阅读说明：本技术 一种燃气轮机轴流气压机及抽气方法 (Axial flow air compressor of gas turbine and air extraction method ) 是由 陈仁贵 沈东萍 牛兵 于 2021-07-14 设计创作，主要内容包括：本发明涉及燃气轮机技术领域,具体涉及一种燃气轮机轴流气压机及抽气方法；两个连接板之间设置有过滤布,第一伺服电机与放置板可拆卸连接,第一伺服电机的输出端设置有输出轴,输出轴上设置有抖动凸轮,抖动凸轮与过滤布相对应,首先利用初步过滤板过滤掉空气中较大的杂质,然后利用过滤布进一步过滤掉空气中的灰尘,当过滤布上堆积的灰尘过多后,启动第一伺服电机,利用输出轴带动抖动凸轮转动,从而利用抖动凸轮带动过滤布抖动,使得过滤布始终保持良好的过滤效果,从而更够持续的对气压机本体输出较为纯净的空气。(The invention relates to the technical field of gas turbines, in particular to an axial flow aerostatic press of a gas turbine and an air extraction method; be provided with the filter cloth between two connecting plates, first servo motor can dismantle with placing the board and be connected, first servo motor's output is provided with the output shaft, be provided with the shake cam on the output shaft, the shake cam is corresponding with the filter cloth, at first utilize preliminary filter to filter great impurity in the air, then utilize the filter cloth further to filter the dust in the air, after piling up the dust is too much on the filter cloth, start first servo motor, utilize the output shaft to drive the shake cam and rotate, thereby utilize the shake cam to drive the filter cloth shake, make the filter cloth remain good filter effect throughout, thereby the comparatively pure air of aerostatic press body output that more can last.)

1. An axial flow air compressor of a gas turbine is characterized in that,

the axial flow gas compressor of the gas turbine comprises a filter chamber, a filter device, a preheating chamber, a preheating pipeline, a heating chamber and a gas compressor body, wherein an air inlet is formed in one end of the filter chamber, an air outlet is formed in the other end of the filter chamber, one end of the preheating chamber is connected with the air outlet pipeline, the other end of the preheating chamber is connected with the heating chamber pipeline, the input end of the gas compressor body is connected with the heating chamber pipeline and is positioned at one end, far away from the preheating chamber, of the heating chamber, the output end of the gas compressor body is provided with the preheating pipeline, and one end, far away from the gas compressor body, of the preheating pipeline corresponds to the preheating chamber;

the filter device is arranged in the filter chamber and comprises a primary filter plate and a deep filter mechanism, the primary filter plate is arranged at one end, close to the air inlet, of the inside of the filter chamber, the deep filter mechanism is arranged at one end, close to the air outlet, of the inside of the filter chamber, the deep filter mechanism comprises connecting plates, filter cloth and shaking components, the connecting plates are arranged on two sides of the inside of the filter chamber, the filter cloth is arranged between the two connecting plates, a placing plate is further arranged on the side wall of the filter chamber, the shaking components are arranged on the placing plate and comprise a first servo motor, an output shaft and a shaking cam, the first servo motor is detachably connected with the placing plate, the output shaft is arranged at the output end of the first servo motor, the output shaft is provided with the shaking cam, and the shaking cam corresponds to the filter cloth.

2. The gas turbine axial flow compressor according to claim 1,

every the connecting plate all includes plate body, connecting frame and two mountings, the plate body with the connection can be dismantled to the filter chamber, and be located the lateral wall of the inside of filter chamber, the connecting frame with plate body fixed connection, the both ends of connecting frame all are provided with first connecting hole, four extreme points department of filter cloth all is provided with the second connecting hole, every the mounting respectively with one first connecting hole and corresponding second connecting hole looks adaptation.

3. The gas turbine axial flow compressor according to claim 1,

the preheating pipe comprises a main pipe and a serpentine coil, a partition plate is arranged in the preheating chamber and divides the preheating chamber into a preheating area and a circulating area, one end of the main pipe corresponds to the output end of the aerostatic press body, the other end of the main pipe is connected with the serpentine coil through a flange, the serpentine coil is located in the preheating area, a first control valve is arranged on the main pipe, and a second control valve is arranged at one end, far away from the main pipe, of the serpentine coil.

