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New solution to increase the safety of operating system with hydrostatic drive

100%

Siwulski T. , Warzynska U.

2018

tom Vol. 50, No. 2(188)

197--207

Hydraulic actuators that commonly used in machine work systems are not equipped with protection features preventing the autonomous insertion and extension of a piston rod because of the influence of external forces. Consequently, a spontaneous fall of working circuits in the event of the loss of tightness of supply lines of an actuator may occur. Currently applied safety features that are sometimes mounted directly on hydraulic cylinders as in the case of mining machinery intended for exploitation in black coal mines protect working systems from uncontrolled lowering. However, their design forces the drive to be started to make it safe to leave the work system. If, for any reason, the drive system of a machine cannot be started and the work system is raised, its lowering can take place only by unsealing the hydraulic system, which is unforeseeable for constructors and carries the danger of crushing a person or persons involved. The paper presents a new solution for hydraulic cylinders, which enables, among other things, the controlled and safe insertion of a piston rod under load without the need for having the drive system started.

The influence of gear micropump body asymmetry on stress distribution

80%

Kollek W. , Osinski P. , Warzynska U.

nr 1

The paper presents the results of numerical calculations of stress distributions in the gear micropump body for applications in hydraulic systems, especially in the marine sector. The scope of the study was to determine the most favorable position of bushings and pumping unit in the gear pump body in terms of stress and displacement distribution in the pump housing. Fourteen cases of gear pump bushings and pumping unit locations were analyzed: starting from the symmetrical position relative to the central axis of the pump, up to a position shifted by 2.6 mm towards the suction channel of the pump. The analysis of the obtained calculation results has shown that the most favorable conditions for pump operation are met when the bushings are shifted by 2.2 mm towards the suction channel. In this case the maximal stress was equal to 109 MPa, while the highest displacement was about 15µm. Strength and stiffness criteria in the modernized pump body were satisfied