Description The present invention relates to a spacer for a fastener and a fastener assembly of a spacer with a fastener particularly but not exclusively for location in a plastics or similar materials to maintain joint tension.

There is a requirement to enable association of components such as panels using fasteners. Components may have varying dimensions and particularly material types as well as conditioning. For example, plastics are subject to creep and even with supporting metal washer or spacer such materials will relax and a fastener assembly forming a joint will loosen particularly where the assembly is subject to vibration and variable loads. An acceptable assembly needs to have fastenings such as screws or bolts which are sufficiently tightened to ensure they remain under permanent tension (within their elastic limits) to maintain a robust assembly upon initial assembly and for a desired operational life. Plastics can in such circumstances present problems with retention of tension in a fastening. Previously a loose washer has been used as a spacer and typically a sleeve retainer engaged by the thread of the fastener bolt or screw. The washer allows some retention of tension despite vibration and material variations such as creep. Such loose washers and bolts in their own right can present fabrication problems in terms of correct presentation and asymmetric forces causing de-centring of the fastener in use as it is assembled and turned.

In accordance with first aspects of the present invention there is provided a spacer for a fastener comprising a sleeve and a flange at one end of the sleeve which extends radially, the flange having flange pips substantially in the direction of the sleeve and the sleeve having radial pips extending away from the sleeve below the flange, the flange pips and the radial pips configured to engage in use material about the spacer to inhibit rotation, as well as initial retention in the case of the radial pips.

Possibly, the radial pips are towards an end of the sleeve away from the flange. Possibly, the flange pips extend below the flange. Possibly at least some of the flange pips extend above the flange as top flange pips.

Possibly, the flange pips and/or the radial pips are substantially symmetrically arranged about the central axis of the sleeve. Possibly, there are at least 3 and advantageously 6 flange pips.

Possibly, the flange pips are formed by pressing. Possibly, the flange pips are rounded and/or have a truncated end.

In accordance with second aspects of the present invention there is provided a fastener assembly comprising a spacer as described above and a fastener arranged to enter the sleeve.

Possibly, the sleeve is located within an orifice formed in a panel whereby upon rotation of the fastener the radial pips and/or the flange pips are held by engagement with the orifice or thereabout. Possibly, the spacer is pressed into the orifice.

Possibly, the flange and/or the flange pips engage around the orifice. Possibly, the flange pips upon rotation of the fastener and/or the flange press in material about the orifice whereby rotation of the spacer is inhibited. Possibly, the sleeve is flexed or stressed in compression to provide tension between the fastener/spacer end and the radial pips. The assembly may include an insert for the fastener. The insert may be below the spacer.

Embodiments of aspects of the present invention will now be described by way of example only with 1 reference to the accompanying drawings in which :-

Figure 1 is a plan view of a spacer in accordance with aspects of the present invention;

Figure 2 is a cross-section of the spacer as depicted in figure 1;

Figure 3 is a more detailed cross-section of a part of a flange from the cross-section as depicted in figure 2; Figure 4 is a schematic cross-section (A-A from Figure 5 below) of a fastener assembly comprising a spacer, a fastener and a panel component in accordance with aspects of the present invention; and,

Figure 5 provides a plan illustration of a spacer from above and as described in figures 1 to 3 showing the impressions of flange pips down for engagement with a component surface and top flange pips.

Fasteners such as bolts and screws tend to have a screw thread which either bites into an insert or orifice or a reciprocal thread. Increasing use of plastics materials necessitate fasteners which can accommodate such materials. Particular problems with plastics materials relate to applications where vibration and other stressing of the fastener assembly can reduce the predictability and consistency of the fastening assembly in use.

Considering figures 1 to 3 of the accompanying drawings providing illustrations of aspects of the invention by way for example only and explanation. A spacer 1 has a head flange 2 which extends radially from a sleeve portion 3 substantially perpendicular to the flange 2. The flange 2 can be formed of any suitable material such as steel. The flange 2 has flange pips 4 with at least some of the pips 4 projecting in a similar direction to the sleeve portion 3 and so below an engagement surface of the flange 4 which engages about a hole or orifice in a component such as a panel (not shown in these figures). The flange pips 4 are typically rounded or have a smooth/flat surface for engagement with the component (not shown) upon assembly in a fastener assembly as described later. Such rounded/flat/smooth contact will limit or avoid contact stress points in the material of the component engaged.