4. The gas turbine axial flow compressor according to claim 3,

an interlayer is arranged on the inner wall of the circulation area, a temperature sensor is arranged at one end, far away from the serpentine coil, of the partition plate, and an electric heating wire is arranged inside the interlayer.

5. The gas turbine axial flow compressor according to claim 3,

the quantity of preliminary filter is a plurality of, and is a plurality of preliminary filter evenly distributed is in the filter chamber is close to the one end of air inlet, the quantity of shake cam is a plurality of, and is a plurality of shake cam evenly respectively on the output shaft, adjacent two shake the cam and be the setting of staggered structure.

6. An air extraction method using the axial flow compressor for a gas turbine according to claim 4, characterized by comprising the steps of:

firstly, filtering larger impurities in the air by using the preliminary filter plate, and then further filtering dust in the air by using the filter cloth;

when the dust accumulated on the filter cloth is excessive, starting the first servo motor, and driving the shaking cam to rotate by using the output shaft, so that the shaking cam is used for driving the filter cloth to shake, and the filter cloth is always kept in a good filtering effect;

when the aerostatic press body is started for the first time, the electric heating wire is started to preheat the filtered air, so that the air is heated by the heating chamber more quickly;

and opening the first control valve, conveying a part of high-temperature gas in the exhaust cylinder of the gas compressor body into the serpentine coil, and preheating the air circulating in the preheating chamber by using the serpentine coil so as to continuously convey the preheated air to the heating chamber after the electric heating wire is closed.

Technical Field

The invention relates to the technical field of gas turbines, in particular to an axial flow gas compressor of a gas turbine and an air extraction method.

Background

The performance and the operation reliability of the gas turbine are closely related to the quality and the cleanness of air entering a unit, so that in order to ensure the high-efficiency and reliable operation of the unit, a good air inlet system must be configured to filter the air entering the unit and remove impurities in the air, and the good air inlet system can improve the quality of the air entering the unit in various environments with temperature, humidity and pollution and ensure the high-efficiency and reliable operation of the unit.

Therefore, the existing gas turbine is provided with an air filter chamber before the air compressor for filtering air, but with the continuous use of the existing air filter chamber, dust can be accumulated on the filter device inside the filter chamber, and the filtering effect is poor.

Disclosure of Invention

The invention aims to provide an axial flow air compressor and an air extraction method of a gas turbine, which solve the problem that dust is accumulated on a filter device in a filter chamber along with continuous use of the existing air filter chamber in the prior art, so that the filter effect is poor.

In order to achieve the purpose, the invention provides a gas turbine axial flow aerostatic press, which comprises a filter chamber, a filter device, a preheating chamber, a preheating pipeline, a heating chamber and a gas compressor body, wherein one end of the filter chamber is provided with an air inlet, the other end of the filter chamber is provided with an air outlet, one end of the preheating chamber is connected with an air outlet pipeline, the other end of the preheating chamber is connected with a heating chamber pipeline, the input end of the aerostatic press body is connected with the heating chamber pipeline and is positioned at one end of the heating chamber far away from the preheating chamber, the output end of the aerostatic press body is provided with the preheating pipeline, and one end of the preheating pipeline far away from the aerostatic press body corresponds to the preheating chamber;

the filter device is arranged in the filter chamber and comprises a primary filter plate and a deep filter mechanism, the primary filter plate is arranged at one end, close to the air inlet, of the inside of the filter chamber, the deep filter mechanism is arranged at one end, close to the air outlet, of the inside of the filter chamber, the deep filter mechanism comprises connecting plates, filter cloth and shaking components, the connecting plates are arranged on two sides of the inside of the filter chamber, the filter cloth is arranged between the two connecting plates, a placing plate is further arranged on the side wall of the filter chamber, the shaking components are arranged on the placing plate and comprise a first servo motor, an output shaft and a shaking cam, the first servo motor is detachably connected with the placing plate, the output shaft is arranged at the output end of the first servo motor, the output shaft is provided with the shaking cam, and the shaking cam corresponds to the filter cloth.

