WO2011107492A1

WO2011107492A1 - Methods of captivating a threaded fastener using a compression limiter

Info

Publication number: WO2011107492A1
Application number: PCT/EP2011/053058
Authority: WO
Inventors: Paul Martin
Original assignee: Psm International Limited
Priority date: 2010-03-02
Filing date: 2011-03-01
Publication date: 2011-09-09
Also published as: GB201003470D0; GB2478308A

Abstract

The invention relates to compression limiters (20; 50; 252, 254) which captivate the thread (24) of a threaded fastener (10).

Description

METHODS OF CAPTIVATING A THREADED FASTENER USING A COMPRESSION

LIMITER

The invention relates to a method of captivating a threaded fastener using a compression limiter; a compression limiter and threaded fastener assembly; a component, compression limiter and threaded fastener assembly; and a component, substrate, compression limiter and threaded fastener assembly. The invention also relates to a method of installing a compression limiter in a component and captivating a threaded fastener by a compression limiter. The invention further relates to a method of making a resilient fastener captivation part and threaded fastener pre- assembly; a resilient fastener captivation part and threaded fastener pre-assembly; another method of captivating a threaded fastener using a compression limiter; another compression limiter and threaded fastener assembly; another component, compression limiter and threaded fastener assembly; and another component, substrate, compression limiter and threaded fastener assembly.

When a threaded bolt is used to fasten a component made of a soft material, such as a plastics engine manifold, to a second component (hereinafter referred to as a substrate) made of a harder material, such as a metal engine block, it is known to make a tapped hole in the substrate of a smaller diameter than an aperture in the component so as to define a shoulder on the substrate, and insert a compression limiter, in the form of a tubular part comprising an inner bore, in the aperture in the softer component, so that it sits on the shoulder, and that the positions of the aperture and hole in the compression limiter, component, and the tapped hole in the substrate coincide. Then upon tightening of the mating bolt thread and a corresponding thread on the tapped hole in the harder substrate, the compression limiter limits the compressive forces transferred to the component during the tightening of the mating bolt thread and a corresponding threaded section in the substrate, thereby reducing deformation or cracking of the component. In this context, it is known to radially crimp the outside surface of a metal compression limiter so that it can captivate a bolt thread, prior to inserting the compression limiter in the aperture in the component.

An aim of the present invention is to provide an improved or at least an alternative method of captivating a threaded fastener with a compression limiter.

According to a first aspect of the invention there is provided a method of captivating a threaded fastener using a compression limiter, the method comprising, providing a threaded fastener which has a threaded section and a plain section between the head and the threaded section, providing a sleeve like compression limiter which defines an inner bore, passing the threaded section of the threaded fastener through the inner bore, axially pressing an end of the compression limiter nearest to the head of the fastener, so as to deform the compression limiter, and reduce the diameter of the bore of the compression limiter, so as to captivate the threaded section of the threaded fastener.

According to a second aspect of the invention there is provided a compression limiter and threaded fastener assembly, the compression limiter and threaded fastener assembly comprising a threaded fastener having a threaded section and a plain section between the head and the threaded section, and a sleeve like compression limiter which defines an inner bore, wherein the threaded section of the threaded fastener is passed through the inner bore, and an end of the compression limiter nearest to the head of the fastener has been axially pressed so as to deform the compression limiter, and reduce the diameter of the bore of the compression limiter, so as to captivate the threaded section of the threaded fastener.

In this way, the compression limiter and threaded fastener can remain connected to each other during transit.

The axial pressing force in the first and second aspect of the invention comes from the underside of the head of the fastener being pressed against the end of the compression limiter nearest to the head of the fastener, whilst the opposite end of the compression limiter is supported. According to a third aspect of the invention there is provided a component, compression limiter and threaded fastener assembly, comprising a compression limiter and threaded fastener assembly in accordance with the first or second aspect of the invention, the component comprising an aperture through it, and the compression limiter being pressed into the aperture in the component.

According to a fourth aspect of the invention there is provided a component, substrate, compression limiter and threaded fastener assembly, comprising a component, threaded fastener and compression limiter assembly in accordance with the third aspect of the invention, wherein the substrate has a threaded hole, the hole in the substrate being smaller than the aperture in the component, the component being arranged against the substrate so that the positions of the aperture and hole coincide, and the threaded fastener being fastened to the substrate by a rotary tightening force on the threaded fastener until the head of the fastener and the substrate exert a force on the compression limiter therebetween. According to a fifth aspect of the invention there is provided a method of installing a compression limiter in a component and captivating a threaded fastener by a compression limiter, the method comprising, providing a component which has an aperture through it, providing a support which has a hole, the hole in the support being smaller diameter than the aperture in the component, arranging the component against the support so that the positions of the aperture and the hole coincide, providing a compression limiter comprising a generally tubular part which defines an internal bore, providing a threaded fastener comprising a threaded section and a plain section between the head and the threaded section, pressing the compression limiter into the aperture in the component towards the support, and pressing the head of the threaded fastener through the bore of the compression limiter, until the threaded part of the threaded fastener enters the hole in the support, so as to deform the compression limiter, and reduce the diameter of the bore of the compression limiter, so that the deformed part of the compression limiter captivates the threaded section of the threaded fastener.

