The invention relates to a lower portion of an electric and electronic enclosure, comprising a bottom and fastening arrangements for fastening a cover to the lower portion with a bayonet-like fastening, and the fastening arrangements comprise a bore and a shoulder-like stopper for receiving a mounting bracket of a spindle-like element.
The invention also relates to an electric and electronic enclosure having a lower portion with a bottom, a cover, and fastening means for fastening the cover to the lower portion with a bayonet-like fastening, the fastening means comprising a bore and a shoulder-like stopper arranged to the lower portion, a through-hole, and a stop face formed on the cover, and a spindle-like element that comprises a top end having a shoulder for resting against the stop face of the cover, and at a distance from the top end a mounting bracket for fastening at the shoulder-like stopper of the lower portion to provide a bayonet-like fastening.
Electric and electronic enclosures of the mentioned type and their lower portions are well known. An advantage of a bayonet-like fastening is that the cover of the enclosure can be quickly and easily fastened to the lower portion of the enclosure. A bayonet-like fastening also has the advantage that it can easily be accomplished in such a manner that the cover can flexibly give way when a possible electric arc ignites inside the enclosure, thus preventing any great damage. One drawback with the bayonet-like fastening is that it is not suitable for situations in which the cover of the enclosure needs to remain fixed to the lower portion. In such a case, ordinary screws are usually used to fasten the cover to the lower portion. In addition, the bayonet screw of the bayonet-like fastening has a complex structure, which makes it difficult and expensive to manufacture in comparison with a conventional screw. A further drawback with a bayonet screw is that it cannot be machine-mounted on the enclosure.
Depending on whether the enclosure needs to be such that the cover is fastened to the lower portion with a bayonet-like fastening or with ordinary screws, the user has to select the lower portion of the enclosure to suit the end use. Thus, there must be two different lower portions depending on the manner in which the cover is to be fastened: a first type of the lower portion comprises bores with a shoulder-like stopper for receiving the mounting bracket of the bayonet screw, whereas a second type of lower portion comprises a bore with threads for receiving the threads of an ordinary screw. The need to manufacture and store lower portions of two different types is naturally a disadvantageous solution that correspondingly increases costs. Sometimes, it is necessary to change the fastening method of the enclosure cover (from a bayonet-like fastening to a screw fastening or vice versa) as the application of the enclosure changes.