Abstract:
A latch is designed to attain and keep full engagement of a sub-assembly in a chassis and to increase the reliability and longevity of connectors by increasing the chances that they remain fully engaged even in the presence of shock and vibration.

Description:
BACKGROUND  
       [0001]     Some electronic module sub-assemblies need to be inserted into a chassis and then be connected and fully mated with a chassis-mounted connector. Examples of such sub-assemblies are power supplies, RAID disks, peripheral devices, fan assemblies, and processors, all of which require a power connection of some sort. When these sub-assemblies have a power connection there is a requirement for sufficient surface contact (barrel contact) to insure adequate performance. Sufficient surface contact is only accomplished and assured with a fully mated or almost fully mated connector.  
         [0002]     Providing for full connector insertion of power connectors (pre-loading) is of vital importance when preventing power failures as is maintaining the fully loaded connection during service. If a power connector loosens or begins to back out and there is less and less surface contact, the power connection and the connector itself may eventually fail. Consequently, yield (longevity and service life of the connector and thus any product) is compromised by a non-fully inserted power connector.  
         [0003]     For purposes of quality and safety, and especially with high voltage, one typically uses an injector tool when inserting a sub-assembly into a chassis, usually then securing the sub-assembly with a lock of some kind and a mounting screw or two.  
         [0004]     Previous solutions include securing screws, locking inserter/ejector levers, and simple locking mechanisms (like a door handle).  
         [0005]     Securing screws can be used to provide enough pre-load to ensure fully mated connectors. The problem is they are often numerous in number and are subject to stripping or cross threading due to alignment problems. There are also tolerance problems in getting the threads started. The screw stripping, screw binding, and screw damage sometimes leaves metal particles and slivers that can short electronics near the failure. Furthermore, since the screws are not initially attached to the chassis or sub-assembly, they can be easily lost or misplaced. Sometimes when this happens, a sub-assembly is secured with less than the full number of required screws, and the connection is either not as complete as it needs to be initially or is prone to earlier failure.  
         [0006]     Inserter/ejector levers themselves are adequate to fully engage a connector pair at time of insertion. The problem is that they generally cannot provide enough pre-loading to overcome extended field shock and vibration, especially in the telecom environment. Furthermore, they generally cannot maintain full engagement during fragility operations such as transportation and shipping because there is no pre-loading spring action.  
         [0007]     Simple locking mechanisms do not provide any pre-load, and thus are inadequate for powered sub-assemblies, especially when the service environment includes shocks and vibrations.  
       SUMMARY  
       [0008]     Generally, the present invention specifies a latch designed to attain and keep full engagement of a sub-assembly in a chassis. Such a latch increases the reliability and longevity of connectors by increasing the chances that they remain fully engaged even in the presence of shock and vibration. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a block diagram of an embodiment of the invention showing a sub-assembly being inserted into a chassis and being secured with a latch.  
         [0010]      FIG. 2  is a block diagram of the front of the sub-assembly of  FIG. 1  showing the components of the latch in an open position according to an embodiment of the invention.  
         [0011]      FIG. 3  is a block diagram of the front of the sub-assembly of  FIG. 1  showing the components of the latch in a closed position according to an embodiment of the invention.  
         [0012]      FIG. 4  is a top and front view of a latch with a keying lock according to an embodiment of the invention.  
     
    
     DESCRIPTION OF THE INVENTION  
       [0013]     In one embodiment of the present invention the inserter/ejector tool is a latch that is part of the sub-assembly. The latch tool is attached to the sub-assembly and is captive and so is not easily lost or misplaced. This pre-loading power latch is a sheet metal plate incorporating a thumb or standard screw operable to attach the latch to the sub-assembly. The latch and the latch screw are always loosely attached to the sub-assembly and cannot be removed and are rigidly attached to the chassis on completion of an insertion operation.  
         [0014]     Referring to  FIG. 1 , in this embodiment of the invention, a component or sub-assembly, such as a power supply,  1  is inserted into a chassis  2 . There is a sub-assembly connector  3  at the rear of the sub-assembly  1  and a chassis connector  4  attached to the inside of the back of the chassis  2 . As the power supply is inserted into the chassis  2 , the sub-assembly connector  3  mates with the chassis connector  4 .  
