CN204866542U - Two accurate graders of powder that drive of intelligence - Google Patents

Two accurate graders of powder that drive of intelligence Download PDF

Info

Publication number
CN204866542U
CN204866542U CN201520500971.2U CN201520500971U CN204866542U CN 204866542 U CN204866542 U CN 204866542U CN 201520500971 U CN201520500971 U CN 201520500971U CN 204866542 U CN204866542 U CN 204866542U
Authority
CN
China
Prior art keywords
rotating cage
meal
powder
pipe
cylinder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201520500971.2U
Other languages
Chinese (zh)
Inventor
吕海峰
曹海宁
徐中州
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jiangsu Jinengda Environmental Energy Science & Technology Co Ltd
Original Assignee
Jiangsu Jinengda Environmental Energy Science & Technology Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jiangsu Jinengda Environmental Energy Science & Technology Co Ltd filed Critical Jiangsu Jinengda Environmental Energy Science & Technology Co Ltd
Priority to CN201520500971.2U priority Critical patent/CN204866542U/en
Application granted granted Critical
Publication of CN204866542U publication Critical patent/CN204866542U/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Abstract

The utility model discloses a two accurate graders of powder that drive of intelligence, contains cyclone, selection powder room, first transmission shaft, a transmission, first motor, the hierarchical rotating cage of well middlings, lead the powder awl, the secondary drive axle, the secondary drive device, the second motor, the hierarchical rotating cage of farine, awl and air inlet discharging device are collected to well middlings, the upper end and a transmission of first transmission shaft link to each other, the dress is worn at the bearing frame that is arranged in the indoor lower part of selection powder through the bearing to the lower extreme of first transmission shaft, the hierarchical rotating cage of well middlings is worn the dress and is fixed the lower part at first transmission shaft, the secondary drive axle is the hollow tube structure, and the upper end of the secondary drive axle of this hollow tube structure and lower extreme and first transmission shaft pass through the bearing and constitute to rotate and is connected, and the lower tip and the hierarchical rotating cage of farine of the secondary drive axle of this hollow tube structure are continuous, leading the powder awl and being arranged in between hierarchical rotating cage of farine and the hierarchical rotating cage of middlings, the lower extreme of the hierarchical rotating cage of farine is arranged in the last port of leading the powder awl, and the lower port of leading the powder awl is arranged in the hierarchical rotating cage of middlings.