The air compressor comprises a primary filter plate, a filter cloth, a first servo motor, an output shaft, a shaking cam, a second servo motor, a first servo motor, a second servo motor, a third servo motor, a fourth servo motor, a fifth servo motor, a sixth servo motor, a fifth servo motor, a sixth servo motor, a fourth servo motor, a fourth servo motor, a fourth servo motor, a fourth servo motor, a fourth servo motor, a fourth, a motor, a fourth servo motor, a fourth filter, a fourth, a motor, a fourth servo motor, a fourth a motor, a motor.

Wherein, every the connecting plate all includes plate body, connecting frame and two mountings, the plate body with the connection can be dismantled to the filter chamber, and be located the lateral wall of the inside of filter chamber, the connecting frame with plate body fixed connection, the both ends of connecting frame all are provided with first connecting hole, four extreme points department of filter cloth all is provided with the second connecting hole, every the mounting respectively with one first connecting hole and corresponding second connecting hole looks adaptation.

The plate body is mounted on the side wall of the inside of the filtering chamber through screws, the filtering cloth is placed between the two connecting frames, and the fixing piece penetrates through the corresponding first connecting hole and the second connecting hole, so that the filtering cloth is mounted inside the filtering chamber.

The preheating pipeline comprises a main pipeline and a serpentine coil, a partition plate is arranged in the preheating chamber and divides the preheating chamber into a preheating area and a circulating area, one end of the main pipeline corresponds to the output end of the aerostatic press body, the other end of the main pipeline is connected with the serpentine coil through a flange, the serpentine coil is located in the preheating area, a first control valve is arranged on the main pipeline, and a second control valve is arranged at one end, far away from the main pipeline, of the serpentine coil.

And opening the first control valve, conveying part of high-temperature gas in the exhaust cylinder of the gas compressor body into the snake-shaped coil pipe, and preheating air circulating in the circulation area through the snake-shaped coil pipe.

An interlayer is arranged on the inner wall of the circulation area, a temperature sensor is arranged at one end, far away from the serpentine coil, of the partition board, and an electric heating wire is arranged inside the interlayer.

When first use during gas turbine axial compressor aerostatic press, start electric heating wire is right preheat indoor air and preheat, works as temperature sensor detects when the temperature in the circulation district is lower, starts electric heating wire is supplementary preheat the return circuit and preheat the air.

The number of preliminary filter is a plurality of, and is a plurality of preliminary filter evenly distributed is in the filter chamber is close to the one end of air inlet, the number of shake cam is a plurality of, and is a plurality of shake cam is even respectively on the output shaft, adjacent two shake the cam and be the setting of staggered structure.

The quantity of preliminary filter is a plurality of, improves the filter effect to the great impurity of air pocket, the quantity of shake cam is a plurality of, and adjacent two the shake cam is the staggered structure setting, makes through the shake cam drives the frequency that the filter cloth trembles is higher, thereby makes the filter keeps good filter effect all the time.

The invention also provides an air extraction method adopting the axial flow air compressor of the gas turbine, which comprises the following steps:

firstly, filtering larger impurities in the air by using the preliminary filter plate, and then further filtering dust in the air by using the filter cloth;

when the dust accumulated on the filter cloth is excessive, starting the first servo motor, and driving the shaking cam to rotate by using the output shaft, so that the shaking cam is used for driving the filter cloth to shake, and the filter cloth is always kept in a good filtering effect;

when the aerostatic press body is started for the first time, the electric heating wire is started to preheat the filtered air, so that the air is heated by the heating chamber more quickly;

and opening the first control valve, conveying a part of high-temperature gas in the exhaust cylinder of the gas compressor body into the serpentine coil, and preheating the air circulating in the preheating chamber by using the serpentine coil so as to continuously convey the preheated air to the heating chamber after the electric heating wire is closed.

