58results about How to "No contamination" patented technology

This invention discloses a fine polishing solution for silicon wafer. The fine polishing solution is composed of: composite abrasive material 5-30 wt. %, surfactant 0.1-1 wt. %, chelating agent 0.1-1 wt. %, pH regulator 1-6 wt. %, and deionized water as balance. The composite abrasive material is composed of water-soluble silica sol and Al2O3 hydrosol or CeO2 hydrosol at a weight ratio of 4:1. The composite abrasive material has particle sizes of 10-60 nm. The fine polishing solution has such advantages as small particle sizes of the composite abrasive material, no damage to wafer surface after polishing, high polishing speed, high fluidity, and no sodium ion contamination (by using organic alkali as the pH regulator). By utilizing nonionic surfactant, the composite abrasive material and the reaction product can be easily removed from wafer surface.

The invention relates to an anti-skid matte ceramic tile. A microporous forming agent is introduced to overglaze of the ceramic tile. Micropores in the glaze layer on the surface of the ceramic tile are formed in a firing process. The microporous forming agent is composed of one or more of fluorite, cryolite and fluorapatite. The ceramic tile is composed of a blank, bottom glaze and surface glazeattached to two faces, separately, and the microporous forming agent introduced into the glaze. The bottom glaze is prepared from the following components: quartz, albite, potash feldspar, calcined talc, zirconium silicate, kaolin, calcined kaolin, aluminum oxide and a matte opacified melt block. The surface glaze is prepared from the following components: calcined zinc oxide, albite, potash feldspar, kaolin, calcined talc, calcined kaolin, dolomite, wollastonite, a matte transparent melt, a bright and transparent melt and the microporous forming agent.

The invention discloses a transport cart for textile winding wheels. The transport cart comprises a box, supports are fixedly connected to the two sides of the back of the top of the box respectively, a handrail is fixedly connected to the top of each support, a first clamping block is fixedly connected to the right side of the top of the box, a through groove is formed in the top of the inner wall of the box, and a first sliding groove is formed in the right side of the bottom of the inner wall of the box. By arranging the box, the first clamping block, the through groove, the first sliding groove, a bearing platform, a second sliding groove, a movable base, a screw, a rotating plate, a handle, a clamping groove, a screw block, a first sliding block, a movable column, a second sliding block, a movable block, a second clamping block, a protection box, a connecting block, a third clamping block, a movable column, a spring and a pulling block which cooperate with one another, the clamping effect is achieved, when workers transport the winding wheels, the winding wheels are not likely to fall off, it is guaranteed that cloth cannot be polluted, the working efficiency of the workers is improved, and the transport cart is suitable for application and popularization.

The invention relates to an anti-skid glaze and an anti-skid ceramic tile, wherein the anti-skid ceramic tile consists of a blank layer, a surface glaze layer, an ink jet layer and an anti-skid glazelayer. The anti-skid glaze comprises 5 to 15 parts of albite, 20 to 30 parts of potash feldspar, 20 to 35 parts of nepheline, 8 to 12 parts of kaolin, 5 to 15 parts of dolomite, 3 to 8 parts of talc,5 to 15 parts of superfine quartz powder, 3 to 8 parts of alpha alumina, 0.4 to 0.8 part of carboxymethyl cellulose and 0.2 to 0.5 part of sodium tripolyphosphate.

The invention provides an electrochromism device which comprises a first transparent substrate and a second transparent substrate which are relatively arranged, wherein a first transparent conductive layer and an electrochromism layer are formed on the internal surface of the first transparent substrate; the first transparent conductive layer is arranged between the first transparent substrate and the electrochromism layer; a second transparent conductive layer and an assistant electrochromism layer are formed on the internal surface of the second transparent substrate; the second transparent conductive layer is arranged between the second transparent substrate and the assistant electrochromism layer; adhering layers are arranged on peripheral edges of the electrochromism layer and the assistant electrochromism layer; the electrochromism layer, the assistant electrochromism layer and the adhering layers enclose a cavity in which an ion conducting layer is arranged, wherein the ion conducting layer is in a form of gel. The invention also provides a preparation method of the electrochromism device. According to the electrochromism device, the ion conducting layer is in the form of the gel, so coloring or discoloring can be carried out by exerting a relatively low voltage; shorter time is used; and high stability is ensured.

