【正文】 he outlet. As it goes on and on, the dust detained outside the filter bag increases, so it causes operating resistance of dust collector rising. If the resistance rises to the preset number(1245－ 1470Pa), the controller will send out signals, first to control the lift valve to do these operations: close the hole of the valve board to cut air current and stop filtering, and then to open the electromagic pulse valve to blow pressed air whose pressure is into filter bag with a short time(－ ). The pressed air immediately expands and swarms into filter bag, that make the bag to distort and vibrate, adding the effect of adverse air current, the dust detained outside of filter bag is dropped into the dust store bin. After the dedusting is finished, lift valve open again, and dust collector begin filtering once more. Plenum pulse bag type collector is made up of several partments, where dedusting is in order, and this is partmentbypartment offline dedusting. Its advantages are that the dedusting partment and the filtering partment do not interfere each other, help realizing longterm consecutive operating and improve dedusting effect. Dust collector using pursetype filter cloth 2 Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. 27. A preferred embodiment of the present invention is constructed so that mixed current containing dust is sucked into the filtering/dust collecting area through the top of the housing to remove fine solid material such as dust, and then purity air is discharged from the bottom of the housing. 30 In pursetype filter cloth 11 shown in FIG. 3, an important ponent of the present invention, retainers 12 of metal are installed in stack according to the vertical length of the pursetype filter cloth, as shown in FIGS. 5 and 6. According to this design, in order to increase the filtering area, the arrangement of the retainers is continuous not intermittent, and in turn the purging area of filtered clean air (purity air) increases in the respective units. Pursetype filter cloth 11 employed into the dust collector of the present invention are divided into various areas as shown in FIGS. 4A4D so that the purging of purity air is optimally performed independent of the load pressure loss of the filtering area and the length of the filter cloth, greatly reducing current resistance. In pursetype filter cloth 11, as shown in FIG. 5, the unit of retainer is established in such a manner that at least one, or multiple, if necessary, retainers 12 are stacked from the top 11a to the bottom 11b of filter cloth 11. In order to prevent filter cloth 11 from being deformed or distorted due to the mechanical operation of the dust collector, as shown in FIGS. 5 and 6, after a plurality of retainers 12 are stacked in filter cloth 11, a push plate 13 are put on a circular portion 11c formed on the mouth of the filter cloth, and then fastened by bolt 14 and nut 15. Referring to FIGS. 7A, 7B and 7C, pursetype filter cloth 11 of the present invention is made in which purity air purging velocity Vpa, intermediate entry velocity Vmi, and filtering position entry velocity Fev are distributed uniformly. In other words, the pursetype filter cloth bees the core of bining dust settling area 16, filtering/dust collecting area 17, purity air purging area 18, and dust discharging area 19. 31 For the respective explanations to the various shapes of the filter cloth such as bag, envelope and purse, the bagshaped filter cloth is cylindrical as shown in FIG. 1C. When this is fixed onto the filter cloth mounting plate, its filtering surfaces are trihedron (upper and lower surfaces and circumferential surface). In order to increase the filtering area, the circumferential surface must be increased in length (Fx) while diameter D is constant. The envelopeshaped filter cloth is rectangular and dihedral. In this case, in order to increase its filtering area, the length of envelope must bee longer, its width be changed, or the length and width of the envelope be increased simultaneously to thereby increase both sides thereof. This type of filter cloth is unfavorable to large or middlesized dust collectors in structure. The purseshaped filter cloth of the present invention is hexahedral, whose top and bottom have similar areas in the original form. In the present invention, two surfaces (upper and lower surfaces) of the hexahedron are set to be constant, and four sides of the twelve sides related to the remaining four surfaces are changed. As the filtering areas of two surfaces increase, the mouth area of the purse increases proportionally to optimally maintain the purging velocity of purity air. By doing so, the pressure loss of the dust collector is pensated to be favorable to the dust collecting function. Though this may be seen as a simple principle, it will be found in the later description that optimal filtering function is exhibited by harmonizing six (front, rear, upper, lower, left and right) kinds of velocity of the filter cloth. Pursetype filter cloth 11 of the present invention assists many functions, and has significantly more advantages than wellknown filter cloths. 32 According to these advantages, filter cloth 11 can be easily manufactured. In addition, pared with the conventional filter cloths whose filtering capacity is determined in design and thus extremely limited, the filter cloth of the present invention can exert the maximum of the filtering capacity according to the front, rear, left, right, upper and lower flow of mixed current from the center thereof. As shown in FIG. 2, the velocity of the current entering housing 1 through hood 5 from the dust source can be divided into a settling tank entry velocity at which mixed curren