A multi-section double-cylinder cylinder for a chuck

Abstract

The utility model discloses a chuck is with multisection double -cylinder air cylinder belongs to air cylinder technical field, and it aims at solving the problem of existing chuck double -cylinder air cylinder stroke is limited, and the single clamping force leads to the narrow adaptation range, and the thin -walled pipe is easy to deform. The air cylinder includes cylinder body, and two first piston cavities of penetrating are symmetrically arranged in the cylinder body, and the big piston is movably embedded in the first piston cavity and is internally provided with the second piston cavity, and the small piston is embedded in the second piston cavity, the air inlet pipeline supplies the gas to the first piston cavity through the gas delivery groove and the cross air inlet groove, and the air return pipeline drives the big / small piston reset through the big piston air return groove and the air return pipe structure respectively, and the big / small piston single section stroke is 45cm, and the total stroke is 90cm. The utility model discloses through the double -piston nesting and the hierarchical gas circuit design, realizes the stroke extension and the clamping force grading, and simultaneously through multiple sealing guaranteeing the air tightness, and the stable structure low -noise, effectively expands the chuck adaptation range, and protects the thin -walled pipe processing quality.

Description

Technical Field

[0001] This utility model relates to the field of cylinder technology, specifically to a multi-section double-cylinder cylinder for chucks, mainly used in pipe clamping scenarios, providing the chuck with a driving function of graded stroke and graded clamping force. Background Technology

[0002] In pipe processing equipment, the chuck is the core component for positioning and clamping pipes, and its clamping power is usually provided by a double-cylinder cylinder. Existing double-cylinder chucks generally use a single-stage piston structure, which presents the following key problems: 1. Limited stroke: The stroke of a single piston is fixed and short (usually only 45cm), which results in a narrow range of pipe diameters that the chuck can hold, making it unsuitable for processing large-span pipe diameters. 2. Single clamping force: The clamping force of a single piston is constant and relatively large, which is only suitable for pipes with large diameter and thick wall. If used to clamp pipes with small diameter and thin wall, the excessive clamping force will directly cause plastic deformation of the pipe, damage the pipe's precision and appearance, and affect the processing quality.

[0003] To solve the above problems, it is urgent to design a double-cylinder cylinder that can achieve long stroke and graded clamping force, so as to expand the chuck's compatibility range and protect thin-walled pipes. Utility Model Content

[0004] To address the shortcomings of existing chucks, the present invention aims to provide a multi-section double-cylinder cylinder for chucks, which solves the problems of limited stroke and single clamping force of existing double-cylinder cylinders for chucks. By adopting a structural design that combines nested double pistons with graded air path drive, stroke extension and graded clamping force are achieved.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A multi-section double-cylinder cylinder for a chuck includes a cylinder body, two large pistons, a second piston chamber, two small pistons, an intake pipe, a return pipe, and a return pipe structure. The cylinder body has two first piston chambers symmetrically distributed along its central axis. The first piston chambers extend through the cylinder body axially. Each first piston chamber has a detachable end cap installed at its bottom. The end caps are sealed to the inner wall of the first piston chamber to seal the first piston chamber. Two large pistons are respectively movably fitted into the two first piston chambers, and the outer wall of the large piston is in sliding sealing fit with the inner wall of the first piston chamber; Each of the large pistons has a second piston chamber that extends through the axial direction of the large piston. Two small pistons are respectively movably embedded in the two second piston chambers, and the outer wall of the small piston is slidably sealed to the inner wall of the second piston. An intake pipe is located at the bottom of the rear side of the cylinder body, running horizontally through the cylinder body. One end of the intake pipe is fitted with a sealing plug, and the other end is connected to an intake connector. The intake pipe is connected to the bottom of both first piston chambers. The sealing plug seals one end of the pipe, and the intake connector connects to the gas pipe to deliver gas, driving the large and small pistons to extend outward. An annular gas delivery groove is formed on the inner wall of the bottom of each first piston chamber, and the gas delivery groove is connected to the intake pipe. A cross-shaped intake groove is formed on the top of the end cap, and the intake groove is connected to the gas delivery groove. Gas enters the annular gas delivery groove through the intake pipe, moves along the circumference of the end cap, and enters the first piston chamber through the four intake positions of the cross-shaped intake groove, driving the large and small pistons to move outward. The return gas pipeline is located on the upper part of the front side of the cylinder body, running horizontally through the cylinder body. One end of the return gas pipeline is equipped with a sealing end, and the other end is connected to a return gas connector. The return gas pipeline is connected to the upper part of both first piston chambers. An annular large piston return gas groove is formed on the upper inner wall of each first piston chamber. The large piston return gas groove is connected to the return gas pipeline. The sealing plug is used to seal one end of the pipeline, and the return gas connector is used to connect the gas pipe to deliver gas and drive the large piston and small piston to reset inward. When the large piston moves to its maximum stroke, the annular large piston return gas groove corresponds to the lower part of the large piston, so that the gas input in the large piston return gas groove can drive the large piston to move to the lower part of the first piston chamber for reset. Each of the large pistons is provided with a return gas pipe structure inside, and the return gas pipe structure is connected to the first piston chamber; each of the second piston chambers has an annular small piston return gas groove on the upper part of the inner wall, and the small piston return gas groove is connected to the return gas pipe structure.

