GB2199883A

GB2199883A - Plastics fasteners

Info

Publication number: GB2199883A
Application number: GB08701135A
Authority: GB
Inventors: Ian Maynard
Original assignee: ITW Ltd
Current assignee: ITW Ltd
Priority date: 1987-01-20
Filing date: 1987-01-20
Publication date: 1988-07-20
Also published as: GB8701135D0

Abstract

A plastics fastener 10 comprises a generally planar clamping surface 12, a locating portion 14 extending axially from the clamping surface 12 and a generally planar anchor member 16 extending axially from the locating portion 14. The anchor member 16 lies generally perpendicularly to the clamping surface 12, being resiliently deformable and presenting a pair of radially opposed inclined clamping edges 18, each of which extends away from the clamping surface 12 whilst extending radially outwardly beyond a respective axially aligned part X of an outline of the locating portion 14. The anchor member 16 must be joined to the locating portion 14 radially inwardly of the outline of the locating portion 14 so that the parts X are spaced from the respective axially aligned parts Y of the clamping edges 18. The result is that the clamping edges 18 are sufficiently resiliently deformable at the parts Y to be secured to a large range of workpiece thicknesses even when the locating portion 14 is exactly complementary in shape to the workpiece aperture. <IMAGE>

Description

PLASTICS FASTENERS The present invention relates to plastics fasteners of the kind which are to be secured to apertures in panels or other sheet-like workpieces by a combination of pushing and turning.

Our associated Company's British patent 1,537,399 discloses a one-piece fastener of resilient plastics material, for application to a non-circular aperture in a panel, including a base portion having a face for abutting one face of the panel, a locating portion projecting from the said face of the base portion and of non-circular outline, when viewed in a direction perpendicular to the said face and towards the base portion, the locating portion being chamfered and thereby decreasing in thickness towards a minimum at extremities of its outline, and an anchor member projecting from the locating portion and having, when viewed in a direction perpendicular to the said face and towards the base portion, a largest dimension substantially equal in size to the largest dimension of the outline of the locating portion, these largest dimensions being angularly offset from each other, the anchor member having inclined shoulders, the dimension between which decreases towards the locating portion from the largest dimension of the anchor member to the width of the locating portion, and means by which the fastener can be rotated about an axis perpendicular to the said face of the base portion.

A disadvantage of that plastics fastener has been that if the workpiece aperture is larger than the outline of the locating portion then the locating portion is loose, whereas if the workpiece aperture is complementary in size to the outline of the locating portion then the anchor member can cope with only a small, if any, range of workpiece thicknesses.

In accordance with the present invention, however, a plastics fastener comprises a generally planar clamping surface, a locating portion extending axially from the clamping surface and a generally planar anchor member extending axially from the locating portion, the anchor member lying generally perpendicularly to the clamping surface, being resiliently deformable and presenting a pair of radially opposed inclined clamping edges, each of which extends away from the clamping surface whilst extending radially outwardly beyond a respective axially aligned part of an outline of the locating portion, characterised in that the anchor member is joined to the locating portion radially inwardly of the outline of the locating portion so that the axially aligned parts of the clamping edges and the outline of the locating portion are axially spaced apart from one another.

In use, the plastics fastener of the present invention is first orientated so that the anchor member can be inserted through a workpiece aperture of non-circular outline. If the workpiece aperture is square, the anchor member should extend between diagonally opposed corners of the square, whereas if the workpiece aperture is oval, the anchor member should extend along the major axis of the oval. Other shapes of workpiece aperture are possible, provided that the maximum radial dimension of the anchor member is both no greater than the maximum radial dimension of the workpiece aperture to permit the anchor member to be passed through the workpiece, and significantly greater than the minimum radial dimension of the workpiece aperture to permit the anchor member to be secured to the workpiece.The maximum radial dimension of the anchor member could equal the diagonal dimension of a- square aperture or the major axis dimension of an oval aperture.

To take full advantage of the present invention, the shape of the locating element should exactly complement that of the workpiece aperture.

The act of securing the plastics fastener of the present invention is a combination of pushing and turning. This results in the workpiece being sandwiched between the clamping surface and the clamping edges with the locating portion being located within the workpiece aperture. The angle through which the plastics fastener, and thus the anchor member, is turned will depend on the particular circumstances. if the workpiece aperture is square the anchor member should be turned through en eighth turn, whereas if the workpiece aperture is oval the anchor member should be turned through a quarter turn.

The fact that the clamping edges are both resiliently deformable and axially spaced from the axially aligned parts of the outline of the locating portion allows the clamping edges to be secured to a large range of workpiece thicknesses whilst avoiding looseness of fit in the workpiece apertures.

Preferably, the anchor member is penetrated by at least one aperture extending close to at least the clamping edges. This enhances the resilient deformability of the anchor member at the clamping edges and saves costby reducing even further the amount of required material.

Moreover the aperture could be used to hold another workpiece in the form of for example a wire or cable threaded through the aperture.

Although the clamping edges could be linear, more desirably they are arcuate, whilst still helping in the securing of the anchor member during the combined pushing and turning by acting as chamfering.