Description

Intelligence is two drives powder fine grading machine
Technical field
The utility model relates to a kind of powder separator, and particularly a kind of intelligence is two drives powder fine grading machine.
Background technology
At present in cement production process, in the whole grinding process of existing one half, containing powder separator in the equipment adopted.This powder separator contains separating chamber, cyclone separator, vertical drive shaft, spreading disk, big blade, meal collection cone, fines collection is bored, spreading disk is arranged on the bottom of vertical drive shaft, also containing middle meal collection cone, vertical guide vane, cage rotor, above-mentioned middle meal collection cone is arranged on the top of spreading disk, in this, meal collection cone is made up of upper and lower two cones, logical powder pipeline is provided with between upper and lower two cones, the lower cone upper outer circumference of above-mentioned middle meal collection cone is provided with vertical guide vane, above between two circumference on the upper lower cone top of above-mentioned middle meal collection cone, cage rotor is installed, this cage rotor excircle column is equipped with demarcation strip, this cage rotor be arranged on vertical drive shaft bottom and this installation site above spreading disk.Above-mentioned powder separator is selecting in powder process and the feed separation drawn off in ball mill can be become fine powder, middle meal and meal.Because above-mentioned powder separator is only that the powder selection device consisted of cage rotor and middle meal collection cone realizes three of powder and is separated, therefore effectiveness of classification is low, fineness regulation scope is little.
Utility model content
The technical problems to be solved in the utility model is to provide a kind of intelligence pair and drives powder fine grading machine, and this intelligence is two drives three separation that powder fine grading machine can not only realize powder, and effectiveness of classification is high, fineness regulation scope is large.
For solving the problems of the technologies described above, a kind of intelligence of the utility model is two drives powder fine grading machine, containing cyclone separator, separating chamber, first power transmission shaft, first transmission device, first motor, middle meal classification rotating cage, powder guiding taper, second driving shaft, second transmission device, second motor, fine powder classification rotating cage, middle meal collection cone and air intake drawing mechanism, first motor is arranged on the top of separating chamber by the first electric machine support, first motor is connected with the first transmission device, first transmission device is arranged on the first electric machine support, the upper end of the first power transmission shaft is connected with the first transmission device, the lower end of the first power transmission shaft is installed on the bearing block being arranged in separating chamber bottom by bearing, this bearing block is connected with one end of fixed bar, the other end of fixed bar is arranged on the inwall of separating chamber, middle meal classification rotating cage installs and is fixed on the bottom of the first power transmission shaft, second motor is connected with the second transmission device, second transmission device and the second motor are all arranged on the second electric machine support, second driving shaft is tubular structure, the second driving shaft of this tubular structure is sleeved on the first power transmission shaft, the top and bottom of the second driving shaft of this tubular structure and the first power transmission shaft consist of bearing and are rotationally connected, the upper end of the second driving shaft of this tubular structure is connected with the second transmission device, and the bottom of the second driving shaft of this tubular structure is connected with fine powder classification rotating cage, powder guiding taper is between fine powder classification rotating cage and middle meal classification rotating cage, and the lower end of fine powder classification rotating cage is arranged in the upper port of powder guiding taper, and the lower port of powder guiding taper is arranged in meal classification rotating cage,
Described middle meal classification rotating cage contains material sliding cone, holder, graded blade and annular plate, material sliding cone is arranged on holder, the lower end of graded blade is uniform to be arranged on the periphery of holder, the upper end of graded blade is uniform to be arranged on annular plate, and graded blade is formed radial, holder is provided with pod apertures, and the central authorities of holder are provided with axis hole, and this axis hole is installed on the bottom of the first power transmission shaft;
Described fine powder classification rotating cage contains deflector, gas deflector cone, upper annular plate, lower annular plate and Connection Block, deflector is uniform to be arranged between upper annular plate and lower annular plate, the lower end of gas deflector cone is arranged on lower annular plate, connecting rod is provided with between the upper end of gas deflector cone and upper annular plate, Connection Block is arranged on the internal upper part of gas deflector cone, Connection Block central authorities are provided with through hole, and this through hole is installed on the bottom of second driving shaft;
Middle meal collection cone is positioned at the bottom of described separating chamber and is fixed on separating chamber, the upper port of middle meal collection cone is arranged in the below of meal classification rotating cage, the lower port of middle meal collection cone is connected with one end of middle meal pipe, and the other end of middle meal pipe is positioned at the outside of separating chamber of institute;
