Pitch changing device of plastic bottle blank blowing machine

Abstract

The invention discloses a plastic bottle blank bottle blowing machine variable pitch device which structurally comprises a supporting frame, a first bottle blowing mold, a second bottle blowing mold and a third bottle blowing mold are arranged in an inner cavity of the upper end of the supporting frame, and supporting legs are welded to the two sides of the supporting frame. A pulling assembly is arranged among the first bottle blowing mold, the second bottle blowing mold and the third bottle blowing mold, a fixing plate is arranged at the lower end of the supporting frame, a pitch changing assembly is arranged at the upper end of the fixing plate, an inflation assembly is arranged at the lower end of the fixing plate, and a positioning assembly is arranged on one side of the pitch changing assembly. According to the bottle blowing device, the hydraulic cylinder can drive the fixing plate to move upwards, and the opening plate on the fixing plate is inserted between the first bottle blowing mold and the second bottle blowing mold through the first through groove, so that the problem of distance change caused by inertia when traction is in place is avoided; and the first bottle blowing mold and the second bottle blowing mold are separated by matching with an inserted opening plate, so that the constant distance between the first bottle blowing mold and the second bottle blowing mold is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of bottle blowing machines, in particular to a variable pitch device for a plastic preform bottle blowing machine. Background Art

[0002] Blow molding machine refers to the machine that blows bottles. The most simple explanation is that it is a machine that can blow plastic particles (softened into liquid) or finished bottle embryos into bottles through certain process means. Blow molding machine is convenient and fast, with a large molding volume. After its appearance, it replaced most manual blow molding and was adopted by most beverage companies. The more common machines include hollow extrusion blow molding machines that use PP and PE for one-time molding, injection stretch blow molding machines that use PET, PC or PP for two-time molding, and the newly developed multi-layer hollow extrusion blow molding and stretch blow molding.

[0003] According to the patent (CN216330017U), a variable pitch device of a plastic preform blowing machine includes a mounting seat, fixed plates are fixedly installed at opposite ends of the mounting seat, and the two fixed plates are symmetrically distributed, two symmetrically distributed screws are rotatably installed between the two fixed plates, a motor is fixedly installed on one side of the fixed plate, and the output shaft of the motor is fixedly connected to the end of the screw on the same side, a first movable block and a third movable block are arranged on the mounting seat, and a plurality of second movable blocks with the same structure are arranged between the first movable block and the third movable block, the first movable block and the second movable block.

[0004] At present, although the existing ones can adjust the spacing between the blowing molds, there are still some shortcomings. For example, inertia will cause different spacings when they are pulled into place, and the spacing cannot be constant. It is also inconvenient to control and adjust the spacing, and it is inconvenient to limit the blowing molds when they are in place, which affects the operation of the blowing machine and thus the blowing effect. Summary of the invention

[0005] The purpose of the present invention is to provide a variable pitch device for a plastic preform blowing machine, which solves the problems raised in the background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a variable pitch device of a plastic preform blowing machine, comprising a support frame, the upper end inner cavity of the support frame is respectively provided with a first blowing mold, a second blowing mold and a third blowing mold, support legs are welded on both sides of the support frame, a pulling assembly is provided between the first blowing mold, the second blowing mold and the third blowing mold, a fixed plate is provided at the lower end of the support frame, a variable pitch assembly is provided at the upper end of the fixed plate, an inflation assembly is provided at the lower end of the fixed plate, and a positioning assembly is provided on one side of the variable pitch assembly.

[0007] As a preferred embodiment of the present invention, the pulling assembly includes a fixed frame, a limit ring, a fixed rod, a fixed block, a first spring, a servo motor, a screw and a screw sleeve. The second bottle blowing mold and the third bottle blowing mold are welded with fixed frames on the front and rear sides. A fixed rod is provided through the middle of the fixed frame. A fixed block is fixedly installed at one end of the fixed rod. A servo motor is fixedly installed on one side of the support frame, and a screw is installed at the output end of the servo motor.

[0008] By adopting the above technical solution, it is convenient to drive the first blowing bottle mold, the second blowing bottle mold and the third blowing bottle mold to move, thereby facilitating the adjustment and control of the distance between the first blowing bottle mold, the second blowing bottle mold and the third blowing bottle mold.

