A quarter-turn fastener has a bolt having a head and a screw-threaded shank, and a retainer assembly threadably secured to the shank as a tight friction fit thereon. The retainer assembly has a pair of abutments for engagement with the rear of a support, through an aperture in which the retainer assembly locates in use. The retainer assembly includes at least one pair of stops for engagement with the sides of the aperture in the support or a corresponding aperture in a panel in which the fastener is mounted in use, to define the inoperative and operative positions of the retainer assembly. A compression spring is located in use between the retainer assembly and an opposed surface of the panel to retain the retainer assembly in its inoperative position under the action of friction, when the retainer assembly is disengaged from the support.

The present invention relates to quarter-turn fasteners such as are 
commonly used to retain, for example, the cover on a cabinet. More 
particularly, the invention relates to such a fastener which has the 
feature of adjustability to enable changes in the spacing between the 
support and the panel attached to it by the fastener, to be accommodated 
automatically by the fastener. 
One simple prior art fastener of this type which is designed for attaching 
a single skin panel or cover to a support, comprising a screw-threaded 
bolt which passes through an aperture in the panel and a plastic retaining 
member which is screw threaded onto the free end of the bolt, but which is 
a very tight interference fit with the bolt so that it is generally held 
in a fixed position on the bolt for rotation with it. The plastic 
retaining member is spaced from the head of the bolt a sufficient distance 
to enable the support to be gripped between the rear face of the panel and 
the opposed faces of respective transversely extending shoulders on the 
retaining element. The support is provided with an elongate hole and the 
retaining member has a similar elongate cross-section so that it can be 
passed through the slot and then rotated through 90.degree. so that its 
transversely extending shoulders grip the rear of the support. In order to 
ensure positive positioning of the retaining element when it is turned 
into the fastening position, at its end nearer to the head of the bolt, 
the retaining element is formed with an axially extending protrusion which 
has a generally lozenge-shaped cross-section. Opposed side faces of the 
protrusion are arranged to lie substantially at 90.degree. to one another 
and the protrusion is of a thickness corresponding approximately with that 
of the support. The side faces of the protrusion effectively limit 
rotation of the retaining element to 90.degree., adjacent side faces 
coming into engagement with the sides of the elongate aperture to define 
the inoperative and fastening positions. 
If, for example, a gasket is interposed between the panel and the support 
then during the life of the fastener the thickness of the gasket may 
shrink slightly and this reduction in thickness will require to be taken 
up by the fastener. This is achieved by virtue of the threading of the 
retaining element on the bolt, so that when the fastener is rotated into 
the fastened position and is held therein, the side faces of the 
protrusion on the retaining element engaging the sides of the slot in the 
support, a slight further rotation of the bolt can take place without 
further rotation of the retaining element, thereby drawing the bolt 
further into the retaining element and lessening the distance between the 
retaining element and the head of the bolt and thus accommodating for wear 
or shrinkage in the gasket. 
Unfortunately, while such fasteners are capable of use in many 
applications, where there is a requirement for greater locking strength 
between the panel and the support a plastic retaining member has to be of 
unacceptably large dimensions in order to have the required strength 
characteristics. Furthermore, of course, there is significant freedom of 
movement of the bolt within the aperture in the panel once the panel has 
been removed from the support and the fastener is also, of course, easily 
rotated by vibration, so that when the panel is re-presented to the 
support the retaining element can be pinched between the panel and the 
support in a position in which it cannot pass through the elongate 
aperture in the support and, being pinched, the friction may be such as to 
prevent rotation of the retaining element on rotation of the head of the 
bolt, requiring the panel to be removed and all the fasteners used on the 
panel properly aligned before any of them is actually rotated into the 
fastened or operative position. 
In accordance with the present invention a quarter-turn fastener comprises 
a bolt having a head and a screw-threaded shank, a retainer element or 
assembly threadably secured to the shank as a tight friction fit thereon, 
the retainer element or assembly having a pair of abutments for engagement 
with the rear of a support, through an aperture in which the retainer 
element or assembly locates in use, the retainer element or assembly 
including at least one pair of stops for engagement with the sides of the 
aperture in the support or a corresponding aperture in the panel through 
which the fastener is mounted in use, to define the inoperative and 
operative positions of the retainer element or assembly, and a compression 
spring located in use between the retainer element or assembly and an 
opposed surface of the panel to retain the retainer element or assembly in 
its inoperative position, under the action of friction, when the retainer 
element or assembly is disengaged from the support. 
The compression spring thus holds the retainer element or assembly under 
the action of friction in the inoperative position when it is disengaged 
from the support so that when the panel is re-presented to the support the 
retainer element is in the correct position to pass through the aperture 
in the support to avoid it being pinched between the support and the 
panel. 
Preferably, the end of the retainer element or assembly remote from the 
head of the bolt has a form which tends to rotate the fastener into the 
inoperative position when the retainer element is presented to the 
aperture in the support and it is not already orientated so as to pass 
through the aperture. 
