An apparatus for progressively lifting a structure such as a grain bin fashioned from series of interconnected rings of corrugated metallic panels, the apparatus comprising;
- (a) at least two sets of substantially identical hydraulic jacks, each set of jacks including an equal number of jacks numbering at least one, each jack having an hydraulic cylinder, a piston that slides within the hydraulic cylinder and a piston rod fixed to the piston that moves in and out of the hydraulic cylinder, each hydraulic cylinder having a lower chamber below the piston and an upper chamber above the piston, the lower chamber receiving hydraulic fluid to push the piston up and expelling hydraulic fluid when the piston is being pushed down, the upper chamber receiving hydraulic fluid to push the piston down and expelling hydraulic fluid when the piston is being pushed up, each jack also comprising a series of masts including a first mast, at least one next mast and a last base mast for supporting the jack and holding the hydraulic cylinder, the first mast having an attachment for mounting to the structure, each mast except the last base mast slidably received by each next mast, each mast except the last base mast having features for engaging the piston rod of the hydraulic cylinder, each mast and each next mast also having features for securing each mast in relation to each next mast when each mast is extended relative to each next mast,
- (b) substantially identical hydraulic circuits for actuating each set of jacks, each hydraulic circuit having access to an hydraulic fluid reservoir and including a substantially identical positive displacement pump, a control valve, lines for hydraulic communication between the reservoir, the control valve and the pump including:
- a line communicating between the reservoir and the pump, a line communicating between the pump to the control valve, lines for communicating between the control valve and the lower chambers of the hydraulic cylinders of a set of jacks, lines for communicating between the upper chambers of the hydraulic cylinders of the same set of jacks and the control valve and a line for communicating between the control valve to the reservoir, the control valve movable between a first position that only allows fluid to flow from the pump toward the reservoir, a second position that allows fluid to flow from the pump, through the valve and toward the lower chambers of the hydraulic cylinders of the set of hydraulic jacks and from the upper chambers of the hydraulic cylinders of the same set of jacks back through the valve and toward the reservoir to cause the set of jacks to raise in unison and a third position that allows fluid to flow from the pump, through the valve and toward the upper chambers of the hydraulic cylinders of the set of hydraulic jacks and from the lower chambers of the hydraulic cylinders of the same set of jacks back through the valve and toward the reservoir to cause the set of jacks to lower in unison,
- (c) a power source for driving the substantially identical positive displacement pumps of each hydraulic circuit at the same rate so that the pumps may pump hydraulic fluid at the same flow rate in each of the hydraulic circuits,
- (d) a connection for connecting the control valves of each of the hydraulic circuits, so that all of the control valves may be moved between the first, second and third positions in unison, whereby the at least two sets of hydraulic jacks may be operated to raise or lower the structure in unison.