CN111189319B

CN111189319B - A raw material calcining device for cement manufacture

Info

Publication number: CN111189319B
Application number: CN202010029893.8A
Authority: CN
Inventors: 张连鹏; 王莉
Original assignee: Inner Mongolia Yidong Jidong Cement Co ltd
Current assignee: Inner Mongolia Yidong Jidong Cement Co.,Ltd.
Priority date: 2020-01-13
Filing date: 2020-01-13
Publication date: 2021-08-20
Anticipated expiration: 2040-01-13
Also published as: CN111189319A

Abstract

The invention relates to the technical field of cement production, and discloses a raw material calcining device for cement production, which comprises a frame, wherein a rotary kiln is arranged at the upper end of the frame, a preheating cylinder is connected at the front end of the rotary kiln, a cooling cylinder is connected at the rear end of the rotary kiln, an air extraction opening is formed in the upper end of the cooling cylinder, a preheating box is communicated with one end of the preheating cylinder, a liquid return pipe is arranged between the side surface of one end of the preheating cylinder and the side surface of one end of the cooling cylinder, a compression refrigerating machine is arranged in the middle of the liquid return pipe, a conveying pipe is arranged between the other side surface of one end of the preheating cylinder and the side surface of the other end of the cooling cylinder, and one end of the air extraction opening is communicated with an air extraction pipe. When the raw materials are calcined and then become high-temperature clinker, the high temperature is generated for full recycling, and the recycled high-temperature heat is utilized to fully preheat the raw materials, so that the calcining efficiency is improved, the waste of resources is avoided, and the high-efficiency recycling of the heat can be realized.

Description

A raw material calcining device for cement manufacture

Technical Field

The invention relates to the technical field of cement production, in particular to a raw material calcining device for cement production.

Background

Cement: a powdered hydraulic inorganic cementitious material. The cement mortar is produced with lime stone and clay as main material and through crushing, compounding, grinding to produce raw material, calcining in cement kiln to produce clinker, adding proper amount of gypsum and other steps.

The present cement raw meal calcining device is mostly before calcining, need carry out preheating treatment through the preheater to the raw meal, but most raw meal preheats the effect perfect inadequately, can not make the raw meal fully preheat, cause the waste of resource easily, and influence calcination effect, the raw meal burns the back simultaneously and becomes high temperature clinker, need discharge after the cooling, but high temperature clinker is when cooling, the heat loss of its production is comparatively serious, the high temperature heat recovery that produces is perfect inadequately in the market when cooling, can not reasonable recycle, the waste of resource has been caused. Accordingly, a raw meal calcination apparatus for cement production is provided by those skilled in the art to solve the problems set forth in the above background art.

Disclosure of Invention

The object of the present invention is to provide a raw meal calcination apparatus for cement production that solves the problems set forth in the background art described above.

In order to achieve the purpose, the invention provides the following technical scheme: a raw meal calcining device for cement production comprises a frame, a rotary kiln is arranged at the upper end of the frame, a preheating cylinder is connected at the front end of the rotary kiln, and the rear end of the rotary kiln is connected with a cooling cylinder, one end of the cooling cylinder is connected with a discharge cylinder, the upper end of the cooling cylinder is provided with an air exhaust port, one end of the preheating cylinder is communicated with a preheating box, the top end of the preheating box is provided with a feeding hole, and the lower end of one side surface of the preheating box is communicated with an air inlet pipe, a liquid return pipe is arranged between the side surface of one end of the preheating cylinder and the side surface of one end of the cooling cylinder, a compression refrigerating machine is arranged in the middle of the liquid return pipe, a conveying pipe is arranged between the other side surface of one end of the preheating cylinder and the other side surface of the cooling cylinder, one end of the air exhaust opening is communicated with an air exhaust pipe, one end of the air exhaust pipe is connected with an air exhaust fan, and the output end of the air exhaust fan is communicated with an air supply pipe.

As a further scheme of the invention: the outer surface of the rotary kiln is provided with a gear ring, one side of the upper surface of the rack, which is close to the rotary kiln, is provided with a driving motor, the output end of the driving motor is connected with a main gear, the main gear is meshed with the gear ring, the driving motor is rotatably connected with the rotary kiln through the main gear and the gear ring, and the lower end of the driving motor is provided with a base.

