Split heat exchanger u-tube welding apparatus and method of use

Abstract

This invention relates to a U-tube welding device for a split-type heat exchanger and its method of use, comprising: a first body for accommodating pipes; a second body for accommodating control and drive components; and a welding head for welding the U-tubes. The welding head is located at one end of the first and second bodies, the first body is fixedly connected to the welding head, and the first and second bodies are detachably connected. A receiving cavity is formed inside the welding head, the receiving cavity having a first opening and a second opening for observation. In the detached state of the second body, the second opening communicates with the outside of the first body. A positioning mechanism is provided on the first body. The U-tube welding device and its method for a split-type heat exchanger obtained by this invention have the following advantages: the second body can be detached relative to the first body, allowing for clearer observation without being obstructed by surrounding pipes to be welded; the positioning mechanism controls the position of the U-tube after it enters, allowing subsequent U-tubes of the same specification to be welded directly.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a welding device for U-shaped tubes of a split heat exchanger and its method of use. Background Technology

[0002] In the prior art, for example, Chinese Invention Patent Publication No. CN119658080B discloses a welding torch for U-shaped dense tubes, including a body and a head. The head is located at one end of the body, and a receiving cavity is formed inside the head. The receiving cavity is open at the end away from the body. A U-shaped tube and two straight tubes connected to the U-shaped tube extend into the receiving cavity of the head from the open end of the receiving cavity, and the end wall of the head away from the body abuts against the outer wall of the heat exchanger casing. A welding mechanism is provided on the side of the head located inside the receiving cavity, and the welding mechanism welds the joint of the U-shaped tube and the straight tubes. However, this welding torch for U-shaped dense tubes only has an observation port on one side of the outer cover and mounting block. After the U-shaped tube is inserted, it is easy to block the small tungsten needle, making it difficult to observe. Moreover, it is located on the side, and when the tube bundle of the heat exchanger is densely arranged, the distance between adjacent U-shaped tubes becomes smaller, and it will be blocked by surrounding tubes, making observation inconvenient and potentially affecting the welding quality. Summary of the Invention

[0003] One objective of this application is to provide a welding device for U-shaped tubes of a split heat exchanger and its usage method, which facilitates observation.

[0004] The technical solution adopted in this application is: a U-shaped tube welding device for a split heat exchanger, comprising: The first fuselage is used to house the piping; The second fuselage houses the control and drive components; The welding head is used for welding U-shaped tubes; The machine head is located at one end of the first body and the second body. The first body is fixedly connected to the machine head, and the first body and the second body are detachably connected. The second body fits into the machine head. A receiving cavity is formed inside the machine head. The end of the receiving cavity away from the first body has a first opening for the passage of the U-shaped tube, and the end of the receiving cavity near the first body has a second opening for observation. A welding mechanism is provided on one side of the receiving cavity. When the second body is detached, the second opening communicates with the outside of the first body. The first body is provided with a positioning mechanism for positioning the U-shaped tube, and the positioning mechanism is arranged facing the second body.

[0005] In some embodiments of this application, the first body is provided with a positioning groove, and the second body is provided with a protrusion that mates with the positioning groove.

[0006] In some embodiments of this application, the first body is provided with a positioning notch, and the second body is provided with a positioning block that cooperates with the positioning notch.

[0007] In some embodiments of this application, the first body is provided with an arc-shaped groove arranged along the length direction, and the second body is provided with an arc-shaped boss that mates with the arc-shaped groove.

[0008] In some embodiments of this application, a locking mechanism is also included. The locking mechanism includes a locking hook and a locking pin that cooperates with the locking hook. The locking hook is rotatably connected to the first body and the locking pin is disposed on the second body. In the locked state, the first body and the second body are fitted together and the locking pin is engaged with the locking hook.

[0009] Furthermore, the locking mechanism also includes a handle, one end of which is connected to a locking hook; two locking hooks, two locking pins, and two locking pins are respectively located on both sides of the second body, and the locking hooks on both sides are connected by a pivot, which passes through the first body; a linkage rod is provided between the two handles.

