GB2560761A

GB2560761A - Assembly

Info

Publication number: GB2560761A
Application number: GB1704716.8A
Authority: GB
Inventors: Victor Stevens Mark
Original assignee: Bankside Patterson Ltd
Current assignee: Bankside Patterson Ltd
Priority date: 2017-03-24
Filing date: 2017-03-24
Publication date: 2018-09-26
Anticipated expiration: 2037-03-24
Also published as: GB2560761B; GB201704716D0; GB2560781A; GB2560781B; GB201716868D0

Abstract

An assembly (50) comprises a first part (52) comprising a first mating surface (62) and a second part (54) comprising a second mating surface (62). The first mating surface (62) is adapted, in use, to contact the second mating surface (62) when the two parts (52, 54) are brought together as part of the assembly (50). The first mating surface (62) comprises a protrusion (70) and the second mating surface comprises an indention (72). The protrusion (70) and indentation (72) are shaped and sized for cooperative engagement when the mating surfaces (62) are brought into contact with one another. The protrusion (70) and indentation (72) each comprise a substantially flat portion (92) comprising a through hole (64, 96) for receiving, in use the shank (102) of a screw (56) or bolt, the screw (56) or bolt comprising a head portion (104) and a shank portion (102), the shank portion (102) being is receivable, in use, in the through holes (94, 96) of the protrusion (70) and indentation (72). The head portion (104) of the screw (56) or bolt comprises a rounded outer underside portion (114), which seats against a substantially dish-shaped parts (90) of the projection (70).

Description

(54) Title of the Invention: Assembly Abstract Title: Assembly (57) An assembly (50) comprises a first part (52) comprising a first mating surface (62) and a second part (54) comprising a second mating surface (62). The first mating surface (62) is adapted, in use, to contact the second mating surface (62) when the two parts (52, 54) are brought together as part of the assembly (50). The first mating surface (62) comprises a protrusion (70) and the second mating surface comprises an indention (72). The protrusion (70) and indentation (72) are shaped and sized for cooperative engagement when the mating surfaces (62) are brought into contact with one another. The protrusion (70) and indentation (72) each comprise a substantially flat portion (92) comprising a through hole (64, 96) for receiving, in use the shank (102) of a screw (56) or bolt, the screw (56) or bolt comprising a head portion (104) and a shank portion (102), the shank portion (102) being is receivable, in use, in the through holes (94, 96) of the protrusion (70) and indentation (72). The head portion (104) of the screw (56) or bolt comprises a rounded outer underside portion (114), which seats against a substantially dish-shaped parts (90) of the projection (70).

FIGURE 9

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FIGURE 9

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FIGURE 10

Title: Assembly

Description:

This invention relates to a new type of assembly, and in particular, an assembly connection that is suitable for connecting components of an assembly to one another.

In many types of assembly, two or more components need to be connected to one another and this can be accomplished by various means, such as by using adhesives, welding, plastic deformation, mechanical fasteners, etc.. Mechanical fasteners, such as screws, rivets, bolts & nuts, etc. are often preferred because they are ubiquitous and therefore easy to come-by. Mechanical fasteners also permit, in many cases, subsequent disassembly and reassembly for repair and maintenance purposes.

When putting together an assembly, it is often necessary to use a jig to ensure that the components being connected are in their correct relative positions and orientations. Fabricating jigs, especially for one-off assemblies, can be expensive and time-consuming.

Further, when using mechanical fasteners, there is a risk that the forces employed when affixing the first few fasteners can cause the components to move relative to one another. Therefore, until such time as a few fasteners have been fitted, the assembly can be somewhat susceptible to misalignment (even where a jig is used), and if not identified early, can lead to permanent incorrect relative positioning of the parts, especially where irreversible drilling operations are involved. For example, when fastening two components together using bolts & nuts, the assembly process typically involves the steps of: aligning and positioning the two components (e.g. by eye, or by using a jig);

drilling through two or more parts of the assembly to form a set of aligned through holes; inserting a bolt shank through the drilled holes; and tightening a nut (and optionally, a washer) onto the bolt shank. Misalignment can occur at any of these stages, for example, if the parts are not correctly placed and aligned in the first place; if the parts move during the drilling procedure; if the drilled holes are not the correct size for the bolt shanks; and during tightening of the nut, which can often cause relative rotation of the parts. Where misalignment occurs, and this is especially the case in critical structural assemblies, the assembly often has to be discarded if it cannot be re-worked, which is wasteful of both materials and time.

