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(11) | EP 0 114 365 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Wire or thread tension controlling dancer roller device |
| (57) A dancer roller device for controlling the tension of a wire, thread or the like,
wherein the tension is maintained constant at all times on the output side, independent
of fluctuations in the tension on the inputs side. First and second sets of rollers
are arranged parallel to one another, with the first set being fixed and the second
set being mounted on a slider. The wire, thread or the like is laid over the two sets
of rollers in a zig-zag manner, alternately passing around ones of the first and second
rollers. A constant-tension spring urges the slider away from the first set of rollers.
The moments of inertia of the first and second rollers, the masses of the rollers,
the mass of the slider, the radii of the first and second rollers, and the number
of passes of the wire, thread or the like between the first and second rollers are
set such that the tension at the output side is always constant. |
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a dancer roller for controlling the tension of wire, thread or the like.
[0002] In an apparatus for producing electric wire or in an apparatus handling wire or thread, a dancer roller is widely used for maintaining constant the tension of the wire or thread. Especially, in a recently developed optical fiber manufacturing apparatus, severe performance requirements are imposed, such' as a requirement for a tension under 100 g with a maximum variation of +5% (±5 g). Such severe performance requirements were not been imposed on earlier wire manufacturing equipment. Accordingly, it has been found necessary to improve the dancer roller to meet such requirements.
[0003] Usually, a dancer roller has a wire/thread inlet side and a wire/thread outlet side, with the wire/thread tension being made constant at the outlet side. That is, a dancer roller is used for making constant the take-up tension at various positions, for example, for making constant the tension at the output side of an extruding station or for making constnt the tension at a twisting point when it is used in a wire/thread twisting apparatus.
[0004] It is known that variations of the wire/thread speed at the inlet side can be a factor affecting the wire/thread tension at the outlet side. For example, if slackening or pulling occurs in the winding of a bobbin at the inlet side, the wire tension will vary not only at the inlet side of the dancer roller, but also at the outlet side because, when the bobbin is used as the pay-off device, wire/thread slackening necessarily occurs since the wire/thread is wound in layers, one upon the other, so that the wire/thread speed varies even if the bobbin rotates at a constant speed.
[0005] A prior art dancer roller device is shown in Fig. 1. In this figure, reference numerals 11, 11' and 11" designate fixed rollers which are rotatably supported, through respective bearings 12, 12' and 12", on a shaft 13 affixed to a rigid frame 14. Reference numerals 15 and 15' designate movable rollers which are rotatably supported on a shaft 17 through bearings 16 and 16'. A slider 18, slidable in the longitudinal direction of a shaft 19, has a slide resistance under several grams. Reference numeral 20 designates a spring which balances with the wire/thread tension, and 21 designates a rack which engages with a pinion 22 attached to a rotating shaft of an electrical displacement detector 23 which converts the displacement of the slider 18 into an electric signal. Reference numeral 24 designates a pay-off reel driven by an electric motor 25 which is controlled by an electrical controller 26, which is in turn actuated by a signal from the displacement detector 23. The spring 20 may be replaced by a weight 28 as shown in Fig. 2.
[0006] In the device described above, if the wire/thread feeding speed varies temporarily due to the slackening of the winding wire/thread, the tension varies at the inlet side of the movable roller 15, and this variation is detected by the slider 18 so as to control the motor 25 through the displacement detector 23.
[0007] In this. device, the speed of the reel 24 has to be tightly controlled to follow the variations in the coil feeding speed, and therefore, a complex and expensive device is required for the electrical controller 26 and a large amount of power is required for the motor 25.
[0008] Accordingly, it is an object of the invention to provide a dancer roller device in which these disadvantages are eliminated. More specifically, it is an object of the invention to provide a dancer roller device in which no variations occur in the tension at the outlet side of the device, even if the wire/thread speed varies at the pay-off side and the tension varies at the inlet side of the device.
SUMMARY OF THE INVENTION
[0009] In accordance with the above and other objects of the invention, there is provided, according to the present invention, a predetermined relationship between the mass of the wire/thread moving elements, including the rollers at the movable side, and the moment of inertia of the rotating elements is maintained, so that variations in the tension at the inlet side are prevented from affecting the tension at the outlet side.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
Fig. 1 is an explanatory diagram of a conventional dancer roller device;
Fig. 2 depicts a modified portion of the device of Fig. 1; and
Fig. 3 is a plan view of the guide roller device use for explaining the principles of the device of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0011] In Fig. 3, which shows a dancer roller device of the invention, I designates a group of fixed guide rollers 1, 3, 5..., n + 1; II, a group of.movable guide rollers 2, 4, 6, ... n provided on a slider 8; 9, a support shaft for the slider 8; 10, a coil spring; 11, a rack formed integrally with the slider 8; 12, a pinion; 13, a displacement detector; 14, a reel; 15, a drive motor; and 16, a controller.