[0006] Furthermore, the return air pipe structure includes four sets of first return air pipes and four sets of second return air pipes. The four sets of second return air pipes are evenly circumferentially opened inside the large piston. Four first return air pipes are evenly circumferentially opened on the lower part of the outer wall of each large piston. The first return air pipes are connected to the second return air pipes. The upper ends of the four sets of second return air pipes are all connected to the return air groove of the small piston.

[0007] Furthermore, an annular retaining ring groove is provided on the lower inner wall of each first piston chamber. The retaining ring groove is located below the end cover, and an elastic retaining ring is fitted in the retaining ring groove. The upper end of the elastic retaining ring abuts against the lower end face of the end cover, and the elastic retaining ring plays a role in positioning the end cover.

[0008] Furthermore, a first sealing ring is fitted on the outer wall of each end cap, and the first sealing ring is pneumatically and statically sealed with the inner wall of the first piston chamber to seal the connection between the end cap and the first piston chamber.

[0009] Furthermore, a large piston pneumatic combination sealing ring is embedded on the upper inner wall of each of the first piston chambers. The large piston pneumatic combination sealing ring is pneumatically sealed with the outer wall of the large piston to seal the connection between the large piston and the upper part of the first piston chamber.

[0010] Furthermore, a small piston pneumatic combination sealing ring is embedded on the upper inner wall of each second piston chamber. The small piston pneumatic combination sealing ring is pneumatically sealed with the outer wall of the small piston to seal the connection between the small piston and the upper part of the second piston chamber.

[0011] Furthermore, a second sealing ring is fitted on the lower outer wall of each of the large pistons. The second sealing ring is pneumatically sealed with the inner wall of the first piston chamber to seal the connection between the large piston and the first piston chamber.

[0012] Furthermore, a third sealing ring is fitted on the lower outer wall of each small piston. The third sealing ring is pneumatically sealed with the inner wall of the second piston cavity to seal the connection between the small piston and the second piston cavity.

[0013] Furthermore, the second return pipe is formed by drilling holes along the axial direction at the bottom of the large piston, and a sealing plug is installed at the bottom opening to keep the second return pipe airtight.

[0014] Furthermore, the single-section stroke of the large piston is 45cm, the single-section stroke of the small piston is 45cm, and the total stroke of the large piston and the small piston when they move together is 90cm.

[0015] Furthermore, the upper end of the small piston is connected to a clamping plate for holding the workpiece, which is used in conjunction with the chuck to clamp the workpiece.