Firstly, filtering larger impurities in the air through the preliminary filter plate, then further filtering dust in the air through the filter cloth, starting the first servo motor after the dust accumulated on the filter cloth is excessive, driving the shaking cam to rotate through the output shaft, driving the filter cloth to shake through the shaking cam, enabling the filter cloth to always keep good filtering effect, starting the electric heating wire when the air compressor body is started for the first time, preheating the filtered air, enabling the air to be heated by the heating chamber more quickly, opening the first control valve after the air compressor body starts to output high-temperature air holes, conveying a part of high-temperature gas in the exhaust cylinder of the air compressor body to the snake-shaped coil pipe, and utilizing the snake-shaped coil pipe to preheat the air circulating in the preheating chamber, so that the preheated air can be continuously delivered to the heating chamber after the electric heating wire is closed.

The invention relates to an axial flow aerostatic press of a gas turbine and an air extraction method, wherein the filter cloth is arranged between two connecting plates, the first servo motor is detachably connected with the placing plate, the output end of the first servo motor is provided with the output shaft, the output shaft is provided with the shaking cam, the shaking cam corresponds to the filter cloth, firstly, the preliminary filter plate is utilized to filter out larger impurities in the air, then the filter cloth is used for further filtering out dust in the air, when the dust accumulated on the filter cloth is excessive, the first servo motor is started, the output shaft is utilized to drive the shaking cam to rotate, therefore, the filter cloth is driven to shake by the shake cam, so that the filter cloth always keeps a good filtering effect, and the air compressor body can output pure air more continuously.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an axial flow gas compressor for a gas turbine according to the present invention.

Figure 2 is a schematic view of the internal structure of the filtering chamber provided by the present invention.

Fig. 3 is an enlarged view of a portion of the structure of fig. 2 a according to the present invention.

Fig. 4 is a schematic view of the internal structure of the preheating chamber provided by the present invention.

Fig. 5 is a schematic structural diagram of the fixing member provided by the present invention.

FIG. 6 is a flow chart illustrating the steps of a method for pumping air using an axial flow gas compressor of a gas turbine according to the present invention.

1-filter chamber, 11-air inlet, 12-air outlet, 13-preliminary filter plate, 14-depth filter mechanism, 141-connecting plate, 1411-plate body, 1412-connecting frame, 142-filter cloth, 143-shaking assembly, 1431-first servo motor, 1432-output shaft, 1433-shaking cam, 144-placing plate, 145-fixing piece, 1451-fixing shaft, 1452-fixing piece, 1453-screw cap, 2-preheating chamber, 21-partition board, 22-preheating zone, 23-circulation zone, 24-temperature sensor, 25-electric heating wire, 3-preheating pipeline, 31-main pipeline, 311-first control valve, 32-serpentine coil, 321-second control valve, 4-heating chamber, 5-air compressor body, 6-a dust removing mechanism, 61-a dust discharging port, 62-a second servo motor, 63-a screw rod, 64-a screw rod sleeve and 65-a dust scraping plate.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention. Further, in the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

Referring to fig. 1 to 6, the present invention provides a gas turbine axial flow aerostatic press, where the gas turbine axial flow aerostatic press includes a filter chamber 1, a filter device, a preheating chamber 2, a preheating pipeline 3, a heating chamber 4, and a gas compressor body 5, one end of the filter chamber 1 is provided with an air inlet 11, the other end of the filter chamber 1 is provided with an air outlet 12, one end of the preheating chamber 2 is connected to the air outlet 12 by a pipeline, the other end of the preheating chamber 2 is connected to the pipeline of the heating chamber 4, an input end of the aerostatic press body 5 is connected to the pipeline of the heating chamber 4 and is located at one end of the heating chamber 4 far from the preheating chamber 2, an output end of the aerostatic press body 5 is provided with the preheating pipeline 3, and one end of the preheating pipeline 3 far from the aerostatic press body 5 corresponds to the preheating chamber 2;

