Pusher Plate Research Articles

HITCH DEVICE MODERNIZATION FOR TRANSLOADING OF BALE CARGO

The operation of unloading bales from a covered railway wagon is one of the most labor-intensive and dangerous operations when transporting bale cargo. The article proposes a modernized outside-mounted load-handling device for a universal light-sized forklift. The device is a mechanical equipment for transloading of bale cargo. The device includes a push-pull attachment (a purchased part) on which a frame, a lever clamp and a hydraulic cylinder are mounted. Тtrolleys are installed on the forks of the loader. The trolley is equipped with a roller in the front part and a frame in the back part for longitudinal movement on the forks. The trolley also has a support for the movable pusher plate and a grip for lifting the front edge of the bale. The trolleys are connected to the stationary pusher plate by a lever-type limiter. Before the start of gripping, the forklift is tilted forward at an angle from 3 to 5°, the trolleys are in the most forward position and are supported by a pusher. In this case, the rollers are in the position where they have moved off the forks. By moving the forklift forward, the trolley grips are inserted under the bale. The pusher is brought into the folded state. The loader moves forward, the noses of the forks abut against the roller and it rolls onto the forks, lifting the front edge of the bale. The forks are fully inserted under the bale. The clamp comes into operation, holding the load on the forks. This allows the bales to be removed from the stack and transported. The trolley was designed using CAD KOMPAS-3D. The proposed device is capable of picking up bales stacked without gaps and can be used inside a covered railway wagon. Commonly used side-clamp devices are not capable of this. The mathematical relation of the required traction force of the loader on the geometric parameters of the trolley is derived. It has been established that the required traction force is 60 to 70 % of the maximum traction force achieved by light-sized forklifts with a lifting capacity of 1000 kg.

Structural improvement and application of cigarette packets pusher for YB65A rigid strip packaging machine

The side baffle of the pusher plate of YB65A packaging machine is used to blocks and locates the cigarette pack. During the production, the cigarette pack contacts the side baffle surface of the pusher plate, causing obvious scratches on the surface of the cigarette pack, reducing the quality of the cigarette packs and causing potential quality hazards. To solve this problem, the distance between side baffle and cigarette packs is increased by redesigning the key parts of the pusher. The application results show that the scratches on the surface of cigarette pack have been solved, the production quality of cigarette pack has been improved.

Method of the Generalized Approach to the Synthesis of Cam Mechanisms

The technique of applying the equation of the geometric connection of links in the higher kinematic pair of a cam mechanism for the complete synthesis of a mechanism with a flat translationally moving pusher with an arbitrary angle of inclination of the plate is considered. A distinctive feature of the technique is that the equation of the cam profile envelope is derived from the equation of the geometric relationship of the cam and the pusher in the Cartesian coordinate system. All transformations, the solution of the original coupling equation and the envelope equation are carried out by the matrix method in the same coordinate system without switching to other coordinate systems and to graphical methods of their interpretation. As a result of the performed studies, calculated relations for determining the coordinates of the cam profile points at an arbitrary angle of inclination of the pusher plate were obtained. The formula for determining the curvature radius of the cam at an arbitrary inclination angle of the plate is derived. The procedure for determining the radius of the main cam circumference is proposed, taking into account the identified features of the cam profile plotting. Based on the developed methodology, software in the MathCad package has been created. The correctness of the methodology and software was tested on a numerical test case. In the course of computer modeling, the reason for the need to limit the value of the inclination angle of the plate is established, due to the phenomenon of cam profile self-intersection, which does not depend on the pressure angle and is not tracked by the condition of the convexity of its profile. The test results allow us to assert that the generalized method of flat cam mechanisms synthesis is correct and effective, therefore it has prospects of application, for example, for a cam mechanism with a flat rotating pusher.

