Lip Seal Research Articles

Prevalence of traumatic dental injuries and its association with binge drinking among 12-year-olds: a population-based study.

To determine the prevalence of traumatic dental injuries and its association with binge drinking among 12-year-old schoolchildren. A cross-sectional study was carried out involving 588 students from a medium-sized city in Brazil. Data were collected through a clinical examination and self-administered questionnaires. Andreasen's classification was used for the determination of traumatic dental injuries. The consumption of alcoholic beverages and binge drinking were evaluated using the Alcohol Use Disorders Identification Test--Consumption. Socio-economic status, overjet, and inadequate lip seal were also analysed. Associations were tested using the multivariate logistic regression analysis. The prevalence rates of traumatic dental injuries, alcohol consumption in one's lifetime, and binge drinking were 29.9%, 45.6%, and 23.1%, respectively. The prevalence of traumatic dental injuries was significantly higher among those who engaged in binge drinking (PR = 1.410; 95% CI: 1.133-1.754) and even higher among those with inadequate lip protection and accentuated overjet (PR = 3.288; 95% CI: 2.391-4.522 and PR = 1.838; 95% CI: 1.470-2.298, respectively). A higher prevalence rate of traumatic dental injuries was found among 12-year-olds who engaged in binge drinking. The high rate of alcohol intake among adolescents is worrisome considering the vulnerability of this population due to the intense transformations that occur in the transition from childhood to adulthood.

Oil Lip Seal and Shaft as a Specific Friction Couple

The oil lip seal operation is affected by the kinematics of the relative motion of the lip surface with respect to the shaft during both assembly and operation. Moreover, the variable position of the contact area along the sealing edge determines the contact pressure distribution and hence the wear rate of the lip.

Low friction multi-lobed seal for pneumatic actuators

The paper describes the design and optimization of an elastomeric piston seal for low-friction, pneumatic cylinders. The performance of the proposed initial geometry was first evaluated by FE, analysis and experimental tests, showing good manufacturing tolerance independence, low friction, force but low wear resistance by comparison with a commercial lip seal. The seal was then re-designed, and optimized by changing its shape at the sliding-contact area to improve the lubrication mechanism. This optimization process resulted in several different configurations with surface texturing and new, cross-sections to generate reservoirs of lubricant close to the contact zone. Accelerated life tests on, seal prototypes were carried out. The best configuration was found to be a multi-lobed annular seal.

Exodoncia de diente supernumerario, canino en transposición y enucleación de odontoma complejo: Reporte de Caso

Las anomalías dentarias más frecuentes e importantes que afectan a los niños son la presencia de piezas supernumerarias, piezas retenidas y odontomas. Algunos dientes retenidos se pueden encontrar en transposición. Reportamos el caso de una paciente de sexo femenino de 11 años de edad con presencia de diente supernumerario, canino en transposición y odontoma complejo situados en la hemiarcada derecha del maxilar superior. El motivo de consulta fue por la presencia de dientes anteriores sobresalidos que no le permitía realizar un buen sellado labial. Al examen clínico, presentaba gingivitis generalizada asociada a placa bacteriana, secuencia de erupción retardada por permanencia de pieza 53, ausencia clínica de pieza 13, aumento de volumen en palatino a nivel de piezas 12 y 11 de consistencia dura y coloración blanquecina que a la presión presentaba isquemia. La presencia del odontoma complejo a nivel cervico mesial de la pieza 16 fue un hallazgo radiográfico. El abordaje quirúrgico se realizó en dos fases debido a las zonas donde se encontraban las tres patologías. El diagnóstico y tratamiento multidisciplinario fueron de vital importancia. En este caso, odontopediatría, radiología, ortodoncia y cirugía estuvieron involucrados.