The invention discloses a method for separating and preparing anti-tumor components ganoderic acid C1 and ganoderic acid F, which comprises the following steps: (1) primarily enriching and purifying the alcohol extract of lucid ganoderma by use of macroporous resin, and separating a ganoderic acid part with purity of 30-60% from the alcohol extract of lucid ganoderma; (2) separating the separated ganoderic acid part through high-speed counter-current chromatography to obtain ganoderic acid with relatively high purity, wherein a solvent system consists of petroleum ether, ethyl acetate, methanol and water at a volume ratio of 5:(3-7):(1-6):(4-9); the upper phase of the solvent is a stationary phase, and the lower phase is a mobile phase; a sample is dissolved with the lower phase solution and fed; the flow velocity of the stationary phase is 10-20mL / min, the flow velocity of the mobile phase is 1.5-3mL / min, and the rotation speed of the host is 600-1,000rpm; the separated object is collected by an automatic fraction collector, and one fraction is collected from every 4-10mL; (3) analyzing and detecting the components of the liquid collected by each test tube by high performance liquid chromatography, collecting, concentrating and drying according to different components, and separating to obtain ganoderic acid C1 and ganoderic acid F with purity up to 95%. The method has the characteristics of high efficiency, high speed, large separation quantity, high recovery rate, solvent saving and the like.

The invention relates to a negative-pressure drainage device and belongs to the technical field of medical equipment. The negative-pressure drainage device comprises a liquid-collecting bag, wherein a closed cover is arranged on the top of the liquid-collecting bag; and a drainage pipe interface and a liquid discharge interface are arranged on the closed cover. The negative-pressure drainage device is characterized by also comprising a bottle body, wherein a tee joint connected with a negative pressure source is arranged on the bottle body; the tee joint is communicated with a bottle body cavity of the bottle body; the liquid-collecting bag is positioned in the bottle body cavity; the closed cover is matched with an opening part of the bottle body; a negative-pressure suction interface communicated with a bag cavity of the liquid-collecting bag is arranged on the closed cover; one end of a connecting conduit is arranged on the negative-pressure suction interface; and the other end of the connecting conduit is connected with the tee joint in a matched manner. The negative-pressure drainage device has the advantages that: the negative-pressure suction effect can be effectively improved; the liquid-collecting bag can be protected by the bottle body, so pollution caused by accidental damage to the liquid-collecting bag is avoided; resource can be saved and using cost is reduced; and the negative-pressure drainage device is convenient to operate.

The present invention is direct synthesis process of hydrophobic nanometer silica line with ZnS powder, and belongs to the field of nanometer material technology. The present invention adopts silicon chip as the reaction substrate and silicon source, solid ZnS powder as reaction supplementary material and inert gas argon as the protecting gas and carrier gas to grow nanometer silica line on the silicon chip, and vaporization coats one layer perfluorosilane on the surface of synthesized nanometer silica line to obtain hydrophobic nanometer silica line with contact angle greater than 140 deg. The process is simple and practical, uses no metal catalyst, and has no environmental pollution and high safety, and the product has high hydrophobicity and wide application.

The invention provides an absorption spectrum collection sample room for analyzing a liquid absorption spectrum. The sample room comprises a sample tube, a light beam transmitting end and a light beam receiving end, wherein a cavity of the sample tube is used for carrying a liquid sample; the light beam transmitting end is connected with a port of the sample tube, and a light beam is guided along the longitudinal direction of the sample tube; the light beam receiving end is connected with the other port of the sample tube to receive the light beam which passes through the liquid sample in the cavity of the sample tube; and the inner wall material of the sample tube and the cross sectional dimension of the cavity of the sample tube are selected to realize that the liquid sample can form a liquid column, which is separated from the two ports, in the horizontal sample tube due to solid-liquid interface tension between the liquid sample and the inner wall of the sample tube, so that the light path of the light beam in the sample tube is from the light beam transmitting end, an air column, the liquid column, an air column to the light beam receiving end in sequence when the absorption spectrum is collected. After the structure and the light path are adopted, the liquid sample, the light beam transmitting end and the light beam receiving end are separated from one another by the air columns, so that the condition that an optical interface is polluted can be avoided, the thickness of an absorption layer can be adjusted and controlled by the volume of added liquid according to actual requirements, and an absorption spectrum signal with higher signal to noise ratio can be obtained.

