Lip Seal Research Articles

A Near-Frictionless Sealing Approach with Innovative, Gas-Lubricated Shaft Seals Made of Elastomer

Due to increasingly stringent environmental regulations, leakage-free shaft seals with minimal friction are growing ever more important. The trend toward higher operating speed (e.g., in the field of e-mobility) additionally aggravates the sealing task. Reliable, leakage-free shaft seals—such as gas-lubricated mechanical seals—are difficult to manufacture and thus expensive. Therefore, there is still significant interest in an efficient and easy-to-manufacture shaft seal design. This study discusses the development of sleeve-type lip seals made of fluoroelastomer with an innovative, sickle-shaped back-structure design. The novel lip seals are capable of operating at near-zero friction. Compared to state-of-the-art, gas-lubricated mechanical seals, near-frictionless sliding on an air film is achieved with a simple, robust, and easy-to-manufacture sealing-lip design.

A Mixed Lubrication Model for Lip Seals Based on Deterministic Surface Microdeformation

With the development of modern industry, rotary lip seals are applied to more complex working conditions. For lip seals with larger or smaller radial force and lip seals with incomplete motion such as robot joint seals, it has been found that the traditional reverse pumping theory has a certain scope of application. Therefore, in this study, a mixed lubrication model based on deterministic surface microdeformation is proposed to calculate the tangent deformation of lip surface asperities without presetting the reverse pumping effect and then assess the effect of reverse pumping behavior. The radial force, contact width, friction torque, leakage rate, static contact pressure, and tangential deformation were either measured or calculated. The results obtained by this study can be used as guidelines for the design and optimization of rotary lip seals.

Activator Treatment in a Girl with Skeletal Class II Malocclusion with Lower Lip Biting Habit

Abnormal oral habits interfere with normal growth of the maxillofacial complex due to imbalance of the muscles involved. In skeletal Class II malocclusion, lip biting habit which emerges as a compensation for excessive overjet can inhibit the forward growth of the mandible. In this case report, the patient had a habit of biting the lower lip, which was trapped between the upper and lower incisors, showing large overjet, deep bite, and retruded mandible. It was necessary to correct the abnormal teeth and jaw relations to break the habit. Orthodontic treatment began with myofunctional therapy for lip seal training and a 2 by 4 appliance to reduce the overjet and make an aesthetic smile. After removing the bonded appliance, an activator was used to accelerate the mandible growth and lip training was continued. Lower lip biting habit disappeared with decreased overjet, leading to balanced facial growth.

A narrative review on the use of lip trainer (Patakara) in oral rehabilitation

The spent time on body exercising is usually given more interest than the exercise of lips, especially after the wide evidence-based demonstrated effects of strong lips on the general health and hence the quality of life. Oral rehabilitation leads to a powerful closure of the lip that can be the first-line defensive mechanism against the many oral dysfunctions as halitosis, snoring, mouth breathing and dryness, and dysfunctions of the oro-gastrointestinal system. The strong lip seal or closure gained from the continuous use of lip muscle trainer (Patakara) not only limits the deteriorated normal physiological oral functions that are associated with the ageing process but also can be considered a good oral rehabilitation device to many oral dysfunctions such as halitosis, snoring, mouth breathing and dryness, and dysfunctions of the oro-gastrointestinal system. Incorporating the use of lip muscle trainer in traditional physiotherapy and rehabilitation programs — especially for geriatrics — is a fundamental part of the whole treatment plan. Physiotherapists must direct their attention toward Patakara utilization in future oral rehabilitation studies to augment and affirm more benefits for this hopeful device. Advising the family relative or caregivers to encourage the elderly to use the lip muscle trainer for maintaining a strong lip is very important.