The sleeve portion 3 has radial pips 5 which extend outward from the sleeve portion 3 and so away from the major axis X-X of the sleeve portion 3. This major axis X-X will also be the axis of rotation of a fastener (not shown) in the spacer 1 in use and of a fastener (not shown) such as a bolt or screw driven into the sleeve and/or insert upon forming a fastener assembly as described later. The radial pips 5 are shaped and configured in the spacer 1 to engage the material of the component until locked by such engagement to prevent rotation in that direction of rotation by the fastener in use. At such a stage in the assembly, the spacer 1 will be substantially immobilized within the aperture, hole or orifice of the component and the fastener can be driven along the sleeve portion 3 or insert until a head of the fastener engages the flange 2 on an exposed side away from the component. Once the head of the fastener engages the flange 2 further rotation is against the friction of engagement with the flange and flexing of the fastener head and the flange 2 itself.

The side of the flange 2 which engages the fastener head can be flat (apart from dimples pressed or otherwise created to form the flange pips 4) so there is a simple surface upon surface friction engagement which generates tension with flexing in the flange/fastener head and so through the fastener to the ‘anchor’ provided by the radial pips 5. This tension will resist release and will tend to squeeze the material of the component below the flange 4 and fastener head to the radial pips 5. In addition to this compression of the plastic throughout the material thickness there will be compression caused by the down pips in the flange.

In an alternative, the flange 2 can have some top flange pips 6 which project away from the upper or exposed surface of the flange 2 and so a component within which the flange is assembled. These top flange pips 6 will naturally first engage the fastener head with an offset gap. These top flange pips 6 will engage the fastener head and provide resistance to turning of the fastener head onto the top flange pips 6 and/or the fastener head deforms to create tension in the fastener (bolt or screw) and so compression as defined above with regard to the material of the component.

Ideally, the engagement between the spacer and the component through the hole or aperture is aligned to avoid tilting upon assembly. Such alignment is achieved in accordance with aspects of the present invention by providing balance in the pips 4, 6, both the flange pips 4 which engage about the surface of the component around the orifice in which the spacer is pressed or jacked into position and with the radial pips 5 that bite into the component material in the surface of the aperture core. The pips 4, 6 and 5 need be consistent to each other in terms of their shaping and size as well as distribution. For example, if the pips have a height or depth which is significantly different on one side of the spacer compared to the other then the spacer as presented and if turned will drag or dip on one side so straining alignment. With regard to the flange pips 4 it will be understood that those projections which are towards and downward onto the component about an aperture or orifice, flange pips 4, will first contact the component so these pips 4 will act to present the flange 2 and so the spacer 1 about the aperture of the component. If one pip 4 has a greater depth then this will tilt the presentation of the flange 4 and so the sleeve portion 3 associated with it which in turn will mis align the desired presentation of the fastener. However, it will also be appreciated that eventually the flange 4 may move towards a near flat surface to surface abutment around the aperture in the component or with a marginally insignificant variation in the gap on one side of the flange to the other. In such circumstances, the shoulder or ‘hinge’ between the flange and sleeve portion can be rendered rigid or with some flex to facilitate such auto alignment upon rotation of the fastener in the spacer 1 in use.

With regard to the radial pips 5 again matching of shape and distribution will avoid greater resistance or drag on one side of the aperture compared to the other until bite is such that rotation of the spacer 1 is prevented. Normally the sleeve will be a snug or near fit within the aperture of a component with a press or jacking process used to locate and engage with the component material of the aperture.

Wth regard to top flange pips 6 their height above the flange 2 will provide pedestals upon which the fastener head will first contact. As such, similar heights and responses to maintain orientation and alignment is preferred. For example, the spacer 1 has an inside sleeve diameter of 7.2mm with 3 equi-spaced pips 5 with a 120 degrees separation with an outside diameter 8 roughly 9.4-9.6mm whilst the flange pips 4 again are equally spaced with respective centres at around 11.5mm diameter 21 and overall head flange 2 with a diameter 22 of around 14 -16mm.

FIG 3 shows that the flange pips 4 has a depth 41 of about 1.1 mm with a nominal flange 2 thickness of 0.7mm and a depth of the sleeve from the bottom surface of the flange 2 to the edge of sleeve of about 3mm. The flange pips 4 are pressed with an inner former 51 of 1 mm and outer 52 of about 1 5mm.