The fastener is preferably installed into the compression limiter bore, and one pressing step preferably presses the compression limiter into the component and deforms the compression limiter so as to captivate the thread.

The method in accordance with the fifth aspect of the invention may comprise providing a compression limiter which has a deformable raised part at its end nearest to the head of the fastener. The length of the compression limiter, from the deformable raised part to the opposing end, preferably exceeds the width of the component.

The deformable raised part of the compression limiter is preferably arranged adjacent the inner bore of the tubular part, most preferably in the form of an annulus adjacent the inner bore.

Such a method is advantageous because a single pressing operation can both fasten the compression limiter to the component and deform the compression limiter so as to captivate the threaded fastener. According to another aspect of the invention there is provided a component, substrate, compression limiter and threaded fastener assembly, wherein the compression limiter is pressed into an aperture in the component, the threaded part of the threaded fastener is installed through a bore of the compression limiter, and the head of the threaded fastener is pressed and turned, or only turned, until the thread of the threaded fastener engages a tapped hole of the substrate, so as to fasten the component to the substrate, the pressing and/or turning causing an upper end of the compression limiter to deform inwardly so as to captivate the fastener thread.

Another aim of the present invention is to provide an improved or alternative design of compression limiter.

According to a sixth aspect of the invention there is provided a method of making a resilient fastener captivation part and threaded fastener pre-assembly, the method comprising providing a threaded fastener comprising a threaded section and a plain section between the head and the threaded section, and providing a resilient compression limiter part, the resilient fastener captivation part comprising a generally tubular part defining a bore, the resilient fastener captivation part having a compression limiter engagement end and a fastener thread captivation end, the tubular part having a radially outward protrusion nearer to the compression limiter engagement end, and the tubular part having a radially inward protrusion nearer to the fastener thread captivation end, the radially outward protrusion comprising a first shoulder, the radially inward protrusion having a second shoulder, forcing the resilient fastener captivation part over the threaded section of the threaded fastener, by resiliently deforming the radially inward protrusion at the fastener thread captivation end outwardly to allow the threaded section of the threaded fastener to pass therethrough, and then allowing the radially inward protrusion to relax to its original diameter so as to captivate the threaded section of the threaded fastener, the radially outward protrusion being for resiliently deformation inwardly, so it can be used to connect to, and resist removal of, another part from the resilient part.

The step of forcing the resilient fastener captivation part over the threaded section of the threaded fastener may comprises axially pressing or screwing the resilient fastener captivation part over the threaded section.

According to a seventh aspect of the invention there is provided a resilient fastener captivation part and threaded fastener pre-assembly, the pre-assembly comprising a threaded fastener comprising a threaded section and a plain section between the head and the threaded section, and a resilient compression limiter part, the resilient fastener captivation part comprising a generally tubular part defining a bore, the resilient fastener captivation part having a compression limiter engagement end and a fastener thread captivation end, the tubular part having a radially outward protrusion nearer to the compression limiter engagement end, the radially outward protrusion comprising a first shoulder, and the tubular part having a radially inward protrusion nearer to the fastener thread captivation end, the radially inward protrusion having a second shoulder, the radially inward protrusion at the fastener thread captivation end having been forced to resiliently deform outwardly to allow the threaded section of a threaded fastener to pass therethrough, and then allowed to relax to its original diameter so as to captivate the threaded section of a threaded fastener, the radially outward protrusion being for resiliently deformation inwardly, so it can be used to connect to and resist removal of another part from the resilient part.

The resilient fastener captivation part may be detachable from the threaded fastener by rotational movement of the resilient fastener captivation part relative to the threaded fastener so that the resilient fastener captivation part can "twist off the threaded section of the fastener. Alternatively, the threaded fastener may comprise an annular ring at the inbound end of the threaded section over which the resilient fastener captivation part engages, so as to resist manual rotational separation of the parts.

According to an eighth aspect of the invention there is provided a method of captivating a threaded fastener using a compression limiter, the method comprising providing a resilient fastener captivation part and threaded fastener pre-assembly in accordance with the sixth or seventh aspect of the invention, and providing a compression limiter, the compression limiter having a tube with an inward lip at one end, pressing the compression limiter onto the resilient fastener captivation part until the inward lip of the compression limiter snaps fits over the radially outward protrusion of the resilient compression limiter part, the inward lip captivating the resilient compression limiter part, which in turn captivates the fastener thread.

According to a ninth aspect of the invention there is provided a compression limiter and threaded fastener assembly, the compression limiter and threaded fastener assembly comprising a resilient fastener captivation part and threaded fastener pre-assembly in accordance with the seventh aspect of the invention, and a compression limiter, the compression limiter having a tube with an inward lip at one end, the compression limiter having been pressed onto the resilient fastener captivation part until the inward lip of the compression limiter snaps fits over the radially outward protrusion of the resilient fastener captivation part, the inward lip captivating the resilient fastener captivation part, which in turn captivates the fastener thread.

Large injection moulded parts such as inlet manifolds contract and distort during cooling. Where the moulded parts form part of an assembly that is joined together using threaded fasteners, large clearance holes, in other words, a large amount of radial float, are required to ensure alignment of the bolt and the threaded hole. The known compression limiter typically provide 0.5 mm float for a M6 bolt or, in other words, about 10% of the thread diameter. Radial clearance of 1.0 mm is commonly required, and sometimes radial clearance of as much as 1.6 mm is required.