Failure analysis of CF/epoxy hollow beam components using digital image correlation and acoustic emission analyses

Testing of carbon fibre epoxy hollow beam components was undertaken using digital image correlation and acoustic emission techniques. Static and fatigue testing was used to characterise the damage mechanisms of the components under two separate compressive loading cases. Firstly, the load was transferred via simple contact of a rectangular pusher plate, whilst in the second case the plate was bolted to the top surface of the beam. Digital image correlation determined the full field deformation and strain on the beams’ side while strain gauges validated the accuracy of the measurements during testing. Acoustic emission analyses provided a more in-depth inspection of the failure location as the first damage event was not visible from an external visual inspection. Acoustic emission captured a precise map of damage events which indicated the failure location at a point under the loading plate edge and centred at the corner of the beam structure. While digital image correlation gives a full field view of strains on the component surface before and after failure, the acoustic emission analysis shows a higher sensitivity to the characterisation of damage, providing a more conservative and accurate estimate of the failure behaviour.

Experimental investigation of right‐left flow balance concepts for a total artificial heart

A total artificial heart (TAH) must be designed to autonomously balance the flows of the systemic and pulmonary circulation to prevent potentially lethal lung damage. The flow difference between the systemic and pulmonary circulation is mainly caused by the bronchial (arteries) shunt flow and can change dynamically. The ReinHeart TAH consists of only one actuator that ejects blood alternately from the right and left pump chamber. This design entails a coupling of the right and left stroke and thus, complicates the independent adaptation of the right and left flow. In this experimental study on the ReinHeart TAH, four concepts to keep the flows well balanced were investigated using an active mock circulation loop for data acquisition. Three concepts are based on mechanical design changes (variation of pusher plate shape, flexible right pump chamber housing, and reduced right stroke volume) to achieve a static flow difference. In combination with these static concepts, a concept influencing the ratio of systole and diastole duration to respond to dynamic changes was studied. In total, four measurement series, each with 270 operating points, to investigate the influence of circulatory filling volume, heart rate, bronchial shunt flow, and lung resistance were recorded. In the course of this study, we introduce a concept deviation indicator, providing information about the efficiency of the concepts to balance the flows based on changes in lung's blood pressures. Furthermore, the distribution of the measured data was evaluated based on bubble plot visualizations. The investigated variation of the right pusher plate shape results in high lung pressures which will cause lethal lung damage. In comparison, a flexible right pump chamber housing shows lower lung pressures, but it still has the potential to damage the lungs. Reducing the stroke volume of the right pump chamber results in proper lung pressures. The flow balance can dynamically be influenced with a positive effect on the lung pressures by choosing a suitable systole-diastole-ratio. The results of this study suggest that an adequate right-left flow balance can be achieved by combining the mechanical concept of a reduced right stroke volume with an active control of the systole-diastole-ratio.

Slingshot Resonance for Ocean Wave Energy Conversion

The slingshot effect and its application to converting ocean wave energy are discussed. It is shown that, owing to the large inertia transported by ocean waves and their periodicity, the slingshot effect can result in the transmission of significant kinetic energy to a puck colliding elastically with a pusher plate driven by ocean wave motion. A simplified geometrical model is used to demonstrate that, despite the stochastic nature of the collisions (whereby collisions occur at random times in the wave cycle), head-on collisions occur more frequently, yielding a net average gain of energy. However, the most promising configuration for applying the slingshot effect to ocean wave energy conversion is that which matches, through appropriate design, the travel time of the puck between collisions with the wave period. Then, only head-on collisions occur, resulting in a significant magnification of the puck kinetic energy. Further research will be required before this slingshot effect can be practically implemented for ocean wave energy conversion.

Investigating the impact of non-Newtonian blood models within a heart pump.

