Textiles: knitting – Miscellaneous
Reexamination Certificate
1999-12-13
2001-01-23
Falik, Andy (Department: 3741)
Textiles: knitting
Miscellaneous
C066S232000, C066S08500A
Reexamination Certificate
active
06176104
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to an actuator device or the controlled movement of members in knitting machines including a brushless motor, of the type comprising an electric motor having an output shaft operable in rotation, an electric energizing unit for a controlled supply of power to said motor, a kinematic transmission mechanism for operatively connecting the output shaft of the motor to a member to be operated in a knitting machine.
DESCRIPTION OF PRIOR ART
It is known that in knitting machines such as crochet machines for warp knitting also called crochet galloon looms, formation of an article of manufacture takes a ace by mutual interlacing, following predetermined patterns, of a plurality of warp yarns and weft yarns, suitably engaged by respective knitting members, such as needles, eye-pointed needles and threading tubes, for example.
These knitting members are operated by synchronized cyclic movements, to cause a mutual interlacing of the threads in accordance with the desired knitting pattern.
Generally, the synchronized and controlled movement of the different knitting members takes place by appropriate kinematic mechanisms made up of cams and mechanical-transmission means for example, that directly or indirectly terminate at a main shaft of the knitting machine, driven in rotation by a motor.
Use of the above mentioned kinematic mechanisms however, involves several problems, among which the most important is a limitation in the operating speed of the knitting machine arid, above all, the difficulty of preparing and setting up the machine each time the type or article of manufacture being produced is to be changed or modified, in addition to all problems connected with the production complexity of the kinematic mechanisms themselves.
In order to obviate the above problems, replacement of given mechanical kinematic mechanisms with appropriate servomotors has been proposed, which servomotors, suitably managed by a programmable electronic control unit, carry out operation of the individual knitting members connected thereto.
In his connection, the same Applicant has developed a driving device for the horizontal movements of the carrier slide bars in a crochet machine for warp knitting, in which the traditional cam chains, usually called “Glider chains” are replaced by a series of stepping motors each of them being connected with one of the carrier slide bars by a connecting rod-crank linkage. Thus, each carrier slide bar is driven in a reciprocating motion in a longitudinal direction, the oscillation amplitude of said bar varying in accordance with predetermined patterns, as a result of angular rotations given to the output shaft of the respective motor according to angular amplitudes correlated with the breadth of the horizontal translation to be transmitted to the bar.
In more detail, each stepping motor s is Managed by an energizing unit electrically activating it in an appropriate manner, depending on the instructions received by a programmable electronic control unit supervising operation of all stepping motors mounted on the knitting machine.
Power supply to each stepping motor takes place by electric-pulse trains, where each pulse corresponds to one rotation of the motor shaft corresponding to a predetermined angular “pitch”.
Following a given instruction received from the electronic control unit, the energizing unit will transmit a pulse train to the respective motor, the number of said pulses being adapted to impose an angular rotation of the desired amplitude to the output shaft, which is correlated with the breadth of the translation to be transmitted to the carrier slide bar.
Since the angular displacement carried out by the output shaft is directly correlated with the number of electric pulses sent to the motor, operation by a stepping motor is conceived as operation with a so-called open-loop control system without feedback. In other words, control of operation of each motor exclusively relies on the number of electric pulses contained in the individual pulse trains which are sent each time to the motor, and no detection is carried out, during accomplishment of the angular rotation, for the purpose of controlling how the rotation actually takes place.
The only verification carried out in known devices is that of ascertaining with the aid of appropriate sensors and after the movement has occurred, whether the preestablished position of the output shaft and/or the carrier slide bar has been reached or not.
The above devices being the object of patents EP 5333630 and EP 654331, have brought important improvements as compared with traditional kinematic mechanical mechanisms.
In particular, important advantages have been achieved in terms of simplification of the operations for setting up the machine each time the type of article of manufacture being produced is to be modified or charged.
In fact the knitting machine lends itself to be set for a new production by merely loading the program relative to the type of article of manufacture to be produced, into the electronic control unit.
However, it has been found that the above mentioned devices using stepping motors still have some problems as regards operation at high operating speeds. In particular, the Applicant has found that these problems essentially result from the fact that operation of stepping motors is such that each motor has a tendency to immediately cause stopping of translation in coincidence with the desired angular position of the output shaft and therefore has a tendency to impose important decelerations to all mechanical members connected to the output shaft itself. However, due to the masses of the components connected with the output shaft, actually it is impossible to obtain an immediate stopping of the translation. On the contrary, stopping occurs aster a short transitory period of time in which the carrier slide bar, or another member connected to the output shaft, performs several oscillations around the nominal stopping point. This phenomenon is emphasized by the fact that, at the nominal stopping point, the stepping motor appears to be unable to produce important torques in opposition to outer forces such as those due to inertia tending to cause rotation of the output shaft.
As a result, in spite of the fact that stepping motors have been conceived In a manner adapted to cause an instantaneous stop of their movements, for the above described reasons they do not appear capable of stopping the carrier slide bars at the exact stop position of their movement in a sufficiently quick manner.
Attempts have been made to obviate these problems by trying to make the carrier slide bars and the kinematic transmission mechanisms as light in weight as possible, but improvements thus achieved are very modest if compared with market requirements.
It has been also found that the great number of electric connections between each energizing unit and the respective motor, carried out as physically distinct and separated units, imposes adoption of particular precautions aiming at neutralizing the effects of electromagnetic waves emitted from the motors themselves and/or other members associated with or close to the knitting machine, that would bring about further negative effects on the operating reliability and precision of the machine taken as a whole.
SUMMARY OF THE INVENTION
In accordance with the present invention, it has been found that the problems of the known art can be brilliantly solved if, instead of the stepping motors, electric motors of the brushless type are used, i.e. electronic-commutation permanent-magnet synchronous
In particular, it is an object of the present invention to provide an actuator device for the controlled movement of members In knitting machines, wherein said electric motor is a brushless motor.
It is a further object of the invention to provide a knitting machine, in particular a crochet machine for warp knitting, equipped with at least one actuator device in accordance with the Invention, as well as use of a brushless motor for
Omodeo Zorini Luigi
Rosso Piermario
Conte Robert F I
Falik Andy
Lee Mann Smith McWilliams Sweeney & Ohlson
Luigi Omodeo Zorini
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