EP0840815B1 - Motorized yarn twisting head - Google Patents

Description

The present invention relates to a motorized head for processing threads, of the type defined in the preamble of Claim 1.

Conventional machines for processing threads, such as spinning machines, twisting machines, spiral covering machines, doubling machines, texturizing machines, winders, et cetera, use processing heads that have the purpose of supporting a spindle or spool of thread while the thread is wound up and subjected to twisting, spiral covering, doubling, or other similar operations.

Each head is essentially formed by a fixed support for the spindle and by a rotating part that moves the thread at high speed, on the order of 15,000 rpm. In conventional machines, the rotation is imparted by a single motor that transmits motion to a long row of heads, with rather antiquated transmission devices, such as for example annular belts that are placed in sliding contact with pulleys formed on the axis of the heads.

The same motor can also be used to actuate, by means of gears, linkages, and various transmission devices, other movements of the machine, such as the oscillation of the beams or thread-guiding eyes or the rotation of the thread spoolers or winders.

In this case, the speed of the single motor of the machine is controlled by means of an adapted electric circuit.

In order to vary the speed of the heads, for example to change the type of processing, it is necessary to manually change the gears and therefore the transmission ratio between the motor and the axes of the individual heads.

This arrangement has the advantage that if a power supply failure occurs, all the components decelerate in step and therefore do not produce tensions or breakages of the thread. However, it has several drawbacks: first of all, the conventional machines produce a very high noise and have low mechanical efficiency. A machine of normal size can in fact have 100 to 300 heads driven simultaneously by these transmission devices, which are subject to considerable friction and impacts, and all together generate noise levels of up to 100 dB. Because of this, the assigned personnel must constantly wear protective earplugs or headsets, which however do not fully eliminate the risk of irreversible damage to the auditory system and often do not comply with health regulations.

Furthermore, the efficiency of these mechanisms is notoriously very low due to the frictions of the very large number of moving parts and heavily affects electric power consumption.

Thirdly, current transmission systems do not ensure high precision because they use inaccurate transmission devices, such as belts, which entail considerable slippage.

Some manufacturers have attempted to solve these problems by applying an independent motor, for example an asynchronous one, to each head. The various motors, which have a power rating of less than 100 W, are supplied and controlled by a single frequency converter for the sake of economic convenience.

While on the one hand this solution solves the noise problem, on the other hand it does not improve precision in speed control, because asynchronous motors notoriously have high slippage, and it does not improve power consumption, because these motors, when they have low power ratings, have efficiencies on the order of 50%.

More recently, some manufacturers have thought to use a frequency converter for each individual motor; this allows to also achieve the goal of precision, but does not solve the power consumption problem and the cost problem; indeed, the latter problem is worsened because of the increase in the number of components of the machine.

Finally, this solution does not eliminate the drawback of the lack of synchronization among the various movements in case of power failure in the mains, causing considerable problems in thread tensioning or integrity during power supply transients.

US-A-5,161,361 discloses a brushless motor-driven assembly for textile ring spinning frame comprising all the features mentioned in the preamble of claim 1. The motor of this known assembly is a variable reluctance motor without permanent magnets.

EP-A-0 389 117 relates to a drive for a spindle of a textile machine or ring frame, also including all the features defined in the preamble of claim 1.

Also in this case, the motor is of the variable reluctance type without permanent magnets thus involving the use of rotors of relatively large diameters and inertia.

Moreover, none of the above referenced citations provide a solution to the problem of synchronizing the revolution of each spindle with that of the other devices connected thereto in case of failure or gaps of power supply to the mains.

The aim of the present invention is to eliminate the drawbaks described above by providing a motorized head with rotating spindle, particularly for thread processing, that features low noise, high efficiency, low cost, and very compact size, minimizing the risk of breakage of threads during power supply transient caused by failure or gaps in the mains.

This aim and other objects that will become apparent hereinafter are achieved by a motorized head with rotating spindle, according to claim 1.

A head of this type produces low noise because it avoids conventional-type transmission devices, and has low consumption because of the use of electrically highly efficient brushless motors. A head of this type also has a high precision due to the fact that it uses a separate control circuit. Moreover, the present head overcomes the problem of lack of synchronization generated by power supply transients in the mains.

Preferably, the speed and power supply control circuit of the motor is a miniaturized frequency converter, built into the frame of the motor.

The power supply current of the control circuit of the converter and the current that supplies power to the motor are both at low voltage, eliminating all risks for the assigned personnel.

A head with these characteristics allows to achieve a manufacturing cost reduction, also by virtue of the mass-production of custom-built integrated circuits.