A detailed computational fluid dynamics (CFD) study of transient, turbulent blood flow through a positive displacement left ventricular assist device is performed. Two common models for non-Newtonian blood flow are compared to the Newtonian model to investigate their impact on predicted levels of shear rate and wall shear stress. Given that both parameters are directly relevant to the evaluation of risk from thrombus and haemolysis, there is a need to assess the sensitivity to modelling non-Newtonian flow effects within a pulsatile turbulent flow, in order to identify levels of uncertainly in CFD. To capture the effects of turbulence, the elliptic blending Reynolds stress model is used in the present study, on account of superior performance of second moment closure schemes previously identified by the present authors. The CFD configuration includes two cyclically rotating valves and a moving pusher plate to periodically vary the chamber volume. An overset mesh algorithm is used for each instance of mesh motion, and a zero gap technique was employed to ensure full valve closure. The left ventricular assist device was operated at a pumping rate of 86BPM (beats per minute) and a systolic duration of 40% of the pumping cycle, in line with existing experimental data to which comparisons are made. The sensitivity of the variable viscosity models is investigated in terms of mean flow field, levels of turbulence and global shear rate, and a non-dimensional index is used to directly evaluate the impact of non-Newtonian effects. The clinical relevance of the results is reported along with a discussion of modelling uncertainties, observing that the turbulent kinetic energy is generally predicted to be higher in non-Newtonian flow than that observed in Newtonian flow. Copyright © 2016 John Wiley & Sons, Ltd.

Case Study: Interrupt-less Servo Motor Controls for Pneumatic Pump in Safety Critical Devicess

Interrupts are often used in safety critical control software, however, a system based on interrupts is difficult to analyze, which increases cost and complexity of software quality assurance, because the behavior may vary depending on the order in which interrupts are detected by the sensors. In the previous work on servo motor controls, an interrupt-driven architecture is successfully converted to the interrupt-less architecture by maintaining time stamps of sensor events. In this paper, interrupt-less servo motor controls for pneumatic pump system in medical devices are evaluated and analyzed in terms of behavior correctness as well as the predictability of the system. Experimental results show negligible differences on the main control variable of servo motor compared to the interrupt-driven controls while it provides better predictability by getting rid of interrupts except an internal timer for periodic handling of time stamps by sensor events including motor, pump pusher plate, and buttons in the user interface.

The Influence of Different Operating Conditions on the Blood Damage of a Pulsatile Ventricular Assist Device.

Because of pulsatile blood flow's benefit for myocardial recovery, perfusion of coronary arteries and end organs, pulsatile ventricular assist devices (VADs) are still widely used as paracorporeal mechanical circulatory support devices in clinical applications, especially in pediatric heart failure patients. However, severe blood damage limits the VAD's service period. Besides optimizing the VAD geometry to reduce blood damage, the blood damage may also be decreased by changing the operating conditions. In this article, a pulsatile VAD was used to investigate the influence of operating conditions on its blood damage, including hemolysis, platelet activation, and platelet deposition. Three motion profiles of pusher plate (sine, cosine, and polynomial), three stroke volumes (ejection fractions) (56 ml [70%], 42 ml [52.5%], and 28 ml [35%]), three pulsatile rates (75, 100, and 150 bpm), and two assist modes (copulsation and counterpulsation) were implemented respectively in VAD fluid-structure interaction simulations to calculate blood damage. The blood damage indices indicate that cosine motion profile, higher ejection fraction, higher pulsatile rate, and counterpulsation can decrease platelet deposition whereas increase hemolysis and platelet activation, and vice versa. The results suggest that different operating conditions have different effects on pulsatile VAD's blood damage and may be beneficial to choose suitable operating condition to reduce blood damage in clinical applications.

Thermonuclear Operation Space Lift

The “Project Orion” small fission bomb propulsion concept proposed the one-stage launching of large payloads into low Earth orbit, but it was abandoned because of the radioactive fallout into Earth’s atmosphere. The idea is here revived by the replacement of the small fission bombs with pure deuterium–tritium fusion bombs, and the pusher plate of Project Orion with a large magnetic mirror. The ignition of the thermonuclear fusion reaction is done by the transient formation of keV super-explosives under the high pressure of a convergent shock wave launched into liquid hydrogen propellant by a conventional high explosive.

