GB2190164A

GB2190164A - Anchoring device

Info

Publication number: GB2190164A
Application number: GB08705878A
Authority: GB
Inventors: Roy J Jackson; David Terry; Dr John Ash
Original assignee: Thos Johnson
Current assignee: Thos Johnson
Priority date: 1986-03-15
Filing date: 1987-03-12
Publication date: 1987-11-11
Anticipated expiration: 2007-03-12
Also published as: GB2190164B; GB8606440D0; GB8705878D0

Abstract

An anchoring device 1 has a resilient collar 5 disposed between a sleeve 4 and a knurled slotted sleeve 6 expandable by a cone nut 7, so that following spreading of the sleeve legs 6a by rotation of the head 2a to secure the anchoring device in a receiving hole, the collar 5 is able to contract axially on further rotation of head 2a allowing further movement of bolt 2 in the hole if need be to firmly locate a member (e.g. cladding) against a wall. The collar 5 may comprise elastomeric material, or a helical metal spring, or a perforated cylinder. The knurling of the sleeve 6 is in the form of ribs, and may extend between 50 and 100% of its length. One of the slots X in the sleeve 6 may extend its full length. <IMAGE>

Description

SPECIFICATION Fastening device This invention relates to a fastening device more particularly of a type known in the art as an 'expanding anchor' device.

Such devices may have a bolt with a hexagon head at one end and a screw-thread. The threaded end of the bolt is introduced through a circular retaining plate and through a sleeve, then through a knurled expanding anchor (to anchor the fastening device in a receiving hole), and finally through a part-conical nut or collet having a thread mating with the thread on the bolt. The fastening device may be used, for example, in the cladding industry to retain a particular item (for example a metal angle piece) in between the circular retaining plate and a wall into which the bolt passes.

On tightening of the bolt the sleeve contacts the anchor and the 'coning' of the nut or collet spreads knurled legs of the anchor apart to retain (or anchor) the fastening device in the receiving hole in the wall. Such devices may tend, in certain instances, not to yield the most desirable fastening characteristics and possibly may not retain the device itself, and the item being retained thereby, in tight, reliable, fashion. Such devices tend to be particularly disadvantageous where the bolt is not initially introduced far enough into the receiving hole. In such an instance, once torque is applied to the device the legs of the anchor spread apart to axially locate the anchor in the hole and this can substantially prevent further axial movement of the bolt into the hole. Thus the item being retained in between the retaining plate and wall will not be secured reliably.

Accordingly, it is an object of the present invention to at least alleviate such disadvantage.

According to the present invention there is provided a fastening device comprising: a bolt having a screw thread and a head at one end; a sleeve; a part-conical nut or collet; a knurled expandable anchor, and a resilient, axially compressible washer or collar, the nut or collet being co-operable in use to spread legs of the anchor to anchor the fastening device in a receiving hole, and the washer or collar being positioned in use in between the anchor and sleeve such that it is able to be contracted axially upon tightening of the fastening device in the receiving hole so as to allow, or at least so as not to prevent, further movement of, the bolt and sleeve into the receiving hole.

The fastening device will usually incorporate a retaining plate at the head of the bolt. Preferably, the washer or collar is a moulded hollow body of a resilient elastomeric material such as E.P.D.M., but may be of any form and of any non-corrosive and corrosion resistant material e.g. rubber, neoprene so as to be resiliently or otherwise sufficiently compressible or crushable. For example, the collar could possibly be a helical metal spring or a ring of metal mesh.

Embodiments of fastening devices in accordance with the present invention will now be described, by way of example only, with reference to the accompanying scaled drawings in which: Figure 1 shows a view of the device prior to assembly in a receiving hole in a wall; Figure 2 shows a longitudinal cross sectional view of the device in an expanded state; Figures 3 and 4 show other forms of collar which can be employed in the device; and Figures 5 to 7 show views of the further embodiments of fastening devices.

Fig. 1 shows a fastening device 1 in its position prior to being fixed in a receiving hole in a wall and Fig. 2 shows the device in an expanded state, fixedly located diagrammatically in a receiving hole H in a wall W with a member M, (which is, for example cladding or an item connected therewith), held against the wall by the fastening device.

