WO2000028224A1

WO2000028224A1 - A blind fastening device

Info

Publication number: WO2000028224A1
Application number: PCT/GB1999/003712
Authority: WO
Inventors: Simon Francis Klippel
Original assignee: Tyco European Metal Framing Ltd
Current assignee: Tyco European Metal Framing Ltd
Priority date: 1998-11-10
Filing date: 1999-11-10
Publication date: 2000-05-18
Anticipated expiration: 2001-05-10
Also published as: AU3789300A; GB9824612D0

Abstract

A blind fastening device (13) for use in clamping a component to a support plate by taking a said fastening devive through aligned openings in the component and in the support plate and in which the fastening device comprises: a slotted sleeve (20); an apertured sleeve plate (16); an apertured compression means (19) located beween the slotted sleeve (20) and the sleeve plate (16); a fastener comprising a threaded fastener portion (14) which can be taken through the slotted sleeve (20), the apertured sleeve plate (16) and the apertured compression means (19); a tightening head (15) provided on the threaded fastener for tightening the fastener; and, a diverging sleeve (23) expanding head is mounted on the fastener portion and engageable with the end (22) of the sleeve (20) remote from the compression means (19) on tightening of the fastener, in order to expand said end rigidly outwards into contact with at least one of said openings to anchor the sleeve; in which the compression means (19) is adapted such that on further tightening of the fastener, the compression means (19) is axially compressed between said sleeve (20) and said sleeve plate (16) so reducing the distance between said sleeve and sleeve plate.

Description

A BLIND FASTENING DEVICE

The present invention relates to a blind fastening device. More particularly, but not exclusively, the present invention relates to a blind fastening device for clamping a component to a support plate.

Rolled hollow metal sections are increasingly being used as part of the supporting structure m industrial buildings. Such sections are typically manufactured in the form of hollow rectangular support columns built up from four metal plate sections. When it is desired to secure fixing brackets, pipe supports, electrical conduits or other similar components to such support columns it is necessary to use a blind fastening device since access cannot readily be obtained to the interior of the column to complete the fastening operation.

A typical known blind fastening device comprises a threaded bolt having a bolt head extending from one end. A conical expansion head is threaded partly along the length of the bolt. Also threaded along the bolt and abutmg against the bolt head is an apertured sleeve plate. Finally, extending between the sleeve plate and the expansion head is a slotted tubular sleeve.

Before use the expansion head is threaded along the bolt until it abuts against the sleeve. The friction between the sleeve and the expansion head then prevents the expansion head from turning when the bolt is rotated within the sleeve.

In order to fasten a component to a support column an aperture in the component is firstly aligned with a corresponding aperture in the column. The bolt and the sleeve of the fastening device are then inserted through the aligned apertures until the sleeve plate abuts against the component. The bolt is then tightened. Because the friction between the conical head and the sleeve prevents the conical head from rotating along with the bolt, the tightening of the bolt causes the conical head to be drawn along the bolt towards the bolt head. This forces the slotted sleeve to expand radially outwards. Eventually, the portion of the sleeve in contact with the head grips the outer wall of the aperture of the support plate. In this way the component and the support column become gripped between the sleeve plate and the expanded end of the sleeve.

Further tightening of the bolt applies a compressive force to the portion of the sleeve located between the conical head and the sleeve plate. However as the sleeve is essentially axially incompressible this tightening does not produce a reduction in the distance between the sleeve plate and the expanded end of the sleeve. Therefore once the sleeve has gripped the aperture it is not possible to press the component and the support column together by further tightening of the bolt of the blind fastening device.

This problem has been partly overcome by connecting the support plate and sleeve together by a weakened sleeve portion. Typically the sleeve, the weakened sleeve portion and the sleeve plate are manufactured from a single metal piece. As previously, when the bolt is tightened this modified sleeve expands and grips the aperture walls. However, as the bolt is further tightened the sleeve is again axially compressed but now collapses, reducing the axial length of the sleeve and compressing the component and support column together. Such blind fastening devices are often difficult to remove once they have been tightened. Even if one removes the bolt and conical expansion head the single piece comprising the support plate and sleeve will still remain m position, gripping the component and support column. In order to remove this piece it is necessary to apply considerable force to the underside of the support plate with a crowbar m order to deform the fingers of the expanded sleeve inwards. This can often damage the aperture and make it unsuitable for re-use.

Accordingly, the present invention provides a blind fastening device for use in clamping a component to a support plate by taking a said fastening device through aligned openings m the component and m the support plate and m which the fastening device comprises a slotted sleeve; an apertured sleeve plate; an apertured compression means located between the slotted sleeve and the sleeve plate; a fastener comprising a threaded fastener portion which can be taken through the slotted sleeve, the apertured sleeve plate and the compression means; the fastener further comprising a tightening head extending from the threaded fastener portion for tightening the fastener; and, a diverging sleeve expanding head mounted on the fastener portion and engageable with the end of the sleeve remote from the compression means on tightening of the fastener, in order to expand said end rigidly outwards into contact with at least one of said openings to anchor the sleeve ; the compression means being adapted such that on further tightening of the fastener the compression means is axially compressible between said sleeve and said sleeve plate so reducing the distance between said sleeve and sleeve plate.