The invention relates to the field of civil engineering, in particular to a structure and a method for preventing reinforcing steel from being corroded in a highly-corrosive environment. The method for preventing the reinforcing steel from being corroded in the highly-corrosive environment comprises the following steps: wrapping exposed reinforcing steel with a plastic thin film, and performing winding and sealing to form a first protective layer by adopting an adhesive tape; sleeving the wrapped exposed reinforcing steel with a sleeve of which the diameter is matched with that of the exposed reinforcing steel to form a second protective layer; sealing the top of the sleeve by virtue of a sealing cover; sealing a gap between the sleeve and a concrete structure by virtue of mortar. According to the structure and the method, the two protective layers are provided for the exposed reinforcing steel, an operation process is convenient, sealing effects are reliable, and anticorrosive effects are prominent; compared with a conventional process for smearing the reinforcing steel with cement slurry to isolate the corrosive environment, the method has the advantages that a cumbersome process of removing the cement slurry in a later period is eliminated, damage to an exposed screw head rolled with a straight thread on the reinforcing steel is avoided, the reinforcing steel is prevented from being polluted by pollutants in an offshore highly-corrosive environment, and influence on the bonding strength of concrete in the later period is eliminated.

The invention relates to a nutrition pump, an infusion device, a control valve and a liquid control method. The nutrition pump comprises a pump body and an infusion device, the infusion device comprises a control valve, and a pump wheel is arranged on the pump body; and the control valve comprises a valve body and a valve core which is in cooperative connection with the valve body, the valve bodycomprises a first input pipe and a second input pipe which are used for being connected to a liquid to be transfused, a cylindrical structure and an output pipe which is used for outputting the liquidto be transfused, one end of a switching shaft is connected to a motor, and the other end is connected to the valve core, so that the motor drives the valve core to rotate through the switching shaft. The nutrition pump can realize the free switching of two liquids, eliminates the liquid tainting risk in the nutrition pump feeding process, and has low cost and high precision.

The invention discloses a microwave rapid dissolving method for rhodium powder. The rhodium powder reaches a certain granularity through mechanical pretreatment; a proper solvent is added into the rhodium powder; and the rhodium powder is dissolved through a working program of a selected microwave instrument in a sealed manner. The rhodium powder with a mass about 0.1 g can be entirely dissolved within 4 hours. The microwave rapid dissolving method for the rhodium powder can be applicable to converting a solid sample into a solution in preparation of a pure rhodium standard solution, purity detection of the rhodium powder, and high-rhodium content rapid and accurate detection.

The present invention relates to a bubble attack method capable of making warship be completely sunken (be captured) and its equipment. It is characterized by that said method can release bubbles with a certain density into water, so that it can forcedly make the specific weight of mixture body of water and air be reduced to make the warship on the water surface lose original buoyant force and can be quickly sunken into water so as to implement the goal of adopting the invented 'bubble trap' mode to attack warship. Its equipment includes the following several portions: submarine, liquid air storage tank boat and liquid air releasing tube group, etc.

The present invention relates to dust-free chalk and its making process. The material for the dust-free chalk consists of stuffing 40-50 weight portions, coloring agent 1-20 weight portions, adhesive30-35 weight portions and assistant 10-15 weight portions. The present invention has the following advantages: clear writing on available blackboard, no dust contaminatino to writer's fingers, face and clothing and no dust residuum on the blackboard after erasting with available blackboard eraser.

The invention discloses a safe long-acting natural lavender solid essential oil, and a preparation method thereof. The safe long-acting natural lavender solid essential oil is prepared from natural lavender essential oil, beta-cyclodextrin, and calcium alginate. The preparation method comprises following steps: 1, a sodium alginate aqueous solution is prepared; 2, a calcium chloride solution is prepared; 3, natural lavender essential oil, an emulsifying agent, and deionized water are subjected to homogeneous emulsification so as to obtain a homogenized emulsion, the homogenized emulsion is added into the sodium alginate aqueous solution, and stirring is carried out so as to obtain a uniform mixed solution; 4, beta-cyclodextrin is added into the uniform mixed solution obtained in step 3; 5, a mixed liquid obtained via step 4 is added into the calcium chloride solution obtained in step 2, and solidification is carried out for 2h so as to obtain a solid essential oil suspension liquid; and 6, the solid essential oil suspension liquid obtained in step 5 is subjected to vacuum suction filtration, washing, and drying so as to obtain the solid essential oil. The preparation method is capable of avoiding defects of liquid essential oil fundamentally; fragrance holding time is long; leakage and contamination are not easily caused; the safe long-acting natural lavender solid essential oil is convenient to use; and the preparation method is scientific, and is convenient.