Figure 4 provides a schematic cross-sectional illustration of a fastener assembly 9 with a spacer 1 in accordance with aspects of the present invention. Similar nomenclature is used for comparison with previous figures 1 to 3. The spacer 1 with head flange 2 and sleeve portion 3 is located in an orifice or aperture 10 formed in a component 11. The spacer 1 is pressed into the orifice or aperture 10 normally with relatively light pressure such that the head flange 2 abuts around the aperture 10. Once so positioned a fastener 12 is located and driven along the sleeve 3 or insert 100 in the direction of arrowhead A. Resistance to rotation is provided by the flange pips 4 and the radial pips 5 so the fastener 12 can be driven at speed along a thread 113 in an insert 100 in a base material 101. The fastener 12 may pass freely through the sleeve 3 or may be self- tapping with the fastener screw thread engaging the inner surfaces of the sleeve or simply moving along such a screw thread in the sleeve.. The spacer 1 will be anchored as the pips 4, 5 bite into the material of the component 11. This process is sometimes called ‘jacking’.

The spacer 1 is anchored until a head 13 of the fastener 12 contacts the upper side of the head flange 2 of the spacer 1 whereupon further turning of the fastener 12 creates tension by stressing of the spacer 1 and possible some deformation of the head flange 2. It will be appreciated that the radial pips 5 bite into the material forming the orifice or aperture 10 so anchoring the sleeve 3 towards one end whilst the friction of the fastener head to head flange 2 causes retention of position of the spacer 1 despite the fastener 12 being turned. Thus, the material around the aperture 10 is not damaged by the spacer 1 with potential consequences in terms of fastener assembly 9 strength.

It will be appreciated rather than provide a screw thread insert 100 or self-tapping screw thread in the sleeve 3 that a nut 14 can be provided either embedded in the material of the component 11 or base material 101 or loosely applied. The fastener head 13 will still engage the head flange 2 such that the spacer 1 is held so creating bite in the material of the component 11 by both the radial pips 5 and the flange pips 4. In such circumstances tension is then created between the nut 14 and the head13/head flange 2 such that the sleeve 3 is compressed or stressed and so the component material is squeezed for retention. However, it will also be understood that one of the objectives of the present invention is to avoid loose parts so a ‘free’ nut might be counter to this objective.

As discussed above, the head flange 2 may include upturned or top flange pips 6 which will be first engaged by the fastener head 13. The top flange pips 6 in such circumstances give an initial gap or stand off between the flange 2 and the fastener head 13. The spacer 1 will not turn along the axis Y-Y of fastener rotation dependent upon pips 4, 5 configuration, distribution and dimensions. The spacer 1 is substantially fixed or jacked further so rotation of the fastener will then compress the top flange pips 6 creating tension in the fastener assembly 9. Typically, the fastener will be turned to a desired torque level 2Nm, 4Nm, 6Nm, 8Nm and then turned a further ¼ turn to achieve the desired tension in the joint.

It has been found that at least 3 effective flange pips 4 and, when used, top pips 6 provide good presentation of the flange 2 to the surface around the aperture in a component and to a fastener head but of course this depends on the diameter of the fastener head. Greater or lesser numbers of flange pips 4, 6 can be used as required and dependent upon other factors. Typically, the pips 4, 6 are pressed so the depth of the pips pressed to form the pips 4,6 may create slight variations in work hardening in this pressing process in the material of the flange 2 worked in this pressing process. Similar responses by the pips is desired so finishing of the spacers 1 for amelioration, consistent hardening or otherwise will be required across the pips in the flange.

For clarity the spacer 1 as shown in the previous figures is depicted in Figure 5 in which top flange pips 6 are shown equally spaced to each other and flange pips 4 which are pressed down for engagement with the component surface.

A particular example of a spacer has a 16mm diameter flange head (0.7mm thick) with a sleeve portion 3.0mm long and 8.6mm diameter. The flange has 6 off under head flange pips which are 1.5mm diameter and 0.65mm high at a PCD of 12.0 and 3 off equidistant sleeve body radiant pips of 9.41mm diameter when measured over the peaks of the 1.5mm diameter pips. The spacer is manufactured from DC01 steel, case hardened to some 114 Rockwell C (Rc) tested in a self-colour state. The spacer is installed into an orifice in a plastic which is 3.2mm thick with a tensile strength of 60-65MPa to form a fastener assembly with a bolt or screw.

A previous 16mm diameter headed spacer had a 2.7mm under head length and three facets in the pilot end of the sleeve body to cut grooves into the plastic about an orifice. This spacer required 0.5Nm to jack (press) the fastener into the hole, estimated to be equivalent to a force of 430N. The cut swarf was found to be very evident and mostly pushed inward as it contacted the face of the mating fastener.

