Background
The welding and normalizing of the steel rail butt welding process are two very important procedures. For a long time, it has been necessary to perform flash welding with a large flash butt welding apparatus and then perform normalizing with a heat treatment device. The two kinds of equipment are required to be converted, so that the flow is complex and the working efficiency is low. To avoid this, the application numbers 201710982481.4 and 201910323785.9 propose a solution for "induction heating device". The intermediate frequency heat treatment mechanism comprises a welding machine static frame, a welding machine movable frame, an intermediate frequency heat treatment mechanism and a hanging frame, wherein the intermediate frequency heat treatment mechanism is fixed between the welding machine static frame and the welding machine movable frame, and the top ends of the welding machine static frame and the welding machine movable frame are fixedly connected through the hanging frame; the latter gives the method of operation of the induction heating device; through the suspension type steel rail flash butt welding medium-frequency heat treatment mechanism, flash welding of steel rails and joint heat treatment under a locking state are completed at one time, and work efficiency is improved.
However, in the conventional flash welding equipment, in a stable 'delta-shaped triaxial structure' formed by a central shaft and conductive shafts of two side boxes of the central shaft, the central shaft is formed by a central shaft and a hollow shaft sleeved outside the central shaft, and the hollow shaft can axially move on the central shaft. The static frame and the dynamic frame of the welding machine are respectively hinged with the mandrel and the hollow shaft, and axially shift along with the mandrel and the hollow shaft. Because the central shaft exists between the static frame and the movable frame of the welding machine, and the interval space of the 'delta-shaped three-axis structure' is very limited, the induction heat treatment device which needs to have procedures of lifting, pushing coils to open and close and the like is very difficult to be added on the basis, and as a result, the prior art has to adopt the structure of changing the central shaft into the 'interrupted' central shaft, so that the installation and the procedures of the induction heat treatment device can be changed into the action space by means of the space of 'removing the central shaft' between the static frame of the welding machine and the movable frame of the welding machine and larger relative displacement. As a result, not only the equipment structure and the operation action are complicated, but also the 'break-off' structure certainly weakens the original structure stability of the penetrating center shaft, has good centering performance, and has the outstanding advantages of inhibiting the butt welding misalignment amount, prolonging the service life of the equipment and the like. In addition, although the induction heater in the prior art has a split type structure, only one transformer is adopted, two split induction coils need to be in butt joint contact to form a current loop when in power-on heating, and the coil loop passes through high current when in induction heating, so that the risk of faults caused by poor contact exists.
More specifically, the intermediate frequency heat treatment mechanism of the technical proposal disclosed in patent documents with application numbers 201710982481.4 and 201910323785.9 is fixed between a welding machine movable frame and a welding machine static frame, and mainly comprises a fixed frame, a lifting oil cylinder, a clamping oil cylinder, a coil clamping frame and the like, and the actions are divided into coil lifting and lower coil clamping. The mechanism realizes the opening or closing of the heating coil by tightening the oil cylinder. The coil may extend transversely across the rail weld joint when open. After crossing the rail bottom and closing, the clamping cylinder compresses the coil contact points at two sides, so that the electric conduction of the coil contact points is good. The induction coil in the technical scheme needs to be clamped by the components such as the clamping cylinder, the coil clamping frame and the swing arm for folding and clamping the coil, has a huge structure, and therefore, no matter in a working state or a non-working state, the induction coil needs to occupy a very large installation space and a very large movable space. In order to provide enough movable space for up-and-down movement and coil opening of the heat treatment mechanism, interference with a welding machine is avoided, an interrupted center shaft is adopted, left and right guide shafts are additionally arranged on the upper parts of the movable and static frames, so that the welding machine realizes the positioning and relative movement of the movable and static frames in a five-shaft mode (wherein the center shaft is only positioned but does not play a guide role), the two upsetting shafts are properly moved outwards, the outer wall of the inner side is reasonably thinned, and the space in the middle of the upsetting shafts meets the space required by coil opening.
Further, chinese patent application No. 201510540567.2 discloses a non-contact split induction heating apparatus for rail welded joints, including left and right heating apparatuses oppositely disposed on both sides of a rail in a lateral direction of the rail. The heating device on each side comprises an actuator, a transformer, a coil, etc., and is also provided with a slideway on both sides. According to the technical scheme, the transformer is made to reciprocate in the transverse direction of the steel rail along the slideway by adopting the actuator, so that the coil is separated and closed, the induction heating device occupies a large space and is necessarily interfered with the upsetting shaft of the welding machine during transverse movement, and therefore, the induction heating device cannot be combined with the welding machine.
