLAIM IS: 1. An anchor for a fastener, including a workpiece engaging outer part and a fasten er engaging inner part, the inner part comprising a resilient thin-walled frusto conical portion and a cylindrical tubular portion formed coaxially therewith and extending from the smaller diameter end thereof, the inner part being joined to the outer part at its end remote from the tubular portion.

2. An anchor according to claim 1, in which the conical portion or the tubular portion of the inner part has circumferen axially spaced weakened section.

3. An anchor according to claim 2, in which the conical portion has weakened sections formed by grooves running parallel to its generators 4. An anchor according to claim 2 or claim 3, in which the weakened sections are of lesser circumferential extend than their intervening portions of the inner part.

5. An anchor according to any preceding claim, in which the workpiece engaging the outer part is a substantially tubular construction, coaxial with the inner part in the unstressed state.

6. An anchor according to claim 5, in which the outer part is formed on its outer surface with a number of barbs.

7. An anchor according to claim 6, in which the barbs are arranged in paraxial rows, there being radially flattened areas between the rows.

8. An anchor according to any of claims 1 to 4, in which the outer part comprises a substantially planar head and includes a radially extending contact surface, the head being further provided with locking means to secure the head to a workpiece.

9. An anchor according to claim 8, in, which the locking means comprises a number of spring legs extending substantially normally to the contact surface, at least one' of which legs is formed with a shoulder facing the contact surface.

10. An anchor according to claim 9, in: which each of the spring legs is formed with a first part extending substantially normally to the contact surface, and a second part extending from the free end of the first part towards the contact surface radially outward of the first part, the second part terminating.

at a position spaced from the contact surface.

11. An anchor according to claim 9 or claim 10, in which radially projecting arrest ing cams extend from the conical portion of the inner part, or from the outer part, at positions between the spring legs.

12. An anchor according to claim 8, in which the locking means comprises a square embossment on the contact surface, the inner part of the anchor lying within the square, the embossment being formed with four projecting portions which are of 'L' shape when viewed along the axis of the inner part, the four projecting portions

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. embossment 27. Besides, the projections 28 are axially offset with respect to the square 27, so that by rotating the entire anchor 24 through 45 , the anchor may be positively interlocked in the square hole 23. Figure 6 and 7 show an anchor 30 of a design similar to that according to Figures 4 and 5 as far as the inner part 31 and the head 32 are concerned. Resilient arms 7 extending from the undersurface of the head to secure the anchor in a sheet metal plate 33 having a square opening 34, the resilient arms 7 being each provided with a shoulder 35 facing the head to exert clamping forces from opposite sides of the sheet metal plate 33. As may be recognised from Figure 7, there are provided two diametrically opposed spring legs 7. Arresting cams 8 are provided at the two other sides of the anchor which come to lie closely against the walls of the opening 34 not abutted by the arms 7, so that the anchor 30 is effectively positioned. Figures 8 and 9 show a sheet metal plate 36 provided with a square opening 37 having an anchor 38 inserted therein which again resembles the anchor shown in Figures 6 and 7. The inner part 39 too is of the same design as that shown in Figures 6 and 7, so that a more detailed description of this part may be omitted. Two diametrically opposed resilient arms 10 are provided to secure the anchor 38 in the opening 37, the arms each having a first part extending away from the head and a second part extending towards the head, arms 10 being positioned closely against the lower edge of the aperture. The resilient arms 10 permit of an extraordinarily easy assembly of the anchor to the panel, and are at the same time effective to bring about increased tightening forces due to the self-locking effect of the spring legs 10. Arresting cams 9 on the two other sides of the anchor may be provided to ensure correct positioning in the square hole 37. The material used for the anchor according to the invention must be sufficiently flexible and yet guarantee a high degree of strength. Therefore, synthetic plastics material is preferably used. WHAT WE CLAIM IS:

1. An anchor for a fastener, including a workpiece engaging outer part and a fasten er engaging inner part, the inner part comprising a resilient thin-walled frusto conical portion and a cylindrical tubular portion formed coaxially therewith and extending from the smaller diameter end thereof, the inner part being joined to the outer part at its end remote from the tubular portion.

3. An anchor according to claim 2, in which the conical portion has weakened sections formed by grooves running parallel to its generators

4. An anchor according to claim 2 or claim 3, in which the weakened sections are of lesser circumferential extend than their intervening portions of the inner part.

at a position spaced from the contact surface.

defining the corners of a second square, the second square being the same size as the embossment and offset angularly by 45" therefrom.

13. An anchor according to any preceding claim, substantially as herein described with reference to Figures 1 to 3, Figures 4 and 5, Figures 6 and 7, or Figures 8 and 9 of the accompanying drawings.