At the present time the greatest part of inventory of the sewing enterprises is formed with the help of universal sewing machines to be more energy-consuming per unit of output.
In the Federal law No. 261-FZ «About energy saving and improving energy efficiency» from 23.11.2009 (an edition of 29.12.2014) in Article 10 it is pointed out that: «goods produced in the territory of the Russian Federation and are imported must contain information about the class of energy efficiency». In the Resolution adopted in connection with this law from December 31, 2009 «Concerning the improving rules of requirements establishment of energy efficiency of goods, works and services» requirements of energy efficiency are established, the drives to sewing machines are also mentioned in the list of goods [1].
Significant economy of the electric power can be reached in case of using regulated electric drives for management of engineering procedures when sewing.
Up to present time at many sewing shops of Russia more than 70 % of sewing machines are completed with the obsolete equipment with electric drives which can be divided into five primary groups [2].
The main types of drives of industrial sewing machines and the analysis of their functionality are presented in table 1.
Table 1
Classifications of the sewing machines’ drives
|
Drive type ШМ |
Advantages |
Disadvantages |
|
Frictional |
produces small fluctuations of speed when operating due to the mass of a friction mechanism and flywheels |
1) Long dispersal and stop of sewing machines. 2) An electric motor can be overheated in case of the frequent activations. 3) The increased electric power expense |
|
Frictional with a reducer |
Stop of working bodies in set position |
1) Impossibility of the automatic start-up and stop, as well as changing rotation frequency of the main shaft. 2) The increased electric power expense |
|
With the auxiliary electric engine |
Stop of sewing machines' working bodies in a set position. Use of the auxiliary electric engine as driving and brake motors |
1) Great mass-dimensional indicators. 2) Hard thermal mode of the auxiliary electric motor. 3) The increased electric power expense |
|
With the collector electric engine |
Possibilities for smooth regulations of rotation frequency of the sewing machine main shaft |
1) Hard thermal engine mode. 2) Availability of mobile electric contacts reducing electric motor service life |
|
With the electromagnetic coupling element |
Needle stop in set position |
1) Complexity of a design. 2) High cost. 3) The increased electric power expense |
1. In the frictional electric drive the flywheel is inserted on a shaft of the electric motor connected through a flange to the friction clutch case. Transferring movement from a shaft of the electric motor and a flywheel to the sewing machine is performed with moving conducted part of the drive inserted in a cover along an axis to the left. Thus the disk, having a slip made of frictional material, is situated on a surface of a flywheel and starts rotating. Together with the disk conducted drive shaft with the pulley is inserted on it in rotating. From a pulley with the help of a belt transmission the movement is transferred to a hand wheel and the main shaft of the sewing machine. When the conducted part of the drive along an axis to the right is moving, the disk with another frictional slip as brake slip is strictly fixed on a friction clutch cover. The conducted part of the drive (a disk, a shaft, and a pulley) and the main shaft of the sewing machine stop [3].
In the course of operation the electric motor is switched on all the time (a long operating mode with variable loading).
Using frictional electric drive we have the following disadvantages: small reloading capability of electric motors of common industrial series and, as a result, long dispersal of the sewing machine; rather long moment of inertia of the drive conducted part which negatively influences the period of dispersal and braking; hard effort of pressing a pedal and, as a result, increased fatigue of a worker who uses the machine.
2. The electric drive with the asynchronous electric motor, a reducer and frictional clutch couplings represents the frictional electric drive of the sewing machine which is supplied with the reducer of rotation frequency switched either mechanically, or by electromagnetic frictional couplings, and a brake mechanism for a stop of working bodies in a set position.
By pressing a pedal the frictional disk nestles on a flywheel, rotation from the electric motor is transmitted directly to the conducted part of the drive and through the belt transmission from the main shaft of the sewing machine.
The process of turning on of the brake electromagnetic coupling may happen only after achieving a rotation frequency of finishing operation by the main shaft and the position of «needle above» or «needle below» position of it [3].
Drives of sewing machines made by English firm «Hansen Glove. Corp». can be related to the same group of electric drives.
We may refer automatic start-up and a sewing machine stop, as well as change of rotation frequency of the main shaft as main disadvantages of this electric drive types.
3. The electric drive with the asynchronous engine and auxiliary electric motor working with the low rotation frequency has had further evolution of the regular frictional drives referred to the first group. It consists of the same basic elements, as the drives presented in the first group, but movement of the machine with the low rotation frequency of the main shaft before a stop in a set position is done through the auxiliary engine [4].
Among the electric drives referred to the third group the electric drive of the sewing machine of the American firm «Union Special Machine» is of special interest. It consists of asynchronous electric motor of the main movement with the raised starting moment and the big moment of inertia and auxiliary asynchronous electric motor with high starting moment and low moment of inertia. The movement from the engine to the machine is transmitted through the frictional clutch coupling.