Comparison of friction performance of four anodised aluminium surfaces for use in a clutch actuator

Clutch actuators in the automotive industry are used to convert the force applied by the driver to the clutch. A typical pneumatic actuator consists of an anodised aluminium cylinder in which a piston, with a rubber lip seal and a PTFE guiding ring, slides. The system is silicone grease lubricated. The aluminium cylinder is most often cast, e.g. permanent mould, sand, or high pressure die cast. An interesting alternative is extrusion. After anodising the cylinders display different surface topography due to, amongst other things, the fabrication method. In this study, the friction behaviour of the anodised surfaces from the four mentioned methods are investigated in a reciprocating sliding test. Two test setups were used, one simulating the real contact situation, and one using a simpler sphere on flat geometry. The extruded surface oxide cracked during testing, resulting in very fluctuating friction behaviour. The high pressure die cast surface showed rather good results, but never the best. However, it is considered not suitable for the application due to its poor oxide properties. The permanent mould cast surface displayed the lowest friction coefficient, while the sand cast surface often showed the highest friction.

Design and operation of a fast electromagnetic inductive massive gas injection valve for NSTX-U.

Results from the operation of an electromagnetic valve, that does not incorporate ferromagnetic materials, are presented. Image currents induced on a conducting disc placed near a pancake solenoid cause it to move away from the solenoid and open the vacuum seal. A new and important design feature is the use of Lip Seals for the sliding piston. The pressure rise in the test chamber is measured directly using a fast time response Baratron gauge. The valve injects over 200 Torr l of nitrogen in less than 3 ms, which remains unchanged at moderate magnetic fields.

On the Normal Stress Effect in Grease-Lubricated Bearing Seals

The film formation in lip seals, due to the non-Newtonian rheology of the lubricant, has been a topic of speculation. Earlier work suggests that normal stresses in grease would be favorable for the film buildup between the seal lip and shaft or bearing ring. In the current article, we evaluate this earlier work and our earlier theoretical seal lip model with a series of experiments. We use a modified concentric cylinder geometry and a model fluid to study the fluid pressure distribution in the seal-type geometry. The results are then related to grease-lubricated seals and our earlier theoretical predictions. The present analysis shows that this earlier work and our earlier predictions are not correct and indicate that normal stresses in the grease pull the seal lip toward the shaft, increasing the contact pressure. However, normal stresses also ensure the presence of grease on the shaft or bearing inner ring, which enhances replenishment of the sealing contact.

The Effect of Wear on the Performance of a Rotary Lip Seal.

Theoretical analysis, combined with experimental verification, is used to study the effect of wear on the performance of a rotary lip seal as characterized by the pumping rate and friction torque. The performance of a rotary lip seal is determined by the sealing lip surface microscopic characteristics and contact characteristics at the sealing zone. The variation of the contact characteristics with wear has been established based on the variation of the sealing lip profiles measured by using a trilinear coordinate measuring instrument. The impression method is used to copy the lip surface microtopography at different wear times and then an optical interferometer is used to measure the impression surface microtopography to obtain the variation of roughness with wear. The variations of the roughness, contact characteristics, and approximate contact temperature with wear are inserted into a mixed lubrication model to obtain the variations of the pumping rate and friction torque. A comparison of the simulated results with those from experimental measurement verifies the validity of the theoretical analysis.

The effect of aging in oil on the performance of a radial lip seal

The effect of aging in oil on the seal performance of a radial lip seal is investigated in the present study by conducting a constant temperature oil bath test to obtain aged rubber samples and seals, and measuring the changes of material properties and seal performance with the aging time. The change of lip surface micro-morphology with the aging time is also measured by using a 3D white light optical interferometer. The leakage and friction torque are computed in a numerical simulation, utilizing a mixed elastohydrodynamic lubrication (EHL) model, to determine how aging in oil affects the lip seal performance. Finally, the simulation results of the EHL model are verified by a bench test on aged lip seals.

A hypothetical, aetiological relationship between the horse's bit, nasopharyngeal asphyxia and negative pressure pulmonary oedema