[0010] In some embodiments of this application, the first fuselage is provided with an inert gas pipe and a water and electricity pipe, the outlet of the inert gas pipe is connected to the receiving cavity, and the water and electricity pipe is connected to the welding mechanism.

[0011] In some embodiments of this application, the second housing is provided with a drive unit, a control switch and a first gear. The control switch and the drive unit are electrically connected. The output end of the drive unit is connected to the first gear. The welding mechanism includes a transmission gear. In the assembled state of the second housing, the transmission gear meshes with the first gear.

[0012] In some embodiments of this application, the positioning mechanism includes a positioning plate, a positioning screw, a slider, and a locking plate. The slider and the locking plate are slidably connected along the length of the first body. The positioning plate is fixedly connected to the slider. The positioning screw passes through the slider and fits against the locking plate. When the U-shaped tube is in place, the positioning plate fits against the U-shaped tube.

[0013] A method for using a U-tube welding device for a split heat exchanger, used to control the aforementioned U-tube welding device for a split heat exchanger, includes the following steps: Step S1: Place the machine head onto the U-shaped tube; Step S2: Disassemble the second body, observe the position of the welding mechanism and the U-shaped tube through the second opening, and adjust the welding position in conjunction with the U-shaped tube; Step S3: Adjust and fix the positioning mechanism to the position of the U-shaped tube; Step S4: Reassemble the second fuselage and begin welding; Step S5: After welding the first U-shaped tube, weld the subsequent U-shaped tubes of the same specification by directly placing the welding head onto the U-shaped tube to be welded and starting the welding process. When changing to a different specification of U-tube, repeat steps S1-S5.

[0014] The present invention provides a split-type heat exchanger U-tube welding equipment and its usage method, which has the following advantages: 1. The separate design of the first and second bodies separates the internal pipes and electrical components, resulting in higher safety. Water leaks will not affect the electrical components, reducing maintenance costs and risks; 2. The second body can be disassembled relative to the first body, exposing a second opening that allows welders to observe the interior of the cavity from above. This observation is clearer and not obstructed by surrounding pipes to be welded. Furthermore, the second body is used for control, and the welding equipment cannot be started after disassembly, avoiding the risk of accidental activation by welders during observation; 3. Electrical components are prone to damage, and if damaged, the second body can be directly replaced for maintenance, reducing downtime; 4. The positioning mechanism controls the position of the U-tube after it enters the machine. U-tubes of the same specification only need to be observed and adjusted during the first welding. Subsequent U-tubes of the same specification can be welded directly without secondary observation, improving the efficiency of batch welding of the same specification. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 This is a cross-sectional view of Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the structure of Embodiment 1 of the present invention with the second fuselage removed; Figure 4 This is a schematic diagram of the structure of the second fuselage of Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the positioning mechanism of Embodiment 1 of the present invention.

[0016] In the diagram: 1. First fuselage; 101. Positioning groove; 102. Positioning notch; 103. Arc-shaped groove; 11. Inert gas pipe; 12. Water and electricity pipe; 13. First housing; 14. First connecting block; 2. Second fuselage; 201. Protrusion; 202. Positioning block; 203. Arc-shaped boss; 21. Driving component; 22. Control switch; 23. First gear; 24. Second housing; 25. Second connecting block; 3. Head; 31. Receiving cavity; 311. First opening; 312. Second opening; 32. Connecting ring; 33. Outer cover; 34. Bottom ring; 35. Silicone sheet; 4. Welding mechanism; 41. Transmission gear; 42. Tungsten needle; 5. Locking mechanism; 51. Locking hook; 52. Locking post; 521. Protruding ring; 53. Handle; 54. Rotating shaft; 55. Linkage rod; 6. Positioning mechanism; 61. Positioning plate; 62. Positioning screw; 63. Slider; 64. Locking plate; 641. Slide groove. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solutions of this disclosure, the following detailed, clear, and complete description of this disclosure is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this disclosure and are not intended to limit it.

