Recent Patents on Mechanical Engineering - Volume 13, Issue 1, 2020

Background: Gangue is the concomitant product of coal mining. The traditional approach for gangue treatment is to transport it from underground to ground level to accumulate and form gangue hills. Objective: On the basis of summarizing previous research results, this paper introduces the hydraulic roller crusher and the electric machine built-in coal gangue roller crusher, which avoids the complex transmission problems caused by the movement of the central axis when the roller crusher is allowed to roll. Methods: The hydraulic counter-roll crusher directly separates large pieces of coal and underground gangue such that large pieces of coal gangue do not escape from the well. The electric machine built-in roller crusher is an explosion-proof electric machine used in the crushing roller. Results: Both of these crushers can be used in the selective crushing technology of coal gangue in a coal mine and can meet the requirements of crushing different material sizes and generally avoid the centre of the roller crusher. Conclusion: Both of these crushers reduce transportation costs, minimise land occupation, prevent surface subsidence, decrease environmental treatment costs, reduce environmental pollution, and decrease the transport volume of gangue underground. Various patents have been discussed in this article.

Background: Molten pool temperature in Laser Additive Manufacturing (LAM) will affect powder efficiency, structural compositions of reactants and products in the molten pool, thus determining the microstructure evolutions and mechanical properties of the final part. An interest in molten pool temperature measurement has been around for a long time since the appearance of LAM. However, a comprehensive summary of the existing methods and their applications does not exist in the literature. Objective: The state-of-the-art of the existed devices and methods for molten pool temperature measurement in various of LAM processes is reviewed in this paper. Methods: The existing temperature measurement methods for molten pool monitoring in LAM processes are discussed. For each method, the existed patents, detailed procedures, advantages and disadvantages, specific applications are specified. In the end, comparisons among the current temperature measurement techniques are made according to data accuracy, operation complexity and cost of implementation. Results: Four methods are currently being used for the molten pool temperature measurement in LAM processes, including (i) Thermocouples, (ii) Infrared pyrometers, (iii) Infrared cameras, and (iv) Charge-coupled-device cameras. Conclusion: Different measurement methods represent different characteristics of the signal, and each has merits and defects. Selecting suitable measurement method according to different process characteristics will be helpful to achieve a preferable and more convincing results.

Background: Electrical Discharge Machining (EDM) technique is an effective and reliable method for machining difficult-to-cut materials with complex shapes. Pulse power supply, a core component of the EDM machine tool, plays a major role in the processing efficiency and processing quality. Thus, more and more attention has been paid to the power types and control methods of pulse power supplies of EDM at present. Objective: To meet the increasing requirement of processing efficiency and processing quality of EDM, the power types and control methods of pulse power supplies are enhanced constantly. Methods: This paper sketches out various current representative patents relevant to the power types and control methods of pulse power supplies of EDM. Results: Through comparing the characteristics of the power types and control methods of pulse power supplies of EDM, the main problems in the present development such as low processing efficiency and poor processing quality are summarized and analyzed. Utilization and conservation of electric energy is also a concern. In addition, the further development tendency towards the power types and control methods of pulse power supplies of EDM is discussed. Conclusion: The optimization and development of the power types and control methods of pulse power supplies of EDM are beneficial to solve the problems of processing efficiency, processing quality and energy utilization in EDM. More interrelated patents on the pulse power supply of EDM will be invented later.

Background: As a successive part, the paper introduces the second mode of abnormal hydrodynamic thrust slider bearings with divergent surface separations registered in the patents, where the boundary slippage is artificially designed both on the stationary surface in the inlet zone and on the whole moving surface. Objective: To introduce a second method for artificially designing the boundary slippage for the formation of abnormal hydrodynamic thrust slider bearings. Methods: The analytical results are presented for the introduced bearings. The performances of the bearings are demonstrated. Results: In appropriate operating conditions, the introduced bearings can have considerable loadcarrying capacities with low friction coefficients on the scales 10-3 or 10-4. With the weakening of the boundary slippage on the moving surface, the load-carrying capacities of the bearings are all increased, while the friction coefficients of the bearings are all reduced. Conclusion: When the boundary slippage is present both on the stationary surface in the bearing inlet zone and on the whole moving surface, abnormal hydrodynamic thrust slider bearings can be designed with the surface separation in the bearing inlet zone lower than that in the bearing outlet zone. The performances of these bearings are quite satisfactory.