A further known problem associated with using bolt & nut fasteners is that it is often necessary to use two tools simultaneously, for example, a spanner (wrench) on the bolt head to keep the bolt still whilst a socket wrench is used on the nut to effect tightening. This complicates the assembly process.

A need therefore exists for a solution to one or more of the above problems. This invention aims to provide a solution to one or more of the above problems, and/or to provide a new and/or alternative assembly method and apparatus. Various aspects of the invention are set forth in in the appended independent claims. In particular, essential features of the invention are set forth in in the appended independent claims and various optional/preferred features of the invention are set forth in the appended dependent claims.

A first aspect of the invention provides an assembly comprising: a first part comprising a first mating surface and a second part comprising a second mating surface, the first mating surface being adapted, in use, to contact the second mating surface when the two parts are brought together as part of the assembly, or a sub-assembly thereof; wherein the first mating surface comprises a protrusion and the second mating surface comprises an indention; the protrusion and indentation being shaped and sized for cooperative engagement when the mating surfaces are brought into contact with one another; and wherein the protrusion and indentation each comprise a substantially flat portion comprising a through hole for receiving, in use the shank of a fastener.

Another aspect of the invention provides a beam assembly comprising: a first beam comprising a first mating surface and a second beam, a portion of which being configured, in use, to overlap a portion of the first beam, the second beam comprising a second mating surface, the first mating surface being adapted, in use, to contact the second mating surface when the two beams are overlapped; wherein the first mating surface comprises a protrusion and the second mating surface comprises an indention; the protrusion and indentation being shaped and sized for cooperative engagement when the mating surfaces are brought into contact with one another; and wherein the protrusion and indentation each comprise a substantially flat portion comprising a through hole for receiving, in use the shank of a fastener.

Another aspect of the invention provides a chassis comprising a beam assembly, the beam assembly comprising: a first beam comprising a first mating surface and a second beam, a portion of which being configured, in use, to overlap a portion of the first beam, the second beam comprising a second mating surface, the first mating surface being adapted, in use, to contact the second mating surface when the two beams are overlapped; wherein the first mating surface comprises a protrusion and the second mating surface comprises an indention; the protrusion and indentation being shaped and sized for cooperative engagement when the mating surfaces are brought into contact with one another; and wherein the protrusion and indentation each comprise a substantially flat portion comprising a through hole for receiving, in use the shank of a fastener.

In certain respects, the invention may be distinguished over known assemblies insofar as it can be an assembly of sheet elements, which are generally difficult to fasten together because the material plies do not readily lend themselves to accepting a thread form of any significant strength due to stripping or pull out. When bolts are used to fasten an assembly together, their failure mode tends to be governed by the bearing capacity of the material, so oversize bolts are generally required.

Larger bolt diameters tend to have relatively larger thread pitches, which can exacerbate the problem as there are fewer thread pitches for the same thickness of material. Larger thread pitches can also cause distortion of the material if self-tapped, and the head and nut diameters and heights become very large. Further, the larger the bolt, the greater the standard fit clearance, and therefore the greater the scope for misalignment caused by slack - angular misalignment on long parts can have a very significant impact on the end result.

In addition, by avoiding or reducing the need for jigs, the invention may reduce or solve the problem of needing multiple jigs for a complex assembly, where, for example, the relative angle between different pairs of parts is different, thereby requiring multiple jig versions. Adjustable jigs or multiple jigs are therefore often required: a problem that the invention helps to solve or solves by providing a self-jigging connection/assembly.

Suitably, the beam assembly of the chassis is a longitudinal beam.

The cooperative engagement of the protrusion and indentation usefully serves to locate two parts during assembly, and can, where a plurality of protrusions and indentations are provided, obviate the need for a jig because the two parts can self-align by such cooperative engagement.

The protrusion and indentation are shaped and sized for cooperative engagement when the mating surfaces are brought into contact with one another.

Each protrusion and indentation comprises a substantially flat portion through which the through hole extends. However, each protrusion and indentation may additionally comprise a respective, complementary cup and cone part, which parts are also shaped and sized for cooperative engagement with one another.

