Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Headed fastener element with nut – washer – securing means or cap – Metallic resilient securing means
Reexamination Certificate
2002-10-23
2004-04-20
Wilson, Neill (Department: 3679)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Headed fastener element with nut, washer, securing means or cap
Metallic resilient securing means
C411S107000, C411S416000, C411S970000, C411S999000
Reexamination Certificate
active
06722832
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an assembly unit including a component and at least one thread forming screw. The component includes a through hole for each screw, and each screw includes a head serving for actuation of the screw, a supporting surface facing said component and a shank at least partly including a thread.
In the field of assembly technology, it is increasingly desired to use assembly units in which a plurality of elements has been pre-assembled to form a pre-assembly unit. In the following, the assembly unit including a component and usually a plurality of screws is connected to a work piece. A typical example of this technology is an upper part and a lower part which have to be interconnected by one or more screws. In such a case, the upper part as the component and the screws form a pre-assembled assembly unit, the screws being captively connected to the component. The assembly unit is then connected to the lower part by screwing the screws into the lower part. The screws may be simultaneously screwed into the lower part, or they may be screwed into the lower part one after the other. Especially, multispindle automatic screwing apparatuses are used for this purpose.
A typical field of use of such assembly units is the automobile industry. For example, a cylinder head cover or a cover of a transmission is the component which is to be connected to the work piece by screws. The work piece is the cylinder block or the housing of the transmission. By using such assembly units, a great level of prefabrication is realized. The screws are already connected to the component in a captive and aligned position. They are prevented from being damaged during transportation, and they may be quickly connected to the work piece.
BACKGROUND OF THE INVENTION
An assembly unit is known from International Application PCT/EP95/00354 published as WO 95/21335 corresponding to U.S. Pat. No. 6,309,156. The known assembly unit includes a component, for example a cover of a housing, and at least one fixing element in the form of a screw. Each screw is associated with a third element, namely a bush being used for captive connection of the screw to the component. The bush is made of metal, especially of sheet metal. The bush increases the production costs of the known assembly unit. During a separate step of pre-assembly, the bush is pressed into a respective through hole being located in the component. The screw has a rather complicated shape. An annular flange is located in the region of the shank of the screw. The annular flange includes annular channels being connected to both sides. The annular flange has to be produced at the shank of the screw in addition to the thread. The size of the annular flange is coordinated with the size of a collar being located at the bush such that there an axial lock is realized, the axial lock still allowing for an axial movement within certain limits. Consequently, the screws are arranged to be captively connected to the work piece, but they are not fixedly connected to the work piece in the pre-assembled position. There also is the possibility of not using an annular flange at the screw. In such a case, special elements have to be located at the bush, these elements in connection with the screw forming an axial lock. Consequently, the bush has a more complicated design. In this case, the thread of the screw may fulfill a part of the function of the axial lock. There is a relationship between the diameter of the through hole in the component and the diameter of the shank of the screw only as far as the screw together with the bush has to be moved through the through hole, and it has to be inserted into the through hole, respectively. However, there is no exact axial alignment of the screw at the component since the screw is movable to a limited extent. This fact may be advantageous for screwing the screw into the work piece if it is ensured that the screw contacts the entrance into the thread into the work piece in a centering way. Due to the danger of tilting effects of the axes of the screw with respect to one another, inserting the free ends of the shanks of the screws into the threads in the work piece is difficult. This disadvantage may be counteracted by the bush as the third element in the known assembly unit having a comparatively great axial length. Especially, the length may be substantially more than the wall thickness of the component. Due to the increase of the length of the bush, the length of the screw also has to be increased. This increase means additional cost expenditure, and it may also have a negative influence on the function in some cases. The additional use of such bushes, meaning using assembly units including at least three separate elements, is disadvantageous as the bush is also clamped when the screw is screwed into the work piece. Especially in the case when a bush being made of comparatively thin deformable sheet metal is used, there is the danger of different deformations of the bushes occurring during tightening of the screws such that it is difficult to apply a reproducible pretension force.
A component being made of plastic to be screwed to a work piece with an intermediate arrangement of a seal is known from German Patent Application No. 196 51 838 A1. A bush is used in a way that it extends through the component. The bush is connected to the seal. The screw has to have an annular flange to be produced in a separate step, the annular flange cooperating with the bush in the sense of an axial lock. In this way, the screw is connected to the bush in a loose but captive way. In addition to the component and the screw, the bush is the third element of the known assembly unit. The bush does not necessarily have to extend through the entire through hole being located in the component. German Patent No. 195 46 072 C2 shows a bush having a shorter axial length and including a conical collar. The collar engages a respective through hole being located in the component and having a partly conical design. The collar only partly engages the through hole under the influence of frictional clamping effects. The captive arrangement is achieved by frictional forces such that there is substantial insecurity. The bush having a disc-like design finally is located between the supporting surface being located at the head of the screw and the respective counter surface being located at the component. The bush is clamped, and there are similar disadvantages as it has been described above.
Furthermore, pre-assembled assembly units also including at least three elements are known, the above described bush being replaced by a clip, a holding clamp or the like. The third elements means additional expenditure which often also has a disadvantageous effect on the function.
SUMMARY OF THE INVENTION
The present invention relates to an assembly unit including a component and at least one screw. The component includes at least one through hole. The screw is associated with the through hole of the component. The screw is designed and arranged to produce a thread. The screw includes a head and a supporting surface to face the component. The screw includes a shank at least partly including a thread. The screw in the region of the shank and close to the supporting surface includes an annular channel, the diameter of the annular channel being less than the core diameter of the thread of the screw and the effective axial length of the annular channel being more than the axial length of the through hole. The diameter of the through hole of the component is more than the core diameter of the thread of the screw and being less than the outer diameter of the thread of the screw.
The novel pre-assembled assembly unit does not require the use of a third element, as for example a bush, a clip element, a clamp element or the like. The screw and the screws, respectively, is captively and fixedly connected to the component in the pre-assembled position of the assembly unit.
The novel assembly unit includes one or more screws being desig
Hartmann Gunther
Sommer Wolfgang
Wagner Frank
Kamax-Werke Rudolf Kellermann GmbH & Co. KG
Thomas Kayden Horstemeyer & Risley LLP
Wilson Neill
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