ИССЛЕДОВАНИЕ ГЕРМЕТИЗИРУЮЩЕЙ СПОСОБНОСТИ КОМБИНИРОВАННОГО МАГНИТОЖИДКОСТНОГО УПЛОТНЕНИЯ ПОДШИПНИКОВЫХ УЗЛОВ

The purpose of the research is to increase the efficiency of hermetic ability of bearing assemblies by using com-bined ferrofluidic sealed. The research objective is theoretic justification of the maximum concentration of ferro-magnetic particles in fluid, investigation of hermatic ability of a combined ferrofluidic seal under conditions of tem-perature changing and speed of a shaft rotation of packing bearing assembly. The study of hermetic ability of lip and ferro-fluidic sealed was carried out on a test bench, allowing to determine the packing ability of seals both in static and dynamic mode. On the basis of theoretical data, formulas were determined to find the maximum concen-tration of hard and magnetic phases in a ferrofluid, and its composition based on a polyethylsiloxane liquid PES-5 with a 40 kA/m saturation magnetization and a 1.2 Pas dynamic viscosity coefficient was developed. A mixture of magnetite with powdered iron was used as the ferromagnetic phase. Oleic acid was used as a surfactant. Studies to determine hermetic capacity have shown a higher efficiency of the combined ferrofluidic seal compared to the lip one. During static test within the temperature range between 20 to 600C, the critical pressure difference of the com-bined seal was 
 4-16% higher than that of the lip seal. Temperature increase of the bearing assembly from 20 to 1200C causes a decrease in critical pressure difference of up to 50%. This is due to a decrease in the sedimentative stability of the magnetic fluid as a result of an increase in temperature. Studies show that the combined ferrofluidic seal has a higher hermetic tightness at the starting torque than the standard lip seal. In contrast to the lip seal (which tends to lose its tightness at the starting torque), no leakage of pressure fluid from the sealed unit was observed of the com-bined ferrofluidic one with a pressure drop of 0.094 MPa. The results obtained allow reasonably select the concen-tration of magnetic particles in the ferrofluid, and also prove the prospects of replacing standard lip seals with com-bined ferrofluidic ones.

Mixed EHL numerical analysis and leakage experiment of skeleton reciprocating oil seal

PurposeThis paper aims to present the mixed elastohydrodynamic lubrication (EHL) model and obtain the leakage characteristics for the skeleton reciprocating oil seal.Design/methodology/approachThe model consists of a finite element analysis of the contact pressure, a fluid mechanics analysis of the fluid film, a contact analysis of the asperity contact pressure, a deformation analysis of the seal lip and an iterative numerical simulation process.FindingsSimulation results show that the leakage is in direct proportion to the seal roughness and speed, and in inverse proportion to the fluid viscosity. Comparisons with the experimental results verify the validity of the mixed EHL model.Originality/valueThis study provides a helpful method to calculate the leakage of the skeleton reciprocating oil seal, which shortens its development cycles.

Theoretical and experimental characterization for macro-micro friction behaviors of EPDM rubber

Friction behaviors of Ethylene Propylene Diene Monomer (EPDM) rubber ring will result in the oil leakage of radial lip seals. This research provides theoretical and experimental characterization for the friction behaviors of EPDM rubber. A friction coefficient prediction model is developed with consideration of the effect of temperature. The friction coefficient of EPDM rubber at different temperatures is studied experimentally, and its wear mechanisms throughout the temperature interval [20, 140] are revealed. Both the contact pressure and friction work density are investigated by using finite element method (FEM). Results show that the deviation between the predicted friction coefficient and experimental one is lower than 10%. The increase of temperature causes a decrease in the friction coefficient and leads to an increase of surface roughness of EPDM rubber, while it results in a reduction in the contact pressure and the friction work density.

Mixed elastohydrodynamic lubrication model of rotary lip seal with non-Gaussian surfaces: experimentation verification and numerical analysis on effects of sealed pressure.

Many published models can be used to analyse the sealing performance of rotary lip seal. The surfaces are normally assumed to be periodic variation. However, the quasi-randomness of surface height distribution should be considered, especially the non-Gaussian distribution. Hence, a mixed elastohydrodynamic lubrication model with non-Gaussian surfaces is proposed and used to analyse the effects of sealed fluid pressure on the seal performance in this paper. Based on digital filter and Johnson's translator system, a rough surface simulation method is introduced to simulate non-Gaussian rough surface. Based on this method the mixed lubrication model with non-Gaussian surfaces is built. The proposed model is verified by comparing the simulation results to experimental observations. Furthermore, it is hardly to find the research focused on the effects of sealed pressure. Hence, the effects of sealed fluid pressure on the seal performance is focused.

Analysis of the tribological interaction of a polytetrafluoroethylene-lined radial lip oil seal, shaft and lubricant sample

To investigate the tribological interaction and wear mechanisms of polytetrafluoroethylene-lined radial lip oil seals in service, a sleeve, seal and lubricant sample taken off a rotating rig are studied. The test was terminated at 72 h, after severe leakage in the final 15 h of the test. All three components are studied using a coherence scanning interferometer and environmental scanning electron microscopy to investigate wear after testing. Results show a wear band on the aerospace grade case-hardened sleeve, appearing as a ‘polished in’ area by the seal. A study of the filler content of the polytetrafluoroethylene coating uncover glass fibres, calcium carbonate, carbon and graphite layers present, assumed responsible for the wear to the sleeve. The polytetrafluoroethylene coating is a 300 μm coating, distinct from the bulk elastomer. This finding is confirmed after observing this layer on both, the tested and new seal lip. Wear of the seal lip is measured and facilitated by comparison to the identical new seal. Lastly, debris from the seal and sleeve wear are found in the lubricant sample.