The fastening device of the present invention has the advantage that it can be simply removed even after tightening without any damage to the aperture. In order to remove the fastening device one unscrews the bolt and pushes the conical head into the support column. As the support plate is not physically attached to the sleeve it can simply be removed. The compression means and the sleeve will then fall into the support column so freeing the aperture for use by a new fastening device.

Additionally, the fastening device of the present invention has the advantage that it is relatively simple to manufacture. Known fastening devices comprise a support plate, sleeve and weakened sleeve portion all manufactured as a single piece. This is time consuming and wasteful of material. The fastening device of the present invention comprises a support plate, sleeve and compression means all of which are separate items. These can be manufactured more easily and is less wasteful of material.

Preferably, the compression means comprises an elastomeric washer. Elastomeric washers are simple to manufacture and can be designed to be axially compressible but capable of withstanding torsional forces during tightening of the blind fastener.

Preferably, the compression means comprises a spring.

Preferably, the apertured sleeve plate has a formation offset from the axis of the threaded fastener portion which IS engageable with a tool to prevent rotation of the sleeve plate whilst the fastener is being tightened.

Such a formation enables the sleeve plate to be held firmly whilst the fastening device is tightened.

Preferably, on compression of the compression means the compression means expands radially outwards to form a seal between the sleeve plate and the component. This seal prevents water from entering into the aligned apertures between the seal plate and the component so preventing corrosion of the bolt .

The diverging sleeve expanding head can be frustoconical .

The present invention will now be described by way of example only and not m any limitative sense with reference to the accompanying drawings, m which:

Figure 1 is a longitudinal cross sectional view of a known blind fastening device;

Figures 2(a) to 2(c) show, m longitudinal cross section, successive stages m the fastening of a component to a support plate using a known blind fastening device;

Figure 3 is a longitudinal cross sectional view of a blind fastening device according to the invention;

Figures 4(a) to 4(d) show, in longitudinal cross section, successive stages in the fastening of a component to a support plate using a blind fastener device according to the invention.

Shown m figure 1 (a) is a known blind fastening device comprising a tubular sleeve and a threaded bolt. The tubular sleeve comprises an apertured sleeve head, a slotted expansion portion and a weakened portion extending therebetween. The expansion portion comprises a number of parallel arcuate fingers separated axially by slots .

Before use the threaded bolt is inserted axially along the tubular sleeve until the head of the bolt abuts against the sleeve head and a portion of the bolt remote from the head extends beyond the sleeve. A frustocomcal expansion head having an engagement face and a base is then threaded along the bolt until it abuts against the sleeve. The diameter of the engagement face is less than the diameter of the tubular sleeve whilst the diameter of the base is greater than the diameter of this tubular sleeve. Further tightening of the expansion head by hand is prevented by the friction between the sleeve and the expansion head.

To use this blind fastening device to clamp together a fixing plate and a support plate an aperture in the fixing plate is firstly aligned with a corresponding aperture m the support plate. The blind fastening device is then slid through these apertures until the sleeve head abuts against the aperture surround as shown m figure 2 (a) .

A gripping tool is attached to the sleeve head to prevent its rotation. A tightening tool is then attached to the bolt head. This tool is used to rotate the bolt along its length relative to the sleeve to tighten the fastening device. Because the expansion head is not free to rotate along with bolt, rotation of the bolt forces the expansion head towards the bolt head. This movement of the expansion head causes the fingers of the sleeve to expand radially outwards and into engagement with the walls of the aperture as shown m figure 2 (b) .

As the bolt is tightened further the expansion head is forced further towards the sleeve head. However, as the sleeve is now anchored to the aperture this results in a compression of the portion of the sleeve within the aperture. When the compressional force reaches a predetermined level the weakened portion of the sleeve axially compresses reducing the axial length of the sleeve and pressing the fixing and support plates together as shown m figure 2 (c) .

Once such a blind fastening device has been tightened it can be difficult to remove. In order to remove the bolt from the fastening device one rotates the bolt anticlockwise until the expansion head reaches the end of the thread. As the bolt is turned further, will drop off the bolt and into the support column. The bolt can then be pulled free from the fastening device. However, even with the bolt removed the sleeve will remain in place gripping the component and support column. In order to remove this sleeve one must insert a crowbar beneath the sleeve head and use this to recompress the fingers of the expanded portion of the sleeve. Once these fingers have been recompressed the sleeve can be axially withdrawn from the aperture. Insertion of the crowbar into the aperture can damage the aperture making it unsuitable for future use.

Shown m figure 3 is a fastening device according to the present invention m longitudinal cross section. The assembled fastening device comprises a threaded bolt having a bolt head extending from one end. Positioned along the bolt and abutting against the bolt head is an apertured sleeve plate. The walls of the aperture of the sleeve plate are smooth enabling the sleeve plate to be slid along the bolt. The outer wall of the sleeve plate is substantially circular but has an offset formation for engagement with a gripping tool to prevent rotation of the sleeve.