[0016] Working principle: When a workpiece needs to be clamped, air is introduced into the air inlet pipe. The gas first drives the two pistons to move together, causing the large piston to extend outward. When the pipe diameter to be clamped is large, it can be clamped by the large piston alone. At this time, the tops of the small piston and the large piston act on the clamping plate and come into contact with it, causing the clamping plate to generate a large clamping force, which is suitable for clamping large pipes. After the clamping plate comes into contact with the large pipe, the large piston and the small piston stop moving. At this time, the small piston is in the second piston chamber. When the pipe diameter to be clamped is small, after the large piston moves outward to its maximum stroke, the gas will drive the small piston to continue moving outward until the clamping plate contacts the pipe. When clamping a small pipe, only the top of the small piston acts on the clamping plate, resulting in a relatively small clamping force. Small-diameter pipes are usually thin, and if the clamping force is too large, the pipe can easily deform. Clamping with the small piston can reduce the clamping force on the small pipe and avoid deformation. It can achieve a segmented clamping force effect. When the pipe is large, the large piston and the small piston work together to clamp the pipe; when the pipe is small, the small piston clamps the pipe.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This utility model, through the nested structure of "large piston + small piston", increases the total stroke from 45cm to 90cm within the same axial space of the cylinder body as the existing single-section piston cylinder, greatly expanding the range of pipe diameters that the chuck can hold, and adapting to the needs of multiple scenarios from thin-walled small-diameter pipes to large thick-walled pipes.

[0018] 2. By using a staged drive of "large piston + small piston", two levels of clamping force are achieved: when clamping large-diameter thick-walled pipes, the large piston and small piston extend together, and their tops work together on the clamping plate to provide a large clamping force; when clamping small-diameter thin-walled pipes, the large piston extends to its maximum stroke first, and then the small piston extends alone and acts on the clamping plate to provide a small clamping force, effectively preventing the thin-walled pipe from deforming due to excessive clamping force.

[0019] 3. Through the design of end cap sealing, large piston lower sealing, small piston lower sealing, large piston pneumatic combination sealing ring, small piston pneumatic combination sealing ring and multiple sealing plugs, the airtightness of each air passage and piston chamber is ensured, avoiding insufficient driving force or unstable stroke caused by gas leakage.

[0020] 5. The positioning function of the elastic retaining ring on the end cover, and the symmetrically distributed double cylinder structure, ensure the structural stability during cylinder operation, reduce vibration and noise, and extend the service life of the equipment.

[0021] Of course, any product implementing this utility model does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this utility model, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1This is a schematic diagram of the overall structure of this utility model.

[0024] Figure 2 This is a schematic diagram of the structure of this utility model from another angle.

[0025] Figure 3 This is a front sectional view of the present invention.

[0026] Figure 4 This is a schematic diagram of the cylinder body in this utility model.

[0027] Figure 5 This is a cross-sectional view of the cylinder body in this utility model.

[0028] Figure 6 This is a schematic diagram of the bottom structure of the cylinder body in this utility model.

[0029] Figure 7 This is a schematic diagram of the structure of the end cap of this utility model.

[0030] Figure 8 This is a partial cross-sectional view of the cylinder body in this utility model.

[0031] Figure 9 This is a partial cross-sectional view of the cylinder body from another angle in this utility model.

[0032] Figure 10 This is a schematic diagram of the structure of the large piston in this utility model.

[0033] Figure 11 This is a cross-sectional view of the large piston in this utility model.

[0034] Figure 12 This is a schematic diagram of the structure of the small piston in this utility model.

[0035] Figure 13 This is a schematic diagram showing the reset state of the large piston and the small piston in this utility model.

[0036] Figure 14 This is a schematic diagram showing the large piston and small piston fully extended in this utility model.

[0037] In the diagram: 1. Small piston; 2. Large piston; 3. Cylinder body; 4. Mounting base; 5. Return air connector; 6. Intake air connector; 7. Bolt; 8. First piston chamber; 9. Second piston chamber; 10. End cap; 11. Intake groove; 12. Large piston pneumatic combination seal ring; 13. Large piston return air groove; 14. Elastic retaining ring; 15. Retaining ring groove; 16. First sealing ring; 17. Intake pipe; 18. Sealing plug; 19. Air delivery groove; 20. Return air pipe; 21. First return air pipe; 22. Second sealing ring; 23. Second return air pipe; 24. Small piston pneumatic combination seal ring; 25. Small piston return air groove; 26. Third sealing ring. Detailed Implementation

[0038] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0039] Example 1: like Figures 1 to 14 As shown, this embodiment provides a multi-section double-cylinder cylinder for chucks, including a cylinder body 3, two large pistons 2, a second piston chamber 9, two small pistons 1, an intake pipe 17, a return pipe 20, and a return pipe structure.