Salivary pH and oral health of Brazilian para-athletes: Saliva and oral health of para-athletes.

This study aimed to investigate the association of the salivary pH and parameters of oral health in Brazilian para-athletes. The sample was composed of 271 Brazilian para-athletes (147 athletics, 61 powerlifting, and 63 swimming); mean age was 31.2 ± 11.7years. Data collected during anamnesis, clinical examination, and saliva collection revealed that salivary pH was different among sports (p=.01) and tends to decrease as age and body mass index (BMI) increase (p=.026, .027, respectively). The mean decay missing filled teeth was 8.8 (±0.57), but there is no correlation with salivary pH (R2 =-0.0852; CI 95%, -0.215-0.047; p=.194) as habits of grinding, clenching teeth, or bruxism was not associated with salivary pH (p=.317, .932, and .444, respectively). Regarding breathing, para-athletes that have buccal breathing had significantly higher salivary pH (p=.04). This data were confirmed by multiple logistic regression (p=.05). Open bite, lip seal, geographic or fissured tongue also were not associated with variation of salivary pH (p>.05). This study provided evidence of an association between salivary pH with age, BMI, type of breathing, and type of sport practiced by the para-athletes.

Hydrophilic sealing material for live centers in machine tools

A live center is an important mechanical component of a lathe. Water-based cutting fluids are used when high-speed machining or cooling properties are required. We performed an implementation experiment of the hydrophilic seal into an actual live center for preventing ingress of water-based liquids, which can protect bearings in the live center. The sealing structure was similar to that of an oil seal, where the seal lip is closely attached to the counter-face. Polyvinyl formaldehyde (PVF) with hydrophilic characteristics and a micro-level three-dimensional porous structure was selected as the seal lip material. The water-based cutting fluid was injected to the hydrophilic live center, which was rotated by servo motor. It was confirmed that the PVF seal could prevent the ingress of cutting fluids because the grease in bearings remained, and a stable frictional torque was achieved. The PVF seal color changed to that of the cutting fluid after the experiment, suggesting that the porous hydrophilic layer adsorbed the cutting fluid appropriately. On the superficial PVF layer, microscopic damage of the PVF was observed, however, the continuous porous structure was retained. It was supposed that the adsorbed cutting fluid acted as a boundary lubrication film for separating the dynamic seal surfaces.

Factors related to mouth-breathing syndrome and the influence of an incompetent lip seal on facial soft tissue form in children

Abstract Background Mouth breathing syndrome (MBS) is defined as a set of signs and symptoms that may be completely or incompletely present in subjects who, for various reasons, replace the correct pattern of nasal breathing with an oral or mixed pattern. Better understanding of the characteristics of MBS at each stage of growth will be helpful for the accurate diagnosis and treatment of MBS. Objective This review aimed to clarify the relevant factors affecting MBS in children and to examine the influence of an incompetent lip seal (ILS) on facial soft tissue form in preschool-aged children. Results Recent data have shown that an ILS affects MBS in children. In addition, the factors associated with MBS in preschool-aged children were not mutually unrelated, and multiple factors such as general conditions, lifestyle, and eating habits may interact with one another. Furthermore, children with an ILS already tended to have a flattened nose and an anteriorly prominent lip at 3 years of age, implying that the adverse effects of an ILS on the growth of the craniofacial region appear relatively early. Conclusions These results suggest the importance of early diagnosis and treatment of MBS. Early treatment of MBS may prevent possible dental and physical problems in the future.

Wear on radial lip seals: a numerical study of the influence on the sealing mechanism

In this paper a numerical approach is applied to analyse the influence of wear on the lubrication and sealing mechanism of radial lip seals. A three-dimensional multi-scale mechanical model is presented. This allows to simulate the macroscopic deformation of the entire radial lip seal and the microscopic deformations in the contact area between the sealing edge and the shaft surface. Furthermore, different wear band widths and surface roughness of sealing edges can be analysed efficiently. In the context of this paper, measurement results of radial lip seals in different wear states out of test runs are applied. The simulation results of the different sealing edges are compared. This allows drawing conclusions about the influence of wear on the performance of radial lip seals. This leads to a better understanding of the potential failure mechanisms of radial lip seals.

