Abstract: A screw-type lift having a ratchet lifting nut assembly providing for the safe lowering of a load while preventing additional lifting of the load upon failure of a lifting nut is disclosed. The ratchet lifting nut assembly includes a lifting nut and an auxiliary nut threadably engaging a lifting screw and a wear gap separating the lifting nut from the auxiliary nut. A ratchet portion is supported on the auxiliary nut and is aligned for engagement with a pawl supported on the lifting nut. During a normal mode of operation, the lifting nut supports the entire weight of a load and the ratchet portion and pawl cooperate to restrain rotational movement of the auxiliary nut relative to the lifting nut. A failure mode of operation is defined when the lifting nut is excessively worn in that it can no longer safely support the load. In this mode, the wear gap is eliminated wherein the auxiliary nut is supported on the lifting nut and the load is supported solely by the auxiliary nut.

Abstract: An in-ground mechanical vehicle lift apparatus including an outer cylinder and a support tube rigidly attached to the outer cylinder. A ram cylinder is located between the outer cylinder and support tube in telescoping relationship to the outer cylinder and the support tube. The drive motor is mounted to the ram cylinder and a drive screw is operably connected to the drive motor for engaging a nut rigidly attached to an upper end of the support tube. The drive screw is driven in rotation by the motor to cause the ram cylinder to move upwardly and downwardly relative to the outer cylinder, and a vehicle support portion is located on an upper end of the ram cylinder for engaging and supporting a vehicle. The lift apparatus is adapted to be installed as a replacement for an in-ground hydraulic lift system wherein the lift apparatus is of a compact design which will fit within an existing in-ground cylinder of the hydraulic system.