SummaryTentative explanations for the aetiology of soft palate instability and dorsal displacement at exercise are based on the proposition that it is caused by one or more, as yet unidentified, neuromuscular or inflammatory diseases. As judged by reviews, none of the treatments based on these assumptions are entirely satisfactory. Most researchers agree that their cause is unknown. In 1999, Cook proposed that they were caused by the bit breaking what should be an airtight lip seal. The present article describes a development of this hypothesis – loss of oral compartment subatmospheric pressure. The feral horse is an obligate nose‐breather and runs with a closed mouth and no air in the oral cavity and oropharynx. Evacuation of air from these compartments is proposed as the primary mechanism, strengthened by the cohesive force of surface tension, whereby the soft palate resists the elevating force of negative pressure on inspiration. It is suggested that subatmospheric pressure in the oral compartment is generated by a single swallow before running. Poll extension supplements the rigidity of the nasopharyngeal tube and reinforces the ostium intrapharyngium seal. In the domesticated horse, the lip seal is broken by a bit and bit‐induced poll flexion, jaw and tongue movement often breaks the ostium seal. Oral atmospheric pressure is proposed as the mechanism for nasopharyngeal asphyxia. It is considered that negative pressure pulmonary oedema – currently known as exercise‐induced pulmonary haemorrhage and conventionally thought to be a separate problem – is one of its clinical signs. It is suggested that the bit is the most common cause of nasopharyngeal asphyxia and that this, in turn, results in a cascade of dynamic obstructions in the larynx and cervical trachea, leading ultimately to pulmonary oedema and ‘bleeding.’ It is concluded that these are sequelae to rules in many disciplines that mandate bit usage.

Experimental Study on the Sealing Mechanism of Bidirectional PTFE Lip Seals

Seals made of polytetrafluorethylene (PTFE) are resistant to heat and chemicals and can run dry, but they do not pump back fluid. PTFE lip seals with a spiral groove do pump back fluid but only in one rotational direction. PTFE lip seals for both rotational directions (bidirectional) are not available on the market. At the Institute of Machine Components (IMA) of the University of Stuttgart, PTFE lip seals with bidirectional sealing aids were developed and analyzed. During the research, the leak-tightness in static and dynamic conditions was continuously improved. The latest design is leak-tight in both rotational directions. The sealing mechanism for this design is explained. The resulting seals can be used in conditions where elastomeric lips seals will fail.

Tri-dimensional eccentricity model of a rod lip seal

In this work, an analytical tri-dimensional eccentricity model of a rod lip seal is presented. In the specific, a thermoplastic polyurethane (TPU) rod lip seal was considered. The analytical model was completed and adjusted by means of numerical results. Experimental tests on selected seals were carried out on a suitable test rig designed to measure reaction forces on seals as a function of rod misalignment. A cross validation between the analytical model and experimental results is provided. The model is used to calculate the contact force distribution on a seal when it is subjected to an eccentric mounting.

Effects of the radial force on the static contact properties and sealing performance of a radial lip seal

The radial force is a critical factor to determine the sealing performance of radial lip seals. The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments. Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used. Radial force, contact width, temperature in the sealing zone, the reverse pumping rate and friction torque are measured. A critical value of interference for a cost-effectively designed radial lip seal is found. Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance. The quantitative results gotten in this study could provide guide for the seal design and improvement.

The effect of texture on the shaft surface on the sealing performance of radial lip seals

On the basis of elastohydrodynamic model, the present study numerically analyzes the effect of various microdimple texture shapes, namely, circular, square, oriented isosceles triangular, on the pumping rate and the friction torque of radial lip seals, and determines the microdimple texture shape that can produce positive pumping rate. The area ratio, depth and shape dimension of a single texture are the most important geometric parameters which influence the tribological performance. According to the selected texture shape, parameter analysis is conducted to determine the optimal combination for the above three parameters. Simultaneously, the simulated performances of radial lip seal with texture on the shaft surface are compared with those of the conventional lip seal without any texture on the shaft surface.

Design methodology for an air-lubricated seal

A methodology to design an air-lubricated piston seal for pneumatic actuators is described. Such a seal permits a small air leakage through a very narrow gap between the seal lip and the counterpart; this air film both avoids contact and ensures lubrication at the seal-counterpart interface thus permitting reduced friction and wear. Subsequently the use of grease could be limited or avoided. A seal geometry equipped with a self-pressurized balancing chamber was designed to make leakage as insensitive as possible to the supply pressure and to the barrel machining tolerances. A prototype was manufactured and tests were carried out.

