A two-pass bending die

Abstract

The present application relates to the technical field of metal forging, and particularly discloses a two-pass bending die, which comprises an upper fixed plate and a lower fixed plate, a first-pass bending upper die and a second-pass bending upper die are arranged on the upper fixed plate, a first-pass bending lower die and a second-pass bending lower die are arranged on the lower fixed plate, a first-pass blank cavity is arranged on the first-pass bending lower die and is used for performing first bending forming on the two end portions close to the blank, and a second-pass blank cavity is arranged on the second-pass bending lower die and is used for performing second bending forming on the middle portion of the blank. The two-pass bending die is arranged to split the bending portion of the forging, and the first-pass bending die and the second-pass bending die are designed to form the bending die, so that the bending of the rod with multiple bending sections and a long branch arm with a large bending angle can be realized. The two-pass bending mode can reduce the reciprocating alternating stress of the blank during the distributed bending process, and the service life of the die is improved.

Description

Technical Field

[0001] This invention relates to the field of metal forging technology, specifically to a two-pass bending die. Background Technology

[0002] In the metal forging process, products with complex structures usually require corresponding blanking processes, such as drawing, upsetting, bending, and flattening. The blanking process is to shape the original material into a shape and structure similar to the product as much as possible before forging, so as to improve material utilization and increase the fullness and success rate of the forging process.

[0003] For the forging of aluminum alloy fork arms for automotive chassis, especially for forgings with multiple bends and deep U-shaped structures, bending processes are usually required during the billet preparation process.

[0004] For aluminum alloy fork arm components, the forging raw material is mostly aluminum alloy extruded round bars. Due to the special properties of aluminum alloy materials, some problems may occur when performing deep U-shaped arm bending on ordinary bending machines. For example, deformation is prone to occur during the bending process when performing multiple bends and deep U-shaped structures at the same time. This is because the overall bending angle required is very large, and the stress is mainly concentrated at the bending point during the bending process, which may lead to excessive local deformation or cracks. The main body deformation during the bending process is not uniform, which can easily lead to excessive deviation in product dimensions after bending.

[0005] While existing bending machine dies can meet bending requirements, they usually require the selection of special bending equipment and the design of special bending dies. For example, local support auxiliary devices are added to the openings on both sides of the lower die, usually by adding a pair of rollers or bearings. The rollers or bearings can change the friction between the blank and the die from sliding friction to rolling friction, reducing friction and stress during the deformation process, which is helpful for bending and forming forgings with multiple bending sections and deep U-shaped arms.

[0006] At the same time, the addition of auxiliary devices such as rollers or bearings to the mold makes the average lifespan of the entire mold depend on the lifespan of the auxiliary devices or the connection mechanism between the auxiliary devices and the mold, which greatly reduces the lifespan of the entire mold. This is especially true for the metal forging industry, where the surface temperature of the metal is usually 400 to 500 degrees Celsius during the bending process. Moreover, the auxiliary mechanisms such as rollers or bearings are subjected to reciprocating alternating stress, and their fatigue life will also affect the use of the entire mold.

[0007] In summary, existing bending machines are not effective and prone to deformation when bending multi-bending sections and deep U-shaped structures. At the same time, the lifespan of dies with special bending equipment and specially designed bending dies, such as those with added rollers or bearings, is short when bending. Summary of the Invention

[0008] The purpose of this invention is to provide a two-pass bending die to solve the technical problems in the prior art, where existing bending machines are not effective and are prone to deformation when bending multiple bending sections and deep U-shaped structures, and where dies with special bending equipment and special bending die designs that add local support devices such as rollers or bearings have low lifespan when bending.

[0009] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0010] A two-stage bending die includes an upper fixed plate and a lower fixed plate. A first-stage bending upper die and a second-stage bending upper die are arranged side by side on the lower surface of the upper fixed plate, and a first-stage bending lower die and a second-stage bending lower die are arranged side by side on the upper surface of the lower fixed plate.

[0011] A primary blank cavity is provided on the lower die of the primary bending process. The primary blank cavity is used to perform a single bending forming on the two ends of the blank when the upper die of the primary bending process and the primary blank cavity are closed.