Disclosure of Invention
The primary object of the present invention is: aiming at the defects existing in the prior art, the induction heating device for the steel rail welding joint is provided, which has a simple and compact structure and small required activity space, so that the induction heating device can be applied to occasions with limited installation or operation space; for example, the welding device is typically applied to a steel rail flash welding device with a traditional triaxial structure, the internal space of which is extremely limited, and the welding device can be directly attached to the steel rail flash welding device without changing the 'delta triaxial structure', so that a foundation is laid for keeping the advantages of stable structure, good centering performance and the like of a welding machine, and a steel rail welding joint with excellent and stable welding quality is more favorably obtained.
A further object of the invention is: an induction heating device capable of avoiding malfunction of a profiling induction coil due to poor contact is provided.
The key to achieving the above object is how to make an induction heating apparatus which occupies a relatively large space in the non-operating state be placed in the longitudinal direction of a rail when not in operation so as to be receivable in a "delta-shaped triaxial structure" such as a flash welding apparatus in which the space is narrow. Through repeated exploration, the basic technical scheme of the rail welding heat treatment induction heating device provided by the invention is as follows:
a mounting for mounting the induction heating device to rail welding equipment;
lifting backboard-forming vertical moving pair with the mounting piece and forming vertical shaft rotating pair with the split profiling induction coil respectively;
a pair of profiling induction coils, which have profiling surface inner profile similar to the profile of the steel rail, and can rotate around the vertical axis between an open state that the profiling surface faces the extending direction of the steel rail and a closed state that the profiling surface faces the steel rail side;
when the lifting backboard rises and is in an open state, the two profiling induction coils are respectively positioned above the two sides of the steel rail, and the lower end of the profiling induction coils is higher than a welding operation space;
when the lifting backboard descends to a preset height and is in an open state, the heights of the profiling surfaces of the two profiling induction coils are matched with the heights of the steel rails;
when the lifting backboard descends to a preset height and then is shifted and is in a folding state, the profiling surfaces of the two profiling induction coils are respectively surrounded on two sides of the steel rail.
Especially when the welding machine is applied to steel rail flash welding equipment, the steel rail flash welding equipment mainly comprises a welding machine static frame provided with an upsetting oil cylinder and a welding machine movable frame provided with a pushing oil cylinder, wherein a left conductive shaft, a right conductive shaft and a central shaft penetrate through the welding machine static frame and/or the welding machine movable frame; the induction heating device is arranged on the central shaft;
when the lifting backboard rises and is in an open state, the two profiling induction coils are respectively positioned at two sides of the central shaft, and the lower end of the profiling induction coils is higher than the welding operation space;
when the lifting backboard descends to a preset height and is in an open state, the two profiling induction coils are respectively positioned in the intervals between the central shaft and the left and right conductive shafts, and the height of the profiling surface is matched with the height of the steel rail;
when the lifting backboard descends to a preset height and then is shifted and is in a folding state, the profiling surfaces of the two profiling induction coils are respectively surrounded on two sides of the steel rail.
Typical positions of the left and right conductive shafts and the central shaft are distributed in a delta shape.
Therefore, after the induction heating device is arranged on the flash welding equipment, the split profiling induction coils can be contained at two sides of the central shaft and the welding operation space is reserved when the split profiling induction coils are in a lifted and opened state through the vertical shaft rotating pair structure attached to the vertical moving pair, so that the welding operation of the flash welding equipment is not influenced; after welding, the split profiling induction coil descends to a proper position, and is surrounded on two sides of the steel rail in an transposition mode, and the required heat treatment can be completed by electrifying. As a result, the original 'delta-shaped triaxial structure' of the flash welding equipment is not required to be changed, the welding and normalizing procedures are efficiently switched, and meanwhile, the original ideal centering performance of the flash welding equipment is maintained, so that the butt welding quality of a track is ensured.
In order to achieve the further purpose, the abutting adjacent surfaces at the top and the bottom of the two profiling induction coils are respectively provided with an insulating piece, and are respectively electrically connected with the corresponding transformers and respectively electrified and heated in an induction mode.
It is easy to understand that the two profiling induction coils are respectively electrified, and short circuits among coils are prevented by the aid of the insulating piece in the folding state, so that the defect that in the prior art, the two induction coils need to be in butt joint contact to form a current loop and faults possibly caused by poor contact can be completely avoided.