Air intake drawing mechanism contains blast pipe, outer cylinder body and tremie pipe, the upper end of outer cylinder body is arranged on the lower end of separating chamber, blast pipe is positioned at outer cylinder body, gap is provided with between blast pipe and outer cylinder body, on gap between the uniform outer wall being arranged on blast pipe lower end and outer cylinder body bottom of tremie pipe, stock guide is provided with between adjacent tremie pipe, the upper end of adjacent stock guide is connected, the lower end of stock guide is arranged on tremie pipe, the dual-side of stock guide is separately positioned on the outer wall of blast pipe and the inwall of outer cylinder body, the top of separating chamber is provided with discharge pipe, this discharge pipe is connected with the import of cyclone separator,
Air intake drawing mechanism contains blast pipe, outer cylinder body and tremie pipe, the upper port of outer cylinder body is arranged on the lower port of separating chamber, blast pipe is positioned at outer cylinder body, gap is provided with between blast pipe and outer cylinder body, on gap between the uniform outer wall being arranged on outer cylinder body lower end and blast pipe bottom of tremie pipe upper port, stock guide is provided with between adjacent tremie pipe, the upper end of adjacent stock guide is connected, the lower end of stock guide is arranged on the suitable for reading of tremie pipe, the dual-side of stock guide is separately positioned on the outer wall of blast pipe and the inwall of outer cylinder body, the top of separating chamber is provided with discharge pipe, this discharge pipe is connected with the import of cyclone separator.
Described first motor and the second motor are buncher.
The pod apertures at least three that the holder that described middle meal classification rotating cage contains is provided with.
Bracing piece is provided with between the annular plate of described middle meal classification rotating cage and material sliding cone.
The tremie pipe at least two that described air intake drawing mechanism contains.
Powder fine grading machine is driven in above-mentioned intelligence pair, owing to have employed middle meal classification rotating cage and fine powder classification rotating cage, and middle meal classification rotating cage and fine powder classification rotating cage are respectively by two motors driven rotary respectively, therefore compared with prior art powder separator, can not only realize three separation of powder, and effectiveness of classification is high, fineness regulation scope is large.
Accompanying drawing explanation
Fig. 1 is the utility model structural representation;
Fig. 2 is A-A view in Fig. 1;
Fig. 3 is the structural representation of middle meal classification rotating cage;
Fig. 4 is the plan structure schematic diagram of Fig. 3;
Fig. 5 is the structural representation of fine powder classification rotating cage;
Fig. 6 is the C direction view in Fig. 5.
Detailed description of the invention
In Fig. 1 and Fig. 2, intelligence is two drives powder fine grading machine, containing cyclone separator, separating chamber 8, first power transmission shaft 4, first transmission device 2, first motor 1, middle meal classification rotating cage 12, powder guiding taper 11, second driving shaft 7, second transmission device 5, second motor 6, fine powder classification rotating cage 10, middle meal collection cone 15 and air intake drawing mechanism 23.First motor 1 is arranged on the top of separating chamber 8 by the first electric machine support 3, and the first motor 1 is connected with the first transmission device 2, and the first transmission device 2 is arranged on the first electric machine support 3.The upper end of the first power transmission shaft 4 is connected with the first transmission device 2, the lower end of the first power transmission shaft 4 is installed on the bearing block 13 being arranged in separating chamber 8 bottom by bearing, this bearing block 13 is connected with one end of fixed bar 14, and the other end of fixed bar 14 is arranged on the inwall of separating chamber 8.Middle meal classification rotating cage 12 installs and is fixed on the bottom of the first power transmission shaft 4.Second motor 6 is connected with the second transmission device 5, and the second transmission device 5 and the second motor 6 are all arranged on the second electric machine support.Second driving shaft 7 is tubular structure, the second driving shaft 7 of this tubular structure is sleeved on the first power transmission shaft 4, the top and bottom of the second driving shaft 7 of this tubular structure and the first power transmission shaft 4 consist of bearing and are rotationally connected, the upper end of the second driving shaft 7 of this tubular structure is connected with the second transmission device 5, and the bottom of the second driving shaft 7 of this tubular structure is connected 10 with fine powder classification rotating cage.Powder guiding taper 11 is between fine powder classification rotating cage 10 and middle meal classification rotating cage 12, and the lower end of fine powder classification rotating cage 10 is arranged in the upper port of powder guiding taper 11, and the lower port of powder guiding taper 11 is arranged in meal classification rotating cage 12.