[0012] A secondary blank cavity is provided on the lower die of the second bending process. The secondary blank cavity is used to perform a secondary bending and forming of the middle of the blank when the upper die of the second bending process and the secondary blank cavity are closed.

[0013] As a preferred embodiment of the present invention, the primary blank cavity includes a first intermediate cavity, and a primary bending cavity is provided at both ends of the first intermediate cavity, and the primary bending cavities at both ends of the first intermediate cavity are centrally symmetrical.

[0014] Wherein, when the primary bending cavity is closed with the primary bending upper die and the primary blank cavity, the two ends of the blank are bent once;

[0015] The first intermediate cavity fits symmetrically with the bottom surface of the first bending upper die.

[0016] In a preferred embodiment of the present invention, the end of the primary bending cavity away from the first intermediate cavity extends horizontally toward the side of the primary bending lower die to form a positioning groove.

[0017] As a preferred embodiment of the present invention, calibration holes are provided on both sides of the first bending upper die, the first bending lower die, the second bending upper die, and the second bending lower die, and the calibration holes on the same side of the first bending upper die, the first bending lower die, the second bending upper die, and the second bending lower die are collinear in the vertical direction.

[0018] As a preferred embodiment of the present invention, the secondary blank cavity includes a second intermediate cavity, and the primary bending cavity is provided at both ends of the second intermediate cavity;

[0019] The second-pass bending upper die includes an upper die body. The bottom of the upper die body is configured as a curved surface structure that cooperates with the second intermediate cavity. The curved surface structure cooperates with the second intermediate cavity to perform a second bending of the middle of the blank.

[0020] As a preferred embodiment of the present invention, positioning blocks are provided at both ends of the upper mold body, and the bottom of the positioning block is provided with an inclined surface. A connecting block is provided at the top of the positioning block. One end of the connecting block is rotatably connected to the upper mold body through a rotating shaft. An elastic corner piece is provided on the side of the upper mold body, and one side of the elastic corner piece is connected to the positioning block.

[0021] The inclined surface is used to mate with the end surface of the blank. When the upper part of the connecting block is subjected to downward pressure, it rotates around the pivot. The elastic corner piece supports the positioning block close to the upper mold body, and when the downward pressure disappears, the elastic corner piece causes the positioning block to return to its initial position.

[0022] As a preferred embodiment of the present invention, a guide groove is provided in the middle of the inclined surface, the guide groove is along the length direction of the inclined surface, and the structure of the guide groove is the same as that of the primary bending cavity.

[0023] As a preferred embodiment of the present invention, a pressure plate is provided above the upper fixing plate, the bottom of the pressure plate cooperates with the upper surface of the upper fixing plate, a pressure main shaft is provided in the middle of the pressure plate, a connecting seat is installed on the pressure main shaft, and a plurality of pressure relief devices are provided on the connecting seat.

[0024] The pressure relief device includes an electromagnetic drive unit and a first guide rod. A through hole is provided on the pressure plate to cooperate with the first guide rod. A second guide rod is provided above the through hole. An electromagnet is provided at the top of the second guide rod. A third guide rod is connected to the bottom of the second guide rod. A guide hole is provided on the axial direction of the first guide rod to cooperate with the third guide rod. A pressure-bearing spring is fitted on the body of the third guide rod.

[0025] As a preferred embodiment of the present invention, a first wedge is provided at the bottom of the second guide rods located on both sides of the upper mold body, and a countersunk hole is provided on the connecting block on both sides of the upper mold body. A second wedge is provided in the countersunk hole to cooperate with the first wedge. The first wedge and the second wedge form a wedge surface transmission pair.

[0026] The wedge-shaped transmission pair formed by the first wedge and the second wedge drives the connecting block to rotate around the rotating shaft.

[0027] As a preferred embodiment of the present invention, before the pressure plate contacts the upper fixed plate, the electromagnetic drive unit is used to linearly increase the force on the electromagnet, so that the second guide rod drives the first guide rod to contact the upper fixed plate under the action of the pressure spring through the third guide rod.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] This invention separates the bending portion of a forging into primary and secondary bends using a two-stage bending die. This allows for the separate bending of deep U-shaped structures and small-radius bends. By performing the bending in stages and designing a two-stage bending die, it is possible to bend bars with multiple bending segments and long support arms at large angles.