[0040] Two first piston chambers 8 are symmetrically distributed inside the cylinder body 3 along its central axis. The first piston chambers 8 are axially connected through the cylinder body 3. An end cap 10 is detachably installed at the bottom of each first piston chamber 8. The end cap 10 is sealed to the inner wall of the first piston chamber 8 to seal the bottom of the first piston chamber 8. An annular retaining ring groove 15 is opened on the lower inner wall of each first piston chamber 8. The retaining ring groove 15 is located below the end cap 10. An elastic retaining ring 14 is installed in the groove. The upper end of the elastic retaining ring 14 abuts against the lower end face of the end cap 10 to achieve the positioning and fixation of the end cap 10.

[0041] A first sealing ring 16 is fitted on the outer side wall of the end cap 10. The first sealing ring 16 is pneumatically and statically sealed with the inner wall of the first piston chamber 8, further enhancing the airtightness of the connection between the end cap 10 and the first piston chamber 8.

[0042] Two large pistons 2 are respectively movably embedded in two first piston chambers 8, and the outer wall of the large piston 2 slides and seals with the inner wall of the first piston chamber 8. The upper inner wall of the first piston chamber 8 is fitted with a pneumatic combination sealing ring of the large piston 2, which pneumatically seals with the outer wall of the large piston 2. At the same time, the lower outer wall of the large piston 2 is fitted with a second sealing ring 22, which pneumatically seals with the inner wall of the first piston chamber 8. The double sealing structure ensures the airtightness between the large piston 2 and the first piston chamber 8.

[0043] Each large piston 2 has a second piston cavity 9 extending through it along its axial direction. Two small pistons 1 are respectively movably embedded in the two second piston cavities 9. The outer wall of the small piston 1 is in sliding sealing fit with the inner wall of the second piston cavity 9. The upper inner wall of the second piston cavity 9 is fitted with a pneumatic combination sealing ring of the small piston 1. The pneumatic combination sealing ring of the small piston 1 is in pneumatic sealing fit with the outer wall of the small piston 1. The lower outer wall of the small piston 1 is fitted with a third sealing ring 26. The third sealing ring 26 is in pneumatic sealing fit with the inner wall of the second piston cavity 9, ensuring the sealing performance between the small piston 1 and the second piston cavity 9.

[0044] The intake pipe 17 is located at the bottom of the rear side of the cylinder 3 and runs horizontally through the cylinder 3. One end of the intake pipe 17 is equipped with a sealing plug 18, and the other end is connected to an intake connector 6. The intake pipe 17 is connected to the bottom of both first piston chambers 8. An annular air delivery groove 19 is provided on the inner wall of the bottom of each first piston chamber 8. The air delivery groove 19 is connected to the intake pipe 17. A cross-shaped air intake groove 11 is provided on the top of the end cover 10. The air intake groove 11 is connected to the air delivery groove 19. After the gas enters the intake pipe 17 through the intake connector 6, it enters the first piston chamber 8 evenly through the air delivery groove 19 and the cross-shaped air intake groove 11, driving the large piston 2 and the small piston 1 to extend outward.

[0045] The return gas pipe 20 is located on the upper part of the front side of the cylinder 3 and runs through the cylinder 3 horizontally. One end of the return gas pipe 20 is equipped with a sealing end and the other end is connected to the return gas connector 5. The return gas pipe 20 is connected to the upper part of both first piston chambers 8. An annular return gas groove of the large piston 2 is opened on the upper inner wall of each first piston chamber 8. The return gas groove of the large piston 2 is connected to the return gas pipe 20. When the large piston 2 moves to the maximum stroke, the return gas groove of the large piston 2 can drive the large piston 2 to reset to the lower part of the first piston chamber 8 through gas.