the filtering device is arranged in the filtering chamber 1, the filtering device comprises a preliminary filtering plate 13 and a depth filtering mechanism 14, the preliminary filtering plate 13 is arranged at one end of the interior of the filtering chamber 1 close to the air inlet 11, the depth filtering mechanism 14 is arranged at one end of the interior of the filtering chamber 1 close to the air outlet 12, the depth filtering mechanism 14 comprises connecting plates 141, filtering cloth 142 and shaking components 143, the connecting plates 141 are arranged at two sides of the interior of the filtering chamber 1, the filtering cloth 142 is arranged between the two connecting plates 141, a placing plate 144 is further arranged on the side wall of the filtering chamber 1, the shaking components 143 are arranged on the placing plate 144, the shaking components 143 comprise a first servo motor 1431, an output shaft 1432 and a shaking cam 1433, and the first servo motor 1431 is detachably connected with the placing plate 144, the output end of the first servo motor 1431 is provided with the output shaft 1432, the output shaft 1432 is provided with the dither cam 1433, and the dither cam 1433 corresponds to the filter cloth 142.

In this embodiment, the primary filter plate 13 is firstly used to filter out larger impurities in the air, then the filter cloth 142 is used to further filter out dust in the air, when the dust accumulated on the filter cloth 142 is excessive, the first servo motor 1431 is started, the output shaft 1432 is used to drive the shaking cam 1433 to rotate, so that the shaking cam 1433 is used to drive the filter cloth 142 to shake, the filter cloth 142 is always kept with a good filtering effect, and the air compressor body 5 can be continuously and continuously output relatively pure air.

Further, each connecting plate 141 includes a plate body 1411, a connecting frame 1412 and two fixing pieces 145, the plate body 1411 is detachably connected with the filtering chamber 1 and is located on a side wall inside the filtering chamber 1, the connecting frame 1412 is fixedly connected with the plate body 1411, two ends of the connecting frame 1412 are respectively provided with a first connecting hole, four end points of the filtering cloth 142 are respectively provided with a second connecting hole, and each fixing piece 145 is respectively matched with one first connecting hole and the corresponding second connecting hole.

In this embodiment, the plate 1411 is mounted on a sidewall of the inside of the filter chamber 1 by using screws, the filter cloth 142 is placed between the two connection frames 1412, and the fixing member 145 penetrates the corresponding first connection hole and the second connection hole, so that the filter cloth 142 is mounted inside the filter chamber 1.

Further, each of the fixing members 145 includes a fixing shaft 1451, a fixing block 1452 and a nut 1453, the fixing shaft 1451 penetrates through the corresponding first connection hole and the second connection hole, one end of the fixing shaft 1451 is fixedly connected to the fixing block 1452, the other end of the fixing shaft 1451 is provided with a thread, and the nut 1453 is adapted to the thread.

In this embodiment, the fixing shaft 1451 is inserted into the corresponding first and second coupling holes, and then the nut 1453 is tightened to complete the installation of the fixing member 145, and the fixing block 1452 is fixedly coupled to the fixing shaft 1451, and is manufactured by an integral molding technique, thereby having a more firm structure.

Further, the preheating pipeline 3 includes a main pipeline 31 and a serpentine coil 32, a partition 21 is disposed inside the preheating chamber 2, the partition 21 divides the preheating chamber 2 into a preheating zone 22 and a circulating zone 23, one end of the main pipeline 31 corresponds to the output end of the aerostatic press body 5, the other end of the main pipeline 31 is in flange connection with the serpentine coil 32, the serpentine coil 32 is located inside the preheating zone 22, a first control valve 311 is disposed on the main pipeline 31, a second control valve 321 is disposed at one end of the serpentine coil 32, which is far away from the main pipeline 31, an interlayer is disposed on the inner wall of the circulating zone 23, a temperature sensor 24 is disposed at one end of the partition 21, which is far away from the serpentine coil 32, and an electric heating wire 25 is disposed inside the interlayer.

In this embodiment, the first control valve 311 is opened to transfer a part of the high-temperature gas in the exhaust cylinder of the aerostatic press body 5 into the serpentine coil 32, the air circulating in the circulation zone 23 is preheated by the serpentine coil 32, when the gas turbine axial flow aerostatic press is used for the first time, the electric heating wire 25 is started to preheat the air in the preheating chamber 2, and when the temperature sensor 24 detects that the temperature in the circulation zone 23 is low, the electric heating wire 25 is started to assist the preheating circuit to preheat the air.