The third group includes electric drive sewing machine and the device for managing it made by American company «Zinger» in accordance with the patent No. 3170424, the device for a sewing machine stop at the set position of a needle produced by the company «American Sovety» in accordance with the patent No. 3149593 and a number of other similar electric drives, as well as aggregate Adler 801 produced by German company «Adler» are intended for processing and a stitching of a patch pocket to a man's shirt, in which is usually used an electric drive Quick-Rotan representing a combination of the electric drives referred to the first and second groups. At the maximal working rotation frequency of the main shaft and the rotation frequency of operational finishing the aggregate is set in motion from the electric drive similar to the Quick-stop drive, and for receiving the intermediate frequency of rotation when performing the composite contours of a seam (corners, clips) the auxiliary electric motor is used. The rotation frequency of this electric motor is twice less than a rotation frequency of the main electric motor of the drive [3, 4].
Despite apparent originality and simplicity of the construction, the aggregate electric drive Adler 801 has only three steps of a rotation frequency. The heavy thermal conditions of the auxiliary electric motor demands to use an auxiliary pneumatic actuator for start-up, stop and switching of a rotation frequency.
4. In electric drives in which collector electric motors of direct and alternating current are used, the rotation frequency is regulated by changing size of additive resistance in an anchor chain. As an example it is possible to represent the electric drive of the sewing machine of the West German company «Frankl Kirchner», adjusted electric drive of sewing machines of the West German company «Fritz Geganf Aktiengesellschaft Berkhina-Neemashinenfabrik» and the electric drive of the sewing machine described in the patent of the USA No. 3125050 which are in focus due to a big rotation frequency of a main shaft of the machine, as the electric motor works as the alternating-current collector engine, and at a low rotation frequency of a main shaft (at finishing work of a needle to set position) the engine of a direct current [4].
The scheme of regulating rotation frequency can be used by opposing electromotive force proportional to a rotation frequency induced in an anchor under anomalous field. influence This tension is used as a feed-back signal of a rotation frequency. Such scheme is especially favorable when operational stability is done at a low rotation frequency of a main shaft of the machine and there are fluctuations of power supply voltage. In electric drives with electric motors of a direct current or the collector asynchronous electric motor regulating a rotation frequency by means of range of speed changes the main disadvantage is rather heavy thermal conditions of engine run, bound to the big frequency of switching.
5. The electric drive with the use of electromagnetic couplings for start-up, stop and regulation of a rotation frequency of a main shaft allows us to use ordinary asynchronous electric motor as a source of a mechanical energy and at the same time to automate the process of start-up, change of a rotation frequency of a main shaft and stop of the sewing machine [4].
There are many electric drives in which the mechanical friction mechanism is replaced with electromagnetic clutch couplings, for example, the electric drive of the sewing machine of the English company «Bark Landen Limited», the electric drive with the device of stop of a needle of the sewing machine in the set position of the company «Frankl Kirchner», the electric drive with the device of the finishing mechanism and stop of a needle of the sewing machine in the set position of the American company «Electrician Brank and Glach Company» can be used and a number of other developing operations.
The electric drive of the sewing machine with an electromagnetic friction coupling consists of continuous rotating shaft of the asynchronous electric motor, a multiplate electromagnetic coupling clutch with a contacting current lead and a multiplate electromagnetic coupling of braking with a non-contacting current lead. The drive is equipped with the control system providing different faltering rotation at the low speed and a needle stop in the set position.
The electric drive of these machines is similar to the Quick-stop drive, but in contrast to this sewing machine drive can work at low rotation frequency of the main shaft that can be carried out not from the main drive through a space belt drive, but from the auxiliary low power electric motor. A disadvantage of drives of this type is rather complex design of electromagnetic couplings and high cost in comparison with the cost of other electric drives [4].
In practice the level of sewing mechanical engineering has considerably grown for the last 10–15 years, technical and technological capabilities of sewing machines have raised, their universal character has been increased. It is reached due to the broad application of electronic components and microprocessor control systems.
The leading machine-building companies of the world factories offer a wide set of new technologies with variable-frequent electric drive with an electronic control system and complete new technical solutions meet the need of consumers and factories.
These companies produce the universal machines of lockstitch only with the electronic drive and a number of electronic and mechanical modules which have allowed to automate a number of functions, as well as to equip the universal machines with padding mechanisms (cutting of edge of materials, change of sheaves, correction of material edge concerning a needle, adjustment of stitch length and others). On the other hand, using electronics allowed to improve technological capabilities of inventory, flexibility and mobility, durability and accuracy of connection, as well significantly reduce servicing time significantly.
References:
1. Russian Federation. The Law regulations. Concerning energy saving and power effectiveness improvement. Federal law No. 261 [is adopted by the State Duma from 23.11.2009].
2. Goryaynov M. F. Decrease in energy consumption of the universal sewing machines using variable frequency drive: thesis by Candidate of Science / Goryaynov M. F. — SRSUES in Shakhty, 2011. — 145 p.
3. Beskorovayny V. V. Technical means of the enterprises of service: Learning guide for higher education institutions V. V. Beskorovayny, L. V. Larina; Under the editorship of V. V. Beskorovayny. — M.: Publishing center «Akademiya», 2003.- 304 p.
4. Storozhev V. V. System techniques and mechatronics of technological machines and inventory: Monography/V.V., N. A. Feoktistov; under the editorship of the Doctor of Technical Science, professor Feoktistov N. A. — M.: Publishing and trade corporation «Dashkov and Co», 2015. — 412 p.