[0046] Each large piston 2 has a return gas pipe structure inside, which is connected to the first piston chamber 8; each second piston chamber 9 has an annular small piston 1 return gas groove on the upper part of its inner wall, which is connected to the return gas pipe structure.

[0047] The return air pipe structure includes four sets of first return air pipes 21 and four sets of second return air pipes 23. The four sets of second return air pipes 23 are evenly opened in the circumferential direction inside the large piston 2 and are formed by drilling holes along the axial direction at the bottom of the large piston 2. A sealing plug 18 is installed at the bottom opening to maintain airtightness. Four first return air pipes 21 are evenly opened in the circumferential direction on the lower part of the outer wall of each large piston 2. The first return air pipes 21 are connected to the second return air pipes 23. The upper ends of the four sets of second return air pipes 23 are all connected to the return air groove of the small piston 1 to realize the reset drive of the small piston 1.

[0048] In this embodiment, the single-stage stroke of the large piston 2 is 45cm, the single-stage stroke of the small piston 1 is 45cm, and when the large piston 2 and the small piston 1 move together, the total cylinder stroke reaches 90cm.

[0049] In addition, the upper end of the small piston 1 is connected to a clamping plate for holding the workpiece. The clamping plate cooperates with the piston to achieve stable clamping of the tube.

[0050] It should be noted that mounting seats 4 are provided on both sides of the cylinder body 3, which are integrally formed with the cylinder body 3 and are used to install and fix the cylinder body 3 in conjunction with external connecting parts. In addition, multiple sets of bolts 7 are longitudinally inserted inside the cylinder body 3 for connecting and fixing the cylinder body 3.

[0051] Example 2: This embodiment provides a working principle of the dual-cylinder cylinder, as detailed below: When the workpiece needs to be clamped, the air inlet pipe 17 starts to intake air. The gas enters the first piston chamber 8 sequentially through the air inlet pipe 17, the air delivery groove 19, and the cross-shaped air inlet groove 11, first driving the large piston 2 and the small piston 1 to move outward synchronously. If the clamped pipe is a large-diameter thick-walled pipe, when the clamping plate contacts the pipe, the large piston 2 and the small piston 1 stop moving synchronously. At this time, the small piston 1 is in the second piston chamber 9. The top of the large piston 2 and the top of the small piston 1 work together on the clamping plate to output a larger clamping force, which is suitable for the clamping requirements of large-diameter thick-walled pipes. If the clamped pipe is a small-diameter thin-walled pipe, the large piston 2 first moves outward to its maximum stroke (45cm), and then the gas continues to drive the small piston 1 to move outward along the second piston chamber 9 until the clamping plate contacts the pipe. At this time, only the top of the small piston 1 acts on the clamping plate, outputting a smaller clamping force, which effectively avoids the thin-walled pipe from deforming due to excessive clamping force.

[0052] When it is necessary to loosen the pipe, air enters through the return air line 20. Part of the gas enters the upper part of the first piston chamber 8 through the return air line 20 and the return air groove of the large piston 2, driving the large piston 2 to reset to the bottom. The other part of the gas enters the first piston chamber 8 through the return air line 20, and then enters the upper part of the second piston chamber 9 through the first return air line 21, the second return air line 23, and the return air groove of the small piston 1, driving the small piston 1 to reset to the bottom, thus completing the clamping and loosening action.

[0053] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating this utility model, and are not intended to limit the implementation of this utility model. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. Any obvious variations or modifications derived from the technical solutions of this utility model are still within the protection scope of this utility model.