In a word, compared with the prior art, the invention is very suitable for being used as an induction heating device for steel rail welding heat treatment, and because the lifting and displacement composite mechanism is created, lifting and displacement folding actions of the non-contact induction heating coil can be completed in a small movable space, a foundation is laid for realizing the related functions of temperature detection, uniform induction heating, rapid cooling and the like of steel rail welding joints, and meanwhile, the risk of faults of the compression coil due to poor conduction is also eliminated. In particular, by the innovative design that the coil imitation surface descends along the direction parallel to the steel rail and is folded at two sides of the steel rail in an transposition way, the small interval space between the central shaft and the guide shaft of the welding machine is fully utilized in an open state, and the movable space occupied by the coil because of opening in a non-working state is obviously reduced, so that the flash welding of the steel rail and the joint heat treatment in a locking state can be completed at one time on the basis of keeping the stable structure and the good centering performance of the original welding machine without changing the 'delta-shaped triaxial structure' of the traditional welding machine, the quality of the welded joint is ensured, and the working efficiency is improved.
It should be noted that the induction heating device of the invention can be added into a flash welding machine with a three-axis structure, or can be added into a suspension type rail flash butt welding medium-frequency heat treatment mechanism with a five-axis structure, such as a rail flash welding machine with an interrupted central axis disclosed by 201710585115.5, and the like.
Description of the embodiments
Examples
As shown in fig. 1 and 2, the welding heat treatment induction heating device of the present embodiment has a basic structure including a fixed back plate 1 as a mounting member, a lifting and indexing composite mechanism (mainly including a lifting back plate 3, a rotary support 15 and a driving motor 6), a transformer 4, a clamp 5, a profiling induction coil 7, a reinforcement 16, a blowing device 8, a support 13, a thermometer 14, and a protection plate 10. The lifting and indexing composite mechanism comprises a lifting oil cylinder 2, a lifting back plate 3, a connecting block 12, a guide rail sliding block 9, a driving motor 6, a rotating bracket 15 of a U-shaped main body and a limiting piece 17. When in installation, the lifting and indexing composite mechanism is fixedly connected with the central shaft C through the fixed back plate 1 (see figures 9-13).
The concrete structure of the fixed back plate 1 is shown in fig. 3, and mainly comprises guide rail seats 1.4 extending upwards symmetrically and vertically at two ends of a horizontal beam plate 1.2, a yielding arch 1.1 is formed in the middle of the horizontal beam plate 1.2, the yielding arch 1.1 is matched with the outer circle of a central shaft C and fixedly connected (specifically fixedly connected through screws or other fixedly connected pieces), the upper end of the guide rail seat 1.4 longitudinally extends out of an oil cylinder mounting table 1.3 parallel to a horizontal plane, and a weight reducing hole 1.5 is formed in the guide rail seat 1.4. The protection plates 10 are arranged at the left end and the right end of the fixed backboard 1 (two thermometers can be arranged at the same end of the lifting backboard 3, and only one end is required to be provided with the protection plates at the moment). To avoid redundancy, the symmetrical structure describes one end, and the other end structure can be analogized. The guide rail seat 1.4 of the fixed backboard 1 is fixedly connected with a vertical rail which forms a moving pair with the guide rail sliding block 9, and the guide rail sliding block 9 is fixedly connected with the end part of the lifting backboard 3 through a connecting block 12.
As shown in fig. 4, the specific structure of the lifting backboard 3 is that two ends of the bridge-shaped backboard main body 3.1 are respectively formed with a pin joint frame 3.3, and a pair of motor bases 3.2 (see fig. 7) respectively provided with a vertical central hole 3.5 extend from the middle upper part. The backboard main body 3.1 extends below the two motor bases 3.2 to form a bearing plate 3.4 with coaxial supporting holes 3.6 corresponding to the center holes 3.5 of the motor bases respectively. The left and right ends of the lifting backboard 3 are respectively provided with a thermometer 14 through a bracket 13 (the two thermometers can also be fixed at the same end, namely, both the thermometers are arranged at the left end or the right end).
The lifting cylinder 2 is arranged on the cylinder mounting table 1.3 of the fixed backboard 1, and referring to fig. 8, the telescopic end 2.1 of the lifting cylinder 2 is connected with the pin joint frame 3.3 of the backboard main body 3.1 through a pin 11, and the pin 11 can be longitudinally mounted or transversely mounted, so that the lifting backboard 3 and the fixed backboard 1 form a lifting moving pair driven by the lifting cylinder 2.