[0018] In the description of this application, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0019] Those skilled in the art should understand that in the disclosure of this application, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on this application.

[0020] Example 1: This embodiment provides a U-tube welding device for a split heat exchanger, such as... Figure 1 , Figure 2 , Figure 3 As shown, it includes: First fuselage 1, used to house the piping; The second fuselage 2 is used to house control and drive components; Machine head 3, used for welding U-shaped tubes; The head 3 is located at one end of the first body 1 and the second body 2. The first body 1 is fixedly connected to the head 3, and the first body 1 is detachably connected to the second body 2. The second body 2 is fitted to the head 3. A receiving cavity 31 is formed inside the head 3. The receiving cavity 31 is provided with a first opening 311 for the passage of a U-shaped tube at the end away from the first body 1. The receiving cavity 31 is provided with a second opening 312 for observation at the end closer to the first body 1. A welding mechanism 4 is provided on one side inside the receiving cavity 31. When the second body 2 is detached, the second opening 312 communicates with the outside of the first body 1.

[0021] The separate design of the first body 1 and the second body 2 separates the internal pipes and electrical components, enhancing safety. Water leaks will not affect the electrical components, reducing maintenance costs and risks. The second body 2 can be disassembled relative to the first body 1, exposing the second opening 312. This allows welders to observe the contents of the receiving cavity 31 from above, providing a clearer view without obstruction from surrounding pipes to be welded. Furthermore, the second body 2 is used for control; its removal prevents the welding equipment from starting, avoiding the risk of accidental activation by welders during observation. Additionally, since electrical components are prone to damage, the second body 2 can be directly replaced for maintenance if damaged, minimizing downtime.

[0022] To facilitate the assembly of the first fuselage 1 and the second fuselage 2, such as Figure 3 , Figure 4 As shown, the first body 1 is provided with a positioning groove 101, and the second body 2 is provided with a protrusion 201 that cooperates with the positioning groove 101. The positioning groove 101 and the protrusion 201 are installed together, which enables the first body 1 and the second body 2 to be quickly positioned and assembled, and prevents the two from wobbling relative to each other after assembly.

[0023] To facilitate the assembly of the first body 1 and the second body 2, the first body 1 is provided with a positioning notch 102, and the second body 2 is provided with a positioning block 202 that cooperates with the positioning notch 102. The positioning notch 102 and the positioning block 202 are installed together, which enables the first body 1 and the second body 2 to be quickly positioned and assembled, and prevents the two from shaking relative to each other after assembly.

[0024] To facilitate the assembly of the first fuselage 1 and the second fuselage 2, the first fuselage 1 is provided with an arc-shaped groove 103 arranged along its length, and the second fuselage 2 is provided with an arc-shaped boss 203 that mates with the arc-shaped groove 103. The arc-shaped groove 103 and the arc-shaped boss 203 are installed together, resulting in a larger contact area between the two, which is more conducive to the fitting of the first fuselage 1 and the second fuselage 2. In addition, the long arc-shaped groove 103 can also play a guiding role, making the assembly of the two more convenient.

[0025] In this embodiment, one arc-shaped groove 103 is provided, which is located on the side of the first body 1 facing the second body 2 and is located in the middle; two positioning notches 102 are provided, which are located on both sides of the arc-shaped groove 103; four positioning grooves 101 are provided, with two on each side of the arc-shaped groove 103, and the two positioning grooves 101 on each side are located on the upper and lower parts of the first body 1, respectively.