Suitably, the protrusion has a primary abutment surface, whose shape and size corresponds to a primary abutment surface of the indentation. The primary abutment surfaces are suitably the respective flat and cup/cone portions that come into contact when the first and second parts of the assembly are brought together. The shape and size of the primary abutment surfaces are ideally an interference fit (that is to say, in intimate contact) when they are brought together.

Any type of fastener may be used in conjunction with the invention, such as a rivet, a screw, a self-tapping screw, and a bolt & nut. In a preferred embodiment of the invention, the assembly further comprises a fastener whose shank is receivable, in use, in the through holes of the protrusion and indentation. The fastener, where provided, suitably comprises a head portion integrally formed with the shank. The shank preferably comprises a screw thread of any suitable type, but a rolled, metric thread is one possible option.

The through hole of the indentation is suitably sized in such a way that the screw thread of the shank of the fastener can self-tap into it. The through hole of the protrusion is suitably sized in such a way as to provide clearance for the shank of the fastener. The threading of the shank, where provided, suitably terminates short of the head - leaving an unthreaded shank portion interposed between the threaded shank portion and the head portion. This configuration usefully enables the shank to self-tap into the through hole of the indentation, but to completely clear the through hole of the protrusion. In addition, because there is an unthreaded shank portion adjacent the underside of the head portion of the fastener, the underside of the head portion of the fastener is thus able to seat cleanly, without extraneous interference, onto at least the substantially flat portion of the protrusion.

Suitably, the protrusion suitably also comprises a secondary abutment portion, which is a surface on an opposite side thereof to the primary abutment portion. The shape of the secondary abutment portion is ideally designed to be an interference fit (in intimate contact) with the underside of the head portion of the fastener.

Preferably, each part or beam comprises a plurality of protrusions and indentations. The mating surfaces suitably comprise substantially flat portions on or in which the or each protrusion and indentation is provided. The mating surfaces may, however, be folded, for example so as to have an

L-shaped, C-shaped, U-shaped, or sigma Σ shaped cross-section. By folding the parts or beams, this usefully provides a plurality of mating surfaces that are inclined with respect to one another. For example, the two parts may have generally U-shaped cross-sections (e.g. having a pair of limb portions connected by a linking portion), and the protrusions/indentations may be provided on the limbs and linking portion such that the protrusions and indentations of one mating surface portion are inclined relative to those of another mating surface portion. Such a configuration can temporarily/semipermanently fix the two parts together because one set of protrusions and indentions can be arranged in opposition to, or in partial opposition with, another set of protrusions and indentions.

The mating surfaces are suitably planar, but they need not necessarily be flat.

Suitably, the shape of the protrusion is of a generally truncated-cone or truncated pyramid type, having a tapered side wall or side walls leading to the substantially flat portion. Likewise, the shape of the indention is suitable designed to be complementary to that of its respective protrusion, being designed, in preferred embodiments, to have a snug, nesting relationship therewith. The provision of a tapered side wall or sidewalls may usefully cause the protrusion and indentation to selfalign when the two parts are brought together, thereby improving the relative alignment and/or positioning of the two parts.

The protrusion and indentation each comprise a substantially flat portion, which as a through hole in it for receiving, in use, the shank of a fastener. One of the through holes may be a clearance hole for a bolt, whereas the other through hole may be tapped (that is to say, internally screwthreaded) for screw-threadingly engaging the screw thread of the shank of a bolt- or screw-type fastener. By threading at least one of the through holes, the need for a nut, or a captive nut, on the opposite side of the assembly to the bolt can be obviated, which can rationalise the assembly and/or greatly facilitate assembly the two parts as an assembly or sub-assembly thereof.

Where one of the through holes is tapped, it may also comprise an integrally-formed tubular portion. The integrally formed tubular portion can be formed, in certain embodiments, by pressforming the through hole instead of, or in addition, to drilling it. The advantage of providing an integrally-formed tubular portion is that the axial length of the screw thread can be increased, thereby reducing the likelihood of bolt or screw pull-out in use, which can be a problem where the part is manufactured from relatively thin cross-sectioned material, or relatively soft material.

Additionally or alternatively, one of the through holes may comprise an integrally-formed tubular portion, which is not tapped. Again, the integrally formed tubular portion can be formed (e.g.

extruded), in certain embodiments, by press-forming the through hole instead of, or in addition, to drilling it. The main advantages of providing an integrally-formed tubular portion without a thread, is that a self-tapping screw can be used for connecting the two parts together, and is the axial length of the engagement between the tubular portion and the self-tapping screw is increased, thereby reducing the likelihood of screw pull-out in use, which can be a problem where the part is manufactured from relatively thin cross-sectioned material, or relatively soft material (as it may need to be to accept a self-tapping screw).