As a still further scheme of the invention: supporting wheels are arranged on the upper surface of the rack below two ends corresponding to the rotary kiln, two ends of the rotary kiln are rotatably connected with the rack through the supporting wheels, and rotating shafts are arranged at the joints of the two ends of the rotary kiln and the cooling cylinder and the preheating cylinder respectively.

As a still further scheme of the invention: the preheating device comprises a preheating box, a conveying hopper, an air inlet pipe, an inner box, a first preheating cavity, inclined plates, a conveying hopper, a conveying opening and a conveying pipe, wherein the inner box is arranged in the preheating box, the first preheating cavity is formed between the preheating box and the inner box, the inclined plates are arranged in the inner box in a staggered mode, the conveying hopper is arranged at the bottom end in the inner box, the bottom end of the conveying hopper is communicated with the conveying opening, and one end of the air inlet pipe penetrates through the side face of the conveying hopper and corresponds to the conveying opening.

As a still further scheme of the invention: one end of the air supply pipe penetrates through the preheating box and is in through connection with the first preheating cavity, the inclined plates are arranged at least three and are arranged obliquely respectively and are arranged on the inner side wall of the inner box in a staggered mode, one end of the air supply pipe is in through connection with the feeding port, and the preheating box is in through connection with the preheating barrel through the feeding port.

As a still further scheme of the invention: the inside of cooling cylinder is provided with first inner tube, be provided with the cooling chamber between cooling cylinder and the first inner tube, and the surface that the inside in cooling chamber is located first inner tube has surrounded first heat exchange tube, the inside of preheating cylinder is provided with the second inner tube, it preheats the chamber to be provided with the second between preheating cylinder and the second inner tube, and the inside in second preheating chamber is located second inner tube surface and has surrounded the second heat exchange tube.

As a still further scheme of the invention: the one end through connection of preheating section of thick bamboo and second heat exchange tube is run through to the one end of returning the liquid pipe, and the other end through connection of cooling cylinder and first heat exchange tube of returning the liquid pipe, the one end through connection of cooling cylinder and the other end through connection of first heat exchange tube is run through to the one end of conveyer pipe, and the other end through connection of preheating section of thick bamboo and second heat exchange tube is run through to the other end of conveyer pipe.

As a still further scheme of the invention: the discharging barrel is in through connection with the cooling barrel, a discharging opening is formed in the lower end of the discharging barrel, and the discharging barrel is fixedly connected with the rack through a support.

Compared with the prior art, the invention has the beneficial effects that: the invention designs a raw material calcining device for cement production, during actual operation, raw materials in a cooling cylinder can be calcined into high-temperature clinker through the application of an exhaust pipe and an exhaust fan, high-temperature gas generated during cooling is extracted and utilized, the raw materials in a preheating box are convenient to preheat, so that the primary preheating of the cement raw materials is realized, in addition, the design of an inclined plate is matched, the raw materials can be conveniently and fully contacted with hot air when entering the inner box, the problem of poor preheating effect caused by raw material accumulation is avoided, in addition, the first heat exchange pipe and the second heat exchange pipe are matched with the application of refrigerating fluid, the heat generated by the inner wall of the first inner cylinder is convenient to be recovered again, in addition, the application of a conveying pipe, a liquid return pipe and a compression refrigerating machine is matched, the cyclic recycling of the heat in the cooling cylinder is convenient to realize, the secondary preheating of the cement raw materials is convenient, the calcining efficiency is improved, the waste of resources is avoided, and meanwhile, the high-efficiency recycling of heat can be realized.

Drawings

FIG. 1 is a schematic view showing the construction of a raw meal calcination apparatus for cement production;

FIG. 2 is a schematic view showing the installation of an exhaust fan and an air supply pipe in a raw meal calcination apparatus for cement production;

FIG. 3 is a schematic view showing the construction of a preheating chamber in a raw meal calcining apparatus for cement production;

FIG. 4 is a schematic view showing the installation of a first heat exchange pipe and a second heat exchange pipe in a raw meal calcination apparatus for cement production;

fig. 5 is a schematic view of a first heat exchange pipe and a second heat exchange pipe in a raw meal calcination apparatus for cement production.

