[0002] The invention relates under a second aspect to a roller for the drafting equipment of a spinning mill machine with an oblong base body and with an outer roller covering essentially surrounding the circumference of the base body.
[0003] Under a third aspect the invention relates to a spinning mill machine with drafting equipment having upper and lower rollers.
[0004] Under a fourth aspect the invention relates to a process for the cooling of at least one roller of drafting equipment of a spinning mill machine.
[0005] When drawing fiber sliver in spinning mills, drafting equipment is used in which the fiber sliver is guided between several pairs of rollers located one after the other, each consisting of an upper and a lower roller. Since the circumferential speeds of the rollers of every roller pair accelerate in the direction of travel of the fiber sliver and since the fiber sliver is clamped along the so-called nip line of each pair of rollers, the fiber sliver is drawn in the drafting equipment.
[0006] When the machine is shut off the roller bearings are still at a very high temperature which is only insufficiently lowered—contrary to continuous operation of the machine thanks to the utilization of a blower. The heat of the bearing is transmitted to the base body of the roller and from there to the roller covering. As a result so-called roll laps may be formed, i.e. the fiber sliver or individual fibers of the fiber sliver which are still conveyed by the coasting rollers roll themselves around the rollers in question and produce interference when the machine is started up again, resulting in renewed shut-off of the machine and time-consuming removal of the roll laps.
[0007] Even if no roll laps have formed upon shutting off the machine while the roller coverings are still warm or hot during renewed running-up, the above-mentioned roll lap process with the same undesirable consequences may be produced when switching on the machine.
[0008] It is the object of the present invention to prevent the formation of roll laps in drafting equipment rollers, in particular when shutting off and/or running up the machine. In addition, easier operation of the drafting equipment should be made possible.
[0009] Furthermore this objective is attained with a roller of the type mentioned initially under its first aspect in that a hollow space is provided in the base body.
[0010] This objective is attained with a roller of the type mentioned under a second aspect in that a thermally insulating layer is provided between the base body and the roller covering.
[0011] In drafting equipment of the type mentioned initially the object of the type mentioned initially is attained under a third aspect of the invention by designing at least one roller according to the first or second aspect of the invention.
[0012] Furthermore the object in a process of the type mentioned initially under a fourth aspect of the invention is attained in that a cooling medium is conveyed through a hollow space in the (at least one) roller.
[0013] The advantages of the invention reside in particular in the fact that the heat transfer from the roller bearings via the base body to the roller covering can be reduced significantly by the hollow space according to the first aspect of the invention—if it receives a cooling medium—and by the thermally insulating layer according to the second aspect of the invention. In particular heat peaks at the bearing locations can be screened effectively thereby. The thermally insulating layer reduces the heat flow from the base roller body to the roller covering, so that the latter is extensively screened thermally. The cooling medium for its part cools the base body so that a smaller amount of heat is transferred from the base body to the roller covering.
[0014] In case that a hollow space is provided in the base body, the heat produced in drafting equipment operation in the roller coverings by the fulling operation can be diverted inward.
[0015] Especially when switching off and running up the machine, a roll lap formation can be effectively prevented through the design of at least one roller according to the invention.
[0016] It is a further advantage of the invention according to its first aspect that the hollow space results in a lower mass of the base body and that therefore less mass inertia is involved when accelerating or braking the roller in question. Consequently these acceleration and braking processes can be carried out with less energy or in shorter time spans, thus achieving savings in cost or time.
[0017] The invention according to its second aspect is especially well suited to be used with upper rollers of drafting equipment which generally are provided with a roller covering, contrary to the lower rollers. If coverings are also used on the lower rollers, the invention can also be applied in that case. The invention according to its first aspect is usable with upper as well as lower rollers, whereby the upper rollers are normally provided with the above-mentioned roller covering, but could also be designed purely as steel rollers.
[0018] To install the roller covering of the upper rollers it is state of the art technology to use an aluminum sleeve and to vulcanize a plastic layer on it. The sleeve together with the plastic layer is then pressed on the base steel body and the roller covering is then ground. The same process can be used in principle for the thermally insulated layer between base body and roller covering according to the invention, i.e. the insulating layer is first applied to the base body, e.g. glued on it, and the aluminum sleeve, generically a metal structure, is pressed on the insulating layer together with the roller covering. This is also followed by the grinding step.
[0019] Alternatively, the thermally insulating layer is applied to the inside of the metal structure or aluminum sleeve, and the sleeve together with the insulating layer on its inside and the roller covering on its outside is pressed on the base body.
