RESEARCH ON TECHNOLOGICAL DESIGN OF MEDICAL KNITTED FABRICS FOR PRESSURE THERAPIES Crina Tiron 1,Beatrice Giugaru 2,Nicolae Constantinescu 3,Marina Roman 4 ; Gabriela Bőhm 5 & Costea Budulan 6 Abstract: The technological design presented in this paper, aims at establishing the technological parameters of manufacturing stages in order to obtain desired performance characteristics of medical knitted fabrics for pressure therapies. Production of various knitted structures, with some predetermined properties, involves technological parameters determining the technological phases. Accurate and precise determination of parameters of the structure have a great importance therefore must consider the usefulness and inexpensive items. 1 INTRODUCTION It has become more and more important the way that the orthotics is permitted to own the most adequate health characteristics, in order to assure the comfort of the subject during variables internal and external conditions of medical knitted fabrics for pressure therapies. The paper refers to the results of some experimental research about the knit. We were interested in how certain parameters and characteristics associated with knitted (loop depth, structure of knitted fabrics, yarn finesse), can improve efficiency items. 2 MEDICAL FABRICS FOR PRESSURE THERAPIES Orthotics is a section within the medical field concerned with the design, manufacture and application of orthoses. An orthosis or orthotic (plural: orthoses or orthotics) is an orthopedic device which support or correct the function of a limb or the torso (Figure 1). An orthopedic brace, "appliance", orthotic, or simply brace is an orthopedic device used to control and/or guide and/or limit and/or immobilize an extremity, joint or body segment for a given reason; to restrict movement in a given direction; to assist movement more generally; to reduce weight bearing forces for a particular mobility purpose; to help with rehabilitation from fractures after the removal of a medical cast; or to otherwise correct the shape and/or function of the body to provide easier movement capability and/or reduce pain. It combines disciplines of study within the health and physical sciences, mathematics and materials engineering, gait analysis, anatomy and physiology, patho-physiology, biomechanics, and psychology contribute to the work done by orthotists, the professionals engaged in the field of orthotics. [2] Orthotics are made from multiple types of materials including elastic, cotton, wool or a combination of other similar materials. Some design can be bought at a local retailer while others are more specific and require a prescription from an specialized physician who will fit the fabric according to the patient's need. The orthotics are basic and available in multiple sizes. The intention of these orthotics is to protect and should never be worn without previously consulting a professional doctor or physical therapist. 1 PhD. Eng Tiron Crina; Gh. Asachi Technical University; B-dul D.Mangeron 53-55,CorpTex1,700050 Iasi, Romania, ctiron@tex.tuiasi.ro.
Figure 1: Codification of orthotics. Orthotic devices improve the quality of life of patients with musculoskeletal lesions and are useful for preventing lesions resulting from strenuous activities, whether performed in the course of daily living or in the pursuit of games and sports. 3 RAW MATERIALS USED FOR ORTHOTICS MANUFACTURE The medical knitted articles are made from a variety of materials in order to provide elasticity, extensibility and tensile strength to wear and to provide a very good skin tolerance. For these products be effective, well tolerated on after wearing them, to obtain good results, it is possible to combine elastomeric yarns with natural yarns as wool and cotton. For research materials was used cotton lycra core yarn, polyamide yarn with elastane core, woollen and rubber covered with polyester. To achieve new types of fabrics for pressure therapies I submitted to research materials what is found in figures no 2 and 3. Figure 2: Yarns testing on Instron machine Figure 3: Structures obtained under test thread
4 TECHNOLOGICAL DESIGN OF MEDICAL KNITTED FABRICS Knit variants studied are obtaining on graphic station Stoll, and the yarns used are seven types, with different gauges and compositions. Knitted ties are jersey 1:1, single jersey 1:1, rib and interlock. In all the structures were used three different depths of looping. Based on experimental research we studied the way in which certain parameters regarding the nature of raw material, the degree of its thinness, the structure, looping depth of knitted fabrics used may also influence the effectiveness of the product and its other sanogenetic characteristics. Technological design, whereby the process is established, shall the machinery and is calculated the technological parameters, specific consumption, production capacity, yield. [1] For a given knit, some structural