[0012] Assuming that T1 and T0 represent the wire/thread tension at the inlet and outlet sides respectively, ai designates the acceleration at the i-th wire/thread position at the inlet side (the direction of the arrow is assumed as the positive direction), and n1 designates the number of wires/thread suspended between the guide roller groups I and II, the respective accelerations α1, a2, α3, ...., n1 + 1 of the wire/thread running portions of the guide rollers 1, 2, 3,... nl+l are expressed as follows:
[0013] Assume that JG designates the moment of inertia of each of the guide rollers 1 ~ nl+l, r designates the radius of each guide roller at its wire/thread running portion, and T2, T3, ···Tn+1 designate the tension of the respective wires/threads suspended between the guide roller groups I and II. Since the guide rollers are accelerated, the wire/thread tension is larger at the outlet side than at the inlet side with respect to each roller. Accordingly:
[0014] Therefore, the total tension of the wire/threads suspended between the groups of guide rollers I and II is expressed as follows:
[0015] In the case where the acceleration a is positive in the direction of the arrow and the slider 8 is positively accelerated in the indicated direction C, the total tension of the wires/threads suspended between the guide roller groups I and II corresponds to a difference obtained by subtracting a value determined by the moment of inertia from the value of the reaction force Te (constant) of the slider 8. Assuming that mG designates the mass of each guide roller and mg designates the mass of the slider 8, the right-hand side of the equation above becomes:
where the acceleration of the slider 8 is a/nl. The lefthand side may be arranged as follows:
Accordingly:
[0016] Since the wire/thread tension T0 at the outlet side is obtained by adding ΔTn+1 ~ ΔT1 to Ti, the wire/thread tension T0 is expressed as follows:
[0017] The second term of the equation immediately above has positive and negative components with an offset relation. Therefore, if the respective constants, the moment of inertia JG of one guide roller, the number n1 of the wires suspended between the guide roller groups I and II, the radius r of the guide roller at its wire/thread running portion, the moment of inertia mG of one guide roller, and the mass mg of the slider 8, are set such that the second term is zero, the equation becomes
[0018] In this case, the wire/thread tension is not affected by the acceleration a at the inlet side. In this case, although the condition that the reaction force Te of the slider 8 is constant is a necessary one, it is not constant in the method utilising the weight 28 as shown in Fig. 2. That is, not only it is necessary to employ a spring 20 as shown in Fig. 1, but it is further required that the spring constant be substantially constant (the spring force does not depend on the amount of flexure). This can be attained by using a coil spring having a constant curvature.
[0019] As will be apparent from the above description, the moment of inertia of the guide rollers, the mass of the movable guide rollers and the mass of the slider are balanced against the number of guide rollers and the radius of the guide rollers, and a substantially constant spring force is used as a force balancing with the tension so that wire/thread speed variations at the inlet side cannot contribute to variations in wire tension at the outlet side. Thus, it is not necessary to cause the bobbin speed to follow with a high response speed variations at the feeding side, and the tension at the outlet side can be maintained constant. Thus, the invention is particularly adapted for use in the manufacture of optical fibers. Moreover, the invention results in a control device having a reduced cost, made possible; in part, by a motor of smaller capacity than was necessitated by prior art approaches.
1. A dancer roller device for controlling the tension of a wire, thread or the like,
comprising:
a plurality of first rollers, fixed in position and arranged in a line;
a slider extending lengthwise parallel to said line of said first rollers and slidable in a direction parallel to said line of said first rollers;
a plurality of second rollers fixed to said slider and arranged in a line parallel to said line of said first rollers, said` wire, thread or the like being laid around said first and second rollers in a zig-zag manner, alternately passing around ones of said first and second rollers; and
a spring having a substantially constant spring constant connected between said slider and a fixed point for urging said slider away from said first rollers, wherein moments of inertia of said first and second guide rollers, passes of said guide rollers, the mass of said slider, radii of said first and second guide rollers and the number of masses of said wire, thread or the like between said first and second rollers being set such that tension in said wire, thread or the like at an output end from said first and second rollers is substantially constant and independent of variations in tension in said wire, thread or the like at an input end of said first and second rollers.
2. The dancer roller device of claim 1, wherein, with said moments of inertia of said
guide rollers represented by JG, said masses of said first and second guide rollers by mG, said mass of said slider by mS, said radii of said guide rollers by r, and said number of passes of said wire, thread
or the like between said first and second rollers by nl, the following relationship is maintained:
3. The dancer roller device of claim 2, wherein said spring comprises a coil spring
of constant diameter.
4. The dancer roller of claim 2, wherein, with respect to a line parallel to said
lines of said first and second rollers, said first and second rollers are staggered
with respect to one another.