[0026] To ensure reliable assembly of the first fuselage 1 and the second fuselage 2, a locking mechanism 5 is also included. The locking mechanism 5 includes a locking hook 51 and a locking pin 52 that cooperates with the locking hook 51. The locking hook 51 is rotatably connected to the first fuselage 1, and the locking pin 52 is disposed on the second fuselage 2. In the locked state, the first fuselage 1 and the second fuselage 2 are fitted together, and the locking pin 52 is engaged with the locking hook 51. The locking mechanism 5 is used to fix the first fuselage 1 and the second fuselage 2 together, preventing the second fuselage 2 from detaching and ensuring reliable welding. The locking hook 51 and the locking pin 52 cooperate; the locking hook 51 is in a "7" shape, and after hooking into the locking pin 52, it prevents the second fuselage 2 from detaching outwards.

[0027] To facilitate locking and unlocking, the locking mechanism 5 also includes a handle 53. One end of the handle 53 is connected to the locking hook 51, and the other end extends in the opposite direction to the locking hook 51. Two locking hooks 51, two locking pins 52, and two handles 53 are provided. The two locking pins 52 are located on both sides of the second body 2, and the locking hooks 51 on both sides are connected by a rotating shaft 54, which passes through the first body 1. A linkage rod 55 is provided between the two handles 53. The handle 53 can drive the locking hook 51 to rotate, which makes it convenient to operate the locking hook 51. The two locking hooks 51 clamp the second body 2 in the middle, which can prevent the second body 2 from falling off to the sides and also play a positioning role, and also make it easy for the locking hook 51 to hook into the locking pin 52. The design of the linkage rod 55 makes the two handles 53 move synchronously, which also makes it easy for the welding personnel to operate.

[0028] In this embodiment, the outer end of the locking post 52 is provided with a protruding ring 521, and the two sides of the locking hook 51 are respectively attached to the protruding ring 521 and the second body 2, so that the locking hook 51 cannot be dislodged from the locking post 52 from the side, ensuring reliable locking; the handle 53 and the locking hook 51 are integrally formed; two linkage rods 55 are provided, and the two ends of the linkage rods 55 are respectively connected to the handles 53 on both sides by bolts.

[0029] To ensure the reliability of the first fuselage 1, an inert gas pipe 11 and a water and electricity pipe 12 are provided inside the first fuselage 1. The outlet of the inert gas pipe 11 is connected to the receiving cavity 31, and the water and electricity pipe 12 is connected to the welding mechanism 4.

[0030] To ensure the reliability of the second machine body 2, a drive component 21, a control switch 22, and a first gear 23 are provided inside the second machine body 2. The control switch 22 and the drive component 21 are electrically connected, and the output end of the drive component 21 is connected to the first gear 23. The welding mechanism 4 includes a transmission gear 41, which meshes with the first gear 23 when the second machine body 2 is assembled. The drive component 21 is used to drive the first gear 23 to perform rotational welding, thereby driving the welding mechanism 4 to perform welding. The control switch 22 is used to control the start and stop of the welding equipment.

[0031] In this embodiment, the first gear 23 and the positioning block 202 are located on the same plane, and the first gear 23 is located between the two positioning blocks 202. The positioning block 202 can protect the first gear 23.

[0032] To facilitate the welding of U-shaped tubes of the same specification, a positioning mechanism 6 is provided on the first machine body 1, and the positioning mechanism 6 is arranged facing the second machine body 2; for example Figure 5 As shown, the positioning mechanism 6 includes a positioning plate 61, a positioning screw 62, a slider 63, and a locking plate 64. The slider 63 and the locking plate 64 are slidably connected along the length of the first body 1. The positioning plate 61 is fixedly connected to the slider 63. The positioning screw 62 passes through the slider 63 and fits against the locking plate 64. When the U-shaped tube is in place, the positioning plate 61 fits against the U-shaped tube. The positioning mechanism 6 is used for positioning the U-shaped tube; the positioning plate 61 is used to fit and position the U-shaped tube; the positioning screw 62 is used to fix the position of the slider 63; the slider 63 is used to slide and adjust the position of the positioning plate 61; the locking plate 64 is used to cooperate with the sliding of the slider 63 and to cooperate with the positioning screw 62 for fixation. In use, after the position of the U-shaped tube is adjusted to the correct position, the positioning plate 61 is moved to fit the U-shaped tube, and then the positioning screw 62 is tightened to fix the slider 63, thereby fixing the position of the positioning plate 61. For subsequent U-shaped tubes of the same specifications, the machine head 3 only needs to be directly placed on the U-shaped tube so that the U-shaped tube fits the positioning plate 61 to reach the appropriate welding position, without the need to disassemble the second machine body 2 for observation and adjustment.