In preferred embodiments, the assembly further comprises one or more additional interengaging features. The additional inter-engaging features may comprise complementary rooftop or partial shear features that further secure/interlock the two parts or beams together.

Advantages of the invention will be apparent to the skilled reader, but may include:

A jig-less assembly, which can self-locate and hold itself together before a fastener is used to secure the connection between the parts/beams;

A single-sided assembly, which does not need a captive nut on the opposite side, or the use of a spanner, wrench, or socket tool on an opposite side to secure the fastener in position; and

A higher moment capacity compared with a known assembly secured using fasteners of an equivalent size (e.g. M8).

A preferred embodiment of the invention shall now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a known chassis;

Figure 2 is a perspective view of a longitudinal beam of the chassis of Figure 1;

Figure 3 is an exploded view of the beam of Figure 2;

Figure 4 is a perspective interior view of a beam in accordance with the invention;

Figure 5 is a perspective view, from an opposite side, of the beam of Figure 4;

Figure 6 is an exploded view of the beam of Figure 5;

Figure 7 is an exploded view of the beam of Figure 5 from an opposite side;

Figure 8 is a schematic force diagram of the beam of Figure 5;

Figure 9 is a partial cross section of Figure 8 on IX-IX; and

Figure 10 is an exploded version of the partial cross section of Figure 9.

Referring to Figures 1, 2 and 3 of the drawings, a chassis 10, such as may be used in a caravan or trailer, comprises a set of longitudinal beams 12, which are supported off the floor by wheels 14 connected to the longitudinal beams 12 via an axle (not visible). The longitudinal beams 12 support a set of transversely connected lateral beams 16, and the chassis 10 is triangulated in places by triangulation beams 18. Corner steadies 20, and a dolly wheel 22, are optionally provided to keep the chassis 10 in a substantially horizontal configuration when it is not being towed or in sited position on stands. The chassis 10 provides a framework upon which another structure (not shown), for example, the superstructure of a caravan can be affixed.

It will be appreciated that certain chassis 10 can be considerably long - often in excess of ten metres in length. This necessitates longitudinal beams 12 of that length, i.e. ten metres in length, and although it is possible to produce long beams to meet this requirement, beams of such length are generally quite difficult to transport prior to assembly. In addition, where, as in the illustrated example, the chassis 10 is supported by a central wheel 14, it is not necessary for the longitudinal beams to have a constant cross-section along their entire length because the distal end parts 24 of the chassis do not bear as much shear, or bending, stress as the central part 26 and so it is desirable, as shown in Figure 1, to taper the longitudinal beams somewhat so as to reduce the weight of the chassis 10 at its ends as well as the amount of material used in its manufacture.

Furthermore, tapering the longitudinal beams 12 enables the chassis 10 to be more easily tipped/tilted 28 about the axle (not visible) of the supporting wheels 14.

The longitudinal beam 12 of Figure 1 is shown in Figures 2 and 3 of the drawings, and it can be seen that it comprises a central beam portion 30 which is affixed, using fasteners 32, to beam end portions 34 on either side. For clarity, an exploded version of Figure 2 is provided in Figure 3 and it can be seen that the end beam portions 34 are swaged 36 at their inner ends where they overlap the central beam portion 30 - to enable one to nest within the other.

It will be appreciated, however, that one of the beams may comprise an inwardly-swaged end or joggle, i.e. a pressed-in step that offsets the material by one thickness, enabling the bulk of a pair of two lap jointed sheet metal parts to be on the same plane as each other even though they are overlapped (which would offset them by a thickness if no joggle was present). An exampleof a suitable joggle 75 is shown in inset Figure 7A of the drawings, which shows how a joggle 75 can be used to keep the top and bottom flanges 60, 64 flush when the assembly is put together. The joggle 75 is formed by a cut slot 77 at the junction between the upright part 62 and the top and bottom flanges

60, 64 to form a tang 79, which is double-bent 81 to offset the tang by one material thickness 83.

In order to assemble the longitudinal beam 12, it is necessary, in most cases, to use a jig (not shown) to ensure that the alignment of the beam portions 30, 34 is correct prior to fasteners 32 (for example bolts and nuts) being used to hold the assembly together. For the reasons stated in the introductory part of this disclosure, this can present a number of problems.

