The basic designs used as underbody dump hoists are in order of succession;
1.gravity
2.winch (hand or axle engagement)
3.direct push hydraulic
4.cam & roller
5.twin arm underbody
6.scissor
Also common these days and most efficient are head lift telescopics which come in three basis designs, direct telescopic, inverted telescopic and bail mount telescopic.
None of these cam be described as a "wedge" design. After 40 years in the business I have yet to run across or even hear of anything called a wedge. Who knows, maybe you have a unique idea.
