This invention relates to a cabinet or housing which holds a number of modules or printed circuit boards in a manner that permits easy insertion and removal of the modules.
With the change of the market from telephone equipment purchased or rented from a telephone company to telephone equipment purchased from a manufacturer of telephone equipment and installed by the customer, there has been an increased demand for modular expandable equipment and systems. The cabinet and related equipment of this invention are particularly suited for such a system because they can provide a small or medium size switching unit that may be readily expanded or changed. The equipment of this invention may, of course, be easily adapted for use in computer systems or in any other system where it is desirable to expand or change the system to meet new requirements.
Hereinafter the term modules will be used and it is intended to include printed circuit boards with components mounted thereon, and printed circuit boards with components mounted thereon and sealed in plastic to form a block or mounted in a casing (with, of course, connecting contacts exposed).
It is known to have a cabinet with contacts on the inner side of the rear wall for engagement with contact members on any module. The modules may be disengaged or removed from the cabinet by gripping finger grips on an outer edge of the module and pulling outwards. A module is inserted by placing the contact members on the rear edge against the contacts on the rear wall and then pressing the module inwards towards the rear wall. Guide members or guide walls may be used to ensure the module is positioned with its contacts against appropriate contact members. It usually requires two hands to conveniently insert or withdraw a module, with one hand at the top and one hand at the bottom of the exposed side of the module.
The contact members or connectors on the module which engage and grip the contacts in the cabinet normally have a considerable spring bias to ensure good and reliable contact is made.
Good contact is, of course, essential. However a large spring bias frequently makes it difficult to engage manually the contact members of a module and the corresponding contacts of a cabinet. A number of means have been devised to provide some form of force to assist in the insertion and removal of a module. One such arrangement is described, for example, in Canadian Patent No. 1,124,346-- Jordan, issued May 25, 1982, where a pivoted lever on a faceplate or cover plate engages a slot in the cabinet to press the printed circuit board inwardly or outwardly. This arrangement adds considerable structure to the cabinet and board.
Another arrangement is described in U.S. Pat. No. 4,313,150-- Chu, issued Jan. 26, 1982. This arrangement comprises printed circuit boards with a pivoted lever at both the top and bottom of the exposed edge of the board. The structure may be less complex than that described in the aforementioned Jordan patent, but insertion and withdrawal requires two hands.