IMPROVED COLLAPSIBLE SHELTER/TENT WITH FRAME LOCKING MECHANISM

1. A collapsible shelter/tent, comprising: a collapsible frame including: a) three or more legs pivotally connected to a first clevis; and b) three or more support bars pivotally connected with respect to said legs at an outer end of said support bars and pivotally connected to a second clevis at an inner end of said support bars; a locking mechanism for locking said first and second clevises together when said shelter/tent is assembled which includes: a) a generally vertical pin extending from one of said first and second clevises, said generally vertical pin having a groove on a side thereof; b) a socket on the other of said clevises having a receiving bore aligned with said generally vertical pin; c) an engaging member supported within said socket that can firmly engage said groove in said generally vertical pin after said generally vertical pin is inserted into said socket; and a plurality sheet-material walls supported on said collapsible frame in the collapsed and uncollapsed states. 2. The collapsible shelter/tent of claim 1, wherein said sheet-material walls include sides around the perimeter of said shelter/tent and a ceiling. 3. The collapsible shelter/tent of claim 2, wherein said sheet-material walls are supported on an outside surface of said frame. 4. The collapsible shelter/tent of claim 1, further included biasing means for biasing said engaging member into said groove automatically upon engagement of said first and second clevises. 5. The collapsible shelter/tent of claim 4, wherein said biasing means includes at least one spring. 6. The collapsible shelter/tent of claim 4, wherein said biasing means includes a gravitational force on said engaging member. 7. The collapsible shelter/tent of claim 1, wherein said first clevis is above said second clevis and said generally vertical pin extends downward from said first clevis towards said second clevis. 8. The collapsible shelter/tent of claim 7, wherein said engaging member is located proximate said second clevis and is manually movable at a position proximate said second clevis and spaced substantially below said first clevis. 9.The collapsible shelter/tent of claim 8, wherein said socket is fixed to said second clevis and Includes a central bore and a widened opening having a funnel-shape receiving surface. 10. The collapsible shelter/tent of claim 9, wherein a diameter across said widened opening having said funnel-shape receiving surface is more than 2 times greater than a diameter across