This invention provides a solution to one or more of the problems mentioned in the introductory part of this disclosure, insofar as it provides various self-alignment features which aid in the assembly or a structure, or structural assembly, such as a longitudinal beam for a chassis.

Referring to Figures 4 to 10 of the drawings, a structural assembly, in the form of a beam 50 is shown.

As can be seen from Figures 4 to 8 of the drawings, the beam 50 comprises two beam portions

52, 54 which are interconnected by a slightly overlapping portion 56, where one of the beam portions nests inside the other beam portion 52 in the overlap region 55. Unlike the prior art beam 10 previously described, the beam portions 53, 54 have slightly different overall dimensions - so that one does not need to be swaged to fit inside the other. However, in inset Figure 7A, the provision of a swaged end or joggle falls within the scope of this disclosure and/or the invention.

The two beam portions 52, 54 are fastened together using fasteners 56, as well as passive interlocking features 58 as shall be described hereinbelow. In the illustrated embodiment, which is exemplary only, there are nine screws 56 and eight passive connection features 58.

For the purposes of completeness only, each beam portion 52,54 is formed from folded sheet steel - into a generally C-shaped cross section profile. This configuration provides three generally planar mating surfaces 60, 62, 64 arranged at substantially 90 degrees to one another, the benefit of which shall become apparent from the following description.

As can be seen, in particular from Figures 6, 7, 9 and 10 of the drawings, the beam parts 52,

54, each have mating surfaces 62 that come together when the beam 50 is assembled. The mating surface of one of the beam parts 52 is provided with projections 70, whereas the mating surface complementary beam part 54 is provided with correspondingly-positioned indentations 72 for mutual cooperative engagement with the projections 70.

In addition, it can be seen, in particular from Figures 6,7, 9 and 10 of the drawings, the mating surface 62 of one of the beam parts 52 is provided with male rooftop projections 58, whereas the mating surface 62 of the complementary beam part 54 is provided with correspondingly-positioned rectangular through holes 76 for mutual cooperative engagement with the male rooftop projections

58.

Thus, when the two beam parts 52, 54 are offered up to one another, as shown in Figures 4, and 8, for example, the projections 70 inter-engage with the indentations 72; and the male rooftop projections 58 inter-engage with the rectangular through holes 76. Also, because the beam parts 52, each have a generally C-shaped cross-section, there are several substantially orthogonal mating surfaces 62, and so some of the projections 70/indentations 72 and rooftop projections 58/through holes 76 cooperate in a vertical sense; whereas as some of the projections 70/indentations 72 and rooftop projections 58/through holes 76 cooperate in a horizontal sense. The configuration usefully enables the beam parts 52, 54 to be retained in cooperative engagement with one another even before the fasteners 58 have been fitted.

Referring to Figure 8 of the drawings, the beam 50 is shown subjected to a bending moment, indicated schematically by the arrow 80 in the drawing, which acts through the centre of the beam

50. The part 82 above the beam's centreline is thus under tension, whereas the part 84 below the beams' centreline is in compression. The fasteners 56/rooftop projections 58 located above the beams' centreline are thus subjected to outward shear stresses 59 (as the two beam parts 52, 54 try to separate axially in that region); whereas the fasteners 56 and rooftop projections 58 located below the beam's centreline are subjected to inward shear stresses 61 (as the two beam parts 52, 54 try to move together axially in that region). As will be understood, the bending moment will vary roughly linearly from compression (below the centreline) to tension (above the centreline), passing through a point of zero bending moment, which, in the illustrated embodiment, will coincide roughly with the beam's centreline.

Relative movement of the beam parts 52, 54 is resisted by the cooperative engagement of the projections 70/indentations 72 and rooftop projections 58/through holes 76.

Referring to Figures 9 and 10 of the drawings, two beam parts 52, 54 each have mating surfaces 62, which are generally flat, but which are respectively provided with projections 70 and indentations 72. The projections 70 and indentations 72 are generally cup-and-cone shaped, and comprise a curved, dish-shaped part 90 leading to a flat part 92.

The flat part 92 of the projection 70 comprises a through hole 94, which is dimensioned to clear the shank 102 of a fastener 56. The flat part 92 of the indentation 72 also has a through hole 96, but this is formed by pressing so as to have a tubular extrusion part 98 that projects beyond the rear of the indentation 72 slightly. The inner diameter of the extrusion part 98 is slightly less than the outer diameter of the fastener's shank 102 for reasons that shall be described below.