Background: Large-scale rotary devices often employ friction drives in order to be manufactured easily and usually select a large driving radius to reduce the friction forces needed. In traditional devices, the driver and driven friction wheels are required to be of higher roundness to avoid slipping between them. This makes the driven friction wheel difficult to be machined. In addition, generating adequate contact load between contacting surfaces is essential for friction drives, and the best way to achieve it is self-actuating loading. Objective: The purpose of this paper is to propose and analyze a patent about a new friction drive device, in which the driver friction wheel can roll along with the driven friction wheel throughout, and the contact load between the driver and driven friction wheels can be generated on the torque demand. Methods: By using two swinging gearboxes, the two driver friction wheels are both swinging, and thus both can roll along with the driven friction wheel floatingly. Therefore, the driven wheel can have some deviation in roundness. Besides, this design offers a condition to construct a torque-actuated loading mechanism. Driven by the input torque, each driver wheel turns and exerts a friction force on the driven wheel, and then the driven wheel applies a reactive force to each driver wheel. This reactive force tends to pull the driver wheel to the driven wheel, producing a wedging action. Thus, an appreciable amount of contact load between the driver and driven wheels will be generated. Results: The results show the contact load between the driver and driven friction wheels is directly proportional to the resistant torque acting on the friction drive device. The results also show that a “frictional locking” condition for the device to avoid slipping between the driver and driven friction wheels is needed and it depends on the geometric parameters of the device. Conclusion: A swinging and self-actuating friction drive device is developed by using two swinging gearboxes. Design principles were described and a design example for this friction drive device was demonstrated. This kind of friction drive device not only offers an alternative way to drive large-scale rotary devices, but also develops a new method to realize self-actuating loading for friction drives.

Background: A transfemoral prosthetic knee is an artificial knee used by above-the-knee amputees. There are two major categories of transfemoral prosthetic knee designs: pin joint-based and polycentric designs. While pin joint-based knee designs only allow pure rotation of the knee, polycentric knee designs allow a combination of rotational and translational knee motion which is exhibited in natural knee motion. Objective: This work presents both the recently-patented design process and the resulting design of a polycentric transfemoral prosthetic knee that approximates natural spatial human knee motion during flexion and extension. Methods: The design process includes tibial motion acquisition, Revolute-Revolute-Spherical-Spherical linkage (or RRSS) motion generation, RRSS linkage axode generation and circle fitting. The polycentric transfemoral prosthetic knee design produced from this process includes a gear joint with a specific spatial orientation to approximate natural spatial human knee motion. Results: Using the design process, a polycentric transfemoral prosthetic knee was designed to replicate a group of five tibial positions over 37.5° of knee flexion (the amount of knee flexion in a standard human gait cycle) with a minimal structural error. Conclusion: The circular gear-based knee design accurately replicated natural spatial knee motion over the tibial position data given for a standard human gait cycle. The knee design method must be implemented over a broader sampling of tibial position data to determine if a circular gear-based knee design is consistently accurate.

Background: The active suspension can be adjusted in real time according to the change of road condition and vehicle state to enhance the performance of active suspension that has received widespread attention. Suspension control strategies and actuators are the key issues of the active suspension, and are the main research directions for active suspension patents. Objective: The numerical analysis method is proposed to study the performance characteristics of the active suspension controlled by different controllers. Methods: The active suspension control model and control strategy based on particle swarm optimization are established, and two active suspensions controlled by the sliding mode controller and the fuzzy PID controller are proposed. Moreover, two active suspension systems are optimized by particle swarm optimization. Results: The results of the analysis show that the performance of the active suspension is significantly improved compared with the passive suspension when the vehicle runs on the same road. The ride comfort of the active suspension controlled by the fuzzy PID controller has the best adaptive performance when the vehicle runs on different grade roads or white noise roads. The active suspension controlled by the fuzzy PID controller has the best ride comfort. Conclusion: A good control strategy can effectively improve the performance of the active suspension. To improve the performance of the active suspension, it can be controlled by utilizing different control strategies. The results lay a foundation for the active suspension experiments, the dynamic analysis and the optimization design of suspension structure.

Background: The vector propulsion device can significantly improve the sensitivity and mobility of the mechanism. Furthermore, thrust vectoring technology with single manipulator and multidimensional attitude is a novel thrust vectoring technique in industry, especially in aviation fields. Numerous progresses made by various research groups and the newest patents in these aspects will be cited in this paper. Objective: To apply the thrust vectoring technology to Autonomous Underwater Vehicles (AUVs), a spherical parallel vectored thruster with three Degree-Of-Freedom (DOF) was proposed based on vector deflection constrained screw method. Methods: Firstly, in the framework of screw theory, the topological structure of the spherical parallel mechanism was modeled to analyze the motion characteristics. Secondly, in terms of closed chain constraint equations, the vectored algebra method was employed to derive the Jacobian matrix of the mechanism. Thirdly, the decoupling structure configuration method was adopted to establish the analytical model of velocity and acceleration. Finally, the dynamic model was established by means of virtual work principle. Results: The forward and inverse solutions of the mechanism was calculated; the Jacobian matrix of the mechanism was derived; the kinematic characters including singularity and dexterity were analyzed; the performance analysis was carried out. Conclusion: This new type of underwater vehicle oriented power plant, which is characterized by simple decoupling structure, strong steering capability, and high cost-efficiency, has broad prospects in the field of AUV.