In the figure: 1. a frame; 2. a cooling cylinder; 3. a gear ring; 4. a rotary kiln; 5. a preheating cylinder; 6. a feed inlet; 7. a preheating box; 8. an air inlet pipe; 9. a liquid return pipe; 10. a compression refrigerator; 11. a drive motor; 12. a riding wheel; 13. a discharge outlet; 14. a discharging barrel; 15. an air extraction opening; 16. an air exhaust pipe; 17. a delivery pipe; 18. an exhaust fan; 19. an air supply pipe; 71. a first preheating chamber; 72. an inner box; 73. a sloping plate; 74. a hopper; 75. a feed port; 21. a first inner cylinder; 22. a first heat exchange tube; 51. a second inner barrel; 52. a second heat exchange tube.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1 to 5, in the embodiment of the present invention, a raw meal calcining apparatus for cement production includes a frame 1, a rotary kiln 4 is disposed at an upper end of the frame 1, a preheating cylinder 5 is connected to a front end of the rotary kiln 4, a cooling cylinder 2 is connected to a rear end of the rotary kiln 4, a discharge cylinder 14 is connected to one end of the cooling cylinder 2, an air extraction opening 15 is disposed at an upper end of the cooling cylinder 2, a preheating tank 7 is communicated with one end of the preheating cylinder 5, a feed inlet 6 is disposed at a top end of the preheating tank 7, an air inlet pipe 8 is communicated with a lower end of one side of the preheating tank 7, a liquid return pipe 9 is disposed between a side of one end of the preheating cylinder 5 and a side of one end of the cooling cylinder 2, a compression refrigerator 10 is disposed in a middle portion of the liquid return pipe 9, a conveying pipe 17 is disposed between another side of one end of the preheating cylinder 5 and another side of the other end of the cooling cylinder 2, an air extraction pipe 16 is communicated with one end of the air extraction opening 15, one end of the air extraction pipe 16 penetrates through the cooling cylinder 2 and is communicated with a first inner cylinder 21, exhaust tube 16's one end is connected with air exhauster 18, air exhauster 18's output intercommunication has blast pipe 19, cement raw meal is when calcining the processing, the raw meal becomes ripe material after calcining and carries out cooling process in cooling cylinder 2, when high temperature grog is at the internal cooling of cooling cylinder 2, can produce high-temperature gas, and then the application through exhaust tube 16 cooperation exhaust fan 18, conveniently take out the high-temperature gas that produces in the cooling cylinder 2, and carry in preheating cabinet 7 through blast pipe 19, be convenient for carry recycle the high temperature heat that the material thing after calcining produced in the cooling cylinder 2.

The outer surface of the rotary kiln 4 is provided with a gear ring 3, one side of the upper surface of the frame 1 close to the rotary kiln 4 is provided with a driving motor 11, the output end of the driving motor 11 is connected with a main gear, the main gear is meshed with the gear ring 3, the driving motor 11 is rotatably connected with the rotary kiln 4 through the main gear and the gear ring 3, the lower end of the driving motor 11 is provided with a base, the upper surface of the frame 1 is provided with supporting wheels 12 corresponding to the lower parts of the two ends of the rotary kiln 4, the two ends of the rotary kiln 4 are rotatably connected with the frame 1 through the supporting wheels 12, the joints of the two ends of the rotary kiln 4 and the cooling cylinder 2 and the preheating cylinder 5 are respectively provided with rotating shafts, the discharging cylinder 14 is communicated with the cooling cylinder 2, the lower end of the discharging cylinder 14 is provided with a discharging opening 13, the discharging cylinder 14 is fixedly connected with the frame 1 through a bracket, and the supporting wheels 12 are used for conveniently rotatably supporting the rotary kiln 4, and the work of cooperation gear circle 3 and driving motor 11 and master gear conveniently utilizes driving motor 11 to pass through the master gear and drives gear circle 3 and rotate, and then drives rotary kiln 4 and rotates, is convenient for calcine the processing to the cement raw material.