Further, the number of the preliminary filter plates 13 is plural, a plurality of the preliminary filter plates 13 are uniformly distributed at one end of the filter chamber 1 close to the air inlet 11, the number of the shaking cams 1433 is plural, the plurality of the shaking cams 1433 are uniformly and respectively arranged on the output shaft 1432, and two adjacent shaking cams 1433 are arranged in a staggered structure.

In this embodiment, the number of the preliminary filter plates 13 is plural, so as to improve the filtering effect on the impurities with large air holes, the number of the shaking cams 1433 is plural, and two adjacent shaking cams 1433 are arranged in a staggered structure, so that the shaking frequency of the filter cloth 142 driven by the shaking cams 1433 is higher, and the filter plates can always maintain a good filtering effect.

Further, the inside of the filtering chamber 1 is further provided with a dust removing mechanism 6, the dust removing mechanism 6 is located at one end of the filtering cloth 142 close to the preliminary filtering plate 13, the bottom of the filtering chamber 1 is further provided with a dust discharging port 61, and the dust discharging port 61 corresponds to the output end of the dust removing mechanism 6.

In the present embodiment, the dust shaken off by the filter cloth 142 by the dust removing mechanism 6 in the filter chamber 1 is discharged through the dust discharge port 61, thereby preventing the dust from accumulating inside the filter chamber 1.

Further, the dust removing mechanism 6 comprises a second servo motor 62, a screw rod 63, a screw rod sleeve 64 and a dust scraping plate 65, the second servo motor 62 is detachably connected with the filtering chamber 1 and is located on one side, away from the dust removing opening, of the filtering chamber 1, the screw rod 63 is arranged at the output end of the second servo motor 62, the screw rod sleeve 64 is arranged on the screw rod 63, and the dust scraping plate 65 is detachably connected with the screw rod sleeve 64 and corresponds to the dust removing opening.

In this embodiment, the second servo motor 62 is started, the screw rod 63 rotates to drive the screw rod sleeve 64 to translate, so that the dust scraping plate 65 is utilized to push the dust accumulated in the filtering chamber 1 to the dust discharging port 61, thereby avoiding the accumulation of the dust.

Referring to fig. 6, the present invention further provides an air extracting method using the above axial flow compressor of a gas turbine, which includes the following steps:

s1: firstly, the primary filter plate 13 is used for filtering out larger impurities in the air, and then the filter cloth 142 is used for further filtering out dust in the air;

s2: when the dust accumulated on the filter cloth 142 is excessive, the first servo motor 1431 is started, the output shaft 1432 is used for driving the shaking cam 1433 to rotate, so that the shaking cam 1433 is used for driving the filter cloth 142 to shake, and the filter cloth 142 is always kept in a good filtering effect;

s3: when the aerostatic press body 5 is started for the first time, the electric heating wire 25 is started to preheat the filtered air, so that the air is heated by the heating chamber 4 more quickly;

s4: the first control valve 311 is opened, a part of high-temperature gas in the exhaust cylinder of the aerostatic press body 5 is conveyed into the serpentine coil 32, and the serpentine coil 32 is used for preheating air circulating in the preheating chamber 2, so that after the electric heating wire 25 is closed, the preheated air can be continuously conveyed to the heating chamber 4.

Wherein, firstly, the primary filter plate 13 filters out larger impurities in the air, then the filter cloth 142 is used for further filtering out the dust in the air, when the dust accumulated on the filter cloth 142 is excessive, the first servo motor 1431 is started, the output shaft 1432 is used for driving the shaking cam 1433 to rotate, the filter cloth 142 is driven to shake by the shaking cam 1433, so that the filter cloth 142 always keeps good filtering effect, when the aerostatic press body 5 is started for the first time, the electric heating wire 25 is started, the filtered air is preheated, so that the heating chamber 4 is used for heating the air more quickly, when the aerostatic press body 5 starts to output high-temperature air holes, the first control valve 311 is opened, and a part of high-temperature air in the exhaust cylinder of the aerostatic press body 5 is conveyed to the serpentine coil 32, the air circulating in the preheating chamber 2 is preheated by the serpentine coil 32, so that the preheated air can be continuously delivered to the heating chamber 4 after the electric heating wire 25 is turned off.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.