As shown in Figure 3 and Figure 4, described middle meal classification rotating cage 12 is containing material sliding cone 25, holder 27, graded blade 28 and annular plate 24.Material sliding cone 25 is arranged on holder 27, on the uniform periphery being arranged on holder 27 in the lower end of graded blade 28, and graded blade 28 is formed radial, the upper end of graded blade 28 is uniform to be arranged on annular plate 24, holder 27 is provided with pod apertures 36, in order to ensure that water conservancy diversion is smooth and easy, and the pod apertures that holder 27 is provided with 36 at least three, in the present embodiment, pod apertures is eight.The central authorities of holder 27 are provided with axis hole 26, and this axis hole 26 is installed on the bottom of the first power transmission shaft 4.In order to the Rigidity and strength of meal classification rotating cage 12 in strengthening, between the annular plate 24 of described middle meal classification rotating cage 12 and material sliding cone 25, be provided with bracing piece 29.
As shown in Figure 5 and Figure 6, described fine powder classification rotating cage 10 is containing deflector 35, gas deflector cone 33, upper annular plate 30, lower annular plate 34 and Connection Block 32.Deflector 35 is uniform to be arranged between upper annular plate 30 and lower annular plate 34, and the lower end of gas deflector cone 33 is arranged on lower annular plate 34, is provided with connecting rod 31 between the upper end of gas deflector cone 33 and upper annular plate 30.Connection Block 32 is arranged on the internal upper part of gas deflector cone 33, and Connection Block 32 central authorities are provided with through hole, and this through hole is installed on the bottom of second driving shaft 7.
Middle meal collection cone 15 is positioned at the bottom of described separating chamber 8 and is fixed on the inside of separating chamber 8, the upper port of middle meal collection cone 15 is arranged in the below of meal classification rotating cage 12, the lower port of middle meal collection cone 15 is connected with one end of middle meal pipe 16, and the other end of middle meal pipe 16 is positioned at the outside of separating chamber of institute 8.
Air intake drawing mechanism 23 is containing blast pipe 17, outer cylinder body 21 and tremie pipe 22, the upper port of outer cylinder body 21 is arranged on the lower port of separating chamber 8, blast pipe 17 is positioned at outer cylinder body 21, gap is provided with between blast pipe 17 and outer cylinder body 21, on gap between the uniform outer wall being arranged on outer cylinder body 21 lower end and blast pipe 17 bottom of tremie pipe 22 upper port, stock guide 19 is provided with between adjacent tremie pipe 22, the upper end 18 of adjacent stock guide 19 is connected, the lower end of stock guide 19 is arranged on the suitable for reading of tremie pipe, the dual-side of stock guide 19 is separately positioned on the outer wall of blast pipe 17 and the inwall of outer cylinder body, the top of separating chamber 8 is provided with discharge pipe 9, this discharge pipe 9 is connected with the import of cyclone separator, not shown in the figures.In order to ensure the unimpeded of blanking, the tremie pipe that described air intake drawing mechanism 23 contains 22 at least two, in the present embodiment, tremie pipe 22 4.
In order to improve effectiveness of classification as much as possible, expand fineness regulation scope, described first motor 1 and the second motor 6 all can adopt buncher.
During work, middle meal classification rotating cage 12 rotates under the drive of the first motor 1 and the first transmission device 2, simultaneously, fine powder classification rotating cage 10 rotates under the drive of the second motor 6 and the second transmission device 5, dusty gas is when the blast pipe 17 of air intake drawing mechanism 23 enters separating chamber 8, the outer surface of the meal in dusty gas and middle meal collection cone 15 bumps against, and enters tremie pipe 22 discharge outside machine after losing kinetic energy along the stock guide 19 of air intake drawing mechanism 23; Dusty gas continues to rise, in passing through during meal classification rotating cage 12, middle meal is selected by middle meal classification rotating cage 12, discharge outside machine by middle meal collection cone 15 and middle meal pipe 16, in the part also contained in air-flow, meal is thrown away by middle meal classification rotating cage 12, enters tremie pipe 22 discharge outside machine along the inwall of separating chamber 8 and the stock guide 19 of air intake drawing mechanism 23; Dusty gas continues to rise, when through fine powder classification rotating cage 10, fine powder is by fine powder classification rotating cage 10, enter cyclone separator from the discharge pipe 9 on separating chamber 8 top to be collected, meal in the part that air-flow also contains, kept off by fine powder classification rotating cage 10, discharge outside machine along powder guiding taper 11 and middle meal collection cone 15 and middle meal pipe 16.Intelligence is two drives powder fine grading machine in the course of the work, when the rotating speed of meal classification rotating cage 12 in changing, and the fineness of adjustable middle meal and effectiveness of classification; Equally when changing the rotating speed of fine powder classification rotating cage 10, the fineness of adjustable fine powder and effectiveness of classification.
Powder fine grading machine is driven in above-mentioned intelligence pair, owing to have employed middle meal classification rotating cage 12, fine powder classification rotating cage 10 and powder guiding taper 11, and middle meal classification rotating cage 12 and fine powder classification rotating cage 10 are respectively by the first motor 1 and the second motor 6 driven rotary respectively, therefore compared with prior art powder separator, can not only realize three separation of powder, and effectiveness of classification is high, fineness regulation scope is large.

