GB2077845A

GB2077845A - Plastics Drive Fasteners

Info

Publication number: GB2077845A
Application number: GB8118360A
Authority: GB
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 1980-06-16
Filing date: 1981-06-15
Publication date: 1981-12-23
Also published as: DE3122402A1; NZ197233A; FR2484566A1; ES258987U; ES258987Y; IT1138397B; DE3122402C2; CA1183707A; GB2077845B; AU7087581A; BR8103489A; IT8122314A0; FR2484566B1; AU540179B2

Abstract

A fastener 10 has a shank 14 presenting four surfaces 16. An opposed pair of the surfaces 16 have respective rows of radially extending wings 18 and the other two surfaces 16 have respective rows of angled wings 30. Although the wings 18 flex about straight lines at their junctures with the surfaces 16, the wings 30 flex about straight lines 36 spaced radially from the surfaces 16 because of thickened sections 34. This substantially increases the force required for removal of the fastener from an apertured workpiece as compared to the force required for introducing the fastener. <IMAGE>

Description

SPECIFICATION One-piece Plastics Drive Fasteners One-piece plastics drive fasteners, while suitable for many applications, have hitherto suffered from a problem. The problem has been that the insertion force for installing the fastener in an apertured workpiece is generally equal to the force required for subsequent removal of the fastener. In some applications it would be desirable to provide a fastener which could be readily installed but which would require a much greater force to be removed.

According to the present invention, a one-piece plastics drive fastener comprises at least one head and an axially extending shank presenting at least one radially outwardly directed generally planar surface, a plurality of axially spaced resilient wings extending outwardly from the or at least one of said surfaces, with at least some of said wings being angularly disposed so as to slope towards the head or heads and being formed with respective means substantially to increase the force required for removal of the fastener from an apertured workpiece, by flexing said angled wings, in comparison with the force required to introduce the fastener into that apertured workpiece Preferably, each of said means includes a knuckled portion to provide a bend line substantially parallel to but spaced radially outwardly from the juncture of the angled wing with its associated surface.The bend line may be spaced from said juncture by a distance generally 1/3 to 1/2 of the length of said angled wing. Moreover, the knuckled portion may include a thickened section at said juncture. The thickened section may span the acute angle between the angled wing and its associated surface, and extend along said associated surface up to the juncture thereof with another of said angled wings closer to the head or heads.

The fastener of the present invention is also preferably such that: the shank has a generally polygonal portion presenting a plurality of said radially outwardly directed generally planar surfaces; each of said surfaces has a plurality of said wings extending outwardly therefrom; and said wings on at least one of said surfaces are all formed as said angled wings.

If said polygonal portion is four-sided, said angled wings may be located along an opposed pair of said sides, with the remaining ones of said wings being located along the other opposed pair of said sides.

As in our British Patent 1,451,009, at least one axially extending pathway is preferably provided between said wings on an adjacent pair of said surfaces, to accept an operating tool, and said wings on at least one of said surfaces are preferably axially offset from said wings on the remaining ones of said surfaces, to provide a variety of grip lengths.

There may be two, or three, of the heads maintained in spaced relation adjacent one end of the shank, whose other end may have any suitable entry or nose configuration.

Finally, the fastener of the present invention is preferably such that it can be economically moulded in a simple two-plate mould.

A fastener in accordance with the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front view of the fastener in accordance with the present 'invention; Figure 2 is a cross-section taken along the line 2-2 of Figure 1; Figure 3 is a cross-section taken along the line 3-3 of Figure 2; Figure 4 is a fragmentary enlarged cross-sectional view showing the junctures of the angled wings with the shank of the fastener of Figure 1; Figure 5 is a front view of a prior art fastener; Figure 6 is a fragmentary view of a fastener having angled wings but not falling within the scope of the present invention; Figure 7 is a fragmentary view similar to Figure 6 but of the fastener of Figure 1; Figure 8A is a schematic view of the wings of the prior art;; Figure 8B is an intermediate development of the type shown in Figure 6; and Figure 8C is a schematic view of the wings of the fastener of Figure 1.

The present invention relates to a one-piece plastics drive fastener which can be readily installed into an apertured panel or a bore within a thick panel, yet where the removal force is far in excess of the force of installation, an embodiment of such a fastener being shown in Figures 1 to 4, 7 and 8C.

An example of a one-piece plastics drive fastener 10 of the improved variety contemplated by the present invention includes a head 12 and a shank 14.

While the head 12 is shown as being a domed ceiling head, it should be recognised by those skilled in the art that other forms of head are possible. Indeed, the fastener can have a single head 12 or may include a multiplicity of axially spaced heads, of the type normally used to fasten trim panels to automotive door interiors. The shank 1 4 has a generally non-circular or polygonal portion which provides a plurality, for example four, axially extending generally flat surfaces 1 6. Normally, any equal number of flat surfaces is preferred.

Extending outwardly from an opposed pair of the flat surfaces 16 is a plurality of axially spaced flexible resilient wings 1 8, each of which is provided with a generally tapered undersurface 20 and a radially extending upper surface 22, as best seen in Figure 2. Along the other opposed pair of the flat surfaces 1 6 is a plurality of further flexible resilient wings 30, which are angular disposed relative to the axis of the shank 14 and slope upwardly towards the head 12, as best seen in Figure 4.

