Technical field

The present invention relates to a coupling element for a roll, which comprises segments.

Background

Spreading rolls are widely used in a number of industries to transversely stretch a sheet materials such as fabrics, papers, plastics, or film traveling thereover. Their one common role is to flatten the sheet material prior to a processing step such as coating, embossing, laminating, printing, slitting, winding and so on. The rolls may prevent the sheet material from shrinking or wrinkling during the chemical or mechanical processing steps.

One type of spreading rolls generally in use today is a bowed (bent) spreading roll, comprising a curved stationary shaft upon which rotating roll segments are mounted on the curved (bent) shaft with the interposition of bearings, which are linked with one another by coupling elements.

European patent EP0842107 discloses a coupling element, which is formed by a rubber ring, an inner sleeve situated inside the ring and metal bracing sleeves that are situated in the corners on the outer circumference of the rubber ring and that have a cross-sectional shape of an angle iron, whereas the ends of the sleeves positioned inside the rubber are rounded. The coupling element according to EP0842107 is both weighty and costly, and the manufacturing process thereof is laborious.

Summary It is an object of the present invention to provide cheaper and lighter coupling elements that are relatively easy to manufacture. Such purpose is achieved by providing coupling elements in which a ring-shaped element contains at least one polymeric material having plastic properties.

According to the invention, the coupling element for coupling segments of a roll together comprises a first ring-shaped element of a flexible material having an outer circumference and two side edges, and the outer circumference of the first ring-shaped element is provided with a second ring- shaped element and a third ring-shaped element along the two side edges of the first ring-shaped element, and at least one of the second ring-shaped element and the third ring-shaped element comprises at least one polymeric material having plastic properties.

In one example, the polymeric material is thermoplastic. In one example, the polymeric material is polyethylene (PE) or polypropylene (PP). In one example, the polymeric material has at least one carbonyl group, such material as polyamides (PA), polyetherketone (PEK), polyamide-imide (PAI), polyetherimide (PEI) or the like. In one example, the first ring-shaped element is made of elastic material. In one example the first ring-shaped element contains at least one thermoplastics or rubber-based materials. In one example, the first ring-shaped element comprises a protrusion extending radially inwards. In one example, the cross-sectional shape of the protrusion is of a bell or trapezoid. In one example, the first ring-shaped element has an outer portion, which is divided into two sub-portions by a hollow having a depth at the centre of the first ring-shaped element. In one example, each of the two sub-portions of the first ring-shaped element has an outer circumference, the outer circumference of one sub-portion is substantially at the same level as the second ring-shaped element, and the outer circumference of another sub-portion is substantially at the same level as the third ring-shaped element. In one example, each the second ring-shaped element and the third ring-shaped element has two side edges, one side edge of the second ring-shaped element opposing one side edge of the third ring-shaped element, and each of the opposing side edges of the second ring-shaped element and the third ring-shaped element comprises a thinned section, whereas the width of said ring-shaped elements on the inner circumference is wider than the width of said ring-shaped elements on the out circumference, and the first ring-shaped element has a profile that fits the profiles of the thinned sections of the second and third ring-shaped element. In one example, the first ring-shaped element is a flexible ring. In one example, the second and third ring-shaped elements are supporting rings. Thanks to the present invention, it is possible to manufacture a lighter coupling element, to reduce manufacturing costs, and to provide flexible design according to different needs.

Brief description of the drawings

Fig. 1 is a side view of a coupling element according to the invention in the direction along the shaft of a roll, in accordance with an embodiment;

Fig. 2 is a cross-sectional view of the coupling element according to the invention, along the A-A line shown in Fig .1 ;

Fig. 3 is a perspective view of the coupling element of Fig .1 ; and

Fig. 4 is a side view of a roll having segments coupled with coupling elements of Fig .1 , in accordance with an embodiment.

Detailed description

According to the invention, the coupling element 9 comprises a first ring- shaped element 1 , a second ring-shaped element 2, and a third ring-shaped element 3. For the sake of easier describing, hereunder the first ring-shaped element 1 is described as a flexible ring, and the second ring-shaped element 2 and the third ring-shaped element 3 are described as supporting rings.

Materials

A supporting ring 2, 3 of the coupling element 9 according to the invention contains at least one polymeric material having plastic properties but which is substantially hard and non-elastic. In other words, the supporting rings 2, 3 are made of material which does not easily compress when an external force is affected to the supporting rings 2, 3. The supporting ring 2, 3 may be substantially composed of a thermoplastic material, for example, based on polyethylene (PE), polyamides (PA), polyetherketone (PEK), polyamide-imide (PAI), polyetherimide (PEI) or the like, including combinations and/or mixtures thereof. The supporting ring 2, 3 may be substantially composed of a mixture of thermoplastic materials and reinforcement materials, such as fiber, e.g. glass fiber, carbon fiber or the like. The supporting ring 2, 3 may also be composed of materials without reinforcement materials.

