Martin Bílek

Needleless coaxial electrospinning: A novel approach to mass production of coaxial nanofibers.

Herein, we describe a simple spinneret setup for needleless coaxial electrospinning that exceeds the limited production capacity of current approaches. The proposed weir spinneret enables coaxial electrospinning from free liquid surface. This approach leads to the formation of coaxial nanofibers with higher and uniform shell/core ratio, which results in the possibility of better tuning of the degradation rate. The throughput and quality increase favor the broader application of coaxial nanofibers from weir spinnerets as systems for controlled drug delivery in regenerative medicine and tissue engineering.

INFLUENCE OF STRUCTURE OF THE YARN ON MECHANICAL CHARACTERISTICS OF YARNS EXPOSED TO DYNAMIC STRESS

Abstract This paper is a direct follow-up of the paper [1] describing in detail the VibTex equipment, which facilitates testing of textiles in a wide range of frequencies of their extension, as well as the determination of corresponding dynamic modules and loss angles. This equipment has been employed for testing polyester yarns of concordant fineness manufactured on ring and rotor spinning frames. At the same time, the material concerned has been subjected to a standard strength test. Therefore, the results of experimental measuring published in this paper allow us to assess the effect of the chosen spinning technology upon the mechanical properties of polyester yarns both at their static and dynamic loading. The introductory section of the paper contains a theoretical analysis of the effect of the chosen manner of spinning upon the mechanical characteristics of yarns. The experimental section indicates the results of measurements at static and dynamic loading, and the final section of the paper confronts the obtained pieces of knowledge with theory. This paper is part of a larger group of publications concerned with the behaviour of various linear textiles when exposed to dynamic loading (see [1], [2], [4], [5], [6]).

Control Optimisation of the New Drive of Small Diameter Knitting Machines

Abstract The article is concerned with the issues of the drive of small diameter knitting machines. In connection to the proposal of optimum structure of the driving systems of the machine, there have been analysed the possibilities of precisely controlled servo drives. An optimised structure of the drives allows for the utilisation of precisely defined position and velocity functions. There is applied here the function of a polynomial of 7th degree, proposed for impact-free course of the acceleration, and it is compared with the results corresponding to the existing structure of drives of knitting machines. At the same time, there is analysis and comparison of the consumption of electric power by the original and optimised systems.

Mathematical Model of the Heald with Damping Element

Abstract This study focuses on the analysis of the existing design solution of shedding mechanism. It is characterised by a heald attachment into the heald shaft with a necessary design allowance. The preparation of a mathematical model for the new concept of the heald attaching to the heald shaft frame is explained in this study. A damping element for dissipating the energy created during the heald impact on the carrying wire of the heald shaft is currently used for the high-speed weaving loom. This system makes use of a damping element, fitted in the profile of the rod at an optimum distance from heald eye. This element provides for reduction of the heald velocity before its drop upon the supporting wire because the opposite section of the heald is pressed into the rubber element. The calculated results of the new concept of the heald attaching to the heald shaft frame are compared with the existing solution without application of the damping element.

Mathematical modeling of the system shedding motion – heald – warp

Abstract The paper is concerned with the description of a mathematical model meant for an analysis of the movement of healds during the weaving cycle. The referred model consists of a mathematical description of shedding motion, coupled with the solution of the heald model of a weaving loom. Principal designing elements of this component have been considered while devising this model. The affected calculations show a high value of acceleration of the heald produced after its drop upon the supporting wire. The referred model allows for analyzing a considerable part of designs of heald shaft that are employed in weaving looms nowadays.

NEW STRUCTURE OF THE DRIVE OF SMALL-DIAMETER KNITTING MACHINES

Abstract: This paper is concerned with the drive of small-diameter knitting machines and its optimal structure in reference to the knitting process. Based on an analysis of existing machines, a new structure is proposed employing controlled drives. In this proposal, emphasis has been laid on minimising the consumption of electric power and on simplifying the mechanical section of the structure. An analysis of the dynamic characteristics of the newly proposed concept, and a comparison with existing machines has been carried out.

Mathematical Model of Elastic Heald

The paper is concerned with description of the mathematical model meant for an analysis of the movement of healds during the weaving cycle. The paper deals with the assessment of the current construction design fastening the heald into the heald shaft. The present condition is characterized by the increased heald loading which is caused by its impact on the supporting wire. As a result of this, the healds get considerably worn out and their service life of the heads is reduced. There is a possibility for passive resistance involvement to reduce the velocity of the heald impact on the supporting wire. In this variant of the solution, the friction between the heald and the supporting wire is used for the decreasing of the impact.

Electronic Link Between the Needle Cylinder and the Dial of the Small Diameter Knitting Machine

The article is focused on verification of the applicability of individual drives in the design of small diameter knitting machines. The current arrangement of the drive ensures the mechanical transmission between the needle cylinder and the dial is via a central servomotor; this mechanical link raises limitations in terms of efficient utilisation of these elements of the machine. The new drive system eliminates the mechanical link and allows separate operation of the individual aggregates used in the knitting process. From the technical viewpoint, it is necessary to ensure compliance with the manufacturer’s prescribed maximum deviation of rotation between the needle cylinder and dial during the working cycle. For this reason, the article discusses an experiment verifying the capability of the new drive system to achieve the above-stated rotation deviation.

Mathematical Modelling of the Heald Shaft

Abstract The manufacturers of weaving equipment recently endeavour to minimise the necessary designing plays in the weaving loom mechanisms. One of the mechanisms most exposed to stress is the shedding motion that defines the held-shaft stroke. Its end part is the heald shaft. The heald shaft constitutes a problematic assembly of the shedding motion. The design employed presently is characterised by dynamic impact loading caused by designing play in the suspension of healds into the heald shaft. During weaving cycle, the healds fly between the main beams of the heald shaft, producing a considerable force pulse. This paper is concerned with the description of dynamic behaviour of the existing design on the basis of mathematical modelling and verification of obtained results by means of experimental analysis.

Mechanical Properties Of Traditional And Nanofibre Textiles

Abstract This study deals with a comparison of mechanical properties of a conventional yarn and a textile from nanofibres. The conventional yarn represents the textile objects with high degree of orientation of fibres and the textile from nanofibres represents the textile objects with low degree of orientation of fibres. The theoretical section is concerned with the issue of internal structure of plied yarn and resulting differences in the orientation and straightening of fibres and in utilisation of deformation properties of fibres in comparison to the referred nano textile. The experimental section describes the manner of realisation of both static and dynamic tests of conventional yarn and strips of nanofibres. The results show differences in the mechanical properties of conventional yarn and textile strip from nanofibres under static and dynamic loading conditions. The processing technology of conventional yarn has been verified in the long term. But textiles from nanofibres are a relatively new material and mechanical properties of the detected differences point out possible problems with their behaviour during standard technological processes.