GB2249804A - Stud fastening device. - Google Patents

Abstract

Fastening device has a headed or other male element (10) having a stem (14) provided with serrations (18) including a series of locking faces (20) directed away from its free end (22); and a mating female element (16) having an annular radially outer skirt (26) whose free edge (28) abuts the face of an article to be secured and which is connected to a stem gripping porting portion (32) by a resilient bridging formation (30), the gripping portion comprising resilient limbs (34) whose ends abut the locking faces to resist withdrawal of the stem once engaged with said skirt abutting the article face and the bridging formation flexed to provide a clamping force.

Description

FASTENING DEVICE This invention relates to fastening devices and has as its object the provision of a fastening device which is economical to produce, simple, and speedy to assemble.

According to the invention there is provided a fastening device comprising interengageable male and female elements, the male element having a stem at least part of which is formed to provide serrations in a lengthwise series and defined by locking faces each constituting an abutment directed away from the operatively free end of the stem and camming faces each tapering in girth toward the free end; and the female element having a skirt portion with a free edge directed endwise to abut a face of an article to be operatively secured by the device and a stem gripping portion spaced within the skirt portion and linked to the latter by a resilient bridging formation, said gripping portion including a plurality of internal resilient limbs having free ends bounding a stem receiving aperture and directed away from said free edge of the skirt portion, whereby said free end of the stem may be engaged through said aperture with the free edge of the skirt portion directed away therefrom, the camming faces permitting the resilient limbs to spring along the serrations in a direction of engagement until the free edge of the skirt portion is urged into clamping abutment with said article face by flexing of the bridging formation but disengagement is resisted by snap engagement of the free ends of the resilient limbs with a said locking face or faces of the serrations.

Conveniently the stem will be circular in cross section throughout its length and the female element will be annular or toroidal in generally overall form.

The male element may include a head formation at the end remote from the free end of the stem, thus the two elements would be used in the manner of a nut and bolt but it will be appreciated that either element may take a variety of forms, e.g. the male element may take the form of a stud anchored to or integral with a component or other article or carrying other fastening or attachment means.

It is contemplated that the male element could include a second matching or different stem portion for receiving a second female element to act in opposition to the first said element e.g. in the manner of a non-headed length of threaded studding with which nuts are engaged from its opposite ends.

Preferably both the male and female elements are mouldings of plastics material though it is also contemplated that one or other, or both, elements could be formed in other ways and/or of other materials such as metal.

An example of the invention is now more particularly described with reference to the accompanying drawings, wherein Figure 1 is a part sectional view of a fastening device in securing condition; Figure 2 is a side elevation of a male element of said device; Figure 3 is a plan view of a female element of said device, and Figure 4 is a cross section on line 4-4 of Figure 3.

The fastening device comprises a bolt-like male element 10 having a head 12 at one end from which extends a coaxial stem 14; and a nut-like female element 16 engageable with said stem in securing condition as shown in Figure 1.

Stem 14 is, in this example, of circular section and of uniform overall diameter throughout its length and is formed, e.g. by moulding plastics material from which the whole of both elements are made to provide a series of serrations 18, in this example along its entire length.

Each serration 18 is defined by a locking face 20 on a respective diametral plane and directed towards head 12 and away from the free end 22 of the stem, and a part conical camming face tapering in diameter towards free end 22.

The female element 16, also a moulding of plastics material, is generally annular in form and includes a cylindrical skirt portion 26 having a free edge 28 constituting one end of the element. The opposite end part of said portion merges with an annular bridging formation 30 which is of reduced thickness so that it is resilient and which, in the free or undeformed condition shown in Figure 4, tapers radially inwardly to merge with a central stem gripping portion 32 of element 16 which is spaced concentrically within skirt portion 26.

Gripping portion 32 comprises a plurality, in this example three, internal resilient limbs 34 disposed equiangularly about the axis of the element and having their free ends 36 directed away from the plane of the free edge 28 of skirt portion 26, a central stem receiving aperture being defined therebetween.