         [0015]     A latch  5  is loosely attached to the front of the sub-assembly  1 . A latch bracket  10  with a slot (not shown in  FIG. 1 ) is rigidly attached to the front of the chassis  2 . As the sub-assembly  1  is pushed into the chassis  2 , one typically feels resistance as the sub-assembly connector  3  is inserted into the chassis connector  4 .  
         [0016]     A latch screw  7  is tightened into the chassis  2 , and the latch  5  is rotated from an open position to a closed position. The latch screw  7  and the latch  5  rotate independently from each other. A latch lip  6  is moved into the latch slot (not shown in  FIG. 1 ) on the latch bracket  10  by a counter-clockwise rotation. A latch guide  8  stops the latch  5  from rotating any more than ninety degrees counter-clockwise as the latch screw  7  is tightened further. The latch guide  8  also serves to ensure the lap lip  6  is centered in the latch slot (not shown in  FIG. 1 ) as the latch screw  7  continues to be tightened.  
         [0017]     Still referring to  FIG. 1 , the power latch  5  starts a pre-loading process with the latch lip  6  in the latch slot (not shown in  FIG. 1 ) at a slight angle as shown. Once the latch lip  6  is in place and the latch screw  7  is further tightened, the latch  5  attempts to straighten itself. As the latch  5  straightens, the latch lip  6  pushes against the outside edge of the latch slot (not shown in  FIG. 1 ) in the latch bracket  10 . This causes a moment inward and, when seated, pre-loads the sub-assembly connector  3  and the chassis connector  4 . That is, straightening the latch  5  causes the connectors  3  and  4  to be fully mated.  
         [0018]     In one embodiment of the invention, the latch guide pins  9  are for use during an ejection operation to keep the latch  5  from rotating more than ninety degrees clockwise as the latch screw  7  is loosened. The combination of the latch guide  8  and the latch guide pins  9  keeps the latch  5  from rotating any more than ninety degrees.  
         [0019]     In another embodiment of the invention, a stop mechanism  12  is attached to the chassis  2 . The stop mechanism  12  is optional and inclusion in a particular embodiment depends upon tolerance and connector robustness. The stop mechanism  12  consists of a block of material such as plastic or metal located near the mating connectors  3  and  4 , and is present to keep the sub-assembly  1  from exerting too much force on the connectors  3  and  4 .  
         [0020]     Referring to  FIG. 2 , the latch  5  of  FIG. 1  is shown in an open position. The latch guide  8  is against the latch guide pins  9 . This prevents the latch  5  from rotating any further in the clockwise direction during an ejection operation. The latch lip  6  is not engaged in the latch slot  11  on the latch bracket  10 , so there is no pre-loading. The sub-assembly  1  is unlatched and thus set either to be completely removed from the chassis  2  or to be subsequently latched to the chassis  2 .  
         [0021]     Referring to  FIG. 3 , the latch  5  of  FIGS. 1 and 2  is shown in a closed position. The latch guide  8  is against the latch bracket  10 . This prevents the latch  5  from rotating any further in the counter-clockwise direction during an insertion operation. This also ensures the latch lip  6  is engaged in the center of the latch slot  11  on the latch bracket  10  so that there is maximum or near-maximum pre-loading. The sub-assembly  1  is latched to the chassis  2  and pre-loading is maximized as the latch screw  7  is tightened.  
         [0022]     Referring to  FIG. 4 , the latch  5  of  FIGS. 1-3  is shown in a top and a front view with a latch lip keying lock  13  on the latch lip  6  according to an embodiment of the invention. The latch lip keying lock  13  prevents the sub-assembly  1  ( FIG. 1 ) from moving up or down after the latch  5  is closed and secured by the latch screw  7 . Since the latch  5  prevents horizontal movement of the sub-assembly and the latch lip keying lock  10  prevents vertical movement of the sub-assembly, the sub-assembly is securely attached to the chassis  2  ( FIG. 1 ).  
         [0023]     In another embodiment of the invention, inserter/ejector levers can be used in conjunction with a power latch depending on the insertion force required to overcome the mating force of the connectors.  
         [0024]     It is envisioned that any electronic chassis with sub-assemblies and a power requirement could use this invention. This includes sound production and reproduction systems and media production and reproduction systems in general.  
         [0025]     It is also envisioned that any module in a computer could use this invention with or without an insertion/extraction lever and with or without a stop mechanism.  
         [0026]     The preceding discussion is presented to enable a person skilled in the art to make and use the invention. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.