[0030] The two-stage bending method in this invention can reduce the reciprocating alternating stress on the billet during the distributed bending process.

[0031] The bending die provided by this invention does not require many auxiliary devices, while ensuring bending quality and reducing the occurrence of blank jamming during the bending process. Attached Figure Description

[0032] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the overall structure of the mold according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the overall right-side structure according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the longitudinal section of the upper and lower dies for a single bending stage according to an embodiment of the present invention.

[0036] Figure 4 This is a schematic diagram of the overall longitudinal section structure of the upper and lower bending molds for the second bending stage according to an embodiment of the present invention.

[0037] Figure 5This is a schematic diagram of a pressure-relieving device provided above the upper fixing plate according to an embodiment of the present invention;

[0038] Figure 6 This is a schematic diagram of the overall structure of the present invention, which includes a connecting block, a positioning block, and a pressure-relieving device.

[0039] Figure 7 This is a schematic diagram of a blank bent by two bending dies and the final formed structure of the blank, according to an embodiment of the present invention.

[0040] The labels in the diagram represent the following:

[0041] 10-Upper fixing plate; 11-Pressure plate; 12-Pressure spindle; 13-Connecting seat; 20-Lower fixing plate; 30-First bending upper die; 40-Second bending upper die; 41-Upper die body; 42-Positioning block; 43-Inclined surface; 45-Rotating shaft; 46-Elastic corner piece; 47-Guide groove; 50-First bending lower die; 51-First blank cavity; 52-First intermediate cavity; 53-First bending cavity; 54-Positioning groove; 60-Second bending lower die; 61-Second blank cavity; 70-Calibration hole; 80-Pressure relief device; 81-Electromagnetic drive unit; 82-First guide rod; 83-Through hole; 84-Second guide rod; 85-Third guide rod; 86-Guide hole; 87-Pressure bearing spring; 88-First wedge; 89-Counterhole. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] like Figures 1 to 7 As shown, the present invention provides a two-stage bending die, including an upper fixed plate 10 and a lower fixed plate 20. A first-stage bending upper die 30 and a second-stage bending upper die 40 are arranged side by side on the lower surface of the upper fixed plate 10, and a first-stage bending lower die 50 and a second-stage bending lower die 60 are arranged side by side on the upper surface of the lower fixed plate 20.

[0044] A primary blank cavity 51 is provided on the lower die 50 for bending. The primary blank cavity 51 is used to bend and form the two ends of the blank when the upper die 30 for bending and the primary blank cavity 51 are closed.

[0045] A secondary blank cavity 61 is provided on the lower die 60 for secondary bending. The secondary blank cavity 61 is used to perform secondary bending and forming of the middle of the blank when the upper die 40 for secondary bending and the secondary blank cavity 61 are closed.

[0046] by Figure 7 The labels in the text are as follows: P101 - the original cylindrical bar stock with D = 50mm x L = 600mm as an example; P102 - the billet obtained after the first bending; P103 - the billet obtained after the second bending.

[0047] In this embodiment, the original extruded aluminum alloy cylindrical bar P101 is heated to a certain temperature. At this temperature, the aluminum alloy is suitable for forging and has sufficiently high process plasticity. The original cylindrical bar is placed on the mold for bending and blanking. The first bending blanking is performed. A primary blank cavity 51 is provided on the lower die 50 of the primary bending. The primary blank cavity 51 is used to bend the two ends of the blank once when the upper die 30 of the primary bending is closed with the primary blank cavity 51, resulting in a blank with partial bending at both ends, which is called a primary bending blank. After the first bending blanking is completed, the second bending blanking is performed to obtain a secondary bending blank. A secondary blank cavity 61 is provided on the lower die 60 of the secondary bending. The secondary blank cavity 61 is used to bend the middle of the blank twice when the upper die 40 of the secondary bending is closed with the secondary blank cavity 61, which is the deep U-shaped arm product structure blank.

[0048] In this embodiment, the middle section of the final blank formed by the mold has a large curvature or a depth relative to the end of the formed blank, while the two sides of the middle section have small curvature bends.