An alternative or additional aim of the present invention is to provide a compression limiter which permits more radial float.

Preferably, in the resilient fastener captivation part and threaded fastener pre-assembly of the seventh aspect of the invention, the threaded fastener can radially float within the resilient part when installed therein. Most preferably, the threaded fastener can radially float by about 0.4 to 0.8 mm within the resilient part.

Preferably, in the compression limiter and threaded fastener assembly of the ninth aspect of the invention, the resilient part can radially float within the compression limiter when installed therein. Most preferably, the resilient part can radially float by about 0.6 to 0.8 mm within the compression limiter when installed therein.

In one preferred embodiment, the resilient part can radially float by about 0.8 mm within the compression limiter when installed therein, and the threaded fastener can radially float by about 0.8 mm within the resilient part, giving a total radial float of about 1.6 mm for a M6 bolt or, in other words, about 20% of the thread diameter. Known compression limiters are longer than the thread length of the bolt so that the thread can be retracted fully inside the compression limiter after the thread is captivated. An alternative or additional aim of the present invention is to provide an improved or at least an alternative compression limiter which allows a shorter compression limiter to be used on a longer thread.

In the compression limiter and threaded fastener assembly of the ninth aspect of the invention the distance between the shoulder of the compression limiter and the end of the compression limiter nearest to the head of the fastener during tightening is preferably less than the distance between the first and second shoulders of the resilient part, thereby increasing the distance that the thread can be retracted so as to retract a greater thread length into a smaller compression limiter length. The first radial protrusion is preferably arranged nearer to, most preferably at, the compression limiter engagement end of the resilient part. The second radial protrusion is preferably arranged nearer to, most preferably at, the fastener thread captivation end of the resilient part.

The telescopic fastener captivating compression limiter in accordance with the invention increases the number of applications for the captive bolt compression limiter assemblies, i.e. enabling the use of the compression limiter with a thinner component.

Preferably, the radially outward protrusion comprises a first tapered surface on its leading side which tapers from a smaller diameter towards the compression limiter engagement end of the resilient part to a larger diameter towards the fastener thread captivation end of the resilient part. The first tapered surface assists inward deformation of the radially outward protrusion under axial force.

Preferably, the radially inward protrusion comprises a second tapered surface which tapers from a smaller diameter towards the compression limiter engagement end of the resilient part to a larger diameter towards the fastener thread captivation end of the resilient part. The first tapered surface assists outward deformation of the radially inward protrusion under axial force.

The length of the resilient part is less than or equal to the length of the compression limiter.

According to a tenth aspect of the invention there is provided a component, compression limiter and threaded fastener assembly, comprising a compression limiter and threaded fastener assembly in accordance with the ninth aspect of the invention, the component comprising an aperture through it, and the compression limiter being pressed into the aperture in the component. Preferably, the compression limiter length is substantially equal to the width of the component.

According to an eleventh aspect of the invention there is provided a component, substrate, compression limiter and threaded fastener assembly, comprising a component, threaded fastener and compression limiter assembly in accordance with the tenth aspect of the invention, wherein the substrate has a threaded hole, the hole in the substrate being smaller than the aperture in the component, the component being arranged against the substrate so that the positions of the aperture and hole coincide, and the threaded fastener being fastened to the substrate by a rotary tightening force on the threaded fastener until the head of the fastener and the substrate exert a force on the compression limiter therebetween.

An alternative or additional aim of the present invention is to provide a compression limiter which has an improved retention.

Any of the aforesaid compression limiters may comprise one or more formation on its outer surface which is/are suitable for providing resistance to axial withdrawal of the compression limiter from a component and/or one or more formation on its outer surface which is/are suitable for providing resistance to rotation of the compression limiter within a component. The axial withdrawal resistant formation preferably comprises one or more tapered fin on its outer surface, most preferably, the compression limiter has between five and ten tapered fins. The fins may be spaced axially along axial length of compression limiter. The rotation resistant formation may comprise one or more axial spline on its outer surface spaced about its periphery. Products corresponding to any one or more steps of the methods of the immediately preceding aspect are envisaged, and vice versa.

Other optional and preferred features are set out in the dependent claims and the description below.

Methods of captivating a threaded fastener using a compression limiter; compression limiter and threaded fastener assemblies; component, compression limiter and threaded fastener assemblies; component, substrate, compression limiter and threaded fastener assemblies; a method of installing a compression limiter in a component and captivating a threaded fastener by a compression limiter; a method of making a resilient fastener captivation part and threaded fastener pre-assembly; a resilient fastener captivation part and threaded fastener pre-assembly; another method of captivating a threaded fastener using a compression limiter; another compression limiter and threaded fastener assembly; another component, compression limiter and threaded fastener assembly; and another component, substrate, compression limiter and threaded fastener assembly; will now be described, by way of example only, with reference to the accompanying drawings, in which,

Figure 1 is a schematic view of a bolt being pressed against a compression limiter, sitting on an anvil, the bolt being shown in side view and the and the other parts being shown in cross section,

Figure 2 is a schematic side view of the parts of Figure 2, when further axial force is applied to the bolt, Figure 3 is a schematic view of a compression limiter and threaded fastener (sub) assembly, resulting from the operation shown in Figure 2,