Statistical analysis of wear of biplanar deterministically-arrayed surfaces for load bearing applications

The use of microscale deterministic surface features has been investigated in many bearing and seal applications in recent research. This paper considers a class of surface textures that are comprised of periodic arrays of deterministic geometric shapes created using photolithography-based manufacturing processes. These features are unique in that they can be modeled as biplanar: the topography of the entire surface ideally lies on one of two parallel horizontal planes. A total of eight such surface textures are analyzed: three comprised of electroplated nickel cavities and five comprised of metal-impregnated polymer asperities. It is shown that for this class of surface textures, closed form solutions for perfectly-manufactured surfaces exist for eleven areal surface parameters—including amplitude (Sa, Sq, St and Sz), spatial (Ssk, Sku and Std) and functional (Sbi, Sci and Svi)—and these are derived and presented for each case. These surface parameters are then used to evaluate manufacturing process errors for the surface textures and to quantify and evaluate the impact of wear on the performance of such surface textures when placed in a tribological application, in this case a radial lip seal. In particular it was found that useful correlations exist between the surface parameters of Sq and Svi and the operating torque in the lip seal application.

A Mixed Lubrication Theoretical Model and Experimental Verification of Rotary Lip Seals

A mixed lubrication model of rotary lip seals using a statistical approach with flow factors based on reverse pumping mechanism has been developed. The model consists of coupled fluid mechanics analysis, asperity contact analysis and deformation analysis. The oil film pressure and shear stress are obtained from solving the Reynolds equation. Using the GREENWOOD- WILLIAMSON surface contact model computes the contact pressure between the lip and shaft. The deformation analysis of lip seals is carried out using the influence coefficient method. Applying the mixed lubrication model to a typical lip seal, the pumping rate and friction torque are the two most important factors of evaluating seal characteristics, which are the output results of theoretical simulation. Most important, the pumping rate and friction torque are measured with bench test designed by the authors. The measurement of these two factors verifies the validity of the mixed lubrication model. For the reverse pumping action of rotary lip seals is resulted from the surface asperities, the influence of roughness on the pumping rate, friction torque and the contact area are carried out by using the verified theoretical mixed lubrication modle.

Dynamic behaviour of rotary lip seal

We report on the dynamic behavior of a rotary lip seal by considering the interaction between lip, film and shaft roughness assumed to have a periodic form. The nonlinearities of stiffness and viscosity of the film are taken into account in a mass-spring-dumper model. Using the harmonic balance method, analytical prediction of the lip displacement is obtained, the frequency response is provided and the effect of the shaft undulation on the amplitude jumps of the lip displacement and on the film thickness fluctuations are discussed. The results have direct applications in reducing leakage that may occur between a smooth lip seal and a rough shaft.

J0230204 生命体における多相界面現象と工業製品への応用([J023-02]多相界面問題とバイオ、エネルギー、環境との関係セッション(2))

Application of multiphase phenomenon in a living system to an engineering product is proposed in this paper. The material characteristics with hydrophilic and continuously porous structure, which mimics articular cartilage, were adopted for the seal lip in order separate between water phase and gas phase. The water sealing system for a rotating shaft could produce low friction and low ingress of water to mechanical system. The material characteristic with low elastic modulus was adopted for the load bearing material in order to produce shock adsorption against externally applied force. In the system, an externally applied electric field to bearing surfaces was proposed in order to control the frictional characteristic, in which the electric field produced the low shear layer lining on the bearing surface.

Prevalence of dental fractures and associated factors in students of Valinhos, SP, Brazil

AIM: To investigate the prevalence of dental fractures and their association with risk factors in the permanent dentition of adolescents in Valinhos, SP, Brazil. METHODS: The study population was obtained using the probability sampling method and comprised 379 students between 13 and 19 years old enrolled in the eight State schools of the city, who were examined by nine pairs of calibrated dentists (Kappa>0.80). The presence of dental fractures in permanent anterior incisors, as well as the presence of considerable overjet (> 5mm) and lip seal was evaluated in a clinical-epidemiological examination. RESULTS: The prevalence of dental trauma was 27.1%. The most frequent lesions were enamel fractures (72.6%) of which falls were the main cause (45.7%). No association was found between the presence of considerable overjet and deficient lip seal (chi-square test; p>0.05). CONCLUSIONS: The prevalence of dental trauma in the studied population was expressive when compared with the literature, but the analyzed oral aspects did not contribute to its occurrence.