Numerical Investigation of Three Patterns of Motion in an Electromagnetic Pulsatile VAD

Hemolysis and thrombus formation which are critical concerns in designing a long-term implantable ventricular assist device (VAD) have impeded the widespread use of VADs. In this study, thus, the three-dimensional fluid domain of blood flow in a small bichamber positive displacement VAD (25 ml) with a magnetically levitated moving pusher plate was simulated by the means of a finite element package called ADINA. To optimize the function of the pump for minimizing shear stress induced blood damage, three different driver patterns (linear, sinusoidal, and Guyton's pulse) were investigated. The first pattern produced a constant flow, whereas the two others created pulsatile flows. The flow pattern and the distribution of shear stress of each pattern were observed for comparison. It was revealed that the three types of motions may induce less than 0.06% red blood cell damage. Moreover, in comparison to the other patterns not only did the sinusoidal motion of the pusher plate cause less risk of hemolysis, but in comparison to the linear pattern, it produced a pulsatile flow which reduced the stagnation areas in chambers, lowering the probability of thrombosis. In addition, this motion eliminates the probability of cavitations as compared with the Guyton's pulse pattern.

Simulation of a pulsatile total artificial heart: Development of a partitioned Fluid Structure Interaction model

Heart disease is one of the leading causes of death in the world. Due to a shortage in donor organs artificial hearts can be a bridge to transplantation or even serve as a destination therapy for patients with terminal heart insufficiency. A pusher plate driven pulsatile membrane pump, the Total Artificial Heart (TAH) ReinHeart, is currently under development at the Institute of Applied Medical Engineering of RWTH Aachen University.This paper presents the methodology of a fully coupled three-dimensional time-dependent Fluid Structure Interaction (FSI) simulation of the TAH using a commercial partitioned block-Gauss–Seidel coupling package. Partitioned coupling of the incompressible fluid with the slender flexible membrane as well as a high fluid/structure density ratio of about unity led inherently to a deterioration of the stability (‘artificial added mass instability’). The objective was to conduct a stable simulation with high accuracy of the pumping process. In order to achieve stability, a combined resistance and pressure outlet boundary condition as well as the interface artificial compressibility method was applied. An analysis of the contact algorithm and turbulence condition is presented. Independence tests are performed for the structural and the fluid mesh, the time step size and the number of pulse cycles. Because of the large deformation of the fluid domain, a variable mesh stiffness depending on certain mesh properties was specified for the fluid elements. Adaptive remeshing was avoided. Different approaches for the mesh stiffness function are compared with respect to convergence, preservation of mesh topology and mesh quality. The resulting mesh aspect ratios, mesh expansion factors and mesh orthogonalities are evaluated in detail. The membrane motion and flow distribution of the coupled simulations are compared with a top-view recording and stereo Particle Image Velocimetry (PIV) measurements, respectively, of the actual pump.

Control Strategies for Afterload Reduction With an Artificial Vasculature Device

Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. An artificial vasculature device (AVD) is being developed that may better facilitate myocardial recovery than VAD by controlling the afterload experienced by the native heart and controlling the pulsatile energy entering into the arterial system from the device, potentially reconditioning the arterial system properties. The AVD is a valveless, 80 ml blood chamber with a servo-controlled pusher plate connected to the ascending aorta by a vascular graft. Control algorithms for the AVD were developed to maintain any user-defined systemic input impedance (IM) including resistance, elastance, and inertial components. Computer simulation and mock circulation models of the cardiovascular system were used to test the efficacy of two control strategies for the AVD: 1) average impedance position control (AIPC)-to maintain an average value of resistance during left ventricular (LV) systole and 2) instantaneous impedance force feedback (IIFF) and position control (IIPC)-to maintain a desired value or profile of resistance and compliance. Computer simulations and mock loop tests were performed to predict resulting cardiovascular pressures, volumes, flows, and the resistance and compliance experienced by the native LV during ejection for simulated normal, failing, and recovering LV. These results indicate that the LV volume and pressure decreased, and the LV stroke volume increased with decreasing IM, resulting in an increased ejection fraction. Although the AIPC algorithm is more stable and can tolerate higher levels of sensor errors and noise, the IIFF and IIPC control algorithms are better suited to maintain any instantaneous IM or an IM profile. The developed AVD impedance control algorithms may be implemented with current VADs to promote myocardial recovery and facilitate weaning.

