Fastening arrangement of an assembly part onto a carrier part

Details Fastening arrangement of an assembly part onto a carrier part Fastening arrangement of an assembly part onto a carrier part

1999-02-26

2001-08-28

Saether, Flemming (Department: 3627)

Expanded, threaded, driven, headed, tool-deformed, or locked-thr

Headed fastener element with nut, washer, securing means or cap

Metallic resilient securing means

C411S107000, C411S999000

Reexamination Certificate

active

06280132

ABSTRACT:

TECHNICAL FIELD
The invention relates to a fastening of an assembly part onto a carrier part.
One possible application of the invention is in automobile technology. e.g., fastening of a cylinder head cover to a cylinder head. Another appreciation is fastening of an intake chamber to a motor.
BACKGROUND ART
Relevant fastenings in which a fastening screw is arranged telescopically in a sleeve, wherein a knurling of the screw shank at a distance from the screw head in cooperation with a necking at the upper end of the sleeve to ensure retention of the fastening screw and sleeve, are already known.
In one embodiment, a head flange of the sleeve is supported on a rubber ring which is pressed into a receiver of a cylinder head cover. A foot flange of the sleeve is buttoned into a through-bore with an undercut of a further rubber part which is arranged between the cylinder head cover and the cylinder head. By way of this a decoupling is effected, i.e. the hard screw head as well as the sleeve are not pressed directly against the cover which may consist of plastic. On the other hand the sleeve of metal prevents excess pressing of the rubber parts. With this arrangement, a secure temporary assembly of the screw, sleeve and rubber parts to the cylinder head cover is possible which permits transport in any position up to assembly on the cylinder head. It is, however of a disadvantage that the screw, when mounting the cylinder head cover, with its lower end may slide over the sealing surfaces of the cylinder head and cause damage. With long screws the knurling may even press against the necking of the sleeve and loosen the temporary assembly. With another fastening, a rubber ring is arranged between the head flange of the sleeve and the assembly part. The rubber ring below has a collar with three hooks distributed on the circumference which engage behind the undercuts in a through-bore of the assembly part. The collar however must have a certain thickness so that on pressing into the through-bore they are not pressed axially together. Because the hooks form the only securement this fastening is not adequately safe in transport. Furthermore the telescoping ability is limited by the abutment of the knurling on the necking so that there prevails a relatively long screwing out of the sleeve and thus the guiding as well as the assembly of the cylinder head cover (assembly part) is made more difficult.
With another fastening the rubber ring is pressed into the assembly part at its large circumference. This sleeve may be arranged in the rubber ring with play so that it may be telescoped up to the abutment of its foot flange on a collar of the rubber ring. Since the screw may also be displaced with respect to the sleeve there results as a whole an enlarged ability to telescope which favours the application on a carrier component. However the circumferential pressing does not ensure any particularly secure preassembly in the assembly part.
With yet another fastening, the foot flange engages behind several undercuts, which in a cover part are preferably injected from plastic. The manufacture requires complicated injection tools. Furthermore the undercuts on pressing in the foot flange may shear off so that the transport securement is not ensured.
It is an object of the invention to provide a fastening of an assembly part to a carrier part, which improves the security of a temporary pre-assembly, favours an assembly without the protrusion of the screw ends out of the assembly part and may be applied in the case of decoupling as well as in the hard screw case.
SUMMARY OF THE INVENTION
A fastening arrangement according to the invention of an assembly part on a carrier part has at least one fastening screw which comprises a screw head with engaging surfaces for a tool, a screw shank, at least one radial projection on the screw shank at a distance from the screw head and a thread at least at the distance of the radial projection from the screw head. The radial projection may be formed from the upper end of the thread. Preferably however at least one special projection is present. With this it may be the case of a single projection which extends only about a part or about the whole circumference, or several radial projections which are distributed over the circumference of the screw shank, in particular in the form of a knurling.
Furthermore the fastening has a sleeve with an inner diameter which corresponds at least to the outer diameter of the radial projection and of the thread, which preferably at the upper end comprises a narrow location with an inner diameter smaller than the outer diameter of the radial projection, however at least as large as the outer diameter of the screw shank between the screw head and the radial projection. The narrow location may be formed by at least one radially inwardly protruding projection of the sleeve. Furthermore the sleeve comprises at the upper end a head flange and at the lower end a foot flange preferably with a smaller diameter than the head flange. Into the sleeve the fastening screw is applied wherein the narrow location is snapped over the radial projection of the fastening screw and is allocated to the screw head of the outer side of the head flange. The applied fastening screw may thus be axially displaced in the sleeve, is however unlosably retained therein by abutment of the radial projection on the narrow location.
Further there is present a flexible assembly ring whose inner diameter is smaller than the outer diameter of the foot flange and which is arranged between the head flange and foot flange on the sleeve. Preferably the assembly ring is elastic so that by broadening, sliding over the flange, preferably the foot flange, and subsequent elastic retraction on the sleeve, it can be assembled on the sleeve. Between the assembly ring and the foot flange there may be present a radial play, by which means a compensation of tolerances and heat expansions is favoured.
A through-bore in the assembly part has an inner diameter, which is at least as large as the outer diameter of the foot flange so that the sleeve with the inserted fastening screw may be inserted into the through-bore. With this the assembly ring is pre-assembled on the sleeve. The inner diameter of the through-bore is dimensioned such that it radially presses together the assembly ring on insertion and by way of this is clamped in and/or the through-bore comprises an undercut with an inner diameter so that the assembly ring under radial compression and subsequent expansion is pushed through the undercut and by which the assembly ring is retained in the through bore. The throughbore may have the undercut at the upper end, which may clamp in the assembly ring in an intermediate position and/or after broadening retain it in a bordering bore section. In the bordering bore section the assembly ring may still be clamped in. The through bore may however have the same inner diameter everywhere so that it clamps in the assembly ring in every possible insertion location. The sleeve is supported with the lower side of the head flange directly over an elastic intermediate position on the upper edge region of the through-bore.
In the carrier part there is present at least one threaded bore into which the thread of the fastening screw is screwed in and on whose edge region there is supported the foot flange of the sleeve. The supporting of the assembly part may either be effected directly or via an elastic intermediate layer.
The fastening according to the invention, by way of the radial projection of the fastening screw and the narrow location of the sleeve, the arrangement of the assembly ring between the head flange and the foot flange and the clamping tight and/or the retaining of the assembly ring in the assembly part, favours unlosable pre-assembly. A protrusion of the fastening screw out of the assembly part is avoided since the fastening screw with respect to the sleeve as well as the sleeve with respect to the assembly ring may be telescoped. The fastening is suitable for the hard screw case as

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