The article is an overview of various materials used in power hydraulics for basic hydraulic actuators components such as cylinders, cylinder caps, pistons, piston rods, glands, and sealing systems. The aim of this review is to systematize the state of the art in the field of materials and surface modification methods used in the production of actuators. The paper discusses the requirements for the elements of actuators and analyzes the existing literature in terms of appearing failures and damages. The most frequently applied materials used in power hydraulics are described, and various surface modifications of the discussed elements, which are aimed at improving the operating parameters of actuators, are presented. The most frequently used materials for actuators elements are iron alloys. However, due to rising ecological requirements, there is a tendency to looking for modern replacements to obtain the same or even better mechanical or tribological parameters. Sealing systems are manufactured mainly from thermoplastic or elastomeric polymers, which are characterized by low friction and ensure the best possible interaction of seals with the cooperating element. In the field of surface modification, among others, the issue of chromium plating of piston rods has been discussed, which, due, to the toxicity of hexavalent chromium, should be replaced by other methods of improving surface properties.
Article citation info: (*) Tekst artykułu w polskiej wersji językowej dostępny w elektronicznym wydaniu kwartalnika na stronie www.ein.org.pl IntroductionBesides the reliability, main requirements for vertical transport are positioning, use of power and reducing of the dynamic loads. For the hoisting mechanism the worst case in terms of appearing overloads is when the lifting operation starts when ropes have clearance. This case is called a jerk of a payload. The case when the ropes clearance is so big that when the ropes tensing began, the angular speed of the drum is near the reference speed. The research of overloads in drive systems usually comes up in the context of their impact on the steel structures of devices. For example in papers [1], [7] and [11] the tests of load dynamics of steel structures of the overhead cranes during payloads lifting were described. In [14], authors presented the model of the hoisting mechanism, where the stiffness of the girder has been taken into account. In these articles there were presented the studies of the behavior of the cranes structures under dynamic loads using FEM method. In [15] the influence of the hoisting mechanism operation on the crane structure was presented. There were presented waveforms of forces in ropes for different methods of increasing the drum speed from linear to inertial with various time constants. The problem of the crane structures load by vertical dynamic forces appeared also in [4] and [16], where the systems with moving mass were described. Reduction of dynamic overloads made by hoisting mechanisms operation provides measurable exploitation benefits, such as: minimization of the structure overload or reducing the power consumption. There were presented also methods of reduction of the steel structure loads by using dampers, eg. in [9]. Research of overloads of hoisting winches for varies cases of lifting were described in [12]. The authors of [10] worked on modeling of hoisting mechanisms equipped with different drive systems.The authors of [3] paid attention to necessity of consideration the various types of the loads of mechanisms caused eg. by the control methods and the limited scope of application of the cranes automation. The conclusion is that the control systems which reduce a temporary load should be used both for automatic and manual control of hoisting winches.In [5] authors pointed the specificity of drives of hoisting winches, which: "are distinguished with respect of their requirements, regarding the control of speed and position and the acceleration phase carried with an active load". The usage of modern drive systems based on frequency inverters, allows meet these requirements.As can be seen the problem of overloads of hoisting mechanisms appears mainly in context of dynamic loads of supporting structures or research of dynamics of hoisting mechanisms. In our opinion, which is based on reading the available literature, the issues of reduce dynamic loads is presented only in context described above.In the paper there is present...
The article presents the experimental investigation of low-lifting capacity hydraulic scissor lift energy consumption. The analysis is based on experimental tests of two individual drives of the scissor lift: the conventional one and the variable-speed electro-hydraulic one. The investigation focuses on the study of the total energy consumption for lifting and lowering the scissor lift with different masses of transported cargo and also power consumptions of each element supplying these systems. Particular attention was paid to the significant impact of power supply on each control component as the main factor of reduction in the energetic efficiency of the low-lifting capacity scissor lift. A comparison of both drives indicated that the mass of transported cargo has a significant influence on the choice of the drive used. Results of the research show that significant energetic savings are obtained, as the modernized propulsion system consumes 67% energy of the standard one. A decrease in the percentage of energy losses with the increase in the mass handled led to the conclusion that the enhancement of propulsion systems in scissor lifts should be especially considered in machines carrying big loads.
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