Optimal Moving Angle of Pusher Plate in Occlusive-Type Pulsatile Blood Pump

Since the occlusive-type pulsatile extracorporeal blood pump (Twin-Pulse Life Support System; Seoul National University, Seoul, Korea) received the CE mark of the European Directives and Korea Food and Drug Administration approval (2004) for short-term applications as an extracorporeal life support system, the pump system has been tested for hemolysis. This pump system was recently upgraded with an ameliorated pusher plate to reduce hemolysis. In this study, numerical analysis and in vitro tests were performed to determine the optimal conditions for increasing the durability of the blood sac and pump output. During the simulation, the minimum sliding interface force (SIF) for the angle of the pusher plate movement (PPM) was calculated (40-70 degrees ). In the in vitro durability test, the angle of the PPM was increased gradually from 40 to 70 degrees in 10 degrees increments, and the mean time to failure (MTTF) of the blood sac was calculated. Fifteen tests were conducted for each case: 40, 50, 60, and 70 degrees (n = 15 each). The MTTF of the blood sac was defined as the time when a crack of the blood sac occurred. The longer lifetime of the blood sac at 60 degrees of the PPM (297.0 h) than that at 50 degrees (197.6 h) was attributed to the lower SIF value (-0.13, normalized value) at 60 degrees of the PPM.

Design of an Artificial Left Ventricular Muscle: An Innovative Way to Actuate Blood Pumps?

Blood pumps assist or take over the pump function of a failing heart. They are essentially activated by a pusher plate, a pneumatic compression of collapsible sacs, or they are driven by centrifugal pumps. Blood pumps relying upon one of these actuator mechanisms do not account for realistic wall deformation. In this study, we propose an innovative design of a blood pump actuator device which should be able to mimic fairly well global left ventricular (LV) wall deformation patterns in terms of circumferential and longitudinal contraction, as well as torsion. In order to reproduce these basic wall deformation patterns in our actuator device, we designed a novel kind of artificial LV "muscle" composed of multiple actively contracting cells. Its contraction is based on a mechanism by which pressurized air, inside such a cell, causes contraction in one direction and expansion perpendicular to this direction. The organization and geometry of the contractile cells within one artificial LV muscle, the applied pressure in the cells, and the governing LV loading conditions (preload and afterload) together determine the global deformation of the LV wall. Starting from a simple plastic bag, an experimental model based on the above mentioned principle was built and connected to a lumped hydraulic model of the vascular system (including compliance and resistance). The wall deformation pattern of this device was validated visually and its pump performance was studied in terms of LV volume and pressure and heart rate. Our experimental results revealed (i) a global LV motion resembling a real LV, and (ii) a close correlation between our model and a real LV in terms of end-systolic volume and pressure, end-diastolic volume and pressure, stroke volume, ejection fraction and pressure-volume relationship. Our proposed model appears promising and it can be considered as a step forward when compared to currently applied actuator mechanisms, as it will likely result in more physiological intracavity blood flow patterns.

Finite element analysis of stresses developed in the blood sac of a left ventricular assist device

The goal of this research is to develop a 3D finite element (FE) model of a left ventricular assist device (LVAD) to predict stresses in the blood sac. The hyperelastic stress–strain curves for the segmented poly(ether polyurethane urea) (SPEUU) blood sac were determined in both tension and compression using a servo-hydraulic testing system at various strain rates. Over the range of strain rates studied, the sac was not strain rate sensitive, however the material response was different for tension versus compression. The experimental tension and compression properties were used in a FE model that consisted of the pusher plate, blood sac and pump case. A quasi-static analysis was used to allow for nonlinearities due to contact and material deformation. The 3D FE model showed that blood sac stresses are not adversely affected by the location of the inlet and outlet ports of the device and that over the systolic ejection phase of the simulation the prediction of blood sac stresses from the full 3D model and an axisymmetric model are the same. Minimizing stresses in the blood sac will increase the longevity of the blood sac in vivo.