[0049] Specifically, two heating holes are provided on the upper die of the first bending stage and two heating holes are provided on the lower die of the first bending stage to heat the die. Specifically, the electric heating tube of the die is placed in the hole to make the die temperature reach 200-300℃. At this temperature, the surface and internal structure of the blank bend are more compact.

[0050] In this embodiment, the bending cavity 53 is designed for bending and forming a specific target blank, that is... Figure 7 The P103 structure in the example, however, if the target blank has an asymmetrical bending structure, then it is still necessary to perform a single bending forming based on the bending portions at both ends of the bending structure with a large depth and curvature (such as a deep U-shaped structure). In other words, this embodiment divides the order of the first and second bending based on the degree of bending of the target blank.

[0051] Therefore, in this embodiment, the primary blank cavity 51 includes a first intermediate cavity 52, and a primary bending cavity 53 is provided at both ends of the first intermediate cavity 52, and the primary bending cavities 53 located at both ends of the first intermediate cavity 52 are centrally symmetrical.

[0052] In the case of the bending cavity 53, when the bending upper die 30 and the blank cavity 51 are closed, the two ends of the blank are bent once.

[0053] The first intermediate cavity 52 mates symmetrically with the bottom surface of the upper bending die 30. To release the stress on the blank generated during a single bending process, the middle of the first intermediate cavity 52 can be provided with a concave arc-shaped structure, such as... Figure 3 As shown, furthermore, instead of bending the middle portion of the billet, a symmetrical concave arc structure is also provided in the middle of the bottom surface of the upper bending die 30. This allows the stress generated by bending at both ends of the billet to be released in the middle portion of the billet.

[0054] The end of the first bending cavity 53 away from the first intermediate cavity 52 extends horizontally toward the side of the first bending die 50 to form a positioning groove 54. The positioning groove 54 can also extend to the end surface of the first bending die 50 to form an open opening or not extend completely to form a retaining edge. The positioning groove 54 is used to position the end of the blank, so that the blank maintains accurate positioning during the first bending and second bending processes.

[0055] Calibration holes 70 are provided on both sides of the first bending upper die 30, the first bending lower die 50, the second bending upper die 40, and the second bending lower die 60. The calibration holes 70 on the same side of the first bending upper die 30 and the first bending lower die 50, the second bending upper die 40 and the second bending lower die 60 are collinear in the vertical direction.

[0056] In this embodiment, the settings can be configured according to the actual structure of the mold. The calibration hole 70 can be used to lock the upper and lower molds of the mold. The upper mold 30 and the upper mold 40 of the first bending and the lower mold 50 and the lower mold 60 of the second bending can be connected by setting the calibration hole 70 on the upper mold 30 of the first bending and the upper mold 40 of the second bending. Specifically, the calibration hole 70 can be a threaded hole. A screw is installed in the threaded hole for connection. Then, the upper mold 30 of the first bending and the upper mold 40 of the second bending and the lower mold 50 and the lower mold 60 of the first bending can be locked by rotating the screw.

[0057] The secondary blank cavity 61 includes a second intermediate cavity 62. A bending cavity 53 is provided at both ends of the second intermediate cavity 62. During the second bending process, the blank after the first bending is still reshaped and positioned through the bending cavity 53. The advantage is that if only the middle part of the blank is bent to a greater depth or a deep U-shaped structure is bent during the second bending process, the bending process will inevitably affect the already bent structure of the first bending.

[0058] Therefore, the upper die 40 for the second bending in this embodiment includes an upper die body 41. The bottom of the upper die body 41 is configured as a curved surface structure that cooperates with the second intermediate cavity 62. The curved surface structure cooperates with the second intermediate cavity 62 to perform a second bending on the middle of the blank.

[0059] Because the billet undergoes significant deformation during the second bending process, the process involves the deformation of the overall structure of the billet and the change in the position of the two sections of the billet.

[0060] Therefore, in order to accommodate the deformation of the blank at both ends during the second bending process, this embodiment provides positioning blocks 42 at both ends of the upper die body 41, and the bottom of the positioning block 42 is provided with an inclined surface 43, and the top of the positioning block 42 is provided with a connecting block 44. One end of the connecting block 44 is rotatably connected to the upper die body 41 through a rotating shaft 45. An elastic corner piece 46 is provided on the side of the upper die body 41, and one side of the elastic corner piece 46 is connected to the positioning block 42.