A pair of rotating brackets 15 with U-shaped cross sections, which are provided with transmission holes 15.1 respectively, are arranged between the two motor bases 3.2 and the bearing plate 3.4, and are used for installing the transformer 4 and form transmission holes connected with a shaft hub with the rotating motor, so that the transformer and the coil can rotate under the drive of the motor, the U-shaped structure of the rotating bracket not only meets the installation requirement of the transformer, but also utilizes the neutral gear of the U-shaped structure in the middle of the bracket to give way to the rotating motor, and the structure is more compact. The motor base 3.2 of the lifting backboard 3 is provided with a driving motor 6, an output shaft of which passes through the central hole 3.5, the transmission hole 15.1 and the supporting hole 3.6 in sequence. The output shaft of the driving motor 6 is respectively in movable fit with the central hole 3.5 and the supporting hole 3.6 and is connected with the transmission hole 15.1 through the flat key 18 to realize circumferential constraint, so that the U-shaped rotary support 15 can be driven to rotate. The lifting backboard 3 is respectively provided with a limiting piece 17 for limiting the rotation of the driving motor 6 at the initial 0-degree position and the position of the rotating 90-degree position corresponding to the driving motor, so that the rotation angle of the coil is restrained, and the coil is accurately positioned at the required initial 0-degree position or the position of the rotating 90-degree position.
The outer side of the rotary support 15 with the U-shaped main body structure is provided with the transformer 4 by means of the clamp 5, and specifically, two supporting legs of the rotary support 15 forming the U-shaped main body structure are connected with a connecting plate of the clamp 5 by bolts. The primary coil and the secondary coil of the transformer 4 are coaxial, the whole transformer is cylindrical with compact structure, and the lower end of the transformer is fixedly connected with the upper end of the profiling induction coil 7. The profiling induction coil 7 is provided with a reinforcement 16 for increasing rigidity, the specific structure is shown in fig. 5, the reinforcement 16 comprises a coil support 6.1, an insulating plate 16.2 and an insulating pressing plate 16.2, the upper part of the coil support 6.1 is fixedly connected with the bottom of the rotary support 5, the insulating plate 16.2 is arranged at the lower part of the coil support, the insulating plate 16.2 extends to the gap of the copper guide tube 7.4 at the access part of the profiling induction coil 7, and after being fastened with the insulating pressing plate 16.2, the copper guide tube 7.4 at the access part between the coil support and the insulating pressing plate is pressed, so that the reinforcement effect is achieved. The lower part of the coil support 16.2 is provided on both sides with a mouthpiece for mounting the blowing device 8. The blowing device 8 is insulated from the profiling induction coil 7. The structure fully utilizes the space gap of the profiling induction coil 7, and has compact structure. Referring to fig. 6, the profile induction coil 7 is formed by bending a copper pipe, and includes a body copper pipe 7.1 configured as a profile body having an inner profile similar to the outer profile of a rail, an access portion copper pipe 7.4 configured to extend rearward and upward from a position of the profile body away from the back side of the profile surface and corresponding to the web, and electrically connected to a transformer, a magnetizer 7.2 attached to the body copper pipe 7.1, and an insulator 7.3. The magnetic conductor 7.2 has the function of strengthening the magnetic field near the coil and is arranged around the rail head, the rail web, the triangular area and the rail foot so as to improve the induction heating efficiency and make the heating effect more uniform; the function of the insulation 7.3 is to prevent a short circuit between the coils on both sides after closing. The reinforcement 16 is provided with blowing devices 8 of the profiled rail profile at the sides of the profiled induction coil 7 for cooling after welding and/or after heat treatment. The blowing device 8 is provided with blowing openings at the rail head, the rail head side surface, the rail head jaw, the rail web and the triangular area, so that the whole contour of the steel rail can be uniformly cooled. Practices show that compared with the structure that the coil in the prior art adopts the copper guide pipe extending from the top and the connecting structure of the transformer output end, the profiling induction coil extends from the rail web to form the connecting part, and the copper guide pipe is fixedly connected with the transformer output end, so that the space on the upper part of the rail head profile can be saved. Particularly for the rail type profiles of 50kg/m, 60kg/m and 75kg/m steel rails, the sufficient distance between the rail head profile and the lower part of the central shaft can be ensured, the induction heating of the lower part of the central shaft after the coil is electrified is avoided, and the same or similar effect can be achieved for the steel rails of other types.