The device 1 has a long bolt 2 with hexagon head 2a and the bolt has a screw thread 2b running from the left-hand end as shown in the Figures along its entire length to the head 2a. The threaded end of bolt 2 is passed through circular retaining plate washer 3, through sleeve 4 (which is about half the length of the bolt) and then through a collar such as the annular, resilient, axially compressible washer or collar 5 shown in Figs. 1 and 2. Next to the washer 5 is a metal, knurled, expandable anchor 6 having four legs 6a which are spread apart in the expanded state (as shown in Fig. 2) by the narrow end of a part-conical nut or collet 7 which is threadably engaged on the threaded end of bolt 2.In use, the device 1 is inserted through the member M into the hole H, and the head 2a is rotated to draw the nut 7 towards the head to expand the anchor 6 to grip the internal surface of the hole H. As soon as the anchor obtains purchase in the hole, continued rotation of the head will tend to draw the head towards the wall, thereby securely clamping the member M to the wall W. The main function of the washer 5 is to yield when subjected to axial compression thereby allowing the sleeve, washer and head to move towards the anchor until the member M is clamped securely. In Fig. 2, the spreading apart of legs 6a has been shown in an exaggerated fashion for ease of illustration.

As should be apparent in Fig. 2 the collar 5 (which is made from a suitable material which is also non-corrosive such as E.P.D.M.) is sandwiched inbetween the sleeve 4 and anchor 6 and is an axially compressed state.

Thus, the legs 6a act against the cylindrical surface of the receiving hole H to retain the fastening device 1 in the wall W with the retaining plate washer 3 firmly up against the outer surface of said member M because of the axially compressible washer 5.

As should be evident from the Figures once the legs 6a are spread apart by the collet 7 on tightening the device 1, so that they dig into the cylindrical surface of the receiving hole H, further tightening of the device yields the axial compression of collar 5 so that the bolt is tensioned with no or minimal move ment of the anchor towards the head, thereby minimising damage to the wall.

The relative dimensions of the washer 5 in relation to the diameter of the bolt 2 are believed to be particularly advantageous.

The function of the washer 5 is to provide an abutment for the anchor which abutment provides sufficient resistance to compression to substantially maintain its axial length, and restrain the anchor from rotation, during initial spreading of the legs until the legs are thrust against the cylindrical surface of the hole; and thereafter to yield if need be as the compressive forces are increased due to the bolt being tensioned. Thus, a variety of other forms of washer or collar and collar-like structures may be possibly employed in lieu of the collar 5.

For example, a collar 5A (Fig. 3) comprising a strip 10 of perforate metal or hard plastics rolled to substantially cylindrical form, or a helical coil spring collar 5B (Fig. 4) of wide pitch may be employed instead of the collar 5.

The scope of the present invention should not be unduly limited by the choice of particular terminology used and any particular term as used herein may extend to any generic or equivalent term where sensible. Individual features, method or function related thereto or combinations thereof may be patentably inventive.

Figs. 5 to 7 show other preferable embodiments of fastening devices in accordance with the present invention. Several very important features of the fastening device are illustrated by the embodiments shown in Figs. 5 to 7.

Each device is generaliy designated d and most importantly each sleeve S is of similar form to sleeve 6 in Fig. 1 and has four equiangularly spaced longitudinal slots defining the legs L. Three of the slots are of the general form shown in Fig. 1 at X finishing a distance (Y=2.5 mm) from the end of the anchor itself and, most importantly, the fourth slot Z extends the entire length of the anchor. This slot combination is advantageous since it provides greater flexibility in expansion of the sleeve allowing better expansion and force holding characteristics. Equally the dimensions of the sleeve are carefully selected so that inherent stresses in the sleeve itself do not tend to close the slot Z thereby distorting the sleeve and rendering it unusable.

The form of the bolts shown in Figs. 5 to 7 are tried and tested and are found to display optimum characteristics so that the fastening device d can easily be introduced and located in its receiving hole without the application of an undue amount of torque on the head of the bolt.

In fact, it is also important that the other three slots X extend to a distance of about 1.5 to 4 mm from the end of the sleeve as shown to yield seemingly optimum expansion characteristics. The three slots X may terminate at, before, or just after, the knurling on the anchor.