The invention discloses a tea pressing method of a tea pressing machine. The tea pressing method comprises the following steps: A, starting a transverse pushing air cylinder for matching a right halftea cake forming mold with a left half tea cake forming mold to form a tea cake cavity; B, adding tea into the tea cake cavity through a tea outlet; C, starting a lifting air cylinder for lifting an extrusion mold into a tea cake extrusion hole; D, starting the transverse pushing air cylinder, driving the right half tea cake forming mold by the transverse pushing air cylinder to push the left halftea cake forming mold to abut against a limiting block; E, starting the lifting air cylinder to enable the extrusion mold to continue to ascend to perform extrusion on the tea in the tea cake cavity;and F, starting the lifting air cylinder to enable the extrusion mold to descend to a tea cake discharge table and taking down a tea cake from the extrusion mold. Compared with the prior art, the teacake produced by the tea pressing method has high smoothness and high hardness and the tea pressing method cannot lead to a phenomenon of contamination of tea and improves the production quality of tea cakes.

The invention provides a cleaning process of a germanium single crystal single-sided polished wafer. The cleaning process is characterized in that germanium single-crystal single-sided polished waferis roughly polished by pasting a UV film on the back surface, the UV film on the back surface of the wafer is removed, the wafer is subjected to soaking in concentrated sulfuric acid twice to remove residual glue contamination on the edge of the germanium single-crystal single-sided polished wafer, fine polishing is performed, cleaning is performed with potassium hydroxide solution after fine polishing, and lastly, an SC-1 liquid cleaning mode is adopted, so surface contamination of the germanium single-crystal single-side polished wafer is effectively removed, the surface requirement of cleaning-free box opening for use is met, the surface quality of the germanium single-side polished wafer is greatly improved, and a good foundation is laid for subsequent improvement of the quality of anepitaxial layer of the germanium single-side polished wafer. The cleaning process is advantaged in that the cleaning process is simple to operate and easy to implement, cleaning difficulty of the germanium single-crystal single-sided polished wafer is reduced, and batch production is easy to realize.

The invention provides a manufacturing method of an array substrate. The method comprises the following steps: forming a gate metal structure on a substrate; forming a gate insulating layer on the gate metal structure; forming a semiconductor structure on the gate insulating layer and forming a channel; forming a metal structure having source and drain electrodes on the semiconductor structure; forming an insulating protection layer on the source and drain electrodes, and forming a via hole on the insulating protection layer; and forming a pixel electrode on the insulating protection layer. In the manner, the phenomenon that a channel semiconductor is polluted by Cu metal oxidation and diffusion can be avoided, so that the characteristics of a thin film transistor (TFT) can be ensured, and the display effect of a display is not affected.

The invention discloses an all-dimensional automatic punching apparatus used for precise pipe fittings. The all-dimensional automatic punching apparatus comprises a machine base, a pipe fittings punching base, a Z-axis cutter mechanism and a microcomputer control mechanism, and is characterized by further comprising an X-axis pipe fittings moving mechanism and an R-axis pipe fittings rotating mechanism; the X-axis pipe fittings moving mechanism comprises an X step motor; the R-axis pipe fittings rotating mechanism comprises an R step motor, a pipe fittings clamp and a rotating wheel; the rotating wheel in the R-axis pipe fittings rotating mechanism is engaged with a screw on an upper crew rod of the X-axis pipe fittings moving mechanism; the Z-axis cutter mechanism comprises a Z step motor, a punching cutter, a cutter control mechanism, and a scrap removing launching mechanism; an instruction signal transmission device is respectively arranged between the microcomputer control mechanism and each mechanism of X-axis, R-axis and Z-axis; the punching apparatus has the following advantages: with the adoption of the technical means of the three-dimensional control, an closely enveloped type air bag clamp, the scrap removing launching mechanism, and the like, the hole position location is exact, the shape error is small, the size precision is high, and the purpose of all-dimensional continuous automatic punching can be fulfilled.