Abutting against the sleeve plate is a compressible apertured washer. The washer is manufactured from an elastomeric material which enables the washer to be slightly deformed axially during the tightening of the fastening device if required.

Abutting against the washer is a tubular sleeve which extends along the threaded bolt. An expansion portion of the sleeve remote from the washer is split into fingers (not shown) by slots which extend parallel to the sleeve. A portion of the end wall is inclined to the axis of the sleeve to form a receiving portion for engagement with an expansion head described in greater detail below.

Threaded along the bolt is a frustocomcal expansion head. The expansion head comprises an engagement face, a base and a contact face extending therebetween. A portion of the contact face proximate to the engagement face is roughened to increase the friction between the sleeve and expansion head in use. The contact face proximate to the engagement face of the sleeve is arranged to be complimentary to the receiving portion so that they initially engage over an extended area.

Before use the expansion head is threaded along the bolt until the roughened portion of the contact face abuts against the receiving portion of the sleeve. The expansion head is then tightened usually by hand, so applying a small compressive force to the compression means and sleeve. This slight compression force causes sufficient friction between the compression means, sleeve and expansion head to prevent these components from rotating with respect to the sleeve plate during tightening.

In use the assembled fastening device is inserted through the aligned apertures of a support plate and fastening plate until the sleeve plate abuts against the fastening plate, as shown m figure 4a.

A gripping tool (not shown) is engaged with the sleeve plate to prevent turning of the sleeve plate during tightening of the fastening device. A tightening tool is then connected to the bolt head and turned to rotate the bolt . As previously discussed the friction between the sleeve plate, washer, sleeve and expansion head prevent the expansion head from rotating with the bolt. The expansion head is therefore drawn along the bolt towards the bolt head so spreading apart the fingers of the expansion portion of the sleeve until the fingers grip the sides of the aperture wall (as shown in figure 4b) .

During this period of expansion the sleeve plate and expansion head apply an axial compression force to the sleeve and washer. The washer is designed to withstand this axial compressive force without any substantial change m axial length.

Once the sleeve has gripped the aperture wall further turning of the bolt head increases the compressive force applied to the sleeve and washer. In response, the washer begins to axially compress and expand radially as shown in figure 4(c) . As the washer compresses the sleeve is pushed towards the sleeve plate so pressing the support plate and fastening plate together.

During this compression phase of tightening the axial load, applied to the washer is comparable to the load which would be applied by the use of a standard bolt and nut . Most of the torsional force applied to the bolt head is converted to a compressional force.

In the final stage of tightening the washer expands outwards until it reaches the aperture wall, so forming a seal between the sleeve plate and fastening plate. This seal prevents the entry of water or other fluids into the aperture, so extending the bolt life.

In an alternative embodiment of the invention the aperture wall of the sleeve plate is threaded and is designed to engage with the thread on the bolt.

In the embodiment of the invention shown in figures 3 and 4 the washer is of approximately the same outer diameter as the sleeve. In a alternative embodiment the washer can have a larger diameter than the sleeve to ensure a tight seal between the washer and sleeve plate when the fastening device is fully tightened.

In an alternative embodiment the elastomeric washer is replaced by a spring. Alternatively the elastomeric washer can be a steel washer.

Claims

1. A blind fastening device (13) for use m clamping a component to a support plate by taking a said fastening device through aligned openings m the component and in the support plate and in which the fastening device comprises: a slotted sleeve (20); an apertured sleeve plate (16); an apertured compression means (19) located between the slotted sleeve (20) and the sleeve plate (16); a fastener comprising a threaded fastener portion (14) which can be taken through the slotted sleeve (20), the apertured sleeve plate (16) and the apertured compression means (19) ; the fastener further comprises a tightening head (15) for tightening the fastener; and, a diverging sleeve expanding head (23) mounted on the fastener portion and engageable with the end (22) of the sleeve (20) remote from the compression means (19) on tightening of the fastener, in order to expand said end rigidly outwards into contact with at least one of said openings to anchor the sleeve; m which the compression means (19) is adapted such that on further tightening of the fastener, the compression means (19) is axially compressed between said sleeve (20) and said sleeve plate (16) so reducing the distance between said sleeve and sleeve plate.

2. A blind fastening device as claimed in claim 1, wherein the compression means comprises an elastomeric washer (19).

3. A blind fastening device as claimed m claim 1, wherein the compression means comprises a spring.

4. A blind fastening device as claimed m any one of claims 1 to 3, wherein said apertured sleeve plate (16) has a formation offset from the axis of the threaded fastener portion which is engageable with a tool to prevent rotation of the sleeve plate while the fastener is being tightened.

5. A blind fastening device as claimed in either of claims 1 or 2 , wherein on compression of the compression means the compression means expands outwardly to form a seal between the sleeve plate and the component.

6. A blind fastening device as claimed m any one of claims 1 to 5, wherein the diverging sleeve expanding head is frustocomcal .