As shown in fig. 9 and 10, the steel rail flash welding equipment provided with the induction heating device for performing welding heat treatment is longitudinal along the direction of the central axis C, and the central lines of the left and right conductive shafts L, R are positioned on the same horizontal plane; the plane formed by the longitudinal axis and the vertical axis is a vertical plane, and the direction perpendicular to the vertical plane is transverse. The welding machine in the induction heating device is similar to the prior art, and mainly comprises a welding machine static frame D2 provided with an upsetting oil cylinder and a welding machine movable frame D1 provided with a tumor pushing oil cylinder. Left and right conductive shafts L, R and a central shaft C which are distributed at intervals in a delta shape penetrate through the space between the welding machine static frame D2 and the welding machine dynamic frame D1. The core innovation is that the central shaft C is provided with an induction heating device Z positioned between a welding machine movable frame D1 and a welding machine static frame 2.
It will be appreciated that the lifting back plate, the rotating bracket, the clamp of the welding heat treatment induction heating device of this embodiment include the arrangement of the external dimensions, etc., firstly, it is ensured that the coil can be stored on both sides of the central shaft when not indexing after the installation of the transformer and the coil, and the overall dimensions of the induction coil assembly (see fig. 16, including the profiling induction coil, the blower device, etc.) are designed and controlled when descending, especially the whole thickness including the blower device is very compact, so that the transmission hole of the rotating bracket 15 and the arrangement of the relative positions of the transformer and the coil can meet the following three requirements through the narrow space between the central shaft and the conductive shaft, without collision with the central shaft and the conductive shaft:
1) After the transposition is finished, the gaps between the inner profile profiling surface of the profiling induction coil and the outer profile of the steel rail are controlled to be uniform as much as possible, for example, the gap range is controlled to be 7mm-12mm, preferably 9mm-11mm, so as to ensure the heating effect; the gap at each specific place can be properly adjusted according to different rail types, for example, the gap range of the rail top is controlled to be less than 10mm, and the gap of the rail web or the rail bottom is controlled to be not more than 12mm;
2) During the indexing process, the area swept by the coils at the two sides cannot be overlapped, so that the motion interference is avoided;
3) After the welding is finished, a certain movable space is reserved between the two welding machine frames for the coil and the transformer to pass through in an indexing way. During indexing, the coil and the area swept by the transformer are both in the movable space, i.e., cannot collide with the welder components.
In operation, the output shaft of the copying induction coil 7 is controlled to be displaced between an open state in which the copying surface faces the rail extending direction and a closed state in which the copying surface faces the rail side. When the welding heat treatment induction heating device is transported by a rail vehicle or a working trolley advances to a welding position along a steel rail, the specific operation control steps of the induction heating device Z are as follows:
first, as shown in fig. 11, when the welding machine welds, the telescopic end of the lifting cylinder 2 is lifted, the profiling induction coils 7 are in a lifted state, the output shaft of the driving motor 6 is in an initial 0-angle position, the two profiling induction coils 7 are respectively positioned at two sides of the central shaft C, the lower end of the profiling induction coils is higher than the welding operation space, and the profiling induction coils are in a lifted and opened non-energized state. At this time, since the lower end of the profile induction coil is higher than the welding operation space, the welding operation space can be separated from the upper space by the slag trap to protect the equipment above the slag trap (e.g., the induction heating coil, etc.).
Second, as shown in fig. 12, the welding machine completes the welding, the telescopic end of the lifting cylinder 2 descends, the profiling induction coil 7 is in a descending state to a specified height, the output shaft of the driving motor 6 is in an initial 0-angle position, the two profiling induction coils 7 are respectively positioned in the interval between the central shaft C and the left and right conductive shafts L, R, the height of the profiling surface of the profiling induction coils is matched with the height of the steel rail G, and the profiling induction coils are in a descending and opening non-electrified state.
And thirdly, as shown in fig. 13, after the two profiling induction coils 7 descend to a specified height, the output shaft of the driving motor 6 rotates by 90 degrees to drive the two profiling induction coils 7 to rotate by 90 degrees, the profiling surfaces of the two profiling induction coils 7 surround the positions on two sides of the steel rail G, and after the profiling induction coils 7 are in a descending and folding state, the blowing device 8 is started to blow air, so that the welding seam of the steel rail G is rapidly cooled to a set temperature required by heat treatment.