The invention discloses a preparation method of a wet-process zinc oxide pre-dispersion master batch, which comprises the following steps: dispersing zinc oxide, an inorganic carrier, a modifier and aprocessing aid in a first part of water to obtain mixed slurry A; uniformly stirring a rubber emulsion, a stabilizer and a second part of water to obtain a rubber liquid B; mixing and flocculating the mixed slurry A and the rubber liquid B to obtain a zinc oxide and rubber compound; and drying and granulating the zinc oxide and rubber compound to obtain the zinc oxide pre-dispersed master batch.Zinc oxide in the prepared zinc oxide pre-dispersion master batch is better in dispersity, smaller in particle size and higher in activity. In the formula, the zinc oxide pre-dispersed master batch isequivalent or reduced by 40% to replace indirect zinc oxide or ZnO-80, the Mooney viscosity, the scorch time and the vulcanization rate of the unvulcanized rubber are basically kept consistent; physical and mechanical properties of vulcanized rubber are basically kept consistent before and after aging.

The invention discloses an antibacterial and bactericidal band-aid. The antibacterial and bactericidal band-aid comprises an adhesive tape, a sterilizing layer which is arranged in the middle of the adhesive tape and a protective film which is arranged on the adhesive tape and covers the sterilizing layer, wherein the sterilizing layer is formed by combining graphene or graphene oxide and P25TiO2.According to the band-aid provided by the invention, the sterilizing layer is formed by applying graphene fibers or graphene and TiO2 nano-fibers, which are prepared by virtue of an electrostatic spinning method, to the adhesive tape layer of the band-aid; the adhesive tape, which is designed to be transparent, is conducive to the implementation of TiO2 photocatalysis, so that effective antibacterial and bactericidal are achieved and wounds are protected from infection or inflammation; and meanwhile, the graphene, which has an extra-large specific surface area and a strong adsorbing capacity,is beneficial for keeping the surfaces of the wounds dry and is capable of accelerating the healing speed of the wounds.

The invention discloses rice wine and production technology thereof. A formula of the rice wine comprises the following ingredients: glutinous rice, purified water, distiller's yeast, sugar and additives; and more specifically, the formula of the rice wine comprises the following ingredients in the following parts by weight: 20-30 parts of glutinous rice, 25-35 parts of drinking water, 0.01-0.03 parts of distiller's yeast, sugar and additives, 5-7 parts of sugar, and 1-3 parts of additives. The production technology of the rice wine comprises the following steps: step one, selecting raw materials; step two, soaking the rice, and carrying out steaming; step three, blending the steamed rice with the distiller's yeast, and carrying out fermentation; step four, carrying out blending and filling; and step five, carrying out sterilizing and warehousing. The additives consist of sodium citrate and potassium sorbate, wherein the sodium citrate and the potassium sorbate are mixed at a ratio of1 to 1; and the sugar comprises one or multiple selected from white granulated sugar, yellow sugar and crystal sugar. The rice wine is rich in nutrients, low in ethanol content, high in calorie, and aromatic, sweet, pure and tasty in flavor; as the ethanol content is low, the rice wine has wide range of applicable people. Being taken in proper quantity, the rice wine is capable of building up a good physique, strengthening the body, dispelling dampness, dispelling toxins, tonifying Qi, nourishing blood, promoting digestion, and activating circulation of the blood to dispel cold; and moreover,the production technology is smooth, good in sanitary conditions and free of contamination, so that the produced rice wine is safe for drinking.

A 'moving trap' weapon sinking ship and its attacking method are mainly decreasing specific gravity of air mixture by shooting bubble for sometime from under water, that is through physical method of decreasing buoyancy to ship, attacking enemy ship with 'bubble trap' to sink it; the weapon is a moving liquid as storage craft under water C; its action is conducted mainly by sonar telecontrol method of our submarine D; the best military way to use it is: hides under water, to fast move into 'trap' water area A meanwhile shoots 'bubble' to attack; the newest war concept realized by it is : to sink and capture enemy ship (including aircraft carrier) B without our injury or death. The invention can be used freely though agreement and supported technically.

