Patent ID: 6035635
Filing Date: 2000-03-14
Classification: B66F,F15B

Abstract:
An improved hydraulic quick lifting unit used in a jack comprising an outer hydraulic cylinder body, an inner hydraulic cylinder body, a lifting shaft, a bonnet, and a base;wherein said outer hydraulic cylinder body is connected at its two ends individually to the bonnet and the base, and contains an outer oil reservoir filled with hydraulic liquid and is completed with a plug 12 that is inserted into an oil inlet formed on the cylinder wall to close the cylinder body after hydraulic liquid is fed into the outer oil reservoir;said inner hydraulic cylinder body, being disposed between the bonnet and the base, includes an inner oil reservoir into which a lifting shaft extends and has an annular groove formed on the inner wall surface near the front end that provides a passage for returning the hydraulic liquid in the inner oil reservoir to the outer oil reservoir when the lifting shaft moves to its farthest position;said lifting shaft has an inner oil chamber formed therein, provided inside which inner oil chamber is a mandrel that is associated to the base by means of a retainer ring disposed at the end of the mandrel and a guide assembly arranged inside a hole at the lower end of the lifting shaft to receive and guide the mandrel in position, said inner oil chamber having an outlet communicated with an oil chamber of a pump, through an oil passage of the mandrel;the bonnet is disposed at the front end of the jack to guide the lifting shaft when the lifting shaft is driven by a hydraulic system to move up and down;the base is at the bottom of the jack and has the pump and an oil return tube respectively provided on the sides thereof; a unidirectional valve provided in the oil chamber of said pump,said oil return tube being at one end connected to the outer oil reservoir through first oil passage and at the other end thereof connected to the oil chamber of the pump and the oil passage of the mandrel via a second oil passage that is in communication at its two ends respectively with a third oil passage of a modulation valve and a fourth oil passage of an equilibrium valve,said equilibrium valve being equipped at its lower end with an upper oil passage and a lower oil passage, with the upper oil passage connected to the inner oil reservoir and the lower oil passage connected to the outer oil reservoir,said equilibrium valve being further provided with a steel ball between the upper and the lower oil passage, and another steel ball between the upper oil passage and the second oil passage thereof, andsaid lower oil passage being in communication with the oil chamber of the pump.