Drop platform structure for a loading dock

Claim 2

A drop platform structure for use with a loading dock or the like, comprising: a pair of elongated telescoping inner and outer frame members, the inner frame member being pivotally secured at a point located on said dock and the other of said frame members being pivotally secured to a brace member pivotally secured at a second point located on said dock, said second point being spaced from and above said first point; normally inactivated first drive means associated with said frame members for telescoping one of said frame members with respect to the other; an elongated extensible tongue member slidably disposed with respect to said frame members; second drive means associated with said tongue member for selectively extending and retracting said tongue member with respect to said telescoping frame members; and means associated with both said tongue member and said first drive means for activating said first drive means during the retraction of said tongue member with respect to said telescoping frame members upon actuation of said second drive means so as to raise said frame members from a generally horizontal to a generally vertical position.

Claim 3

The platform structure of claim 1 wherein said frame members are hollow and said tongue member is slidably disposed inside of said frame members.

Claim 4

The platform structure of claim 1 wherein the pivot point of said brace member on said dock is spaced inwardly a short distance toward said dock from the vertical with respect to said first-mentioned pivot point.

Claim 5

The platform structure of claim 1 wherein said normally inactivated drive means includes an elongated mast pivotally mounted at said first-mentioned pivot point and extending within said telescoping frame members, said mast including at least a pair of sprockets, one of said sprockets being disposed at the end of said mast pivotally mounted to said dock and the other of said sprockets being secured to the free end of said mast, and a control chain engaging said sprockets, one end of said control chain being secured to said outer frame member and the other end of said chain being secured to a first block movable within said frame members; said means associated with both said tongue member and said first drive means including a second block fixed to the end of said tongue member interior of said frame members and forwardly of said first block in a direction away from said first-mentioned pivot point; said means associated with both said tongue member and said first drive means further including selectively engageable portions on each of said blocks whereby upon activation of said second drive means and retraction of said tongue member, said second block engages said first block to thereby move said first block to drive said control chain and thus extend said outer frame member connected to saiD control chain to thereby raise said frame members to their substantially vertical position.

Claim 6

The platform structure of claim 4 wherein said selectively engageable and disengageable portions on each of said blocks include a pin integral with said first block extending in a direction substantially normal to the direction of travel of said control chain and a notch on said second block for receiving said pin therein.

Claim 7

The platform structure of claim 4 wherein said second drive means includes a reversible motor, a first drive chain driven by said reversible motor and a third sprocket in driving engagement with said first drive chain, said third sprocket being integral with a fourth sprocket pivotally mounted at said first-mentioned pivot point, and a second drive chain in driving engagement with both said tongue member and said fourth sprocket.

Claim 8

The platform structure of claim 5 including keeper means associated with both said dock and said second block for retaining said pin in said notch during extension of said tongue member upon movement of said frame members from a substantially vertical to a substantially horizontal position.

Claim 9

The platform structure of claim 7 including downward movement limiting means associated with both said dock and said inner frame for limiting the downward movement of said frame members.

Claim 10

The platform structure of claim 8 including means associated with said dock for disengaging said downward-movement limiting means when said keeper means is retaining said pin within said notch.

Claim 11

The platform structure of claim 1 including a carriage structure associated with said dock, said carriage structure being movable longitudinally of said dock, and said first-mentioned pivot point being disposed on said carriage structure.