Filter for avionic line replacement unit

Claim 2

A filter assembly for prefiltering coolant air that enters an avionic line replaceable unit (LRU) box through holes in the top surface of the box and exits through at least one hole in the bottom of the box which is coupled in airflow communication with a negative pressure plenum when said LRU box is in an avionic tray, said avionic tray providing support members arranged, respectively, proximate to opposite ends of said top surface of the box, said filter assembly comprising: a frame comprised of side and end wall members that have upper and lower rims, said wall members arranged to define a plenum opening for passage of coolant air into the LRU and the frame is adapted for being positioned with the wall members superimposed on the margins of said top surface of the LRU box with sealing means between said frame and the top surface, a filter element supported in said frame for spanning across said opening at a distance from the LRU box top surface such that the filter element, the top surface and the walls of the frame define a plenum under the filter element, a hold-down cover for being superimposed in compressive relation on said filter element and having an open area for filtered air to flow into the plenum, and means for releasably attaching said hold-down cover to said support members provided by the tray such that when said hold-down cover is released said filter element is accessible without removing said LRU box from said avionic tray.

Claim 3

The filter assembly according to claim 1 including: means for swingably connecting said hold-down cover to one of said support members and latch means for releasably latching said hold-down cover to the other of said support members, to provide for accessing said filter element without removing said LRU by unlatching and swinging said cover.

Claim 4

The filter assembly according to claim 1 wherein: said hold-down cover is comprised of walls including opposite front and rear walls and opposite side walls for depending along the walls of the frame and having a top side comprised of rims projecting inwardly of the walls to define the margins of said open area of the cover, a selected one of either said rear wall of the cover or said support member proximate to the end of the top of the LRU having a slot and the other of the rear wall of the cover or the support member not having said slot having a tongue projecting into said slot to effect a hinge connection between the cover and said support member to provide for accessing said filter element without the need for removing the LRU from the tray by swinging said cover on said hinge connection, and means for releasably latching said cover at its front wall to the other support member.

Claim 6

An air filter assembly for an avionic line replaceable unit (LRU) box adapted for containing electrical devices, the box top having a flat nominally rectangular configuration containing upstream cooling air inlet means, the box bottom containing downstream air outlet means for being disposed in airflow communication with a chamber having negative pressure, the box being configured to be installed in an avionic tray that has fixed laterally extending longitudinally spaced apart support members for the filter assembly at a height about equal to the height of the box, a plenum frame having opposite laterally extending end walls and opposite longitudinally extending sidewalls formed as a rectangle for being superimposed on the laterally and longitudinally extending margins, respectively, of the LRU top surface, a sealing gasket interposed between the plenum frame and the LRU top surface, support surfaces on the plenum frame, a filter element supported from said support surfaces and a sealing gasket interposed between the margins of the filter element and the support surfaces, said filter element being supported in the plenum frame at a distance from the box top for defining a plenum over the box top in conjunction with the walls of the frame and the LRU top surface, a hold-down member for bearing on said margins of the filter element and means for engaging the hold-down member with said laterally extending support members such that the hold-down member exerts a compressive force on the filter element and on said sealing gasket.

Claim 7

An air filter assembly for an avionic line replaceable unit (LRU) box adapted for containing electrical devices, the box top having a flat nominally rectangular configuration containing upstream cooling air inlet means, the box bottom containing downstream air outlet means for being disposed in airflow communication with a chamber having negative pressure, the box being configured to be installed in an avionic tray that has fixed laterally extending longitudinally spaced apart support members for the filter assembly at a height about equal to the height of the box, a plenum frame having opposite laterally extending end walls and opposite longitudinally extending sidewalls formed as a rectangle for being superimposed on the laterally and longitudinally extending margins, respectively, of the LRU top surface, a sealing gasket interposed between the plenum frame and the LRU top surface, support surfaces on the plenum frame, a filter element supported from said support surfaces and a sealing gasket interposed between the margins of the filter element and the support surfaces, said filter element being supported in the plenum frame at a distance from the box top for defining a plenum over the box top in conjunction with the walls of the frame and the LRU top surface, a hold-down member for bearing on said margins of the filter element and means for engaging the hold-down member with said laterally extending support members such that the hold-down member exerts a compressive force on the filter element and on said sealing gasket.

Claim 8

The device according to claim 5 wherein said hold-down member has opposite laterally extending end wall members and opposite longitudinally extending sidewall members arranged as a rectangle defining an opening, and a rim extending inwardly of the opening from the front, rear and sidewall members for bearing on the margins of said filter element, said means for engaging said hold-down member comprises hinge means connecting an end wall of the hold-down member to one of said laterally extending support members of the avionic tray, and locking means for locking and alternately unlocking the hold-down member to the other laterally extending support member of the avionic tray, such that when the hold-down member is unlocked it can be swung on the hinge means to allow access to the filter element for removing it without being required to remove the box from the tray.

Claim 9

The filter assembly according to claim 5 wherein said hold-down member has at least one slot and a support member has a tongue registered in the slot to serve as a hinge for the hold-down member and provide for swinging the hold-down member for accessing the filter element without moving the LRU in the tray.