Meanwhile, the fastener 56 has a particular shape, which is specifically-designed for this application. The fastener 56 has a shank 102 and a head 104 integrally formed therewith. The junction between the shank 102 and head 104 is formed so as to have a slightly smaller narrower outer diameter than the shank 102 itself. The shank 102 comprises a rolled thread portion 106 extending along the majority of its distal end, whereas a proximal portion 108 of the shank 102, in a narrower junction region, is unthreaded. Alternatively, a clearance hole may be provided in the first material ply so as provide a means by which the first ply will not be engaged by the fastener thread, so, suitably, inhibiting the coming together of the material plies.

The outer diameter of the threaded portion 106 is slightly larger than the inner diameter of the extrusion part 98, and so the fastener 56 can be self-tapped into the through hole 96 of the second beam part 56. The extrusion part 98 extends the axial length of the thread that is formed as the fastener 56 is self-tapped into the through hole 96, and thus the pull-out strength 93 of the fastener

56 is greatly increased: compared to if the extrusion part 98 were not present and the axial length of the thread that is formed as the fastener 56 is self-tapped into the through hole 96 were merely the thickness 110 of the second beam part 54.

The threaded engagement of the fastener may be formed or cut. However, forming may be preferred since it may have any one or more of the following advantages overs cutting: generating no free cuttings; work hardening some materials (e.g. steel) making a stronger thread; being less disruptive to protective coatings; and providing an inherent resistance to loosening of the thread in service. The use of other available means of thread forming and resistance to loosening in service are not precluded or outside the scope of this disclosure.

As can be seen from Figure 10 of the drawings, when the assembly is assembled and the fastener 56 engaged, the unthreaded part 108 of the fastener's shank 102 partially clears the through hole 94 in the first beam part 52, thereby meaning that there is no interference between the underside

114 of the head 104 of the fastener 56 and the flat part 92 of the projection 70.

Referring to Figures 9 and 10 of the drawings, it can be seen that the head 104 of the fastener has a specific shape, which comprises a rounded or part-conical outer part 112, whose profile matches that of the curved, dish-shaped, or part-conical part 90 of the projection 70, and central, flat part 114 on its underside that seats precisely against the flat part 92 of the projection 70. The fit between the underside of the head 104 of the fastener 56 and the interior profile of the projection is a close, interference fit, and so shear forces 114 can be borne not only by the shank 102 of the fastener 56 in the usual way, but also by the curved part 112 of the head 104 engaging with the complementarily25 shaped, curved, dish-shaped part 90 of the projection 70. This greatly increases the shear loading strength of the connection, compared with a known beam assembly using conventional bolts/screws.

Referring back to Figure 8 of the drawings, it can be seen that the placement/arrangement of the fasteners 56 in and around the rooftop projections 58 is such that lateral/out-of-plane loads 120 (e.g. caused by torsion or bending of the beams 52,54) that might otherwise cause the mating surfaces of the beam parts 52, 54 to separate, and possibly release the rooftop projections 58 from their corresponding through holes 76, is resisted. Thus, the rooftop projections 58 and through holes 76 can play an active role in the strength of the connection between the beam parts 52, 54, even under considerable bending moments and/or applied torques.

For the sake of completeness, the head 104 of each fastener 56 comprises a tool-engaging part 122, in the illustrated embodiment, a female hex-socket, but this could be of any suitable shape/configuration.

The invention is not restricted to the details of the foregoing embodiments, which are merely exemplary of the invention. For example, any shapes, dimensions, materials (whether express or implied) are illustrative only, and any references to direction (e.g. vertical/horizontal, up/down, front/back etc.) are simply to aid cross-references to the drawings and are not intended to limit the scope of the invention to any particular directions and/or orientations. Further, the invention is not limited in any way to the dimensions of the overlap, or the number of fasteners used as shown in the drawings.

Claims

Claims:

1. An assembly comprising: a first part comprising a first mating surface and a second part comprising a second mating surface, the first mating surface being adapted, in use, to contact the second mating surface when the two parts are brought together as part of the assembly, or a sub-assembly thereof; wherein the first mating surface comprises a protrusion and the second mating surface comprises an indention; the protrusion and indentation being shaped and sized for cooperative engagement when the mating surfaces are brought into contact with one another; and wherein the protrusion and indentation each comprise a substantially flat portion comprising a through hole for receiving, in use the shank of a fastener.

