Collapsible frame for a shelter

1. A frame for a portable shelter, the frame being selectively articulable between an erected state and a collapsed state, the frame comprising:

(a) first and second frame supports,

each frame support comprising a pair of center frame members rotatably coupled about a center joint, and a pair of lateral frame members, each lateral frame member being rotatably coupled to one of the center frame members about a lateral joint,

each pair of center frame members being selectively moveable between a first position when the frame is in the erected state and a second position when the frame is in the collapsed state, wherein the first and second frame supports are selectively lockable in the first position;

each pair of lateral frame members being selectively moveable between a first position when the frame is in the erected state and a second position when the frame is in the collapsed state; and

(b) a plurality of purlin assemblies, each purlin assembly comprising first and second purlin members rotatably coupled about a purlin mid joint, a first end of the purlin assembly being pivotally coupled to the first frame support, a second end of the purlin assembly being pivotally coupled to the second frame support, the purlin assembly being selectively lockable in an extended position when the frame is in the erected state, the purlin members being rotatable to a folded position when the frame is in the collapsed state,

a first one of the purlin assemblies being pivotally coupled to the first and second frame supports at respective center joints, a second one of the purlin assemblies being pivotally coupled to the first and second frame supports at one pair of respective lateral joints, and a third one of the purlin assemblies being pivotally coupled to the first and second frame supports at another pair of respective lateral joints.

2. The frame of claim 1 , wherein each center joint comprises a pivot pin assembly defining an axis of rotation of the center joint, each first purlin member being rotatable about the axis of rotation of the first center joint.

3. The frame of claim 2 , wherein each first purlin member is rotatable about a second axis of rotation normal to the axis of rotation of the first center joint.

4. The frame of claim 2 , wherein each second purlin member is rotatable about the axis of rotation of the second center joint.

5. The frame of claim 4 , wherein each first purlin member is rotatable about a second axis of rotation normal to the axis of rotation of the first center joint, and wherein each second purlin member is rotatable about a third axis of rotation normal to the axis of rotation of the second center joint.

6. The frame of claim 1 , each purlin assembly further comprising a sleeve slidably associated with each first purlin member, the sleeve being selectively positionable to lockingly engage the purlin mid joint.

7. A portable shelter, comprising:

(a) a plurality of selectively collapsible frame supports spaced apart in a series along a longitudinal axis, each frame support extending transversely with respect to the longitudinal axis, each frame support comprising a pair of center frame members rotatably coupled about a center joint, and a pair of lateral frame members, each lateral frame member being rotatably coupled to one of the center frame members about a lateral joint;

(b) a plurality of purlin assemblies extending longitudinally between the frame supports, a first one of the purlin assemblies pivotally connecting one frame support to an adjacent frame support at respective center joints, a second one of the purlin assemblies pivotally connecting one frame support to an adjacent frame support at one pair of lateral joints, and a third one of the purlin assemblies pivotally connecting one frame support to an adjacent frame support at another pair of lateral joints, the plurality of purlin assemblies selectively maintaining a space between adjacent frame supports, each of the plurality of purlin assemblies being foldable to move adjacent frame supports towards each other; and

(c) a flexible structure supported by the frame support members.

8. The portable shelter of claim 7 , wherein at least one of the collapsible frame supports comprises at least two frame members rotatably coupled to each other, the at least two frame members being selectively rotatable between an erected position and a collapsed position.

9. The portable shelter of claim 7 , wherein each of the plurality of purlin assemblies is selectively lockable in an extended position.

10. The portable shelter of claim 7 , further comprising a fly supported by at least one of the collapsible frame supports and at least partially disposed over the flexible structure.

11. The portable shelter of claim 10 , wherein the fly comprises:

(a) at least one of a low gas permeable material and a non gas permeable material; and

(b) one or more longitudinally extending areas of a mesh sized and configured to permit air flow therethrough.

12. The portable shelter of claim 11 , wherein the one or more longitudinally extending areas of a mesh includes a first area located on a lower portion of the fly and a second area located on an upper portion of the fly, the first and second areas cooperating to induce convectional air flow between the flexible structure and the fly.

13. A method of collapsing a portable shelter frame as recited in claim 1 , the method comprising:

(a) rotating each lateral frame member about the corresponding lateral joint from a first lateral member position, in which the lateral member extends in a downward direction from the lateral joint, to a second lateral member position, in which the lateral frame member is aligned with the corresponding center frame member;

(b) moving the spaced apart frame supports together so that each frame support is proximate to one or more adjacent frame supports, movement of the frame supports folding each of the plurality of purlin assemblies about a respective purlin mid joint; and

(c) rotating the two center frame members of each frame support from its first position to its second position in which the two center frame members are aligned.

14. The method of claim 13 , further comprising unlocking the center joints and the lateral joints.