Figure 4 is a schematic view of the compression limiter and threaded fastener (sub) assembly of Figure 3 being pressed into a component, sitting on an anvil,

Figure 4A is a schematic view of the compression limiter and threaded fastener (sub) assembly, and component, being attached to a substrate,

Figure 5 is a schematic side view of an alternative compression limiter, which has an external profile in accordance with the invention, which can be used instead of the compression limiter of Figure 1,

Figure 6 is a schematic side view of a bolt ready to be pressed against a compression limiter in a component, sitting on an anvil,

Figure 7 shows the compression limiter of Figure 6 captivating the bolt,

Figure 7A shows the compression limiter, bolt and component of Figure 7 being fitted to a substrate,

Figure 8 shows a standard sized threaded bolt captivated by a compression limiter, and in its fully retracted position so that its thread lies within the compression limiter,

Figure 9 shows the parts of Figure 8, in an unretracted position,

Figure 10 is a side view of a further compression limiter assembly in accordance with the invention,

Figure 11 is a schematic perspective view of a resilient fastener captivation part of the compression limiter assembly of Figure 10, Figure 12 is a first end view of the part of Figure 11 ,

Figure 13 is a second end view of the part of Figure 11,

Figure 14 is a first side view, partly in cross section, of the part of Figure 11,

Figure 15 is a second side view of the part of Figure 11, Figure 16 is a schematic view of a bolt in a position ready to be pressed against a resilient fastener captivation part, the bolt being shown in side view and the resilient fastener captivation part being shown in cross section,

Figure 17 is a schematic view of the resilient fastener captivation part of Figure 16 installed on the bolt,

Figure 18 is a schematic view of the bolt and resilient fastener captivation part of Figure 17 attached to another compression limiter part, Figure 19 shows a side view of a bolt,

Figure 20 is view in cross section of a compression limiter part,

Figure 21 is a view from one end of a resilient fastener captivation part,

Figure 22 is a view in cross section of the resilient fastener captivation part,

Figure 23 is a side view of the resilient fastener captivation part, Figure 24 shows a shorter compression limiter length for a standard sized threaded bolt, retracted like in Figure 8, and

Figure 25 also shows the parts of Figure 12 with the bolt fully installed in the compression limiter, unretracted like in Figure 9.

Referring to Figure 1, a tube-like compression limiter 20, made of brass, steel or aluminium, sits on an anvil 3. The compression limiter 20 is surrounded by a radial support 5, to provide resistance against buckling of the tubular wall of the compression limiter. The length of the tubular wall of the compression limiter 20 is slightly greater than the width of the radial support 5. An upper end (as shown in Figure 1) of the compression limiter 20 comprises an annular protrusion 6, of continuous form, proximal to the inside surface of the compression limiter, which extends away from the radial support 5.

The inside surface of the compression limiter 20 is diametered to provide a suitable clearance for the threaded part 24 of the bolt 10, and the shank which is narrower than the threaded part. The inside surface 38 of the bore of the compression limiter 20 and the outside surface of the compression limiter 20 are approximately parallel with each other, and intended to lie parallel with the longitudinal axis of the bolt 10. The threaded section 24 of a threaded bolt 10 is inserted freely through the bore in the compression limiter 20, until the threaded section 24 passes freely through a corresponding opening 7 in the anvil 3, and the head 40 of the bolt approaches the annular protrusion 6.

Referring to Figure 2, the threaded bolt 10 is pressed downward until the head 40 of the bolt deforms the annular protrusion 6 of Figure 1. The arrows in Figure 2 show a radial component of deformation of the compression limiter 20, so as to form a radial lip 42. This inward deformation of the compression limiter 20 is sufficient that the minimum diameter of the compression limiter 20 at the inside of the lip 42 is less than the diameter of the thread 24 of the bolt 10, thereby permitting the compression limiter 20 to captivate the bolt, but still exceeds the diameter of the shank of the bolt 10, so that the bolt 10 is able to move axially to a degree within the compression limiter. As mentioned in detail below, there is also some radial float.

Referring to Figure 3, the compression limiter 20 is no longer manually separable from the bolt 10.

Referring to Figure 4, the threaded bolt 10, the thread 24 captivated by the compression limiter 20, is pressed into a component 12 made of plastic, rubber or another suitable softer material (for example an engine manifold), with a support anvil 3 lying beneath. The material of the compression limiter 20 is harder than the component 12.

The component 12 defines a component opening 16. In accordance with the invention, the compression limiter 20 is sized for press fit insertion into the component opening 16. The axial length of the compression limiter 20 in Figure 4 is approximately equal to the width of the component 12.

Referring to Figure 4A, the component 12 can now be fastened to a substrate 14 made of a harder material such as metal (for example an engine block). The substrate 14 has a substrate opening 18. The substrate opening 18 is tapped to provide a female thread which corresponds to the male thread 24 of the threaded bolt 10. The substrate opening 18 is shown as a through opening but it could be blind. Referring to Figure 4A, during assembly, the component 12, with the bolt 10 captivated by the compression limiter installed therein, is arranged against the outer surface of the substrate 14.