[0033] In this embodiment, the locking plate 64 is fixedly connected to the first body 1; the locking plate 64 is provided with a slide groove 641 arranged along the length direction of the first body 1, the slide groove 641 is T-shaped, and the cross-section of the slider 63 is T-shaped and cooperates with the slide groove 641.

[0034] The welding equipment is generally flat. When the second body 2 is combined with the first body 1, the second body 2 can completely cover the second opening 312. In this embodiment, when the second body 2 is combined with the first body 1, the outer surface of the second body 2 and the outer surface of the head 3 are on the same plane or the same arc surface.

[0035] The first body 1 includes a first housing 13 and a first connecting block 14, with the bottom of the first housing 13 connected to the top of the first connecting block 14. The second body 2 includes a second housing 24 and a second connecting block 25, with the bottom of the second housing 24 connected to the top of the second connecting block 25. A positioning groove 101 and an arc-shaped groove 103 are provided on the first housing 13, and a positioning notch 102 is provided on the first connecting block 14. A protrusion 201 and an arc-shaped boss 203 are provided on the second housing 24, and a positioning block 202 is provided on the second connecting block 25. A locking plate 64 is fixedly connected to the first connecting block 14.

[0036] The machine head 3 includes a connecting ring 32, an outer cover 33 and a bottom ring 34 from top to bottom. The upper and lower ends of the outer cover 33 are connected to the connecting ring 32 and the bottom ring 34 respectively. The bottom of the first connecting block 14 is connected to the top of the connecting ring 32, and the bottom of the second connecting block 25 is connected to the top of the connecting ring 32.

[0037] The welding mechanism 4 includes a tungsten needle 42.

[0038] A silicone sheet 35 is provided on the first opening 311. Two silicone sheets 35 are provided and are staggered. The two silicone sheets 35 are respectively connected to the two sides of the bottom ring 34. The silicone sheets 35 can reduce the leakage of inert gas from the first opening 311 and improve the welding effect.

[0039] Example 2: This embodiment provides a method for using a U-tube welding device for a split heat exchanger, used to control a U-tube welding device for a split heat exchanger as described in Embodiment 1, including the following steps: Step S1: Place the machine head 3 onto the U-shaped tube; Step S2: Disassemble the second body 2, observe the position of the welding mechanism 4 and the U-shaped tube through the second opening 312, and adjust the welding position in conjunction with the U-shaped tube; Step S3: Adjust and fix the positioning mechanism 6 to the position of the U-shaped tube; Step S4: Reassemble the second fuselage 2 and begin welding; Step S5: After welding the first U-shaped tube, weld the subsequent U-shaped tubes of the same specification by directly setting the machine head 3 onto the U-shaped tube to be welded and starting the welding process. When changing to a different specification of U-tube, repeat steps S1-S5.

[0040] After disassembling the second body 2, observation can be performed through the second opening 312. There is no risk of accidental contact during observation, making it more convenient. The position of the U-shaped tube after it enters is controlled by the positioning mechanism 6. U-shaped tubes of the same specification only need to be observed and the welding position adjusted during the first welding. Subsequent U-shaped tubes of the same specification can be welded directly without secondary observation, which can improve the efficiency of batch welding of the same specification.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A welding device for U-shaped tubes of a split heat exchanger, characterized in that, include: The first fuselage (1) is used to house the pipelines; The second fuselage (2) is used to house control and drive components; The welding head (3) is used for welding U-shaped tubes; The head (3) is located at one end of the first body (1) and the second body (2). The first body (1) is fixedly connected to the head (3), and the first body (1) is detachably connected to the second body (2). The second body (2) is in contact with the head (3). A receiving cavity (31) is formed inside the head (3). The receiving cavity (31) is provided with a first opening (311) for the passage of the U-shaped tube at the end away from the first body (1). The receiving cavity (31) is provided with a second opening (312) for observation at the end close to the first body (1). A welding mechanism (4) is provided on one side inside the receiving cavity (31). In the disassembled state of the second body (2), the second opening (312) is connected to the outside of the first body (1). A positioning mechanism (6) for positioning the U-shaped tube is provided on the first body (1). The positioning mechanism (6) is arranged facing the second body (2).

2. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, The first body (1) is provided with a positioning groove (101), and the second body (2) is provided with a protrusion (201) that cooperates with the positioning groove (101).

3. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, The first fuselage (1) is provided with a positioning notch (102), and the second fuselage (2) is provided with a positioning block (202) that cooperates with the positioning notch (102).

4. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, The first fuselage (1) is provided with an arc-shaped groove (103) arranged along the length direction, and the second fuselage (2) is provided with an arc-shaped boss (203) that cooperates with the arc-shaped groove (103).

5. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, It also includes a locking mechanism (5), which includes a locking hook (51) and a locking pin (52) that cooperates with the locking hook (51). The locking hook (51) is rotatably connected to the first body (1), and the locking pin (52) is set on the second body (2). In the locked state, the first body (1) and the second body (2) are in contact and the locking pin (52) is engaged with the locking hook (51).

6. The U-tube welding equipment for a split heat exchanger according to claim 5, characterized in that, The locking mechanism (5) also includes a handle (53), one end of which is connected to a locking hook (51); two locking hooks (51), two locking pins (52) and two handles (53) are provided, the two locking pins (52) are located on both sides of the second body (2), the two locking hooks (51) are connected by a pivot (54), the pivot (54) is passed through the first body (1); a linkage rod (55) is provided between the two handles (53).

7. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, The first fuselage (1) is provided with an inert gas pipe (11) and a water and electricity pipe (12). The outlet of the inert gas pipe (11) is connected to the receiving cavity (31), and the water and electricity pipe (12) is connected to the welding mechanism (4).

8. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, The second body (2) is provided with a drive unit (21), a control switch (22) and a first gear (23). The control switch (22) and the drive unit (21) are electrically connected. The output end of the drive unit (21) is connected to the first gear (23). The welding mechanism (4) includes a transmission gear (41). When the second body (2) is assembled, the transmission gear (41) meshes with the first gear (23).

9. The U-shaped tube welding equipment for a split heat exchanger according to claim 1, characterized in that, The positioning mechanism (6) includes a positioning plate (61), a positioning screw (62), a slider (63), and a locking plate (64). The slider (63) and the locking plate (64) are slidably connected, the positioning plate (61) and the slider (63) are fixedly connected, and the positioning screw (62) passes through the slider (63) and is in contact with the locking plate (64). When the U-shaped tube is in place, the positioning plate (61) is in contact with the U-shaped tube.

10. A method of using a U-shaped tube welding device for a split heat exchanger, characterized in that, A device for controlling the welding of U-shaped tubes in a split heat exchanger as described in any one of claims 1-9 includes the following steps: Step S1: Place the machine head (3) onto the U-shaped tube; Step S2: Disassemble the second body (2), observe the position of the welding mechanism (4) and the U-shaped tube through the second opening (312), and adjust the welding position in conjunction with the U-shaped tube; Step S3: Adjust and fix the positioning mechanism (6) to the position of the U-shaped tube; Step S4: Reassemble the second fuselage (2) and begin welding; Step S5: After welding the first U-shaped tube, weld the subsequent U-shaped tubes of the same specification by directly putting the machine head (3) onto the U-shaped tube to be welded and starting the welding. When changing to a different specification of U-tube, repeat steps S1-S5.

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