2. The assembly of claim 1, wherein the first part and second parts comprise beam parts of the assembly.

3. The assembly of claim 1 or claim 2, wherein the protrusion comprises a primary abutment surface, whose shape and size corresponds to a primary abutment surface of the indentation.

4. The assembly of claim 3, wherein the primary abutment surfaces comprise substantially dishshaped parts interposed between each parts' respective mating surfaces and their respective flat portions.

5. The assembly of claim 4, wherein the dish-shaped parts are substantially any one or more of the group comprising: part-hemispherical in shape; part-conical in shape; part-toroidal in shape; and truncated conical in shape

6. The assembly of claim 4 or claim 5, wherein the corners/junctions between the flat and dishshape parts are broken by filet radii.

7. The assembly of any of claims to 6, wherein the shape and size of the primary abutment surfaces are an interference fit, that is to say, in intimate contact, when they are brought together.

8. The assembly of any preceding claim, wherein the or each fastener comprises a screw.

9. The assembly of claim 8, wherein the screw comprises a head portion and a shank portion, the shank portion being is receivable, in use, in the through holes of the protrusion and indentation.

10. The assembly of claim 9, wherein the shank portion comprises a screw-threaded portion.

11. The assembly of claim 9 or claim 10, wherein the shank comprises an un-threaded portion.

12. The assembly of claim 11, wherein the un-threaded portion is interposed between the head portion and the screw threaded portion, and wherein the unthreaded portion has a smaller outer diameter than the screw threaded portion.

13. The assembly of any of claims 9 to 12, wherein the flat part of the projection comprises a through hole, whose inner diameter is slightly larger than the outer diameter of the shank.

14. The assembly of any of claims 9 to 13, wherein the flat part of the indentation comprises a through hole, whose inner diameter is slightly smaller than the outer diameter of the shank.

15. The assembly of any preceding claim, wherein the through hole of the indentation comprises a tubular extrusion part that projects beyond the rear of the indentation.

16. The assembly of any of claims 9 to 15, wherein the head portion of the screw comprises a flat underside portion, which seats against the flat portion of the projection.

17. The assembly of any of claims 9 to 16, wherein the head portion of the screw comprises a rounded outer underside portion, which seats against the substantially dish-shaped parts of the projection.

18. The assembly of claim 16 or claim 17, wherein the flat underside portion and the rounded or part-conical outer underside portion seat against the interior of the primary abutment surface of the projection.

19. The assembly of any preceding claim, wherein the first and second parts each comprise a plurality of protrusions and indentations.

20. The assembly of any preceding claim, wherein the mating surfaces are substantially flat.

21. The assembly of any preceding claim, wherein the first and second parts comprise a plurality of inclined mating surfaces.

22. The assembly of claim 21, wherein at least two of the inclined mating surfaces are oriented at substantially 90-degrees to one another.

23. The assembly of claim 22, wherein the first and second parts each comprise three mating surfaces arranged in a C-shape or Σ-shape when viewed in cross-section.

24. The assembly of any of claims 20 to 23, wherein at least one of the mating surfaces comprises a joggle.

25. The assembly of claim 23 or claim 24, wherein at least some of the indentations are projections are arranged in opposite directions to one another.

26. The assembly of any preceding claim, wherein each mating surface further comprises complementary, supplementary inter-engaging features.

27. The assembly of claim 26, wherein the complementary, supplementary inter-engaging features comprise a rooftop feature in one of the first or second part, and a complementarily receiving aperture in the other one of the first or second part.

28. The assembly of claim 26 or claim 27, wherein at least one fastener is located adjacent at least one of the complementary, supplementary inter-engaging features, to inhibit, in use, disconnection of the complementary, supplementary inter-engaging features.

29. A chassis comprising an assembly of any preceding claim

30. The chassis of claim 29, comprising a longitudinal beam formed by interconnected first and second beam portions.

31. The chassis of any of claims 26 to 30, wherein the chassis further comprises any one or more of the group comprising: a wheel; an axle; a transverse lateral beam; a triangulation beam; a corner steady; a dolly wheel; and a superstructure.