[0009] As a preferred embodiment of the present invention, the variable pitch assembly includes a hydraulic cylinder, a fixed plate, an expansion plate, a slider, a slide groove, a second spring and a first through groove. A hydraulic cylinder is arranged on the other side of the support frame, a fixed plate is installed on the output end of the hydraulic cylinder, an expansion plate is arranged on the upper end of the fixed plate, slide grooves are provided on both sides of the upper end of the fixed plate, a slider is fixedly installed on the lower end of the expansion plate, and a first through groove is provided in the middle part of the lower end of the support frame.

[0010] By adopting the above technical solution, it is convenient to set the first through groove, so that when the fixed plate moves upward, it is convenient to insert the support plate between the two bottle blowing molds, thereby adjusting the pitch of the bottle blowing molds.

[0011] As a preferred embodiment of the present invention, the inflation assembly includes an electric cylinder, a barrel, a piston head, a hose and an inflation airbag. The electric cylinder is fixedly installed on the lower end of the fixed plate, the piston head is installed on the output end of the electric cylinder, the barrel is provided on the side close to the electric cylinder, and the inflation airbag is provided in the middle of the two expansion plates.

[0012] By adopting the above technical solution and setting the expansion airbag, the distance between the two support plates can be adjusted, and then the distance between two adjacent bottle blowing molds can be adjusted during the upward movement of the support plate.

[0013] As a preferred embodiment of the present invention, a limiting ring is welded on one side of the fixed frame, a first spring is sleeved on the outer side of the fixed rod, one end of the first spring is fixedly connected to the fixed block, the rear sides of the first blowing bottle mold, the second blowing bottle mold and the third blowing bottle mold are all welded with fixed blocks, the fixed block is slidably connected to the second strip groove, a screw sleeve is fixedly installed on the front end of the first blowing bottle mold, the size of the screw rod is matched with the size of the screw rod sleeve, and the screw rod is threadedly connected to the screw rod sleeve.

[0014] By adopting the above technical solution, the first blowing mold can be driven to move by cooperating with the screw rod and the screw rod sleeve, and then cooperated with the fixed rod and the first spring to drive the second blowing mold and the third blowing mold behind the first blowing mold to follow the movement.

[0015] As a preferred embodiment of the present invention, the size of the slider is matched with the size of the slide slot, and the slider is slidably connected to the slide slot. A second spring is fixedly installed in the inner cavity of the slide slot, and the other end of the second spring is fixedly connected to the slider.

[0016] By adopting the above technical solution and setting the second spring, a reaction force is applied to the slider during the movement of the expansion plate to both sides, thereby facilitating the expansion plate to be reset.

[0017] As a preferred embodiment of the present invention, a first strip groove and a second strip groove are respectively provided on the inner side of the upper end of the support frame, and a blowing port is provided on the upper ends of the first blowing mold, the second blowing mold and the third blowing mold.

[0018] By adopting the above technical solution, the first strip groove and the second strip groove cooperate with each other, so as to ensure the stability of the first blowing mold, the second blowing mold and the third blowing mold moving above the support frame.

[0019] As a preferred embodiment of the present invention, the inner cavity size of the cylinder is adapted to the size of the piston head, and the cylinder is movably connected to the piston head. The air outlet end of the cylinder is connected to a hose, and the other end of the hose is connected to the air inlet end of the inflation airbag.

[0020] By adopting the above technical solution and providing a hose, the air discharged from the cylinder can be guided, thereby achieving the effect of adjusting the distance between the support plates.

[0021] As a preferred embodiment of the present invention, the positioning assembly includes a limit frame, a limit block, a positioning groove and a second through groove, the limit frame is welded on one side of the upper end of the fixed plate, the limit block is welded on the upper end of the limit frame, and the lower ends of the first blowing mold, the second blowing mold and the third blowing mold are all provided with positioning grooves.

[0022] By adopting the above technical solution, it is convenient to set the second through groove, so that during the movement of the fixed plate, the limiting block on the limiting frame can be inserted into the positioning groove, thereby achieving the effect of limiting the bottle blowing mold.