An inner box 72 is arranged in the preheating box 7, a first preheating cavity 71 is arranged between the preheating box 7 and the inner box 72, inclined plates 73 are arranged in the inner box 72 in a staggered manner, a feeding hopper 74 is arranged at the bottom end in the inner box 72, the bottom end of the feeding hopper 74 is communicated with a feeding port 75, one end of an air inlet pipe 8 penetrates through the side surface of the feeding hopper 74 and corresponds to the feeding port 75, one end of an air supply pipe 19 penetrates through the preheating box 7 and is communicated with the first preheating cavity 71, at least three inclined plates 73 are arranged and are respectively arranged in an inclined manner and are arranged on the inner side wall of the inner box 72 in a staggered manner, one end of the air inlet pipe 8 is communicated with the feeding port 75, the preheating box 7 is communicated with the preheating cylinder 5 through the feeding port 75, high-temperature gas in the cooling cylinder 2 is pumped into the first preheating cavity 71 in the preheating box 7 through the air supply pipe 19 matched with an exhaust fan 18, the inner box 72 is convenient to treat and increase the internal temperature, and then make things convenient for cement raw material when entering into inner box 72 by feed inlet 6, utilize the crisscross cooperation of swash plate 73, make things convenient for dumping of raw material through swash plate 73 to be the formula of scattering whereabouts, and then can make the raw material fully contact with the heat in inner box 72, can improve the preheating effect of raw material, and the raw material after preliminary preheating can fall into in the hopper 74, and then the cooperation of cooperation air-supply line 8 is used, can blow in preheating cylinder 5 with the raw material of whereabouts through pay-off mouth 75, the convenience carries out secondary preheating process to it.

A first inner cylinder 21 is arranged in the cooling cylinder 2, a cooling cavity is arranged between the cooling cylinder 2 and the first inner cylinder 21, a first heat exchange tube 22 is arranged on the outer surface of the first inner cylinder 21 in the cooling cavity, a second inner cylinder 51 is arranged in the preheating cylinder 5, a second preheating cavity is arranged between the preheating cylinder 5 and the second inner cylinder 51, a second heat exchange tube 52 is arranged on the outer surface of the second inner cylinder 51 in the second preheating cavity, one end of a liquid return tube 9 penetrates through the preheating cylinder 5 and is connected with one end of the second heat exchange tube 52 in a penetrating manner, the other end of the liquid return tube 9 penetrates through the cooling cylinder 2 and is connected with one end of the first heat exchange tube 22 in a penetrating manner, one end of a conveying tube 17 penetrates through the cooling cylinder 2 and is connected with the other end of the first heat exchange tube 22 in a penetrating manner, the other end of the conveying tube 17 penetrates through the preheating cylinder 5 and is connected with the other end of the second heat exchange tube 52 in a penetrating manner, and refrigerating liquid is arranged in the first heat exchange tube 22 and the second heat exchange tube 52, during operation, as the raw material is calcined to become high-temperature clinker, and then the high temperature is subjected to cooling treatment in the cooling cylinder 2, although the high-temperature gas in the cooling cylinder 2 is extracted and utilized through the exhaust pipe 16, the first inner cylinder 21 in the cooling cylinder 2 is subjected to heat transfer of the high-temperature clinker, and the temperature of the inner wall of the cooling cylinder is higher, and then the first heat exchange pipe 22 arranged on the surface of the first heat exchange pipe is matched with the use of the refrigerant in the first heat exchange pipe 22, the high temperature of the inner wall of the first inner cylinder 21 can be absorbed through the effect of the heat transfer, so that the refrigerant in the first heat exchange pipe 22 is heated and vaporized to become high-temperature high-pressure gas refrigerant, the gas refrigerant after heat absorption and vaporization is subjected to the influence of pressure and is conveyed into the second heat exchange pipe 52 in the preheating cylinder 5 through the conveying pipe 17, and the high-temperature gas refrigerant is subjected to the influence of the low temperature on the surface of the second inner cylinder 51 and the low temperature of the second heat exchange pipe 52, the heat transfer takes place, then the high-temperature gas refrigerating fluid can meet cold liquefaction and release heat, the realization is preheated to second inner tube 51, and then the liquefaction becomes the liquefied refrigerating fluid of low temperature and can export compression refrigerator 10 department through liquid return pipe 9, and then the compression of compression refrigerator 10, form high-pressure cryogenic liquid refrigerating fluid, again through the effect of liquid return pipe 9, flow into in the inside first heat exchange tube 22 of cooling cylinder 2 once more, absorb heat once more, conveniently realize carrying out circulation collection utilization to the high-temperature heat that 2 inside produced of cooling cylinder, and realize the preheating to preheating cylinder 5, conveniently carry out secondary preheating to the cement raw meal that gets into in preheating cylinder 5, improve the calcination efficiency of cement raw meal, and the consumption of the calcination energy has been practiced thrift.