The present fastener assembly with a spacer as described above was tightened with a recessed star drive grade 12.9mm bolt without any washers under the head and was able to reach a desired specified tightening torque of 8Nm without any rotation of the spacer due to the engagement of the radial pips and the flange pips upon the component surface. Tightening by an additional 90 degree turn produced an extraordinary increase in torque to 15Nm, requiring either a 10.9 grade bolt (14.72Nm max), or a grade 12.9 bolt (17.66Nm max). At no time did the spacer rotate with indentation marking visible in the top face of the brass headed insert. The indentations help to resist any spacer rotation.

Additionally, a spacer in accordance with aspects of the invention worked well being jacked (pressed) into an 8.8mm diameter plain drilled hole. It required 0.30Nm to jack the fastener into the hole, leaving the under-head flange pips standing proud and stopping when a 0.70mm feeler gauge was contacted. This was estimated to be equivalent to a force of 260N. The spacer was then fully jacked in such that the six under-head pips were 0.05mm short of being fully installed into the plastic, equivalent to a force of 606N or 0.6kN.

It was found with a M6304 grade stainless, 11 8mm diameter head bolt, a new bolt without any washers under the head was able to reach a staged tightening torque of 8Nm without any rotation of the spacer. It was noted that, as the spacer was forced into the plastic, the head flange bevelled or bellowed, the under-head gap rising from an initial 0.05 to 0.25 between 1.0Nm and 6Nm, the feeler gauge entering by some 2mm, only dropping back to zero at 8Nm. A 13mm diameter head will more securely clamp over the under-head pips and hold the head flatter.

Tightening by an additional 90 degree turn produced an increase in torque to 14.1 Nm with no rotation of the spacer. On disassembly, the body of the spacer looked visibly undamaged.

With a lesser number of under-head flange pips there may be concern that, when tightening, the friction under the head flange may not be in equilibrium and that the bolt would tend to move off centre. Thus, some top flange pips on the head flange can be provided which extend to engage the head flange rather than the plastic around the orifice and to stop that movement taking place.

For example, use of six flange pips instead of three was found to balance the surface area when the head slid over the cavity of the under-head flange pips engaging the surface about the orifice. The design produces a stable position of the bolt head, only really moving off centre at the 8Nm plus 90 degree rotation of the bolt by about 0.5mm. Typically, where a number of fastening joints are required to secure the assembly, all bolts will be assembled first of all, before any final 90 degree turn, so that movement will not be of any significance. Furthermore, special bolts with the larger diameter heads should reduce the movement even more.

The spacer can be case hardened and initially work hardened during the drawing process. The spacer can have a hardness of 50Rc to 70RC with an example being 67Rc becoming 114Rc after hardening. Hardening will reduce the degree of distortion in the head as it presses the pips into the plastic, only being partially supported.

Top flange pips prevent the bolt from moving over to accommodate the shrinkage variation in multiple hole positions in a moulding but it will be understood that a hardened 16mm diameter flange headed spacer, without top pips, may also be effective.

A 14mm diameter head variant can be configured so that it doesn’t rotate at 8Nm application torque, and will only have moved less than 5 degrees in relation to a 2.5mm wide paint mark when tightened to 10Nm with a 90 degree additional turn.

The sleeve section of the body may be distorted to a similar extent to previous spacers as it contacted the top face of the installed inserted fastener.

A 16mm diameter larger flange head will absorb more of the application torque (i.e. that torque using the actual bolts and mating components in the application) required to compress the plastic, so that less torque is active in compressing the spacer itself, so reducing any possible damage, with the fastener being hardened. The example spacer typically has no rotation at 8Nm but dependent upon the configuration and nature of the material in which the spacer is installed lower or higher limits for rotation can be achieved. Deformation on the head flange of the spacer typically is over about 30 degrees of the head and remains. With a large clearance hole for a fastener such as a M6 screw, the bolt when tightened is able to become off-centre with the compression limiter. The area of head that is still sitting proud is right in line with the under-head flange pips that is not being clamped by the off-centre bolt so indirectly the flange pips can cause deformation unless care is taken but clearly continuing to control the rotation of the spacer in the fastener assembly. The fastener assembly as shown with the radial pips and flange pips engaged upon assembly that when untightened after torques of 3Nm,4Nm,6Nm,8Nm and 8Nm+90° create assembly forces whereby after assembly tightening then dis assembly the spacer did not rotate in an anti-clockwise direction so retained in the component.

The spacers are typically heat treated, ZnNi plated and trivalent passivated.

While the invention has been illustrated and described in detail in the drawings and preceding description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. Each feature of the disclosed embodiments may be replaced by alternative features serving the same, equivalent or similar purpose, unless stated otherwise. Therefore, unless stated otherwise, each feature disclosed is one example of a generic series of equivalent or similar features.

In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.