Intellectual

Property

Office

Application No: GB 1704716.8 Examiner: Peter Macey

31. The chassis claim 30, wherein the longitudinal beam comprises a first, central beam portion and a pair of second beam portions affixed to opposite ends of the first beam portion.

32. The chassis of claim 31, wherein the second beam portions are tapered.

33. The chassis of any of claims 29 to 32, being a caravan or trailer chassis.

34. The chassis of any of claims 29 to 33, wherein the chassis further comprises any one or more of the group comprising: a wheel; an axle; a transverse lateral beam; a triangulation beam; a corner steady; a dolly wheel; and a superstructure.

Amendments to the Claims have been filed as follows:Claims:

1. An assembly comprising: a first part comprising a first mating surface and a second part comprising a second mating surface, the first mating surface being adapted, in use, to contact the second mating surface when the two parts are brought together as part of the assembly, or a sub-assembly thereof; wherein the first mating surface comprises a protrusion and the second mating surface comprises an indention; the protrusion and indentation being shaped and sized for cooperative engagement when the mating surfaces are brought into contact with one another; and wherein the protrusion and indentation each comprise a substantially flat portion comprising a through hole for receiving, in use the shank of a screw or bolt, the screw or bolt comprising a head portion and a shank portion, the shank portion being is receivable, in use, in the through holes of the protrusion and indentation, and wherein the head portion of the screw or bolt comprises a rounded outer underside portion, which seats against a substantially dish-shaped part of the projection.

7. The assembly of any of claims 1 to 6, wherein the shape and size of the primary abutment surfaces are in intimate contact when they are brought together.

8. The assembly of any preceding claim, wherein the shank portion comprises a screw-threaded portion.

9. The assembly of any preceding claim, wherein the shank comprises an un-threaded portion.

10. The assembly of claim 9, wherein the un-threaded portion is interposed between the head portion and the screw threaded portion, and wherein the unthreaded portion has a smaller outer diameter than the screw threaded portion.

11. The assembly of any preceding claim, wherein the flat part of the projection comprises a through hole, whose inner diameter is slightly larger than the outer diameter of the shank.

12. The assembly of any preceding claim, wherein the flat part of the indentation comprises a through hole, whose inner diameter is slightly smaller than the outer diameter of the shank.

13. The assembly of any preceding claim, wherein the through hole of the indentation comprises a tubular extrusion part that projects beyond the rear of the indentation.

14. The assembly of any preceding claim, wherein the head portion of the screw or bolt comprises a flat underside portion, which seats against the flat portion of the projection.

15. The assembly of any preceding claim, wherein the flat underside portion and the rounded or part-conical outer underside portion seat against the interior of the primary abutment surface of the projection.

16. The assembly of any preceding claim, wherein the first and second parts each comprise a plurality of protrusions and indentations.

17. The assembly of any preceding claim, wherein the mating surfaces are substantially flat.

18. The assembly of any preceding claim, wherein the first and second parts comprise a plurality of inclined mating surfaces.

19. The assembly of claim 18, wherein at least two of the inclined mating surfaces are oriented at substantially 90-degrees to one another.

20. The assembly of claim 19, wherein the first and second parts each comprise three mating surfaces arranged in a C-shape or Σ-shape when viewed in cross-section.

21. The assembly of any of claims 17 to 20, wherein at least one of the mating surfaces comprises a joggle.

22. The assembly of claim 20 or claim 21, wherein at least some of the indentations and projections are arranged in opposite directions to one another.

23. The assembly of any preceding claim, wherein each mating surface further comprises complementary, supplementary inter-engaging features.

24. The assembly of claim 23, wherein the complementary, supplementary inter-engaging features comprise a rooftop feature in one of the first or second part, and a complementarily receiving aperture in the other one of the first or second part.

25. The assembly of claim 23 or claim 24, wherein at least one fastener is located adjacent at least one of the complementary, supplementary inter-engaging features, to inhibit, in use, disconnection of the complementary, supplementary inter-engaging features.

26. A chassis comprising an assembly of any preceding claim

27. The chassis of claim 26, comprising a longitudinal beam formed by interconnected first and second beam portions.

28. The chassis claim 27, wherein the longitudinal beam comprises a first, central beam portion and a pair of second beam portions affixed to opposite ends of the first beam portion.

29. The chassis of claim 28, wherein the second beam portions are tapered.

30. The chassis of any of claims 26 to 29, being a caravan or trailer chassis.