The thread 24 of the bolt 10 engages with the tapped substrate opening 18, and the bolt is tightened by applying a rotary tightening force to the head in the usual manner. When the bolt thread is tight, the distance from the underside of the head 40 of the fastener to the top of the substrate 14 is approximately equal to the length of the compression limiter 20 and the width of the component 12. The compression limiter 20 reduces the compressive force transferred to the component 12 in the vicinity of the component opening 16 during the tightening of the mating bolt 10 and threaded substrate opening 18, thereby reducing deformation or cracking of the softer component 12.

Referring to Figure 5, and in accordance with the invention, the outside surface of the compression limiter 20 can be provided with an anti-rotation and anti-withdrawal arrangement 32, which comprises one or more tapered fins 34a, 34b, 34c, preferably 5 or 6 tapered fins, which tapered fins taper from a smaller diameter (towards the lower end in Figure 5) to a larger diameter (towards the upper end in Figure 5), and can be of annular form, as shown schematically in Figure 5, and a longitudinal spline arrangement 36 towards the upper end of the compression limiter as viewed in Figure 5. The tapered fins 34 and longitudinal splines 36 are optimised to provide, respectively, excellent resistance to withdrawal from the soft material component 12 and rotation within the soft material component 12. The tapered fins 34 and longitudinal splines 36 are omitted from some Figures, for reasons of conciseness, but should be understood to be compatible with them. If the outside surface of the compression limiter 20 has anti rotation and anti withdrawal arrangement, the radial support 5 shown in Figures 1 and 2 can optionally be profiled to correspond to the outer radius of the anti rotation and anti withdrawal arrangement.

Referring to Figures 6 and 7, in another embodiment of the invention, a compression limiter 20 with annular protrusion 6 like in Figure 1, is pressed directly into the opening 16 in the component 12, with a support anvil 3 below. At this stage, it will be appreciated that the compression limiter 20 does not captivate the thread of the fastener 10. Axial force is then applied to the bolt 10 which causes the head of the bolt to press the annular protrusion 6, deforming the annular protrusion 6. A significant part of the deformation is radially inward in the direction of the pair of arrows shown in Figure 7 so as to form a radial lip 42. This inward deformation of the compression limiter 20 is sufficient that the minimum diameter of the compression limiter in the region of the lip 42 is less than the diameter of the thread 24 of the bolt 10, thereby permitting the compression limiter 20 to captivate the bolt if the bolt thread loosens.

Referring to Figure 7A, the component 12 is removed from the support anvil 3, and rearranged on a substrate 14. The thread 24 engages the tapped opening 18 in the substrate 14. With continued controlled application of rotary tightening force, the component 12 is fastened to the substrate 14.

Due to axial compression and deformation of the compression limiter 20, in particular in the region of the lip 42, the final position of the head 40 of the bolt 10 is flush with both the outer surface of the component 12 and the free end 26 of the compression limiter 20. The compression limiter 20 reduces the compressive force transferred to the component 12 in the vicinity of the component opening 16 during the tightening of the mating bolt 10 and threaded substrate opening 18, thereby reducing deformation or cracking of the softer component 12.

An advantage of this embodiment in comparison with the embodiment shown in Figures 1 to 4 is that this embodiment, with its "crumple zone" is less likely to lose clamping force between the bolt 10, compression limiter 20 and substrate opening 18 over time, and so there is less chance of detachment of the bolt 10 from the tapped hole 18 over time.

Referring to Figures 8 and 9, all of the thread 24 of the bolt 10 must be below the captivation part 42 for captivation to work. Therefore the minimum axial length of a compression limiter 20 should exceed the length of the bolt thread 24. The length of a compression limiter 20 is generally fixed by the local thickness of (for example the plastic of) the softer component 12 at the fastening point, although sometimes the thickness of the softer component 12 is increased by forming a thicker localized boss (not shown for conciseness). Referring to Figures 8 and 9, the bolt thread engagement 24 into the tapped hole 18 is generally 2 x the thread diameter, for example for a standard M6 bolt = 12 mm. At the point of assembling the bolt 10 to the compression limiter 20, the bolt has to fully retract into the compression limiter 20 to allow the components to be joined, to come together. Therefore the normal shortest length of an M6 captive compression limiter 20 is typically 14 mm (12 mm + 2 mm to captive part).

Referring to Figures 10 to 25, in another embodiment of the invention, a compression limiter assembly 50 comprises a compression limiter 52 and a resilient part 54.

Looking at for example Figures 10, 17 and 18, the compression limiter 52 is made of a relatively rigid material, for example a metal such as steel, or a very rigid thermo setting plastic that is resistant to plastic creep. The compression limiter 52 is in the form of a tube 56 with a radially inward wall 58 towards its free end that gives rise to an inverted L-shaped cross section. Figures 17 and 18 show the radially inward wall 58 defines a shoulder 59, suitable for retaining an end of a resilient part 54 as described below.

Referring to for example Figures 10 to 15, and 24 to 25, the resilient part 54 comprises a sleeve like part 60 which has a leading end (i.e. a compression limiter engagement end) 62 and a rearward end (i.e. a fastener thread captivation end) 64. The resilient part 54 is made of plastic material such as 30% glass filled polyamide selected for its rigidity (also known by the trade name NYLON). It could also be made of metal e.g. spring steel.

