By Pusher Mechanism Patents (Class 83/719)
- Independently adjustable (Class 83/723)
- With additional means to retract elements (Class 83/724)
- Power derived from movement of reciprocating means (Class 83/725)
- Power derived from fluid pressure means (Class 83/726)
- Movement by screw means (Class 83/727)
- Movement by rack and pinion or pawl (Class 83/728)