In a particularly preferred plastics fastener, according to the invention, there is a single aperture in the anchor member bounded by a peripheral rim which is generally D-shaped when viewed in a direction parallel to the clamping surface and perpendicular to the anchor member, the locating portion is of non-circular outline in radial cross section and the clamping surface forms one face of a plate element whose opposed face is formed with a support member, such as a cable clamp or a shelf carrier.

A plastics fastener, according to the present invention, will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of the plastics fastener; Figure 2 is a side view taken in the direction of the arrow A of Figure 1; and Figure 3 is an end view taken in the direction of the arrow B of Figure 2.

A plastics fastener 10 according to the present invention is shown as an integral moulding including a generally planar clamping surface 12, a locating portion 14 extending axially from the clamping surface 12 and a generally planar anchor member 16 extending axially from the locating portion 14. The anchor member 16 lies generally perpendicularly to the clamping surface 12, being resiliently deformable and presenting a pair of radially opposed inclined clamping edges 18, each of which extends away from the clamping surface 12 whilst extending radially outwardly beyond a respective axially aligned part X of an outline of the locating portion 14.

Most significantly, each of the clamping edges 18 has a part Y which is axially spaced apart from the respective axially aligned part X of the outline of the locating portion 14 as a result of the anchor member 16 being joined to the locating portion 14 radially inwardly of the outline of the locating portion 14. The axial spacings X - Y mean that the clamping edges 18 are not constrained in the immediate vicinity of the parts Y.

There is thus greater freedom for resilient deformation of the parts Y than would be the case if the clamping edges 18 were joined to the locating portion 14 at the outline of the locating portion 14. The result is that the clamping edges 18 are sufficiently resiliently deformable at the parts Y to be secured to a large range of workpiece thicknesses even when the locating portion 14 is exactly complementary in shape to the workpiece aperture.

The clamping surface 12 forms one face of a plate element 20 whose opposed face is formed with a double-pronged cable clamp 22 whose construction is of no relevance to the present invention other than in forming a convenient torque transmitting means during fastening.

The locating portion 14 is shown as having an oval outline 24 in radial cross section and the intention is that this oval outline 24 is exactly complementary in shape to that of an aperture through a workpiece to which the plastics fastener 10 is to be secured.

The anchor member 16 is of particular relevance to the present invention. It is required to be generally planar, meaning that some departure from a perfectly flat anchor member would be permissible. It includes an aperture 26 bounded by a peripheral rim 28 which is generally D-shaped when viewed in the direction of the arrow A, i.e. parallel to the clamping surface 12 and perpendicular to the anchor member 16. The peripheral rim 28 is of a generally uniform square cross section along its length but could be for example of circular cross section. Although straight part 30 of the peripheral rim 28 is shown as being at one axial extremity of the plastics fastener 10, this is not necessarily so, because the plastics fastener 10 could conceivably extend axially beyond the straight part 30 of the peripheral rim 28. It will be noted that the aperture 26 extends close to the clamping edges 18, that the peripheral rim 28 joins the locating portion 14 radially inwardly of the oval outline 24 of the locating portion 14, and that the anchor member 16 slopes away from the clamping surface 12 as the clamping edges 18 extend further radially outwardly. These features, both individually and in combination, result in the anchor member 16 being of a particularly cheap and simple yet effective construction which is easy to use.

In use, the anchor member 16 is inserted through an oval aperture in a workpiece before being both pushed and turned through a quarter turn to allow the locating portion 14 to snap into the oval aperture in the workpiece, whose position has been marked in phantom at 32 in Figure 2.

Claims

1. A plastics fastener comprising a generally planar clamping surface, a locating portion extending axially from the clamping surface and a generally planar anchor member extending axially from the locating portion, the anchor member lying generally perpendicularly to the clamping surface, being resiliently deformable and presenting a pair of radially opposed inclined clamping edges, each of which extends away from the clamping surface whilst extending radially outwardly beyond a respective axially aligned part of an outline of the locating porti.on, characterised in that the anchor member is joined to the locating portion radially inwardly of the outline of the locating portion so that the axially aligned parts of the clamping edges and the outline of the locating portion are axially spaced apart from one another.

2. A plastics fastener according to claim 1, in which the anchor member is penetrated by at least one aperture extending close to at least the clamping edges.

3. A plastics fastener according to claim 1 or claim 2, in which the clamping edges are arcuate.

4. A plastics fastener according to claim 2 and claim 3, in which there is a single aperture in the anchor member bounded by a peripheral rim which is generally D-shaped when viewed in a direction parallel to the clamping surface and perpendicular to the anchor member.

5. A plastics fastener according to any preceding claim, in which the locating portion is of non-circular.

outline in radial cross section.

6. A plastics fastener according to any preceding claim, in which the clamping surface forms one face of a plate element whose opposed face is formed with a support member.

7. A plastics fastener substantially as hereinbefore described with reference to the accompanying drawings.

8. A plastics fastener according to any preceding claim, when secured to a workpiece so that the workpiece is sandwiched between the clamping surface and the clamping edges, with the locating portion being located within a workpiece aperture which is complementary in shape to that of the locating portion.