Claims (5)

1. an intelligence pair drives powder fine grading machine, it is characterized in that: containing cyclone separator, separating chamber, first power transmission shaft, first transmission device, first motor, middle meal classification rotating cage, powder guiding taper, second driving shaft, second transmission device, second motor, fine powder classification rotating cage, middle meal collection cone and air intake drawing mechanism, first motor is arranged on the top of separating chamber by the first electric machine support, first motor is connected with the first transmission device, first transmission device is arranged on the first electric machine support, the upper end of the first power transmission shaft is connected with the first transmission device, the lower end of the first power transmission shaft is installed on the bearing block being arranged in separating chamber bottom by bearing, this bearing block is connected with one end of fixed bar, the other end of fixed bar is arranged on the inwall of separating chamber, middle meal classification rotating cage installs and is fixed on the bottom of the first power transmission shaft, second motor is connected with the second transmission device, second transmission device and the second motor are all arranged on the second electric machine support, second driving shaft is tubular structure, the second driving shaft of this tubular structure is sleeved on the first power transmission shaft, the top and bottom of the second driving shaft of this tubular structure and the first power transmission shaft consist of bearing and are rotationally connected, the upper end of the second driving shaft of this tubular structure is connected with the second transmission device, and the bottom of the second driving shaft of this tubular structure is connected with fine powder classification rotating cage, powder guiding taper is between fine powder classification rotating cage and middle meal classification rotating cage, and the lower end of fine powder classification rotating cage is arranged in the upper port of powder guiding taper, and the lower port of powder guiding taper is arranged in meal classification rotating cage,
Described middle meal classification rotating cage contains material sliding cone, holder, graded blade and annular plate, material sliding cone is arranged on holder, the lower end of graded blade is uniform to be arranged on the periphery of holder, the upper end of graded blade is uniform to be arranged on annular plate, and graded blade is formed radial, holder is provided with pod apertures, and the central authorities of holder are provided with axis hole, and this axis hole is installed on the bottom of the first power transmission shaft;
Described fine powder classification rotating cage contains deflector, gas deflector cone, upper annular plate, lower annular plate and Connection Block, deflector is uniform to be arranged between upper annular plate and lower annular plate, the lower end of gas deflector cone is arranged on lower annular plate, connecting rod is provided with between the upper end of gas deflector cone and upper annular plate, Connection Block is arranged on the internal upper part of gas deflector cone, Connection Block central authorities are provided with through hole, and this through hole is installed on the bottom of second driving shaft;
Middle meal collection cone is positioned at the bottom of described separating chamber and is fixed on separating chamber, the upper port of middle meal collection cone is arranged in the below of meal classification rotating cage, the lower port of middle meal collection cone is connected with one end of middle meal pipe, and the other end of middle meal pipe is positioned at the outside of separating chamber of institute;
Air intake drawing mechanism contains blast pipe, outer cylinder body and tremie pipe, the upper end of outer cylinder body is arranged on the lower end of separating chamber, blast pipe is positioned at outer cylinder body, gap is provided with between blast pipe and outer cylinder body, on gap between the uniform outer wall being arranged on blast pipe lower end and outer cylinder body bottom of tremie pipe, stock guide is provided with between adjacent tremie pipe, the upper end of adjacent stock guide is connected, the lower end of stock guide is arranged on tremie pipe, the dual-side of stock guide is separately positioned on the outer wall of blast pipe and the inwall of outer cylinder body, the top of separating chamber is provided with discharge pipe, this discharge pipe is connected with the import of cyclone separator,
Air intake drawing mechanism contains blast pipe, outer cylinder body and tremie pipe, the upper port of outer cylinder body is arranged on the lower port of separating chamber, blast pipe is positioned at outer cylinder body, gap is provided with between blast pipe and outer cylinder body, on gap between the uniform outer wall being arranged on outer cylinder body lower end and blast pipe bottom of tremie pipe upper port, stock guide is provided with between adjacent tremie pipe, the upper end of adjacent stock guide is connected, the lower end of stock guide is arranged on the suitable for reading of tremie pipe, the dual-side of stock guide is separately positioned on the outer wall of blast pipe and the inwall of outer cylinder body, the top of separating chamber is provided with discharge pipe, this discharge pipe is connected with the import of cyclone separator.
2. intelligence according to claim 1 is two drives powder fine grading machine, it is characterized in that: described first motor and the second motor are buncher.
3. intelligence according to claim 1 is two drives powder fine grading machine, it is characterized in that: the pod apertures at least three that the holder that described middle meal classification rotating cage contains is provided with.
4. intelligence according to claim 1 is two drives powder fine grading machine, it is characterized in that: be provided with bracing piece between the annular plate of described middle meal classification rotating cage and material sliding cone.
5. intelligence according to claim 1 is two drives powder fine grading machine, it is characterized in that: the tremie pipe at least two that described air intake drawing mechanism contains.
CN201520500971.2U 2015-07-13 2015-07-13 Two accurate graders of powder that drive of intelligence Active CN204866542U (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201520500971.2U CN204866542U (en) 2015-07-13 2015-07-13 Two accurate graders of powder that drive of intelligence