The operation of the device is as follows. Assuming that it is wished to secure together a pair of articles, for example two plate or sheet metal components 38,40 (Figure 1) in face-to-face relationship, the stem 14 of element 10 will be entered through aligned apertures in the components until head 12 abuts one face thereof, and the free end 22 of the stem will be entered into the aperture of female element 16, the latter having the free edge 28 of its skirt portion 26 directed toward the other face of the components.

Element 16 will be urged along the stem by axial pressure applied, at least at the final stages of tightening, to the central gripping portion 32 (a tubular tool sized to clear stem 14 may conveniently be provided for this purpose).

During this process the camming faces 24 of the serrations 14 spring the limbs 34 apart so that the stem can be forced through the aperture.

At the final stage of securing, the free edge 28 of the skirt portion will be in abutment with the face of the component and the resilient bridging formation 30 will be flexed axially inwardly to clamp the two components together. Pressure is continued until the free ends 36 of limbs 34 snap engage with the innermost possible locking face 20 of an appropriate serration 18 so resisting disengagement of element 16 from stem 14, serrations 18 acting in the manner of ratchet teeth, the resulting securing condition being shown in Figure 1.

Once secured the fastening device is rattle and vibration proof, the forces carried by limbs 34 are substantially in compression along their length, and securing is achieved very quickly and simply by rectilinear axial engagement of the two elements much more speedily than assembling and tightening screw threaded fastening elements.

The stem need not necessarily have serrations over its full length, it could be provided with a plain shank portion and be serrated only along a part which will be engaged by the female element in the secured condition e.g. to suit the fastening of articles of uniform known overall thickness or range of thicknesses.

It is also to be understood that the serrations could take various forms and need not necessarily be of uniform size and type along the stem. It is also within contemplation that the serrations could consist of successive turns of one or more helical screw thread type formations of the stem.

It will also be appreciated that it is not essential that the stem be of circular section or generally cylindrical, thus serrations could be provided on the otherwise generally planar faces of a stem of square, triangular or other polygonal section.

A further advantage of the invention is that the stem of a male element, e.g. provided in the form of lengths of studding having serrations along its whole length, can readily be cut to any desired length prior to assembly and without hindering subsequent engagement of the female element thereon, in contrast to screw threaded studding where cutting usually distorts or damages the "start" of the thread making subsequent engagement of a nut thereon tiresomely difficult.

Claims (11)

1. A fastening device comprising interengageable male and female elements, the male element having a stem at least part of which is formed to provide serrations in a lengthwise series and defined by locking faces each constituting an abutment directed away from the operatively free end of the stem and camming faces each tapering in girth toward the free end; and the female element having a skirt portion with a free edge directed endwise to abut a face of an article to be operatively secured by the device and a stem gripping portion spaced within the skirt portion and linked to the latter by a resilient bridging formation, said gripping portion including a plurality of internal resilient limbs having free ends bounding a stem receiving aperture and directed away from said free edge of the skirt portion, whereby said free end of the stem may be engaged through said aperture with the free edge of the skirt portion directed away therefrom, the camming faces permitting the resilient limbs to spring along the serrations in a direction of engagement until the free edge of the skirt portion is urged into clamping abutment with said article face by flexing of the bridging formation but disengagement is resisted by snap enggement of the free ends of the resilient limbs with a said locking face or faces of the serrations.

2. A device as in Claim 1 wherein the stem is circular in cross section throughout its length and the female element is annular or toroidal in generally overall form.

3. A device as in Claim 1 or 2 wherein the male element includes a head formation at the end remote from the free end of the stem.

4. A device as in Claim 1 or 2 wherein the male element is in the form of a stud anchored to or integral with a component or other article or carrying other fastening or attachment means.

5. A device as in Claim 4 wherein the male element includes a second natching or different stem portion for receiving a second female element to act in opposition to the first said element.

A A device as in any preceding claim wherein both the male and female elements are mouldings of plastics material.

7. A device as in any preceding claim wherein the serrations are of uniform size and type.

8. A device as in any preceding claim wherein the serrations consist of successive turns of one or more helical screw thread type formations of the stem.

9. A device as in any one of claims 1 to 7 wherein the stem is of non-circular section.

10. A fastening device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

11. An assembly including a fastening device as in any preceding claim.