The working principle of the invention is as follows: when the invention works, cement raw materials are calcined to become high-temperature clinker, then the clinker is conveyed into the cooling cylinder 2 for cooling treatment, when the high-temperature clinker is cooled in the cooling cylinder 2, high-temperature gas is generated, the high-temperature gas generated in the cooling cylinder 2 is conveniently pumped out by the aid of the air pumping pipe 16 and the exhaust fan 18, and is conveyed into the first preheating cavity 71 in the preheating box 7 by the aid of the air supply pipe 19, so that the interior of the inner box 72 is conveniently heated, the raw materials are conveniently preheated primarily when entering the inner box 72 from the feed inlet 6, the raw materials are obliquely scattered when entering the inner box 72 under the action of the inclined plate 73, the contact area between the raw materials and hot gas in the inner box 72 is increased, the preheating effect of the raw materials is accelerated, and the raw materials preheated primarily fall into the feed hopper 74 and are matched with the air inlet pipe 8 for use, the falling raw materials can be blown into the preheating cylinder 5 through the feeding port 75, so that the secondary preheating treatment can be conveniently carried out;

when the high-temperature gas in the cooling cylinder 2 is extracted and utilized by the extraction pipe 16, but the inner wall temperature of the first inner cylinder 21 in the cooling cylinder 2 is higher due to the heat transfer of the high-temperature clinker, so that the first heat exchange pipe 22 in the cooling cylinder 2 is matched with the low-temperature liquid refrigerant therein to exchange heat and absorb the high-temperature heat on the inner wall of the first inner cylinder 21, and then the heat-absorbed high-temperature gaseous refrigerant is sent into the second heat exchange pipe 52 in the preheating cylinder 5 by matching with the conveying pipe 17, and the high-temperature gaseous refrigerant is subjected to heat transfer in the preheating cylinder 5 under the influence of the low-temperature second heat exchange pipe 52 and the low-temperature second inner cylinder 51, so that the high-temperature gaseous refrigerant is liquefied, and the liquefied liquid refrigerant flows into the first heat exchange pipe 22 again through the liquid return pipe 9 in cooperation with the compression refrigerator 10 to be absorbed again, thereby realize recycling the inside thermal recovery of cooling cylinder 2, also can realize preheating the quick of preheating cylinder 5 simultaneously, reach the secondary preheating treatment effect to the raw meal, make things convenient for the calcination of raw meal to handle, practiced thrift the waste of resource, realized thermal recovery again.

It should be noted that: the driving motor 11 adopts an industrial servo motor with the model of MCA17N23-RS0B0, and the exhaust fan 18 adopts a high-temperature resistant industrial exhaust fan commonly used in the market.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. A raw meal calcining device for cement production comprises a rack (1) and is characterized in that a rotary kiln (4) is arranged at the upper end of the rack (1), a preheating cylinder (5) is connected to the front end of the rotary kiln (4), a cooling cylinder (2) is connected to the rear end of the rotary kiln (4), a discharge cylinder (14) is connected to one end of the cooling cylinder (2), an air extraction opening (15) is formed in the upper end of the cooling cylinder (2), a preheating box (7) is communicated with one end of the preheating cylinder (5), a feed inlet (6) is formed in the top end of the preheating box (7), an air inlet pipe (8) is communicated with the lower end of one side face of the preheating box (7), a liquid return pipe (9) is arranged between the side face of one end of the preheating cylinder (5) and the side face of one end of the cooling cylinder (2), and a compression refrigerating machine (10) is arranged in the middle of the liquid return pipe (9), a conveying pipe (17) is arranged between the other side face of one end of the preheating cylinder (5) and the other end side face of the cooling cylinder (2), one end of the air suction opening (15) is communicated with an air suction pipe (16), one end of the air suction pipe (16) is connected with an air exhauster (18), and the output end of the air exhauster (18) is communicated with an air supply pipe (19).