The invention discloses a rice frog breeding system and a rice field frog breeding method. The rice frog breeding system comprises a rice field and anti-escape devices arranged around the field balksof the rice field; a plurality of feeders are arranged at the field balks of the rice field; and the feeders comprise fecal material storing devices and fodder discharging pipes, the fecal material storing devices are used for storing fecal materials and fly maggots, one ends of the fodder discharging pipes communicate with the fecal material storing devices, and the other ends, serving as fodderdischarging outlets, of the fodder discharging pipes extend into a frog breeding area of the rice field. By building the fecal material storing devices and the fodder discharging outlets on the fieldbalks of breeding rice field parcels, the fecal material storing devices are filled with the fermented fecal materials, egg collecting materials are put on the fecal materials to trap flies to lay eggs or maggot pupas are directly put into the egg collecting materials, when the maggot eggs hatch, the fly maggots gather towards the fodder discharging pipes under trapping of light of the fodder discharging outlets and climb out from the fodder discharging outlets, and thus foodstuffs are continuously provided for frogs.

The invention provides a production process of a stainless steel water meter shell. The production process mainly comprises the following steps: processing and manufacturing of various components of the water meter shell, welding assembling, sand blasting treatment of the shell after the welding assembling is completed, installation size processing, machine core positioning groove processing, and sealing and pressure resistance pressing test process flows. By utilizing the process, the production and manufacturing of the stainless steel water meter shell can be realized, the quality of the water meter shell can be improved, meanwhile, compared with the traditional casting process, the technological process has no serious air environment pollution problem, and is beneficial to popularization and application, furthermore, in the technological process, the number of components is small, and assembling is easy to realize, so that the production efficiency of the water meter shell can be greatly improved.

The invention discloses a microbial organic compost and a preparation method thereof. The microbial organic compost is prepared from a main raw material and an addition microbial inoculum, the main raw materials comprises, by weight, 50-70 parts of mud, 80-100 parts of water hyacinth, 50-80 parts of wood chip, 20-30 parts of peat, 5-10 parts of urea, 10-20 parts of slaked lime, 30-50 parts of leaf, 6-14 parts of phosphoric acid and 30-50 parts of bone meal, and the addition microbial inoculum comprises, by weight, 3-8 parts of a decomposition agent, 4-10 parts of zymocyte, 5-8 parts of a biocatalyst, 3-6 parts of an EM microbial solution, 5-10 parts of Bacillus spp. and 2-5 parts of cellulase. The microbial organic compost has the advantages of long fertilizer effect, large fertility, environmental protection, promotion of absorption and growth of plants, and improvement of the fertile degree of land.

The invention discloses an intelligent plastic stool machining device capable of achieving centralized waste material recycling. The intelligent plastic stool machining device comprises a track for collecting waste materials generated during plastic stool machining, the track is of a spiral structure, and a standing area for a worker to stand is arranged on the middle portion of the track. When the worker stands in the standing area to conduct burr removal machining on a plastic stool, redundant burrs on the plastic stool can directly fall on the surface of the track when being cut off, the waste materials can slide down along the surface of the track, a movable plate can be operated to obliquely and upwards open due to elastic deformation of a rubber block, and therefore the worker in the standing area can enter and leave the standing area, and the intelligent plastic stool machining device is convenient and practical. When the worker stands in the standing area to conduct burr removal operation on the plastic stool, the falling waste materials can directly fall on a circle of the track, the phenomenon that contamination is caused when the waste materials fall on the ground and are swept up for use is avoided, and practicability is high.

Provided is an intermittent printing apparatus capable of preventing a slip and a deviation in printing registration from being caused when a base material to be printed is travelled. A step-back roller 6 on a sheet introducing side and a step-back roller 10 on a sheet discharging side are synchronously and rotationally driven forwardly to make a base material to be printed W travel forwardly, sothat image printing is effected on the base material to be printed by an impression cylinder 9 and a blanket cylinder 8, and the step-back roller 6 on the sheet introducing side and the step-back roller 10 on the sheet discharging side are synchronously and rotationally driven backwardly to make the base material to be printed W travel backwardly. The base material to be printed W is wound arounda peripheral surface of the impression cylinder 9 at a prescribed winding angle, the base material to be printed W is pressed against the peripheral surface of the impression cylinder 9 by a nip roller 42 for impression cylinder, and the impression cylinder 9 is rotationally driven forwardly and backwardly in synchronization with the step-back roller 6 on the sheet introducing side and the step-back roller 10 on the sheet discharging side.