LATCH/SWITCH ARRANGEMENT FOR SECURING CIRCUIT MODULES INTO CIRCUIT HOUSINGS WITH CIRCUIT SWITCHING ACCOMPLISHED DURING THE INSERTION OF THE MODULE INTO THE HOUSING

Abstract: A latch/switch mechanism is attached to and operative for inserting and securing circuit modules into a housing while at the same time creating differing electrical connections during the insertion process. The latch/switch mechanism includes a latch lever with a cam and also includes means to engage a support housing such as a notch or clip in the lever. The cam portion sequentially engages a plurality of conductive leaf springs and as the lever is rotated, the cam forces the making and breaking of certain connections of the conductive leaf springs to effect the various desired circuit connections and disconnections.

Description: Field of the Invention This invention relates to circuit modules including latch/switch mechanisms for inserting and securing the circuit modules into an apparatus support housing and for sequentially enabling and disabling electrical connections during inserting and securing the circuit module into the housing (see e.g. WO-A-8 505 243). Background of the Invention It is desirable to combine a switching arrangement with a latching mechanism that connects and disconnects certain sub circuits as a circuit module is inserted into and locked or secured into a circuit panel support housing. A typical circuit module mounted arrangement for synchronizing or combining a latch and switch (i.e., latch/switch) operation involves a mechanical interaction between a toggle switch on a circuit module and a latch also mounted on the module. As the latch is actuated to secure the circuit module into a support housing, it engages the toggle switch and moves it to successive positions engaging first one then another selected electrical circuit on the module as it is locked into place in the support housing. When the circuit module is removed from the housing, the opening of the latch moves the engaged toggle switch to de-energize the circuit module as it is removed so that no electrical hazard condition occurs as the circuit module is disengaged from the backplane. A disadvantage of this arrangement is the fragility of the toggle switch making it readily susceptible to damage during assembly and soldering of the circuit module. A further problem with the above arrangement is the required preciseness of the mechanical interconnection between the latch and toggle switch. The difficulty of matching latch positions with toggle switch positions, especially with a three position toggle switch, necessitates strict dimensional tolerances during manufacture adding considerably to the overall cost of the latch/switch mechanism. This latch/switch arrangement is furthermore readily susceptible to mechanical failure in actual field operation, wherein damage may cause the latch/switch arrangement to partially fail and accordingly fail to de-energize a circuit as expected thereby causing a dangerous electrical hazard. It may, on the other hand, allow electrical power to be applied prematurely to the circuit module resulting in damage to electrical components contained thereon. It is apparent from the foregoing that a suitable latch/switch arrangement must be readily manufacturable without undue narrow tolerance requirements if it is to be economically viable. It must also be mechanically reliable in providing the necessary sequential circuit connections during insertion and removal operations to minimize electrical hazards and protect circuit components. Summary of the Invention A circuit module including a latch/switch mechanism embodying the principles of the invention as defined in claim 1 attached to and operative for inserting and securing the circuit modules into a housing while at the same time creating differing electrical connections during the insertion process. The latch/switch mechanism includes a latch lever with a cam and also includes means to engage a support housing element such as a notch or clip in the lever. The cam portion engages one of a plurality of conductive leaf springs and as the lever is rotated, the cam forces the making and breaking of certain connections of between the various conductive leaf springs to effect the various desired circuit connections and disconnections. Brief Description of the Drawings FIGS. 1, 2 and 3 are a schematic of the various operative positions of a latch/switch arrangement mounted on a circuit module 10 and embodying the principles of the invention; and FIG. 4 is a perspective view of the latch/switch arrangement of FIGS. 1, 2 and 3 mounted on a module or panel partially inserted into a support housing. Detailed Description A latch/switch arrangement mounted on a circuit module 10 and embodying the principles of the invention is shown in each of three distinct operational states or stages in FIGS. 1, 2 and 3 respectively. The first state is illustrated in FIG. 1 wherein a circuit module or panel 10, containing electrical circuits connected to conductors 1, 2 and 3 and a latch/switch arrangement is partially inserted into an apparatus support housing 15. In this stage of operation the panel back end (not shown) has not yet engaged the back plane electrical connectors of the apparatus support housing. The circuit panel 10 (shown in a fragment form) is assumed to contain various electrical circuits connected to conductors 1, 2 and 3 and that initially there exists a first circuit connection that is to be established for a finite duration during locking the circuit panel into the housing and at least a second circuit connection that is to be established for a finite duration during the insertion process and then changed or disconnected when the circuit panel is fully locked into the apparatus support housing 15. As shown in the schematic diagram in FIG. 1 a circuit panel 10 has been initially inserted into an apparatus support housing 15 which may include tracks or channels 17 to hold the panel edges and guide it into an aligned electrical connector at a back plane. The latch portion of the arrangement (shown in fragment form) includes a lever 21 which is pivoted around a supporting axis 22 and is displaced at a first arc distance 41 from the vertical. When rotated to the vertical it eventually secures the circuit panel 10 into the apparatus support housing 15. One end of the lever 21 includes a notch 23 which is positioned to engage a lip member 16 of the apparatus support housing 15. Associated with the lever 21 is a conductive leaf spring contact arrangement 30 having three conductive leaf springs 31, 32 and 33. The conductive leaf spring 31 is flexible and is positioned to be engaged directly by a cam element 24 of the lever 21. A second conductive leaf spring 32 is also flexible and is positioned to be transitively flexed when leaf spring 31 is sufficiently flexed. A third conductive and flexible leaf spring 33, is positioned to normally engage the conductive leaf spring 32 with a minor interference bias (i.e., slight connecting pressure) prior to insertion of the circuit panel 10. This is to assure a good conductive connection between lead springs 32 and 33 and a finite duration of connection. This minor interference assures good conductivity and finite duration connections during the entire operational range described below. Contact nodes designated 35, 36, 37 and 38 are included on different ones of the conductive leaf springs to facilitate designated electrical connections between the various conductive leaf springs. Each leaf spring is preferable electrically conductive and is conductively connected to a separate circuit path 1, 2 or 3 on the circuit panel 10. As shown in FIG. 1, prior to the panel being engaged and locked into housing 10, the cam element 24 of the lever 21 has not yet engaged the conductive leaf spring 31 and the contact nodes 36 and 37 are in contact with each other electrically connecting the two conductive leaf springs 32 and 33. This contact is enhanced by the minor interference bias discussed above. The contact nodes 35 and 38 are disengaged from each other, and hence conductive leaf spring 31 is not electrically connected to any of the others. During this initial state, there is the slight flexural interference between leaf springs 32 and 33 resulting in contact pressure between contact nodes 36 and 37 for a finite arc of rotation of lever 21. Leaf spring 31 is in its relaxed position and will remain so until the cam element 24 of the lever 21 engages it. The next stage of the insertion process, shown in FIG.2 represents a stage when the lever 21 has rotated to a second arc distance 42 and the notch 23 has engaged the lip 16 and the back end of the panel is beginning to engage connectors in the back plane of the apparatus housing. Rotation of the lever 21 about the supporting axis 22 applies a force to the panel 10 at supporting axis 22 enabling it to begin to fully engage the electrical contacts of the back plane (not shown). At this particular stage, the cam element 24 has engaged conductive leaf spring 31 and displaced it sufficiently so that the two contact nodes 35 and 38 are electrically connected, thereby, electrically connecting the conductive leaf springs 31 and 32. The contact nodes 36 and 37 continue to remain in contact as they did in FIG. 1 for a finite arc of rotation of the lever 21 and its cam element 24. This finite duration of contact is controlled by and due to the minor interference bias discussed above. During this stage which extends over a predetermined finite arc of lever movement, the conductive leaf spring 31 is electrically connected to conductive leaf spring 32 and conductive leaf spring 32 is also electrically connected to conductive leaf spring 33. In the final stage of the insertion process depicted in FIG. 3, the lever 21 has been moved into its locked position wherein it locks the panel securely into the housing 15 and has contacts at the back end of the panel fully engage the electrical contacts in the back plane. The cam element 24 has fully depressed the conductive leaf spring contact 31 which in turn has fully depressed the conductive leaf spring 32 via the force contact between contact nodes 35 and 38. As a result the contact nodes 35 and 38 remain in contact with each other and the contact nodes 36 and 37 have separated from each other and the conductive leaf springs 32 and 33 are no longer electrically connected with each other. A perspective view of the latch/switch arrangement is shown in FIG. 4 where the lever 21 is shown in its open position prior to the locking process to secure the panel into an apparatus support housing. The supporting apparatus support housing includes a front structural member 16 which is a lip to which a notch 23 in the lever 21 is engaged in order to lock the panel 10 into the apparatus support housing. The panel itself fits into a channel member 17 which supports it and guides it into properly engaging the connectors in the back plane. The channel member 17 has a paired top channel member associated with it (not shown) to engage the top edge of the panel 10 (not shown). The conductive leaf spring contact arrangement 30 is mounted on the panel 10 and has its top conductive leaf spring 31 extended toward the lever 21 where it is positioned to be engaged by the cam element 24 of the lever. A second conductive leaf spring 32 below it is subsequently engaged when the top leaf spring 31 is sufficiently deflected. This deflection as described above enables the specified connections and disconnections of electrical circuit arrangements.