Preferably, the fastener is designed for use with a panel comprising a pair 
of skins, and the stops on the retainer element or assembly are arranged 
to engage with an aperture in a first of the skins lying adjacent the 
support, and the compression spring is a coil spring extending from the 
end of the retainer element adjacent the head of the bolt to the underside 
of the second skin on the opposite side of which is located the head of 
the bolt. Alternatively, if the fastener is to be used on a panel having 
only a single skin the compression spring may be in the form of a spiral 
compression spring located between the underside of the panel surface and 
the adjacent end of the retainer element or assembly and the stops on the 
retainer element or assembly may either cooperate with the aperture in the 
panel or with the aperture in the support. 
A gasket may be interposed between the panel and the support. Initial 
rotation of the bolt causes the retainer element to move into the 
operative or fastening position automatically setting the retainer element 
in the correct position on the bolt, eliminating problems associated with 
panel thickness variation. In use, if the gasket reduces in thickness, 
then further rotation of the bolt after the retainer element has moved 
into the operative position causes the bolt to move further through the 
retainer element thereby preventing any slackness in the fastening of the 
panel to the support and accommodating the reduction in thickness of the 
gasket. 
Preferably, the retainer element or assembly comprises a bush which is a 
sliding fit on the shank of the bolt, the bush having a counterbore 
receiving a nut non-rotatable therewithin, the nut being retained 
permanently within the counterbore and the nut having a suitably deformed 
screw-thread providing a tight friction fit with the screw-thread on the 
shank of the bolt, the abutments and stops being located on the bush. 
Advantageously, the screw-threaded nut is relatively movable along the 
counterbore against the action of a compression spring within the 
counterbore, so that the bush is movable towards the head of the bolt. By 
this means, changes in the thickness of the gasket can be compensated for 
even when the fastener is out of use and thinning of the gasket is taking 
place whilst the panel is retained on the support. 
An abutment may be formed at the end of the shank of the bolt remote from 
the head to prevent accidental unthreading of the retainer assembly from 
the bolt. The abutment may be formed by a conventional self-locking or 
plastic nut. 
The nut may comprise a conventional self-locking nut or may be a plastic 
nut. Preferably the retainer element is a metal die casting and the nut is 
retained within the counterbore by swaging over the end of the 
counterbore. 
As an alternative or in addition to locating a compression spring within 
the retaining element or assembly a similar compression spring may be 
mounted underneath the head of the bolt between the head of the bolt and 
the front surface of the panel. 
The retainer element or assembly may be formed, respectively, as an 
integral die-casting or as a plastic bush retaining, with a snap or 
push-fit, a transverse element providing the abutments for engagement with 
the rear of the support.

As can be best seen from FIG. 1a a fastener 1, which is used to mount a 
double-skinned panel 2 to a support frame 3, has a bolt 4 which has a head 
5 and a shank 6 which has an end portion 7 which is screw-threaded as 
shown at 8. The end of the shank adjacent the head of the bolt is 
un-threaded. The bolt extends through a circular aperture of slightly 
larger diameter than that of the shank 6 of the bolt 5 and through a space 
9 between the two skins 10 and 11 of the panel 2. The skins 10 and 11 are 
spaced apart by a filler material 12. Onto the threaded end 7 of the shank 
6 is located a die-cast metal retainer element 13 which has an internally 
threaded bore slightly larger than the threaded part 7 of the shank 6 and 
between the two is provided what is known as a "helicoil", that is to say 
a helical wire coil which acts to provide a threaded connection between 
the threads 8 on the shank 6 and the internal bore 14 in the retainer 
element 13. The helicoil is not shown. However, the helicoil provides a 
sufficiently tight frictional fit between the element 13 and the shank 6 
that the retainer element is rotatable with the bolt unless it is 
prevented from rotation by abutment. 
The element 13 has a pair of transverse shoulders or abutments 15 and a 
part 16 which has a generally lozenge-shaped cross section such as can be 
seen in FIG. 4, to provide stops 17 and 18 which limit the rotational 
movement of the element 13 between the operative and inoperative positions 
through an angle of 90.degree., the surfaces 17 and 18 being substantially 
at 90.degree. to one another. 