[0023] As a preferred embodiment of the present invention, a second through slot is provided on one side of the first through slot, the size of the limit block is matched with the size of the positioning slot, and the limit block is movably connected to the positioning slot.

[0024] By adopting the above technical solution, the limit block cooperates with the positioning groove, so that the position of the bottle blowing mold above the second through groove can be limited while the distance adjustment is completed, thereby ensuring the operation of the bottle blowing machine.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: the hydraulic cylinder can drive the fixed plate to move upward, and the expansion plate on the fixed plate can be inserted between the first blowing bottle mold and the second blowing bottle mold through the first through groove, thereby avoiding the problem of distance change caused by inertia while being pulled into place, and then the inserted expansion plate is used to block the first blowing bottle mold and the second blowing bottle mold, thereby ensuring the constant distance between the first blowing bottle mold and the second blowing bottle mold.

[0026] The piston head can also be driven to move rightward by an electric cylinder, and the piston head discharges the air in the cylinder into the expansion airbag. The expansion of the expansion airbag pushes the expansion plate, thereby adjusting the spacing of the expansion plates, and then the expansion plate is inserted between the first blowing mold and the second blowing mold to adaptively adjust the spacing of the variable pitch.

[0027] When the opening plate is in place, the limit frame on the fixed plate can move with it, so that the limit block on the limit frame is inserted into the positioning groove, thereby limiting the position of the bottle blowing mold moved above the second through groove, thereby ensuring the operation of the bottle blowing machine and improving the bottle blowing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0029] Figure 1 It is a three-dimensional structural schematic diagram of a variable pitch device of a plastic preform blowing machine of the present invention;

[0030] Figure 2 It is a bottom perspective schematic diagram of a support frame of a variable pitch device of a plastic preform blowing machine according to the present invention;

[0031] Figure 3 It is a schematic diagram of the front cross-sectional structure of a variable pitch device of a plastic preform blowing machine of the present invention;

[0032] Figure 4 This is a partial enlarged view of position A of a variable pitch device of a plastic preform blowing machine of the present invention;

[0033] Figure 5 This is a partial enlarged view of position B of a variable pitch device of a plastic bottle preform blowing machine of the present invention.

[0034] In the figure: 1. support frame; 11. first strip groove; 12. second strip groove; 13. first bottle blowing mold; 14. second bottle blowing mold; 15. third bottle blowing mold; 16. bottle blowing mouth; 17. support leg; 2. fixed frame; 21. limit ring; 22. fixed rod; 24. first spring; 26. servo motor; 27. screw; 28. screw sleeve; 3. hydraulic cylinder; 31. fixed plate; 32. opening plate; 33. slider; 34. slide groove; 35. second spring; 36. first through groove; 4. electric cylinder; 41. cylinder; 42. piston head; 43. hose; 44. expansion airbag; 5. limit frame; 51. limit block; 52. positioning groove; 53. second through groove. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] See also Figure 1-Figure 3 The present invention provides a technical solution: a variable pitch device of a plastic preform blowing machine, comprising a support frame 1, wherein the upper inner cavity of the support frame 1 is respectively provided with a first blowing mold 13, a second blowing mold 14 and a third blowing mold 15, support legs 17 are welded on both sides of the support frame 1, a pulling assembly is provided between the first blowing mold 13, the second blowing mold 14 and the third blowing mold 15, a fixing plate 31 is provided at the lower end of the support frame 1, a variable pitch assembly is provided at the upper end of the fixing plate 31, an inflation assembly is provided at the lower end of the fixing plate 31, and a positioning assembly is provided on one side of the variable pitch assembly.