parameters are determined practically by measurements and others are calculated using relations liaison. The orthotics basic feature is fully knitted elasticity increased from 50% to 120% in both direction and rows of stitches. To obtain the desired elasticity, both longitudinal and transverse direction, using cotton lycra core of the finesse of 20tex, polyamide yarn with elastane core with the finesse of 270dtex, woollen yarn with the fineness of 64tex and rubber covered with polyester with the finesse of 167tex. For the orthotic to maintain the portion configuration of the body that is required to apply and comfort parameters needed to analyze various structures. The main parameters which characterizing the structure are : the step and height of the stitch, horizontal and vertical densities, coefficient of density, length of yarn from stitch, knit mass, correlation coefficients between different parameters and structure. Stitches step, A [mm] is given by the distance between the centers of two rows of a adjancent stitches, on the same side of the knitting measured in the stitches direction. Stitches height, B (mm) is the distance between the centers of two adjacent stitches measured in the direction stitches. Density in the horizontal direction or stitches, Do [l/50mm], the number of lines of stitch one side on knit of unit length contained in 50 mm. Vertical density, Dv (r/50mm), the number of rows of stitches contained in unit length of 50 mm. Length of yarn in the stitch, l (mm), is length of yarn for the different elements of structure, in the free disposal of knit. Unit area or mass of produc, M (g/m2) is mass of necessary yarn used for production of that product or surfaces. Relationship between structural parameters and yarn consumption is a factor of prime importance for production planning, to estimate the need for wires and even to assess the cost of production, prior to knit on the machine. Submit research some structures like rib, jersey and interlock with weft yarn, stitch, and loop.
Figure 4. Caption of M1, tubular rib with elastic yarn With this moistures of knits is made the design calculations for each knitted structure (Table 1). Table no 1: Parameters of structure for variants of knit realized No.crt. Structure Yarn finesse 1. Single jersey Density step Do [line/50mm] Dv [row/50mm] l[mm] x[mm] M[g/mp] Observaţii 33 tex 11 46 36 5.2372 2.25 184,245 Wool and rubber yarn covered with PES,114tex, Stoll Based on these calculations were drawn diagrams of correlation between various parameters of structure: correlation between the vertical density and length of yarn from stitch, between density on vertical and depth on looping and between yarn length from stitch and depth of looping (Figure no 5). Figure 5: Diagrams of correlation between various parameters By analyzing these correlations we conclude that tendency to decrease of vertical density with increasing with length from the stitch and this increasing in the same time with depth on looping. The density has a variation dependent of length from stitch. For variants of knit realized from wool with 33tex finesse and rubber yarn covered with PES, with 114tex, correlations between physical properties, namely permeability, porosity, thermal conductivity, and correlations between physical properties and extensibility has both a strong bond and average, this orthotics can be used for diseases with a low degree of immobilization of joints or limbs. There have been several variants of knits knitted on rectilinear machines of Stoll graphic station (Figure 4). Variants of knit were made in various combinations of different types of
yarn with different finesses. At these variants were measured and calculated parameters of their structure. Based on these measured and calculated values were determined by calculating the looping depth of these knits. Method of calculating the depth of looping is on Milcenko method (Figure 6). Figure 6: Milcenko method This method is used to calculate the depth at machines which forms the loops on the knitting process by final looping at the knitting on the single needle bar. 5 CONCLUSIONS It is important the opportunity to achieve a predetermined values to managing the properties of these orthotics depending on destination. The theoretical and experimental research of this paper fits into the overall objective of reevaluation and reappraisal of the importance that the new non-conventional technologies have for the placement of orthotics for certain levels of performance. Calculations and analysis enabling the design of knitted fabrics made with improved characteristics. References [1.] Budulan, R.: Bazele tehnologiei tricoturilor, I.U, Iasi, (1976). [2.] Gouvas, H.: Orthotics, http://en.wikipedia.org/wiki/orthotics Accessed: 2010-10-25. Research conducted in the project BRAIN POSDRU/6/1.5/S/26 co-financed by European Social Fund Operational Programme Human Resources Development 2007-2013.