2. A raw meal calcining apparatus for cement production as set forth in claim 1, characterized in that the outer surface of the rotary kiln (4) is provided with a gear ring (3), one side of the upper surface of the frame (1) close to the rotary kiln (4) is provided with a driving motor (11), the output end of the driving motor (11) is connected with a main gear, the main gear and the gear ring (3) are meshed with each other, the driving motor (11) and the rotary kiln (4) are rotatably connected through the main gear and the gear ring (3), and the lower end of the driving motor (11) is provided with a base.

3. A raw meal calcination device for cement production as claimed in claim 1, wherein the upper surface of the frame (1) is provided with riding wheels (12) below the two ends corresponding to the rotary kiln (4), the two ends of the rotary kiln (4) are rotatably connected with the frame (1) through the riding wheels (12), and the joints between the two ends of the rotary kiln (4) and the cooling cylinder (2) and the preheating cylinder (5) are provided with rotating shafts respectively.

4. The raw meal calcining device for cement production as claimed in claim 1, characterized in that an inner box (72) is arranged inside the preheating box (7), a first preheating chamber (71) is arranged between the preheating box (7) and the inner box (72), inclined plates (73) are staggered inside the inner box (72), a hopper (74) is arranged at the bottom end inside the inner box (72), a feeding port (75) is communicated with the bottom end of the hopper (74), and one end of the air inlet pipe (8) penetrates through the side surface of the hopper (74) and corresponds to the feeding port (75).

5. A raw meal calcination device for cement production according to claim 4, wherein one end of the blast pipe (19) penetrates through the preheating chamber (7) and is communicated with the first preheating chamber (71), at least three inclined plates (73) are arranged, are respectively arranged in an inclined manner and are arranged in a staggered manner on the inner side wall of the inner chamber (72), one end of the blast pipe (8) is communicated with the feed port (75), and the preheating chamber (7) is communicated with the preheating barrel (5) through the feed port (75).

6. A raw meal calcination device for cement production according to claim 1, wherein the cooling cylinder (2) is internally provided with a first inner cylinder (21), a cooling chamber is arranged between the cooling cylinder (2) and the first inner cylinder (21), the inside of the cooling chamber is positioned on the outer surface of the first inner cylinder (21) and is surrounded by a first heat exchange pipe (22), the inside of the preheating cylinder (5) is provided with a second inner cylinder (51), a second preheating chamber is arranged between the preheating cylinder (5) and the second inner cylinder (51), and the inside of the second preheating chamber is positioned on the outer surface of the second inner cylinder (51) and is surrounded by a second heat exchange pipe (52).

7. A raw meal calcination device for cement production according to claim 6, characterized in that one end of the liquid return pipe (9) penetrates through the preheating cylinder (5) to be connected through with one end of the second heat exchange pipe (52), the other end of the liquid return pipe (9) penetrates through the cooling cylinder (2) to be connected through with one end of the first heat exchange pipe (22), one end of the delivery pipe (17) penetrates through the cooling cylinder (2) to be connected through with the other end of the first heat exchange pipe (22), and the other end of the delivery pipe (17) penetrates through the preheating cylinder (5) to be connected through with the other end of the second heat exchange pipe (52).

8. A raw meal calcination device for cement production according to claim 1, characterized in that the outlet shaft (14) is connected through to the cooling shaft (2) and the lower end of the outlet shaft (14) is provided with a discharge opening (13), the outlet shaft (14) is fixedly connected to the frame (1) by means of a bracket.