And fourthly, when the welding line of the steel rail welding joint is reduced to be lower than the set temperature, the air blowing device 8 is closed, the two profiling induction coils 7 are respectively electrified independently, after the welded steel rail welding joint is heated to the set temperature range in an induction mode, the air blowing device 8 is started again to blow air, the induction heating area of the steel rail G is cooled rapidly, and the heat treatment of the welding line is completed.
Compared with the prior art, the lifting and indexing mechanism based on innovative design can efficiently finish lifting and indexing folding actions of the non-contact induction heating coil in a small movable space, and the movable space during integral structure and induction heating operation is very compact, so that the lifting and indexing mechanism is particularly suitable for steel rail welding equipment with limited installation space or use space, and has the following specific advantages:
because the 'delta-shaped triaxial structure' of the original welding machine is not required to be changed, good centering performance is ensured, and the misalignment during the butt welding of the steel rail can be effectively restrained, so that the butt welding quality of the rail is practically ensured.
The induction heating device can be directly arranged at a proper position of the existing welding machine (such as a suspension type steel rail flash butt welding medium-frequency heat treatment mechanism with a three-axis structure or a five-axis structure or other similar steel rail welding equipment), so that the integrated device of track welding and heat treatment induction heating is formed, and the flash welding of the steel rail and the joint heat treatment under the locking state can be completed at one time.
The induction heating coils are split and non-contact, namely after the profiling induction coils on the left side and the right side are folded, a certain gap is formed between the top or the bottom of each profiling induction coil, and the gap is approximately compensated by the insulating piece. The two profiling induction coils are independently electrified and heated. The phenomenon of poor contact and ignition of contact surfaces, which are easily caused by the fact that coils on two sides need to be in a contact compression state when heating in the prior art, such as 201710982481.4, is thoroughly avoided. And parts such as a pushing coil opening and closing, a clamping oil cylinder, a swinging arm and the like are omitted, and the structure is simpler and more reliable.
Considering that the welding joint can be subjected to heat treatment operation only when the welding joint is converted into pearlite, the blowing device with the blowing pipes arranged in a comb-shaped structure is reasonably arranged, the whole outline of the welding joint can be cooled, and the welding and heat treatment efficiency is improved.
The induction heating device is also provided with a temperature measuring instrument for detecting and collecting the temperatures of the rail top and the rail bottom, a protection plate or a protection cover for protecting the temperature measuring instrument, and a welding splashing prevention protection facility, thereby laying an advantageous foundation for ensuring the smooth operation of the induction heating process. If the protection plate (or the slag plate) which is detachably arranged on the central shaft is arranged during welding, the protection plate can be timely removed after the welding is completed, the induction heating device can be effectively protected, and the heat treatment quality can be effectively controlled.
The induction heating device, the steel rail flash welding machine comprising the induction heating device and the induction heating method of the steel rail welding joint can be applied to the welding engineering application of newly-built or existing track seamless lines of high-speed railways, inter-city railways, subways, tramways and the like in China.
Examples
The basic structure of the welding heat treatment induction heating device of this embodiment is the same as that of the first embodiment, except that the air blowing device 8 is plate-shaped with an internal cavity structure, has a contour similar to the shape of the rail toward the rail, and is provided with a plurality of small air blowing holes, as shown in fig. 14.
Examples
The basic structure of the welding heat treatment induction heating device of this embodiment is the same as that of the first embodiment, except that as shown in fig. 16, a cover 21 replaces the protection plate or the protection cover of the first embodiment, and is fixedly or detachably connected with the fixed back plate 1 as a mounting member, a thermometer 14 is mounted in the cover 21, and a temperature measuring window is left on the inner side surface of the bottom of the cover 21 for collecting temperature. The baffle 20 is hinged to the housing 21 through a hinge hole 20.1. The hinge holes 19.1 and 19.2 at the two ends of the connecting rod 19 are respectively hinged with the lifting backboard 3 and the baffle 20 to form a connecting rod mechanism. The lifting motion of the lifting backboard 3 drives the baffle 20 to rotate around the hinge hole 20.1, so that the automatic opening and closing of the temperature measuring window is realized. When the lifting backboard 3 is at the lifting position, the baffle 20 shields the temperature measuring window to form a totally-enclosed shell structure, so that the damage of the thermometer caused by welding splashing is avoided; when the lifting backboard 3 is in the descending position, the baffle 20 opens a temperature measuring window, so that the temperature measurement required in the heat treatment can be realized.
In addition to the embodiments described above, other embodiments of the invention are possible. All technical schemes formed by equivalent substitution or equivalent transformation fall within the protection scope of the invention.