The length of the resilient part 54 is less than or equal to the length of the compression limiter 52, in this embodiment the parts are of approximately equal length. Referring to for example Figures 11, 14, and 15, the compression limiter engagement end 62 of the resilient part 54 comprises a radially outward wall 66. Referring to Figures 11 and 14, the radially outward wall 66 has a first tapered surface 68, facing outwardly, which tapers from a smaller diameter towards the compression limiter engagement end 62 of the resilient part to a larger diameter towards the fastener thread captivation end of the resilient part. The first tapered surface 68 assists inward deformation of the radially outward wall 66 when an axial force is applied. The radially outward wall 66 also defines a first shoulder 69 arranged to abut against the shoulder 59 of the compression limiter 52 to resist removal thereof.

Referring to for example Figures 11 to 15, the resilient part 54 has a first group of slits 70, preferably four slits, at its compression limiter engagement end 62, each extending, parallel to the longitudinal axis, from the compression limiter engagement end 62 towards, but not as far, as the fastener thread captivation end 64. The centres of successive slits 70 are radially spaced apart at 90 degrees. Slits 70 make it easier to deform the compression limiter engagement end 62 inwardly to a reduced effective diameter.

Referring to for example Figure 14, the rearward (i.e. the upper) end 64 of the resilient part 54 comprises a radially inward wall 72. The radially inward wall 72 has a second tapered surface 74, facing inwardly, which tapers from a smaller diameter towards the compression limiter engagement end 62 of the resilient part 54 to a larger diameter towards the fastener thread captivation end 64 of the resilient part. The second tapered surface 74 assists outward deformation of the radially inward wall 72 when an axial force is applied. The radially inward wall 72 is arranged to resiliently deform to allow a bolt 10 to pass therethrough.

The resilient part 54 has a second group of slits 76, preferably four slits, at its fastener thread captivation end 64, each extending, parallel to the longitudinal axis, has four slits 76 in the tube, each extending axially, from the fastener thread captivation end towards, but not as far as, compression limiter engagement end 62.

Slits 76 make it easier to deform the rearward end 64 outwardly to an increased diameter. The centres of successive slits 76b are radially spaced apart at 90 degrees. Also slits 70 are 45 degrees out of phase with the slits 76.

The radially inward wall 72 also defines a second shoulder 78 arranged to abut against the upper part of the threaded section 24 of the bolt 10 so as to captivate the bolt, so as to resist removal thereof.

Referring to Figures 14 and 16, during assembly, first, the resilient part 54 is pressed over the threaded section 24 of the bolt 10 towards the head of the bolt. Optionally an anvil can be used with the press. In particular, the foremost end of the threaded section 24 of the bolt 10 comes into contact with the second tapered surface 74 of the radially inward wall 72 at the fastener thread captivation end 64 of the resilient part 54.

As axial force is continued, the slits 76 widen, the radially inward wall 72 of the resilient part 54 resiliently deforms outwardly, and the threaded section 24 of the bolt 10 passes through the radially inward wall 72 at the fastener thread captivation end 64 of the resilient part 54. When the radially inward wall 72 reaches the shank of the fastener, the radially inward wall relaxes to a diameter less than the thread, causing the compression limiter 20 to captivate the bolt thread 24.

Referring to Figures 10, 14 and 17, next, the compression limiter 52 is pressed over the resilient part 54. Optionally an anvil can be used with the press. In particular, the upper surface of the compression limiter 52 comes into contact with the tapered surface 68 at the compression limiter engagement end 62 of the resilient part 54. The slits 70 narrow, the compression limiter engagement end 62 of the resilient part 54 resiliently deforms inwardly, and the radially outward wall 66 passes the radial wall 58 of the compression limiter 52. These three joined parts can be easily transported to a production line, and maintain their integrity, so as to minimise production time.

Next, the bolt 10 with the thread captivated by compression limiter 52 and the resilient part 54 is pressed into an opening 16 in a component. Optionally an anvil can be used with the press.

Finally, the component 12, with the bolt 10 with the thread captivated by compression limiter 52 installed therein, is arranged on a substrate, and the fastener is threaded into the tapped opening 18 in the substrate 14 in a similar manner to Figure 4 A. Referring to Figures 4 and 18, when the bolt 10 is fastened to the substrate 14, the ends of the compression limiter and resilient part coincide, the upper ends in contact with the head of the bolt, and the lower ends in contact with the substrate. Referring to Figures 8 to 9, 14, and 24 to 25, it should be noted that the distance between the shoulder 59 of the compression limiter 52 and the resilient part engagement end of the compression limiter 52 is less than the distance between the first shoulder 69 and the second shoulder 78 of the second part 54, thereby increasing the length of thread which can be retained by the compression limiter assembly 50, which can be useful in certain applications, for example where a relatively shorter compression limiter is desired and a relatively longer bolt thread length is desired.

The radially outward wall 66 and the radially inward wall 72 both snap-lock. Referring to Figures 24 and 25, the telescopic action of the two piece compression limiter 50 allows it to be shorter than the single piece compression limiter 20 in Figures 1 to 9. For example, if each of the two parts 52, 54 of the compression limiter 50 is approximately 8 mm, the compression limiter can, allowing for approximately 4 mm overlap (shown in Figures 24 and 25) hold a bolt threaded section 24 of 12 mm, whereas the single piece compression limiter 20 above would require a length of 14 mm to achieve the same.