Claims

1. A multi-section double-cylinder cylinder for a chuck, characterized in that, include: The cylinder (3) has two first piston chambers (8) symmetrically distributed along its central axis. The first piston chambers (8) penetrate the cylinder (3) axially. Each first piston chamber (8) has an end cap (10) detachably installed at the bottom. The end cap (10) is sealed to the inner wall of the first piston chamber (8). Two large pistons (2) are respectively movably embedded in the two first piston chambers (8), and the outer wall of the large piston (2) is slidably sealed to the inner wall of the first piston chamber (8); Each of the large pistons (2) has a second piston chamber (9) which extends through the large piston (2) along the axial direction. Two small pistons (1) are respectively movably embedded in the two second piston chambers (9). The outer wall of the small piston (1) is slidably sealed to the inner wall of the second piston. An intake pipe (17) is located at the bottom of the rear side of the cylinder (3) and runs through the cylinder (3) horizontally. One end of the intake pipe (17) is equipped with a sealing plug (18), and the other end is connected to an intake connector (6). The intake pipe (17) is connected to the bottom of both first piston chambers (8). An annular air delivery groove (19) is provided on the inner wall of the bottom of each first piston chamber (8). The air delivery groove (19) is connected to the intake pipe (17). A cross-shaped air intake groove (11) is provided on the top of the end cap (10). The air intake groove (11) is connected to the air delivery groove (19). A return gas pipeline (20) is located on the upper part of the front side of the cylinder body (3) and runs through the cylinder body (3) horizontally. One end of the return gas pipeline (20) is equipped with a sealing end and the other end is connected to a return gas connector (5). The return gas pipeline (20) is connected to the upper part of both first piston chambers (8). Each first piston chamber (8) has an annular large piston (2) return gas groove on its upper inner wall. The large piston (2) return gas groove is connected to the return gas pipeline (20). Each of the large pistons (2) is provided with a return pipe structure inside, and the return pipe structure is connected to the first piston chamber (8); each of the second piston chambers (9) has an annular small piston (1) return groove on the upper part of its inner wall, and the small piston (1) return groove is connected to the return pipe structure.

2. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: The return air pipe structure includes four sets of first return air pipes (21) and four sets of second return air pipes (23). The four sets of second return air pipes (23) are evenly circumferentially opened inside the large piston (2). The lower part of the outer wall of each large piston (2) is evenly provided with four first return air pipes (21) along the circumferential direction. The first return air pipes (21) are connected to the second return air pipes (23). The upper ends of the four sets of second return air pipes (23) are all connected to the return air groove of the small piston (1).

3. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: Each of the first piston chambers (8) has an annular retaining ring groove (15) on its lower inner wall. The retaining ring groove (15) is located below the end cap (10). An elastic retaining ring (14) is fitted inside the retaining ring groove (15). The upper end of the elastic retaining ring (14) abuts against the lower end face of the end cap (10).

4. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: Each of the end caps (10) is fitted with a first sealing ring (16) on its outer side wall, and the first sealing ring (16) is pneumatically sealed to the inner wall of the first piston chamber (8).

5. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: Each of the first piston chambers (8) is fitted with a pneumatic combination sealing ring for the large piston (2) on the upper inner wall, and the pneumatic combination sealing ring for the large piston (2) is pneumatically sealed to the outer wall of the large piston (2).

6. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: Each of the second piston chambers (9) is fitted with a small piston (1) pneumatic combination sealing ring on the upper inner wall, and the small piston (1) pneumatic combination sealing ring is pneumatically sealed with the outer wall of the small piston (1).

7. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: Each of the large pistons (2) is fitted with a second sealing ring (22) on the lower outer wall, and the second sealing ring (22) is pneumatically sealed to the inner wall of the first piston chamber (8).

8. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: Each of the small pistons (1) is fitted with a third sealing ring (26) on its lower outer wall, and the third sealing ring (26) is pneumatically sealed to the inner wall of the second piston chamber (9).

9. The multi-section double-cylinder cylinder for chucks according to claim 2, characterized in that: The second return pipe (23) is formed by drilling holes along the axial direction at the bottom of the large piston (2), and a sealing plug (18) is installed at the bottom opening.

10. The multi-section double-cylinder cylinder for chucks according to claim 1, characterized in that: The single-section stroke of the large piston (2) is 45cm, the single-section stroke of the small piston (1) is 45cm, and the total stroke of the large piston (2) and the small piston (1) when they move together is 90cm.

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