Further characteristics and advantages will become apparent from the description of an embodiment of the head according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

Figure 1 is a schematic side view of a head with rotating spindle according to the invention;

Figure 2 is an electric diagram of a thread processing machine that uses a series of head with rotating spindle according to the invention.

With reference to Figure 1, a head according to the invention, generally designated by the reference numeral 1, comprises a hollow pivot 2 that acts as support for a spindle or reel 3 of thread and is open in an upper region to allow the passage of a thread 4. The lower part of spindle 3 is surrounded by a rotor 5 that has a hollow central shaft 6 that is connected to pivot 2 and to a radial hole 7 for the passage of thread 4.

Shaft 6 of rotor 5 is directly coupled to an actuation motor 8. Preferably, shaft 6 is formed monolithically from the shaft of motor 8.

Motor 8 can be provided with studs 9 for anchoring the entire head to a supporting frame 10 of a thread processing machine, for example a twisting machine, so as to allow interchangeability of the head 1 with other heads of the same type.

Motor 8 is of the brushless type, with cylindrical permanent magnets and with high efficiency, between 70% and 85%, even for low power levels on the order of 70W, as indeed required for the heads according to the invention. For this purpose, small brushless motors with cylindrical permanent magnets are used which have been applied so far in computer hard disks, compact discs, and similar devices.

A frequency-variation speed converter 11 is associated with motor 8 to control the power supply and the speed of the motor, promptly adapting them, without any manual or mechanical actuation of the coupling to the motor, as a function of the type and thickness of the thread to be processed. It also ensures extremely accurate speed control, with an error of less than 1% with respect to the preset speed.

Preferably, converter 11 is miniaturized so that it is inserted and integrated in the frame of motor 8 and so as to be supplied together with it, achieving great compactness with respect to previous heads.

Converter 11 is connected to the power supply bus by means of cables 12 and to a microprocessor-based central control unit 14 by means of cables 13. Unit 14 can be connected to other motors 15 for the actuation of different devices, for example thread guiding eyes or winders that are associated with each individual head, by means of respective converters 16.

Central unit 14 also internally comprises a closed-loop regulator circuit 17, using for example a P.I.D. regulator, which has the purpose of synchronizing the deceleration of the individual heads with the deceleration of the other devices associated with them if mains power fails; this circuit is of the type described and claimed in the Italian patent application No. VI95A000112 in the name of this same Applicant.

Advantageously, the power supply current of motor 8 is at low voltage, for example 48V. In this manner it is possible to use the same bus to supply the converters as well, providing considerable reductions in insulation costs and increasing the intrinsic safety of the unit, since the assigned personnel can safely handle the heads with no danger of electrocution.

From the above description it is evident that the motorized head with rotating spindle according to the invention achieves the intended aim and all of the objects, and in particular its high efficiency, its low noise level, and its compact size, flexibility, and safety are pointed out.

The motorized head according to the invention is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept as expressed in the accompanying claims.

Claims (7)

1. A motorized head for multiple-head machine for twisting threads or for similar operations, each head comprising a supporting pivot (2) for a threaded spindle or reel, motor means connected to said rotor (5) to promote rotation thereof, being said rotor (5) coaxial to said pivot (2) for winding up and twisting the threads, said motor means comprising a single electric motor (8) of the high-efficiency, brushless-type coupled to said rotor (5), an electronic circuit (11) for controlling the speed and power supply of said motor (8), independent of the circuits of the other heads, said electronic circuit (11) being a miniaturized frequency converter integrated in the motor frame, characterized in that each head is coupled to other motorized devices such as thread guiding eyes or winders, said brushless-type motor (8) having permanent magnets of cylindrical shape, said electronic circuit (11) having means for connection to an external closed-loop regulator circuit (17) adapted to synchronize the speed of the head with those of the other devices connected thereto in case of failure or gaps in the mains power supply.
2. The motorized head according to claim 1, wherein said rotor (5) has a shaft (6) which is formed monolithically from the shaft of the motor (8).
3. The motorized head according to claim 1, wherein said shaft (6) is hollow and connected to a radial hole (7) for the passage of the thread (4).
4. The motorized head according to claim 2, wherein the power supply current of said electronic circuit (11) and said motor (8) are both at low voltage.
5. The motorized head according to claim 4, wherein said electronic circuit (11) and said external closed-loop regulator circuit (17) are connected to a programmable central control unit (14) for controlling the operating parameters of the different heads.
6. The motorized head according to claim 1, wherein said means for connection between electronic circuit (11) and said external closed-loop regulator circuit (17) are chosen among serial-type or shift-register connections.
7. The motorized head according to claim 4 or 6, wherein said electronic and external closed-loop regulator circuits (11, 17) and said central control unit (14) are of the microprocessor-type.

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