The two part telescopic compression limiter 50 increases the number of applications for the captive bolt compression limiter assemblies. Also, with the known compression limiter captivation methods, it is not possible to achieve a 1.0 mm to 1.6 mm clearance. The two-part telescopic compression limiter 50 allows clearance between the bolt 10 and the inside of the sleeve like part 60 of the resilient part 54 , and also clearance between the outside of the sleeve like part 60 and the inside of the compression limiter 52, effectively doubling the clearance.

There is a gap between the radially outward wall 62 of the resilient part 54 and the tubular part 56 of the compression limiter 52. There is a further gap between the radially inward wall 58 of the compression limiter 52 and the sleeve part 60 of the resilient part 54. Due to these gaps, the resilient part 54 floats radially by about 0.6 to 0.8 mm in the compression limiter 52.

There is a gap between the threaded section 24 of the bolt 10 and the sleeve part 60 of the resilient part 54. There is a further gap between the radially inward wall 72 of the resilient part 54 and the unthreaded shank of the bolt 10. Again, due to the arrangement, the bolt 10 then floats radially about 0.4 to 0.8 mm in the plastic snap-fit part 54. Moreover, the compression limiter 50 provides a greater tolerance in the event of the axis of bolt 10 being out of alignment with the axis of the compression limiter.

Figures 19 to 23 show some variations in another embodiment of the invention. Referring to Figure 19, a bolt 200 (which corresponds to bolt 10 in the aforementioned embodiments) comprises an annular ring 202 between the thread and the shank 204. Referring to Figures 19 and 22, the bolt 200 can be passed through a tapered surface 274 of the resilient part 254 (which corresponds to the resilient part 54 in the aforementioned embodiments), in a manner similar to that shown in Figure 16. Since thread diameter (T) > opening (O) defined by radially inward wall 272 > shank diameter (S), the parts remain connected. Then, referring to Figure 20, the compression limiter 252 (which corresponds to compression limiter 52 in the aforementioned embodiments) is pressed onto the resilient part 254, so that the tapered opening 259 at the radially inward wall 258 of the compression limiter 252 passes over the radially outward wall 262. It should also be noted from Figures 22 and 23 that the proportions of the resilient part 254 are better suited to when a short compression limiter 50 is desired because the resilient part 254 provides a telescopic effect. The annular ring 202 can prevent the bolt thread from being removed over the resilient part 254. Alternatively, the thread of the bolt can be deformed to achieve the same effect. The terms "bolt" and fastener are used interchangeably in this text. The component can be a sheet, a part made from a sheet, a layer of material, or a component within such a sheet, part or layer. The substrate may be made of metal or another material such as plastics, with a threaded metal tubular insert defining the threaded hole 18, so that the surrounding substrate material is not deformed by the compression limiter.

Compatible features of different embodiments may be combined accordingly.

Claims

1. A method of making a resilient fastener captivation part and threaded fastener pre- assembly, the method comprising providing a threaded fastener comprising a threaded section and a plain section between the head and the threaded section, and providing a resilient fastener captivation part, the resilient fastener captivation part comprising a generally tubular part defining a bore, the resilient fastener captivation part having a compression limiter engagement end and a fastener thread captivation end, the tubular part having a radially outward protrusion nearer to the compression limiter engagement end, and the tubular part having a radially inward protrusion nearer to the fastener thread captivation end, the radially outward protrusion comprising a first shoulder, the radially inward protrusion having a second shoulder, forcing the resilient fastener captivation part over the threaded section of the threaded fastener, by resiliently deforming the radially inward protrusion at the fastener thread captivation end outwardly to allow the threaded section of the threaded fastener to pass therethrough, and then allowing the radially inward protrusion to relax to its original diameter so as to captivate the threaded section of the threaded fastener, the radially outward protrusion being for resiliently deformation inwardly, so it can be used to connect to, and resist removal of, another part from the resilient part.

2. A resilient fastener captivation part and threaded fastener pre-assembly, the pre-assembly comprising a threaded fastener comprising a threaded section and a plain section between the head and the threaded section, and a resilient fastener captivation part, the resilient fastener captivation part comprising a generally tubular part defining a bore, the resilient fastener captivation part having a compression limiter engagement end and a fastener thread captivation end, the tubular part having a radially outward protrusion nearer to the compression limiter engagement end, the radially outward protrusion comprising a first shoulder, and the tubular part having a radially inward protrusion nearer to the fastener thread captivation end, the radially inward protrusion having a second shoulder, the radially inward protrusion at the fastener thread captivation end having been forced to resiliently deform outwardly to allow the threaded section of a threaded fastener to pass therethrough, and then allowed to relax to its original diameter so as to captivate the threaded section of a threaded fastener, the radially outward protrusion being for resiliently deformation inwardly, so it can be used to connect to and resist removal of another part from the resilient part.

3. A method of captivating a threaded fastener using a compression limiter, the method comprising providing a resilient fastener captivation part and threaded fastener pre-assembly in accordance with Claim 1 or 2, and providing a compression limiter, the compression limiter having a tube with an inward lip at one end, pressing the compression limiter onto the resilient fastener captivation part until the inward lip of the compression limiter snaps fits over the radially outward protrusion of the resilient compression limiter part, the inward lip captivating the resilient compression limiter part, which in turn captivates the fastener thread.