Once again due to the manner in which the anchor sleeve expands a greater holding force is, advantageously, achievable with a knurling extending over substantially the entire exterior surface of the sleeve and/or substantially over the entire length of the sleeve. This is due to the slot Z which allows a greater surface area and greater length of the sleeve to contact the surface defining the receiving hole (rather than something less than 50% of the length extending from the nut 7).

Additionally, the relative dimensions of the washer (axial length, thickness and diameter) are thought to be most advantageous and particularly in relation to the bolt diameter as depicted in the drawings. Figs. 5 to 7 show bolts designed for different applications, the device shown in the Fig. 5 being for heavy duty application. In such a case, the distance comparable with distance Y in Fig. 1 may be greater and may be e.g. 4 mm. The axial thickness of the washer is chosen to allow sufficient inward movement of the bolt relative to the sleeve.

It is also important that the annular edge face of the sleeve 4 adjoining the collar 5 is entirely flat to avoid any possibility of the collar riding up over the sleeve which, in fact, has occurred in practice with some designs.

The radial dimensions of the sleeve are chosen so that the washer will not block the hole thereby affecting the expansion of the anchor.

The axial thickness of the washer most preferably exceeds the radial thickness and is preferably at least twice or even three or four times the radial thickness. Preferably, the axial length of the sleeve exceeds the axial length of the anchor.

For easy comparison of dimensions the length of the fastening devices shown in Figs.

5 to 7 are 105 mm, 75 mm, and 105 mm respectively. The axial thickness of the washer or collar in Figs. 1 to 5 is 11 mm, 7 mm, and 7 mm respectively.

Additionally, the knurled surface of the anchor is most preferably a 'raised" knurled surface (of about 0.4 mm) as shown and once again, for greater holding force bearing in mind the spread of the legs in conjunction with opening of the slot S, the knurling is preferably in the form of longitudinal ribs.

Claims

1. A fastening device comprising: a bolt having a screw thread and a head at one end, a sleeve; a part-conical nut or collet; a knurled expandable anchor, and a resilient, axially compressible washer or collar, the nut or collet being co-operable in use to spread legs of the anchor to anchor the fastening device in a receiving hole, and the washer or collar being positioned in use inbetween the anchor and sleeve such that it is able to be contracted axially upon tightening of the fastening device in the receiving hole so as to allow, or at least so as not to prevent, further movement of the bolt into the receiving hole.

2. A device as claimed in Claim 1 in which the knurling on the anchor extends substantially over the entire axial length of the anchor or at least over more than 50% of the axial length.

3. A device as claimed in Claim 1 or Claim 2 in which the anchor is provided with a slot extending the entire axial length of the anchor.

4. A device as claimed in any one of the preceding claims in which the anchor has four equiangularly spaced slots.

5. A device as claimed in Claim 4 in which at least some of the slots terminate at a distance of about 1.5 to 4 mm from one end thereof.

6. A device as claimed in any one of the preceding claims in which the edge face of the sleeve adjoining the washer or collar is entirely flat.

7. A device as claimed in any one of the preceding claims in which the washer or collar is a moulded hollow body of elastomeric material.

8. A device as claimed in Claim 7 in which the elastomeric material is E.P.D.M.

9. A device as claimed in any one of preceding claims in which the axial thickness of the washer or collar exceeds the radial thickness.

10. A device as claimed in Claim 9 in which said axial thickness is at least twice the radial thickness.

11. A device as claimed in Claim 10 in which said axial thickness is three or four times the radial thickness.

12. A device as claimed in any one of the preceding claims in which the knurled surface is a raised surface of, for example, 0.4 mm.

13. A device as claimed in Claim 12 in which the knurled surface comprises longitudinal ribs.

14. A device as claimed in any one of preceding claims which also comprises a retaining plate.

15. A fastening device as claimed in Claim 1 and substantially as shown in Figs. 1 and 2 of the drawings or when modified substantially as shown in Fig. 3 or Fig. 4 of the accompanying drawings.

16. A fastening device substantially as herein described with reference to Fig. 5, or Fig. 6 or Fig. 7 of the accompanying drawings.

17. A fastening device as claimed in Claim 1 in which the anchor and/or washer/collar is substantially as shown in Figs. 1 and 2, or Fig. 5, or Fig. 6 or Fig. 7 of the accompanying drawings.