[0038] In the present invention, when the pitch is changed, the servo motor 26 is used to drive the screw rod 27 to rotate, and the screw rod 27 cooperates with the screw rod sleeve 28 to drive the first bottle blowing mold 13 to move, and then cooperates with the fixing rod 22 and the first spring 24 to pull and move the second bottle blowing mold 14 and the third bottle blowing mold 15 behind the first bottle blowing mold 13. When the first bottle blowing mold 13 is in place, the hydraulic cylinder 3 is opened, and the hydraulic cylinder 3 drives the fixed plate 31 to move upward, and the expansion plate 32 on the fixed plate 31 is inserted between the first bottle blowing mold 13 and the second bottle blowing mold 14 through the first through groove 36, thereby avoiding the problem of inertia causing the spacing change when the bottle is pulled into place, and then cooperates with the inserted expansion plate 32 to block the first bottle blowing mold 13 and the second bottle blowing mold 14, thereby ensuring that the first bottle blowing mold 13 The distance between the first blowing mold 13 and the second blowing mold 14 is constant. When the distance between the first blowing mold 13 and the second blowing mold 14 needs to be adjusted, the electric cylinder 4 drives the piston head 42 to move to the right, and the piston head 42 discharges the air in the cylinder 41 into the expansion airbag 44. The expansion airbag 44 expands to push the expansion plate 32, thereby adjusting the distance between the expansion plates 32, and then the expansion plates 32 are inserted between the first blowing mold 13 and the second blowing mold 14 to adaptively adjust the distance between the variable pitches. At the same time, when the expansion plates 32 are in place, the limit frame 5 on the fixed plate 31 will move with it, so that the limit block 51 on the limit frame 5 is inserted into the positioning groove 52, thereby limiting the position of the blowing mold moved above the second through groove 53, thereby ensuring the operation of the blowing machine, thereby improving the blowing effect.

[0039] In an optional embodiment, the pulling assembly includes a fixed frame 2, a limit ring 21, a fixed rod 22, a fixed block, a first spring 24, a servo motor 26, a screw 27 and a screw 27 sleeve. The second bottle blowing mold 14 and the third bottle blowing mold 15 are welded with a fixed frame 2 on both the front and rear sides. A fixed rod 22 is provided through the middle of the fixed frame 2, and a fixed block is fixedly installed at one end of the fixed rod 22. A servo motor 26 is fixedly installed on one side of the support frame 1, and a screw 27 is installed at the output end of the servo motor 26.

[0040] It should be noted that it is convenient to drive the first blowing mold 13, the second blowing mold 14 and the third blowing mold 15 to move, thereby facilitating the adjustment and control of the distance between the first blowing mold 13, the second blowing mold 14 and the third blowing mold 15.

[0041] In an optional embodiment, the pitch changing assembly includes a hydraulic cylinder 3, a fixed plate 31, a support plate 32, a slider 33, a slide groove 34, a second spring 35 and a first through groove 36. The hydraulic cylinder 3 is arranged on the other side of the support frame 1, and the output end of the hydraulic cylinder 3 is installed with a fixed plate 31, and the upper end of the fixed plate 31 is provided with a support plate 32. Slide grooves 34 are provided on both sides of the upper end of the fixed plate 31, and a slider 33 is fixedly installed at the lower end of the support frame 1. A first through groove 36 is provided in the middle part of the lower end of the support frame 1.

[0042] It should be noted that, by providing the first through slot 36 , it is convenient to insert the support plate 32 between the two bottle blowing molds during the upward movement of the fixed plate 31 , thereby adjusting the pitch of the bottle blowing molds.

[0043] In an optional embodiment, the inflation assembly includes an electric cylinder 4, a cylinder 41, a piston head 42, a hose 43 and an inflation airbag 44. The electric cylinder 4 is fixedly installed at the lower end of the fixed plate 31, the piston head 42 is installed at the output end of the electric cylinder 4, the cylinder 41 is arranged on one side close to the electric cylinder 4, and the inflation airbag 44 is arranged in the middle of the two expansion plates 32.

[0044] It should be noted that, by providing the expansion airbag 44 , the distance between the two expansion plates 32 can be adjusted, and thus the distance between two adjacent bottle blowing molds can be adjusted during the upward movement of the expansion plate 32 .

[0045] In an optional embodiment, a limiting ring 21 is welded to one side of the fixed frame 2, a first spring 24 is sleeved on the outer side of the fixed rod 22, one end of the first spring 24 is fixedly connected to the fixed block, and the rear sides of the first blowing mold 13, the second blowing mold 14 and the third blowing mold 15 are all welded with fixed blocks, the fixed blocks are slidably connected to the second strip groove 12, and a screw sleeve 28 is fixedly installed at the front end of the first blowing mold 13, the size of the screw 27 is matched with the size of the screw sleeve 28, and the screw 27 is threadedly connected to the screw sleeve 28.