Mathematical Modeling of the Thermal Regime of Lip Seal

In this article, on the basis of mathematical modeling, simplified models of the thermal process of the lip seal are presented. Comparison of the computational results revealed that for the model, taking into account the reciprocating motion of the rod (the “with moving source” model), the simplified model with a fixed uniform distribution of the heat flux taking into account convective heat transfer from the free friction surface is the closest model - the “to lack” heat source. It is established that the traditionally used simplified model with a fixed uniform distribution of the heat flux, which does not take into account convective heat transfer from the friction surface (the “with excess” model), deviates over time from the “with moving source” model. Methods are proposed for determining the oscillation frequencies of the rod at which the simplified model describes the temperature field in the seal with suitable accuracy for practical use.

Contact Pressure of a Rubber Cuff on a Shaft

The pressure between a shaft and a reinforced rubber cuff (a lip seal) is considered. An algorithm is derived for calculating the contact pressure, taking account of the properties of the material, the thickness of the cuff’s active section, its inclination to the shaft, the spring’s tensile force, and the geometric parameters of the cuff’s free section.

Stern tube seals operation: A practical approach

Stern tube seals are a key component of the propulsion system of a ship. The purpose of these sealing rings is to ensure a reliable sealing condition, preventing the spillage of lubricant to the environment. The research on these large rotary seals is limited due to their complex accessibility: stern tube seals are located below the seawater level on a moving ship. A dynamic setup replicating the operating conditions of a stern tube seal is presented together with a novel arrangement for monitoring the flow rate across the seal. The frictional torque, the operating temperature, and the lubricant migration across the seal are measured under various shaft velocities and pressure differences. The existing theory for rotary lip seals is reviewed for the stern tube seal application. From the results it is deduced that the stern tube seals tested operate within the elastohydrodynamic regime with film thicknesses in the sub-micrometer range.

Prevalence of an incompetent lip seal during growth periods throughout Japan: a large-scale, survey-based, cross-sectional study

BackgroundSystemic and local factors may lead to disruption of craniofacial growth and development, causing an imbalance between the orofacial skeleton, muscle and soft tissue, dental occlusion, and the dental arch during growth periods. We aimed to reveal whether the prevalence of incompetent lip seal (ILS) varies with age and region, as well as to clarify the factors related to an ILS, in a national, large-scale epidemiological study.MethodsWe surveyed 3399 children, from 3 to 12 years of age, visiting 66 pediatric dental clinics throughout Japan. For this survey, we employed a questionnaire consisting of 44 questions regarding daily health conditions and lifestyle habits. We evaluated the differences in ILS prevalence by age and region (using a Cochran-Armitage test for trend and a Kruskal-Wallis test), and the relationship between ILS and factors investigated in the questionnaire (using Spearman’s rank correlation coefficient).ResultsWe observed that 30.7% of Japanese children exhibited an ILS and that the ILS rate increased with age (p < 0.001). There were no regional differences in the rate of ILS in Japanese children (p = 0.506). We revealed that 12 of 44 survey items exhibited a statistically significant correlation with ILS (p < 0.001), using Spearman’s rank correlation coefficient. These items involved orofacial morphology, mouth breathing, and possibly, allergic rhinitis.ConclusionThe rate of ILS seems to increase with age in children, throughout Japan. Therefore, this disorder may not self-correct during the growth periods in these children. Guidelines are required for pediatric dentists to recognize ILS among children aged 3–12 years.

Numerical Simulation and Experimental Study on Sealing Performance and Frictional Property of Rotary Lip Seal

The hydrodynamic theoretical lubrication model of the friction pair between the rotary shaft and the lip seal under the state of full film lubrication was established in this paper. The Reynolds equation was solved by using the finite difference method, and the influence of the viscosity‐temperature characteristics of the lubricant was taken into account in the solution process. The distribution of the film thickness and the hydrodynamic pressure in the sealing area was obtained. At the same time, the bench test was carried out and the correctness of the model was verified by comparing the simulation results and test results of reverse pumping rate and friction torque under different rotational speed of the shaft. The microasperity of the lip surface is a necessary condition for achieving the sealing effect. Therefore, the influences of the contact load of the seal and the root mean square deviation of the lip surface on the sealing performance and frictional property were analyzed by using the theoretical model. The analysis results show that the sealing performance and frictional property can be changed by changing the contact load and surface roughness of the lip, but a single increase in the influence of a certain factor cannot achieve good results, and comprehensive consideration is required in product design.

Influence of Alternating Temperature Levels on the Wear Behavior of Radial Lip Seals: Test Rig Design and Wear Analysis

Influence of Alternating Temperature Levels on the Wear Behavior of Radial Lip Seals: Test Rig Design and Wear Analysis

Surface texturing on rotating shaft for sliding surface against seal lip for waterproof

Surface texturing on rotating shaft for sliding surface against seal lip for waterproof