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201520500971.2U CN204866542U (en) 2015-07-13 2015-07-13 Two accurate graders of powder that drive of intelligence

Publications (1)

Publication Number Publication Date
CN204866542U true CN204866542U (en) 2015-12-16

Family

ID=54810973

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201520500971.2U Active CN204866542U (en) 2015-07-13 2015-07-13 Two accurate graders of powder that drive of intelligence

Country Status (1)

Country Link
CN (1) CN204866542U (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104941912A (en) * 2015-07-13 2015-09-30 江苏吉能达环境能源科技有限公司 Intelligent and precise double-drive powder grading machine
CN106944157A (en) * 2016-01-07 2017-07-14 中国石油化工股份有限公司 A kind of catalytic cracking catalyst prepares moulding process and system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104941912A (en) * 2015-07-13 2015-09-30 江苏吉能达环境能源科技有限公司 Intelligent and precise double-drive powder grading machine
CN106944157A (en) * 2016-01-07 2017-07-14 中国石油化工股份有限公司 A kind of catalytic cracking catalyst prepares moulding process and system

Similar Documents

Publication Publication Date Title
CN205269787U (en) Raymond mill
CN203291915U (en) Ultrafine powder differential swing arm roller grinding machine
CN204866542U (en) Two accurate graders of powder that drive of intelligence
CN104984910A (en) High-dispersibility vortex powder selecting machine
CN102319673A (en) Cylindrical powder concentrator
CN104941912B (en) Intelligence is double to drive powder body fine grading machine
CN206008867U (en) A kind of adjustable roll mill apparatus with back-blowing sealing structure of wind speed
CN204892373U (en) High dispersivity vortex selection powder machine
CN203556411U (en) Coal grinding mill
CN205868517U (en) Separator and grinder are ground to stirring formula
CN106031901A (en) Cage type rotor eddy flow ultra-fine powder concentrator
CN204035032U (en) A kind of wind formula of sweeping is association of activity and inertia high efficiency dust separator
CN205948975U (en) Heated air circulation selection powder device that wind speed adjustable anti -blow is sealed
CN203899672U (en) Ultra-thin vertical roll mill
CN208373209U (en) A kind of all-round flour mill of pendulum-type
CN206008868U (en) A kind of hot air circulation powder selection device with back-blowing sealing structure
CN207357594U (en) A kind of more rotor powder concentrators of high sharpness of separation
CN206464024U (en) A kind of high-efficiency vertical roller mill
CN106669902B (en) A kind of swing ball mill
CN206701727U (en) The ultra-fine two-wheel gas flow sizing machine system of tandem
CN202070424U (en) Vortex combination powder separator
CN104438042A (en) Material screening device
CN200995192Y (en) Turbine classifier of swing powder grinder
CN204724256U (en) Rod pin nanometer sand mill
CN108465636A (en) A kind of high-efficiency cyclone-type powder concentrator

Legal Events

Date Code Title Description
GR01 Patent grant
C14 Grant of patent or utility model