Unlike in the prior art fastener shown in Figure 5, where all of the wings are similar to the wings 18, and unlike in the intermediate development shown in Figure 6 including angled wings 32, the angled wings 30 incorporated in the fastener 10 of the present invention do not flex along straight lines formed at their junctures with their associated surfaces 1 6.

Each of the angled wings 30 of the fastener 10 of the present invention has a knuckle portion 34 in the form of a thickened section at its juncture with the associated surface 1 6. As best seen in Figure 7, this results in the angled wings 30 having bend lines 36 which are generally parallel to the associated surface 1 6 but are radially spaced outwardly therefrom. In essence, this creates short stubby wings 30 that can be readily inserted into an aperture or bore but which resist with great tenacity the removal of the fastener from the aperture or bore.

Tests were conducted on various configurations of wings and comparative measurement taken showing the forces required to push the fastener in and to pull the fastener out. The figures are displayed with reference to the wing configurations shown in Figures 8A, 8B and 8C, the latter being the embodiment of the present invention.The test results are as follows:- Fig. 8A Fig. 8B Fig. 8C In Out In Out In Out 24 32 10 18.5 30 75 21 23 11.5 14.5 35 75 20 23 11 16.5 20 70 19 22 10.5 13 25 80 24 21 10.5 15 25 82.5 22 21 10 14.5 35 65 22 23 10.5 12.5 25 87.5 22 20 10 12.5 20 75 21 19 10 12 22.5 75 20 18 10 12 27.5 72.5 Averages 21.5 22.2 10.4 14.1 23.8 75.8 Remo valfinsertion Ratios 1.0 1.4 3.2 As will be noted there is a dramatic unexpected result for the fastener of the present invention as shown in Figure 8C.

It will be recognised that the amount of force for removal can be controlled dependent upon the number of the surfaces 1 6 provided with the angled wings 30 having the knuckle portions 34. All of the surfaces 1 6 could utilise such wings 30. However, where only one or two surfaces 1 6 are provided with wings 1 8 and/or 30, it has been found desirable to provide means, such as an axially extending rib (not shown) to locate the fastener for optimum operating conditions relative to the cooperating aperture or bore.

The wings 1 8 and/or 30 need not necessarily extend over the entire width of the surfaces 1 6. If the wings 1 8 are less wide than their associated surfaces 16, as best seen in Figure 3, four axially extending pathways 40 will be provided for accepting an axially extending tool. Moreover, the wings 18 and/or 30 need not necessarily all lie in the same level. For example, as best seen in Figure 1 , the wings 1 8 may lie in different levels from the angled wings 30, to provide a variety of grip lengths.

The free end of the shank 14 may be blunt or rounded, or may have a nose portion 44 which is arrow-shaped, pointed or of some other configuration as desired.

Claims

1. A one-piece plastics drive fastener comprising at least one head and an axially extending shank presenting at least one radially outwardly directed generally planar surface, a plurality of axially spaced resilient wings extending outwardly from the or at least one of said surfaces, with at least some of said wings being angularly disposed so as to slope towards the head or heads and being formed with respective means substantially to increase the force required for removal of the fastener from an apertured workpiece, by flexing said angled wings, in comparison with the force required to introduce the fastener into that apertured workpiece.

2. A fastener according to Claim 1, in which each of said means includes a knuckled portion to provide a bend line substantially parallel to but spaced radially outwardly from the juncture of the angled wing with its associated surface.

3. A fastener according to Claim 2, in which said -bend line is spaced from said juncture by a distance generally 1/3 to 1/2 of the length of said angled wing.

4. A fastener according to Claim 2 or Claim 3, in which each of said knuckled portions includes a substantially thickened section at said juncture of the angled wing with its associated surface.

5. A fastener according to Claim 4, in which said thickened section spans the acute angle between the angled wing and its associated surface.

6. A fastener according to Claim 5, in which said thickened section extends along said associated surface to the juncture of said associated surface with another of said angled wings closer to the head or heads.

7. A fastener according to any preceding claim, in which the shank has a generally polygonal portion presenting a plurality of said radially outwardly directed generally planar surfaces.

8. A fastener according to Claim 7, in which each of said surfaces has a plurality of said wings extending outwardly therefrom.

9. A fastener according to Claim 8, in which said wings on at least one of said surfaces are all formed as said angled wings.

1 0. A fastener according to Claim 9, in which said polygonal portion is four sided, with said angled wings being located along an opposed pair of said sides, and the remaining ones of said wings being located along the other opposed pair of said sides.

11. A fastener according to any one of Claims 8 to 10, in which at least one axially extending pathway is provided between said wings on an adjacent pair of said surfaces.

1 2. A fastener according to any one of Claims 8 to 11, in which said wings on at least one of said surfaces are axially offset from said wings on the remaining ones of said surfaces.

13. A fastener according to any one of Claims 1 to 12, in which there are two of the heads maintained in spaced relation adjacent one end of the shank.

14. A fastener according to any one of Claims 1 to 12, in which there are three of the heads maintained in spaced relation adjacent one end of the shank.

1 5. A fastener according to Claim 1 and substantially as hereinbefore described with reference to Figures 1 to 4, Figure 7 and Figure 8C, of the accompanying drawings.