[0020] The thermally insulating layer can also be applied to the base body or to the inside of the metal structure, e.g. by immersion, covering with film, vulcanization, electrostatic coating, thermal spraying, whirl sintering etc.
[0021] If necessary an axial safety device is provided for the thermally insulating layer so that it may not slip around on the base body during the operation of the machine.
[0022] The thermally insulating layer preferably contains a plastic or compound material with the required thermal characteristics for extensive suppression of heat conductivity between base body and roller covering. Thermoplastics, duroplastics, particle-reinforced compound materials, layered compound materials, fiber-reinforced compound materials and ceramics can be used here.
[0023] The roller according to the first aspect of the invention is preferably characterized in that the base body is made in form of a hollow shaft and the hollow space is essentially enclosed by the wall of the base body. This design has the advantage that relatively easy production of the base body is possible by means of inside turning. Two base body halves each with a bearing axle journal at their faces are then advantageously welded together at their other faces. Here the hollow space is preferably designed so as to be essentially asymmetric relative to the longitudinal axis of the base body.
[0024] It is furthermore a considerable advantage of the hollow shaft that the roller mass can be reduced significantly, so that lower mass inertia occurs during running up and stopping of the machine. The drafting equipment can thus be accelerated more rapidly to its normal speed, for example. In addition, the roller can return to its starting position more rapidly than the conventional heavier rollers t hanks to its lower mass inertia during vertical moves such as are triggered e.g. by thick spots in the material to be processed. The roller is thus better able to follow the contour of the fiber sliver, so that a better drawing result can be obtained.
[0025] In order to achieve the most efficient cooling possible, the hollow space extends essentially along the base body so that the heat transfer paths between cooling medium and every point of the base body's circumferential surface are as short as possible.
[0026] In a preferred embodiment of the invention under its first aspect the hollow space extends into the axle journals that are normally made in one piece with the base body. This makes it possible to achieve further mass reduction with the advantages mentioned earlier. In addition larger volumes of cooling medium can be used.
[0027] With a preferred cooling method for the base body a fluid, in particular air or water, is used as the cooling medium. A slightly condensing liquid is advantageously used, as in this case the high degree of evaporative cooling causes the base body to be cooled efficiently. The hollow space may be filled either in part or completely with a suitable liquid.
[0028] In an advantageous embodiment of the invention under its first aspect the hollow space is closed. In this case the hollow space is e.g. in essence completely inside the base body and is delimited at its face either by the sides of the base body or by the axle journals of the roller. The cooling medium is then locked into the hollow space.
[0029] Alternatively the hollow space is designed open for the passage of the cooling medium through it. This design has the advantage that the cooling medium can receive thermal energy from the base body in the hollow space and can release it again outside the base body in a heat exchanger, a cooling aggregate or similar device, so that it can then advantageously be returned to the hollow space.
[0030] In the embodiment described above, in which the hollow space extends into the axle journals, the hollow space may be open as well as closed. In case of an open hollow space, it extends axially symmetrically e.g. from the face of one of the axle journals to the face of the opposite axle journal. In this case the cooling medium can be directed through the entire roller, possibly in a circuit as described above.
[0031] In an especially preferred embodiment air, in particular air in the environment of the spinning machine, can enter the open hollow space as the cooling medium without requiring a special pumping system for the air. The air exchange alone contributes in this case to the desired heat exchange. In addition a pumping system can be provided to increase the air flow.
[0032] The cooling medium performs advantageously a double function: In addition to cooling the base body it can be used as a means to lubricate the roller bearings. For this suitable compartmentalization and corresponding passage connection from hollow space to roller bearing are required. This compartmentalization is either closed or open, whereby the cooling and lubricating medium is preferably moved in a circuit in the latter variant, with the suitably designed cooling elements being provided outside the rollers.
[0033] According to the invention, its characteristics under its first aspect (hollow space) and those under its second aspect (thermal insulating layer) can also be realized together in one and the same roller.
[0034] Advantageous further developments are characterized by the characteristics of the sub-claims.
[0035] Different examples of embodiments of the invention are explained in further detail below through the drawing.
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[0043] FIGS.
[0044] The roller bearings
[0045] According to
[0046] The layer
[0047]
[0048] The hollow space
[0049] In the area of one face a passage bore
[0050] In an alternative embodiment not shown here the hollow space
[0051] The hollow space
[0052] The hollow space
[0053] In the embodiment of
[0054] In the embodiment of the invention shown in
[0055] Different designs are possible for the seal between the bush bearings or roller bearings of the roller
[0056] The lower rollers