[0046] It should be noted that the screw 27 cooperates with the screw sleeve 28 to drive the first blow mold 13 to move, and then cooperates with the fixed rod 22 and the first spring 24 to drive the second blow mold 14 and the third blow mold 15 behind the first blow mold 13 to follow and move.

[0047] In an optional embodiment, the size of the slider 33 is adapted to the size of the slide slot 34 , and the slider 33 is slidably connected to the slide slot 34 , a second spring 35 is fixedly installed in the inner cavity of the slide slot 34 , and the other end of the second spring 35 is fixedly connected to the slider 33 .

[0048] It should be noted that, by providing the second spring 35 , a reaction force is applied to the slider 33 during the movement of the expansion plate 32 to both sides, thereby facilitating the expansion plate 32 to be reset.

[0049] In an optional embodiment, a first strip groove 11 and a second strip groove 12 are respectively formed on the inner side of the upper end of the support frame 1 , and a blowing port 16 is provided on the upper ends of the first blowing mold 13 , the second blowing mold 14 and the third blowing mold 15 .

[0050] It should be noted that, through the cooperation between the first strip groove 11 and the second strip groove 12 , the stability of the first blowing mold 13 , the second blowing mold 14 and the third blowing mold 15 moving above the support frame 1 can be ensured.

[0051] In an optional embodiment, the inner cavity size of the cylinder 41 is adapted to the size of the piston head 42 , and the cylinder 41 and the piston head 42 are movably connected, the air outlet end of the cylinder 41 is connected to a hose 43 , and the other end of the hose 43 is connected to the air inlet end of the expansion airbag 44 .

[0052] It should be noted that, by providing the hose 43 , the air discharged from the cylinder 41 can be guided, thereby achieving the effect of adjusting the distance between the expansion plates 32 .

[0053] In an optional embodiment, the positioning assembly includes a limit frame 5, a limit block 51, a positioning groove 52 and a second through groove 53. The limit frame 5 is welded to one side of the upper end of the fixed plate 31, the limit block 51 is welded to the upper end of the limit frame 5, and the lower ends of the first blowing mold 13, the second blowing mold 14 and the third blowing mold 15 are all provided with a positioning groove 52.

[0054] It should be noted that, by providing the second through slot 53 , the limiting block 51 on the limiting frame 5 can be inserted into the positioning slot 52 during the movement of the fixing plate 31 , thereby achieving the effect of limiting the bottle blowing mold.

[0055] In an optional embodiment, a second through slot 53 is provided on one side of the first through slot 36 , the size of the limiting block 51 is matched with the size of the positioning slot 52 , and the limiting block 51 is movably connected to the positioning slot 52 .

[0056] It should be noted that, by cooperating with the limiting block 51 and the positioning groove 52 , the position of the bottle blowing mold above the second through groove 53 can be limited while the distance adjustment is completed, thereby ensuring the operation of the bottle blowing machine.

[0057] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0058] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A variable pitch device for a plastic preform blowing machine, comprising a support frame (1), characterized in that: The inner cavity at the upper end of the support frame (1) is respectively provided with a first blowing mold (13), a second blowing mold (14) and a third blowing mold (15); support legs (17) are welded on both sides of the support frame (1); a pulling assembly is provided between the first blowing mold (13), the second blowing mold (14) and the third blowing mold (15); a fixing plate (31) is provided at the lower end of the support frame (1); a variable distance assembly is provided at the upper end of the fixing plate (31); an inflation assembly is provided at the lower end of the fixing plate (31); and a positioning assembly is provided on one side of the variable distance assembly.

