Self-locking chocks for a semi-trailer

An automatically self-locking chock for a conventional semi-trailer having a plurality of wheels at a rearward end of the trailer and a dolly for a forward end of the trailer, said chock comprises in combination:

• (a) a freely movable dolly wheel platform;
• (i) said platform being set in the lateral center of the roadbed of a truck yard and occupying the area of said roadbed where a dolly of a parked semi-trailer normally rests;
• (ii) said platform being positioned above a dolly platform pit having rigidly affixed load support means set to limit vertical movement of said platform;
• (iii) said platform having at least one vertically positioned platform bar affixed to its underside;
• (b) at least one pair of pivoted chock plates;
• (i) said plates being set horizontally in the plane of said roadbed above a chock plate pit beneath said roadbed;
• (ii) each said chock plate being pivoted along one edge on an axis perpendicular to the length of a parked semi-trailer;
• (iii) said plates being positioned in relation to said dolly platform such that the pivoted edge of each said plate lies laterally across the parked semi-trailer's position at a distance from said platform permitting said plates to contact the wheels of said semi-trailer when pivoted upward;
• (iv) said plates having a minimum width of one foot between said pivoted edge and said free edge;
• (c) cylindrical rotatable members in contact with each said chock plate;
• (i) the axis of rotation of said members being parallel to the axis of pivoting said plates;
• (ii) each said members being mounted on a freely movable chock support means
• (d) a freely movable lever means connecting said platform bar in said dolly pit with said chock support means in said chock plate pit;
• (i) said lever means being pivotably and journalably mounted such that downward movement of said platform bar is mechanically converted into magnified upward motion of said chock support means;
• (ii) said lever means being constructed such that when said dolly platform rests on said load support means under load of a semi-trailer, said rotatable members and said chock support means have pushed said chock plates pivotably upward against the wheels of said semi-trailer;
• and
• (e) positioning means for holding said lever means, when said dolly platform is unloaded, in a position such that said chock plates remain parallel to and approximately in the plane of said roadbed and said platform is a short distance above said load support means.