Pulsatile blood pump with a linear drive actuator

The main purpose of this study was to develop an implantable direct-electromagnetic left ventricular assist system driven by a linear actuator (linear LVAS). The linear LVAS is a pulsatile pump with a pusher plate that is driven directly by a linear oscillatory actuator (LOA) without any movement converters. This prototype pump unit with a LOA was 100 mm in diameter, 50 mm in thickness, and weighed 740 g. The full-fill/full-eject driving method was applied to the control algorithm. In addition, a mechanism to detect and release sucking was realized to overcome this problem that accompanies the active-filling type of VAS. The performance of the linear LVAS was evaluated in a long-term animal experiment using a goat (56 kg). The goat survived for 42 days. The reason why we terminated this experiment was that thrombus was found in the pump. There was no frictional debris found around the LOA. The linear LVAS did not exhibit electrical or mechanical problems during the first animal experiment.

THE JUSTIFICATION FOR DEVELOPING THE PHOENIX-7 ELECTROHYDRAULIC ARTIFICIAL HEART (EHAH)

After 50 years of research and billions of dollars from federal funding, the world has not yet seen an artificial heart that lives up to its name. With over 25 years of research and development in diaphragm and pusher plate artificial hearts, the Maximum Stroke Volume (MSV) is severely influenced and restricted by the AP dimension of the cardiothoracic cavity. This 25 year-old trade-off game between AP dimension and cardiac output will always end in failure and will become even worse in an EHAH development situation. The fundamental objectives of this paper will not only address and reveal the shortcomings of the popular diaphragm and pusher plate designs of artificial hearts, but also to present the design criteria and research procedures behind the successful animal and clinical implantation of the pneumatic PHOENIX-7 artificial heart. To properly overcome the restrictions of the cardiothoracic cavity and MSV, the pneumatic PHOENIX-7 artificial heart consists of a 7 cm AP dimension, 100ml MSV, egg shaped flat base plate, and a synchronized centrally actuated pumping action. The successful development of the PHOENIX-7 EHAH will not only require utilizing the basic design criteria and specifications behind the pneumatic PHOENIX-7 artificial heart, but also must include a redundancy mechanism in order to ensure the safety of the patient.

THE FLOW CHARACTERISTICS OF A REDESIGNED 50cc PENN STATE LVAD

Recent measurements in the original Penn State 50cc LVAD found a strong flow field dependence on mitral valve (MV) orientation and areas of low wall shear. The inflow through the MV is the controlling factor in adequately maintaining washout throughout the cardiac cycle. Here, we investigate the flow fields in a new design of our 50cc pump, with focus on the impact of MV orientation and the nature of the blood analog fluid. Planar particle image velocimetry (PIV) is used to quantify the pump flow field characteristics. A Bjork-Shiley Monostrut MV is rotated in 15° increments from -15° to 45°, relative to the horizontal axis of the pump. Both Newtonian and non-Newtonian blood analog solutions are used. Flow field data are acquired over three planes parallel to the pusher plate. Phase averaged velocity data is measured over the entire cardiac cycle. The data shows better overall flow penetration and washout characteristics along the perimeter of the device during mid to late diastole at the larger valve angle orientations. The Non-Newtonian blood analog creates a more coherent inlet jet through the mitral valve than the Newtonian fluid suggesting that the overall rotational flow pattern will lead to improved washout.

The 50cc Penn State Left Ventricular Assist Device: A Parametric Study of Valve Orientation Flow Dynamics

We investigated the flow fields associated with the Bjork-Shiley Monostrut mechanical heart valve in the mitral position of the 50 cc Penn State left ventricular assist device. The valve orientation was adjusted whereby flow field data was collected using planar particle image velocimetry. The mitral valve was rotated from 0 to 45 degrees, in 15-degree increments. For each valve orientation, measurements were made in three planes (3, 5, and 8 mm from the front wall) parallel to the device pusher plate. Penetration of the inlet jet was affected by the valve orientation with more intense and longer duration wall washing motion occurring at 45 degrees. As a result, the 45-degree mitral valve orientation is recommended to help prevent areas of thrombus deposition. Valve orientation is an important aspect of assist device design.