2. A variable pitch device for a plastic preform blowing machine according to claim 1, characterized in that: The pulling assembly comprises a fixed frame (2), a limiting ring (21), a fixed rod (22), a first spring (24), a servo motor (26), a screw (27) and a screw (27) sleeve; the second bottle blowing mold (14) and the third bottle blowing mold (15) are both welded with a fixed frame (2) on both the front and rear sides; a fixed rod (22) is provided through the middle of the fixed frame (2); a fixed block is fixedly mounted on one end of the fixed rod (22); a servo motor (26) is fixedly mounted on one side of the support frame (1); and a screw (27) is mounted on the output end of the servo motor (26).

3. A variable pitch device for a plastic preform blowing machine according to claim 2, characterized in that: The pitch-changing assembly comprises a hydraulic cylinder (3), a fixed plate (31), an opening plate (32), a slider (33), a slide groove (34), a second spring (35) and a first through groove (36); the other side of the support frame (1) is provided with a hydraulic cylinder (3); the output end of the hydraulic cylinder (3) is provided with a fixed plate (31); the upper end of the fixed plate (31) is provided with an opening plate (32); slide grooves (34) are provided on both sides of the upper end of the fixed plate (31); the lower end of the opening plate (32) is fixedly provided with a slider (33); and the middle part of the lower end of the support frame (1) is provided with a first through groove (36).

4. A variable pitch device for a plastic preform blowing machine according to claim 3, characterized in that: The inflation assembly comprises an electric cylinder (4), a barrel (41), a piston head (42), a hose (43) and an expansion airbag (44); the electric cylinder (4) is fixedly mounted on the lower end of the fixing plate (31); the piston head (42) is mounted on the output end of the electric cylinder (4); the barrel (41) is arranged on one side close to the electric cylinder (4); and the expansion airbag (44) is arranged in the middle of the two expansion plates (32).

5. The variable pitch device of a plastic preform blowing machine according to claim 4, characterized in that: A limiting ring (21) is welded on one side of the fixing frame (2), a first spring (24) is sleeved on the outer side of the fixing rod (22), one end of the first spring (24) is fixedly connected to a fixing block, the rear sides of the first blowing bottle mold (13), the second blowing bottle mold (14) and the third blowing bottle mold (15) are all welded with fixing blocks, the fixing blocks are slidably connected to the second strip groove (12), a screw rod sleeve (28) is fixedly installed on the front end of the first blowing bottle mold (13), the size of the screw rod (27) is matched with the size of the screw rod sleeve (28), and the screw rod (27) is threadedly connected to the screw rod sleeve (28).

6. A variable pitch device for a plastic preform blowing machine according to claim 5, characterized in that: The size of the slider (33) is matched with the size of the slide groove (34), and the slider (33) is slidably connected to the slide groove (34). A second spring (35) is fixedly installed in the inner cavity of the slide groove (34), and the other end of the second spring (35) is fixedly connected to the slider (33).

7. A variable pitch device for a plastic preform blowing machine according to claim 6, characterized in that: A first strip groove (11) and a second strip groove (12) are respectively provided on the inner side of the upper end of the support frame (1), and a blowing port (16) is provided on the upper ends of the first blowing mold (13), the second blowing mold (14) and the third blowing mold (15).

8. The variable pitch device of a plastic preform blowing machine according to claim 7, characterized in that: The inner cavity size of the cylinder (41) is matched with the size of the piston head (42), and the cylinder (41) and the piston head (42) are movably connected. The air outlet end of the cylinder (41) is connected to a hose (43), and the other end of the hose (43) is connected to the air inlet end of the expansion airbag (44).

9. The variable pitch device of a plastic preform blowing machine according to claim 8, characterized in that: The positioning assembly comprises a limiting frame (5), a second limiting block (51), a positioning groove (52) and a second through groove (53); the limiting frame (5) is welded to one side of the upper end of the fixing plate (31); the limiting block (51) is welded to the upper end of the limiting frame (5); and the lower ends of the first bottle blowing mold (13), the second bottle blowing mold (14) and the third bottle blowing mold (15) are all provided with positioning grooves (52).

10. The variable pitch device of a plastic preform blowing machine according to claim 1, characterized in that: A second through slot (53) is provided on one side of the first through slot (36), the size of the limit block (51) matches the size of the positioning slot (52), and the limit block (51) is movably connected to the positioning slot (52).

Images