Thanks to the characteristics of the materials used for manufacturing the supporting rings 2, 3 according to the invention, the supporting rings 2, 3 have outstanding radiation resistance, wear resistance, chemical resistance at elevated temperatures and they do not easily deform due to external forces affecting them, and therefore are applicable for the coupling elements 9 for rolls used in different industries where parts are exposed to heat and aggressive media and need anti-chemical erosion, corrosion resistance, thermal stability and so on. Also, thanks to the characteristics of the materials used for manufacturing the supporting rings 2, 3 according to the invention, the supporting rings 2, 3 have high impact resistance as well as excellent compressive strength, stiffness and toughness, and the excellent dimen- sional stability allows the supporting rings 2, 3 support higher loads without permanent deformation, and therefore are applicable for the coupling elements 9 for rolls 1 1 (Figure 4) used in different industries where parts are exposed to stress and vibration. Structure

According to the invention, the first ring-shaped element 1 of the coupling element 9, namely the flexible ring 1 , is substantially composed of an elasto- meric material, for example, based on natural rubber, synthetic rubber, elas- tic thermoplastic, thermoplastic elastomer, or a single component or multi- component polyester or polyether urethane system, including combinations and/or mixtures thereof. In one example, the flexible ring 1 contains thermoplastic polyurethane. The flexible ring 1 also has physical properties such as chemical and temperature resistance and hardness suited for the contemplated use or application of the roll. According to the invention, the supporting rings 2, 3 are bonded or moulded on the outer circumference of the flexible ring 1 to form a single composite part. In one example, the sides of the coupling element 9 that are formed of the flexible ring 1 and supporting rings 2, 3 are substantially straight. The flexible ring 1 may comprise a protrusion 5 extending radially inwards, in such a configuration that it allows the coupling element 9 to act as a good turning joint. The protrusion 5 may be, for example but not limited, in a shape of a bell, a trapezoid or the like in a cross-sectional view. According to an embodiment of the invention, the first ring-shaped element 1 has an outer portion 10, which is divided into two sub-portions 10a, 10b by a hollow 6 having a depth at the centre of the first ring-shaped element 1 . The hollow 6 extends into the flexible ring 1 to a depth sufficient to substantially de-couple the two outermost portions 10a, 10b of the flexible ring 1 , in terms of lateral swayings. Each of the two outermost portions 10a, 10b of the partly spit body of the flexible ring 1 engages with the end portion 7, 8 of a respective supporting ring 2, 3, swaying to one side and to the other in revolving about the bowed shaft, in opposite directions to the swaying of the other portion 7, 8 that engages the end of the other supporting ring 2, 3.

According to an embodiment of the invention, each of the two sub-portions 10a, 10b of the first ring-shaped element 1 has an outer circumference, the outer circumference of one sub-portion 10a is substantially at the same level as the second ring-shaped element 2, and the outer circumference of another sub-portion 10b is substantially at the same level as the third ring-shaped element 3. Each of the second ring-shaped element 2 and the third ring- shaped element 3 has two side edges, one side edge of the second ring- shaped element opposing one side edge of the third ring-shaped element, and each of the opposing side edges of the second ring-shaped element and the third ring-shaped element comprises a thinned section 7, 8, whereas the width of said ring-shaped elements 2, 3 on the inner circumference is wider than the width of said ring-shaped elements 2, 3 on the out circumference, and the first ring-shaped element 1 has a profile that fits the profiles of the thinned sections 7, 8 of the second and third ring-shaped element 2, 3. Manufacturing process

Adequate engagement between the flexible ring 1 with the supporting rings 2, 3 may be established in many different ways. For example, a moderate compression of a machined or precisely moulded supporting rings upon forcibly installing thereon can establish a secure interference-engagement of the parts that makes them to rotate as one piece. Gluing is another viable technique. For example, a flexible ring 1 is firstly made with any known techniques, following by the formation of two supporting rings 2, 3, separately or simultaneously, on the outer circumference of the flexible ring 1 . The supporting rings 2, 3 can be directly vulcanized onto the flexible ring 1 . For example, injection moulding can be used. The vulcanization temperature used may depend on the properties of the material used. For example, the vulcanization temperature can be 170°C. The pressure during moulding may depend on the properties of the material used. For example, the pressure used can be 300 bar. When this kind of vulcanizing process is used, the material of the two supporting rings 2, 3 should withstand the temperatures occurring during the vulcanizing process. For example, polyamides, polyet- herketone, polyamide-imide and polyetherimide may contain polymers which are suitable for vulcanization.

Polyethylene and polypropylene may be suitable materials especially when gluing is used to engage the flexible ring 1 with the supporting rings 2, 3, because temperatures occurring during gluing are usually lower than vulcanization temperatures.

Figure 3 shows the coupling element 1 of Figure 1 as a perspective view and Figure 4 shows an example of a roll 1 1 in which several segments 12 of the roll 1 1 have been coupled together by using coupling elements 1 . Figure 4 illustrates how coupling elements 1 enable bending the roll 1 1 slightly.

The present invention is not restricted to the above described embodiments but it can be modified within the scope of the appended claims.