Between the front skin 10 of the panel 2 and the adjacent end of the 
element 13 there is disposed an elongate helical compression spring 19 
which serves to bias the head of the bolt into the recess 20 formed in the 
front skin 10 so as to bias the retaining element 13 into the leftward 
position shown in FIG. 1a. In use, a gasket 21 is interposed between the 
panel 2 and the frame 3 and to fasten the panel to the frame the retaining 
element 13 is inserted through the aperture 22 in the frame in the 
position at 90.degree. to that shown in FIG. 1b so that the shoulders 15 
can pass through the aperture and can then be rotated, by rotation of the 
head 5 of the bolt 4 into the position shown in FIGS. 1a and b. If the 
gasket reduces in thickness over a period of time, perhaps due to frequent 
removal and reattachment of the panel, the firm fixing of the panel to the 
frame can be maintained by slight over rotation of the bolt head 5 once 
the operative position of the fastener has been achieved. By such 
over-rotation the screw threaded connection between the retainer element 
13 and the shank 6, acting by means of the helicoil, causes the shank of 
the bolt to move further through the retainer element thus lessening the 
distance between the shoulders 15 and the head of the bolt and thus 
reducing the gap between the panel and the frame. 
In a first alternative construction for the retaining element 13, there is 
shown in FIG. 2 an example in which the retaining element comprises a 
die-cast bush having a counterbore 23 of hexagonal cross-section. The 
counterbore receives a helical coil spring 24 and a plastic retaining nut 
25 which has an internal screw thread adapted to provide a tight friction 
fit with the screw thread 8 on the shank 6 of the bolt. In order to retain 
the hexagonal nut and springs in the counterbore 23 the opening of the 
counterbore is swaged as shown at 26. 
The retainer element 13 includes the other features of that of the FIG. 1 
example, including the lozenge cross-sectioned portion 16 which provides 
stop surfaces 17 and 18 which engage with the sides of the aperture 27 in 
the inner skin 11 of the panel 2 to define the inoperative and operative 
positions of rotation of the retaining element. In order to accommodate 
for reducing thickness of the gasket 21 even when the panel remains in 
place on the frame, the spring 24 is arranged to be pre-stressed when the 
fastener is first operated, by over-rotating the head of the bolt so that 
after the retaining element 13 has been moved into the operative position 
the nut 25 moves, by action of its threaded cooperation with the shank of 
the bolt, towards the head of the bolt thus compressing the spring 24. 
Then, if the gasket 21 shrinks in use, the spring automatically allows for 
the reduction in gap between the panel and the supporting frame to prevent 
the panel from becoming loose. 
In FIG. 3 there is shown a modified retainer assembly 13, in which a 
similar nut 25 is retained within a counterbore 23' which has a shorter 
axial length, there being no spring and the nut being constrained to 
prevent relative axial movement between the nut and the retaining element. 
It can be seen that there is a difference between the shape of the part 16 
of the retaining element 13 which provides the stops 17 and 18 between 
FIG. 4 and FIGS. 2 and 3. In FIGS. 2 and 3 the cross-section is 
substantially lozenge-shaped, the surfaces 17 and 18 meeting at a point 
and those on the same side of the central axis being connected by an 
arcuate portion 28. However, in FIG. 4, the corner between adjacent stops 
17 and 18 has been removed, being replaced by a curved portion 29. Removal 
of the corner facilitates rotation of the retaining element 13 within the 
aperture 27 in the inner skin 11 of the panel 2. 
In FIG. 5 there is shown a further fastener with a modified retainer 
assembly 13 which comprises a plastics sleeve 30 having an internal smooth 
bore into which the thread 8 self taps to provide a tight friction fit on 
the end portion 7 of the shank 6 of the bolt 4, the plastics sleeve 30 
having a transverse slot 31 through which is fitted a metal plate 32 which 
provides the shoulders 15 for engaging the rear surface of the support 3. 
A further modification which is present in this example and which has a 
substantially similar effect to the spring 24 provided in the retaining 
assembly 13 shown in FIG. 2, comprises a spring 33 of substantially 
helical form located beneath the head 5 of the bolt 4, between the head 
and the front skin 10 of the panel 2. The spring not only accommodates a 
reduction in thickness of the gasket 21 whilst the fastener is in the 
engaged position, but also serves to provide an indication of this 
reduction in thickness by biasing the head of the bolt outwardly from the 
front surface of the panel so that inspection of the fastener will reveal 
the reducing thickness of the gasket. 
In other respects, the fastener shown in FIG. 5 is the same as that shown 
in the remaining examples and the method of operation is identical. 
Although, in all the examples, the part 16 has been shown as cooperating 
with the aperture 27 in the inner skin 11 of the panel, it may be possible 
for the part 16, that is to say the stop surfaces 17 and 18 to cooperate 
with the aperture 22 in the support. However, it is preferred that the 
surfaces 17 and 18 cooperate with the aperture in the panel as this 
provides a closer fit of the fastener in the panel and enables a greater 
latitude in the relative alignment between the panel and support than is 
possible if the surfaces 17 and 18 require to cooperate with the aperture 
in the support, as the aperture in the support can be formed with larger 
tolerances. If the panel is of a single skin construction then the 
relative axial lengths of the bolt and retainer assembly or element will 
be correspondingly reduced and the spring 19 shown in FIG. 1, can be 
replaced by a spiral compression spring located between the single skin of 
the panel and the retainer assembly or element 13.