Claims: A circuit module including a latch/switch arrangement for inserting and securing the circuit module (10) into an apparatus housing, said circuit module comprising a lever arrangement (21) pivotably mounted relative to the circuit module (10) for inserting and securing the circuit module into the apparatus housing, CHARACTERISED BY a switching arrangement (30) mounted relative to the circuit module including first (31) second (32) and third (33) conductive leaf springs, the lever arrangement including a cam suface (24) to engage and apply pressure to displace the first conductive leaf spring from a rest position, when the latch is rotated to secure the circuit module into the housing, the second and third conductive leaf springs being situated to be conductively connected in an absence of displacement of the second conductive leaf spring, the cam surface initially flexing the first conductive leaf spring as the lever arrangement is rotated causing the first and second conductive leaf springs to be conductively joined, further rotation of the lever causing the cam to displace the first conductive leaf spring sufficiently to flex the second leaf spring causing it to disengage from the third conductive leaf spring. Circuit module as claimed in claim 1, CHARACTERISED IN THAT the second and third leaf spring have a flexible interference whereby the second and third leaf spring remain engaged with each other for a finite arc of rotation of the lever arrangement after the first and second leaf springs have engaged each other. Circuit module as claimed in claim 1, CHARACTERISED BY means for inserting and securing the module in the housing, said means including a notch (23) in the lever arrangement positioned to engage a lip structure (16) of the apparatus housing. Circuit module as claimed in claim 1, CHARACTERISED IN THAT each of the leaf springs includes at least a contact node for facilitating electrical connections between the leaf springs.

Inventors: BARWICK, MORRIS LUCIAN, PRAUGHT, RONALD BENJAMIN
Applicants: AMERICAN TELEPHONE AND TELEGRAPH COMPANY
Application year: 1988
Main classification: H05K7
IPC codes: H01H21, H01H1, H05K7