4. A compression limiter and threaded fastener assembly, the compression limiter and threaded fastener assembly comprising a resilient fastener captivation part and threaded fastener pre-assembly in accordance with Claim 2, and a compression limiter, the compression limiter having a tube with an inward lip at one end, the compression limiter having been pressed onto the resilient fastener captivation part until the inward lip of the compression limiter snaps fits over the radially outward protrusion of the resilient fastener captivation part, the inward lip captivating the resilient fastener captivation part, which in turn captivates the fastener thread.

5. A component, compression limiter and threaded fastener assembly, comprising a compression limiter and threaded fastener assembly in accordance with Claim 4, the component comprising an aperture through it, and the compression limiter being pressed into the aperture in the component.

6. A component, substrate, compression limiter and threaded fastener assembly, comprising a component, threaded fastener and compression limiter assembly in accordance with Claim 5, wherein the substrate has a threaded hole, the hole in the substrate being smaller than the aperture in the component, the component being arranged against the substrate so that the positions of the aperture and hole coincide, and the threaded fastener being fastened to the substrate by a rotary tightening force on the threaded fastener until the head of the fastener and the substrate exert a force on the compression limiter therebetween.

7. A method of captivating a threaded fastener using a compression limiter, the method comprising, providing a threaded fastener which has a threaded section and a plain section between the head and the threaded section, providing a sleeve like compression limiter which defines an inner bore, passing the threaded section of the threaded fastener through the inner bore, axially pressing an end of the compression limiter nearest to the head of the fastener, so as to deform the compression limiter, and reduce the diameter of the bore of the compression limiter, so as to captivate the threaded section of the threaded fastener.

8. A compression limiter and threaded fastener assembly, the compression limiter and threaded fastener assembly comprising a threaded fastener having a threaded section and a plain section between the head and the threaded section, and a sleeve like compression limiter which defines an inner bore, wherein the threaded section of the threaded fastener is passed through the inner bore, and an end of the compression limiter nearest to the head of the fastener has been axially pressed so as to deform the compression limiter, and reduce the diameter of the bore of the compression limiter, so as to captivate the threaded section of the threaded fastener.

9. A component, compression limiter and threaded fastener assembly, comprising a compression limiter and threaded fastener assembly in accordance with Claim 7 or 8, the component comprising an aperture through it, and the compression limiter being pressed into the aperture in the component.

10. A component, substrate, compression limiter and threaded fastener assembly, comprising a component, threaded fastener and compression limiter assembly in accordance with Claim 9, wherein the substrate has a threaded hole, the hole in the substrate being smaller than the aperture in the component, the component being arranged against the substrate so that the positions of the aperture and hole coincide, and the threaded fastener being fastened to the substrate by a rotary tightening force on the threaded fastener until the head of the fastener and the substrate exert a force on the compression limiter therebetween.

11. A method of installing a compression limiter in a component and captivating a threaded fastener by a compression limiter, the method comprising, providing a component which has an aperture through it, providing a support which has a hole, the hole in the support being smaller diameter than the aperture in the component, arranging the component against the support so that the positions of the aperture and the hole coincide, providing a compression limiter comprising a generally tubular part which defines an internal bore, providing a threaded fastener comprising a threaded section and a plain section between the head and the threaded section, pressing the compression limiter into the aperture in the component towards the support, and pressing the head of the threaded fastener through the bore of the compression limiter, until the threaded part of the threaded fastener enters the hole in the support, so as to deform the compression limiter, and reduce the diameter of the bore of the compression limiter, so that the deformed part of the compression limiter captivates the threaded section of the threaded fastener.

12. A method of captivating a threaded fastener using a compression limiter substantially as described herein with reference to Figure 1 and/or Figure 2 and/or Figure 3 of the drawings.

13. A compression limiter and threaded fastener assembly substantially as described herein with reference to Figure 3 of the drawings.

14. A component, compression limiter and threaded fastener assembly substantially as described herein with reference to Figure 4 of the drawings.

15. A component, substrate, compression limiter and threaded fastener assembly substantially as described herein with reference to Figure 4A of the drawings.

16. A method of installing a compression limiter in a component and captivating a threaded fastener by a compression limiter, substantially as described herein with reference to Figures 6, 7 and 7A of the drawings.

17. A component, substrate, threaded fastener and compression limiter assembly substantially as described herein with reference to Figures 6 and 7 and 7A of the drawings.

18. A method of making a resilient fastener captivation part and threaded fastener pre- assembly substantially as described herein with reference to Figure 16, and 11 to 15 or 21 to 23, of the drawings.

19. A resilient fastener captivation part and threaded fastener pre-assembly substantially as described herein with reference to Figure 16 and 11 to 15 or 21 to 23 of the drawings.

20. A method of captivating a threaded fastener using a compression limiter substantially as described herein with reference to Figure 16 to 18 of the drawings.

21. A compression limiter and threaded fastener assembly substantially as described herein with reference to Figure 10, 18, or 24 of the drawings.

22. A component, compression limiter and threaded fastener assembly substantially as described herein with reference to Figures 4 and 18 of the drawings.

23. A component, substrate, threaded fastener and compression limiter assembly substantially as described herein with reference to Figures 4 and 18 of the drawings.