[0061] In this embodiment, the elastic corner piece 46 is specifically a metal spring with shape memory metal, specifically a rectangular structure. One side of the metal spring piece is connected to the bottom of the connecting seat 13, and the other side is connected to the side of the upper mold body 41, both of which can be designed to be detachable. Therefore, the elastic corner piece 46 can be used as a consumable part, can be replaced, and does not affect the performance of the mold itself.

[0062] The inclined surface 43 is used to fit the end surface of the blank. When the upper part of the connecting block 44 is subjected to downward pressure, it rotates around the rotating shaft 45. The elastic corner piece 46 supports the positioning block 42 close to the upper mold body 41, and when the downward pressure disappears, the elastic corner piece 46 makes the positioning block 42 return to its initial position.

[0063] A guide groove 47 is provided in the middle of the inclined surface 43. The guide groove 47 is along the length of the inclined surface 43 and has the same structure as the primary bending cavity 53.

[0064] A pressure plate 11 is provided above the upper fixed plate 10. The bottom of the pressure plate 11 is engaged with the upper surface of the upper fixed plate 10. A pressure spindle 12 is provided in the middle of the pressure plate 11. A connecting seat 13 is installed on the pressure spindle 12. Multiple pressure relief devices 80 are provided on the connecting seat 13.

[0065] Furthermore, in this embodiment, the pressure relief device 80 includes an electromagnetic drive unit 81 and a first guide rod 82. A through hole 83 that cooperates with the first guide rod 82 is provided on the pressure plate 11. A second guide rod 84 is provided above the through hole 83. An electromagnet is provided at the top of the second guide rod 84. A third guide rod 85 is connected to the bottom of the second guide rod 84. A guide hole 86 that cooperates with the third guide rod 85 is provided axially on the first guide rod 86. A pressure-bearing spring 87 is fitted on the body of the third guide rod 85.

[0066] A first wedge 88 is provided at the bottom of the second guide rod 17 located on both sides of the upper mold body 41. A countersunk hole 89 is provided on the connecting block 44 on both sides of the upper mold body 41. A second wedge that cooperates with the first wedge 88 is provided in the countersunk hole 89. The first wedge 88 and the second wedge form a wedge surface transmission pair.

[0067] The wedge-shaped transmission pair consisting of the first wedge 88 and the second wedge drives the connecting block 44 to rotate around the rotating shaft 45.

[0068] Before the pressure plate 11 contacts the fixed plate 10, the electromagnetic drive unit 81 linearly increases the force on the electromagnet, so that the second guide rod 84 drives the first guide rod 82 to contact the fixed plate 10 through the third guide rod 85 under the action of the pressure spring 87.

[0069] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A two-stage bending die, comprising an upper fixed plate (10) and a lower fixed plate (20), wherein a first-stage bending upper die (30) and a second-stage bending upper die (40) are arranged side-by-side on the lower surface of the upper fixed plate (10), and a first-stage bending lower die (50) and a second-stage bending lower die (60) are arranged side-by-side on the upper surface of the lower fixed plate (20), characterized in that, A primary blank cavity (51) is provided on the primary bending lower die (50). The primary blank cavity (51) is used to perform a one-time bending forming on the two ends of the blank when the primary bending upper die (30) and the primary blank cavity (51) are closed. A secondary blank cavity (61) is provided on the lower die (60) of the second bending process. The secondary blank cavity (61) is used to perform a secondary bending and forming of the middle of the blank when the upper die (40) of the second bending process and the secondary blank cavity (61) are closed. The primary blank cavity (51) includes a first intermediate cavity (52), and a primary bending cavity (53) is provided at both ends of the first intermediate cavity (52), and the primary bending cavities (53) located at both ends of the first intermediate cavity (52) are centrally symmetrical; The primary bending cavity (53) performs a primary bending on the two ends of the blank when the primary bending upper die (30) and the primary blank cavity (51) are closed. The first intermediate cavity (52) fits symmetrically with the bottom surface of the first bending upper die (30); The secondary blank cavity (61) includes a second intermediate cavity (62), and the primary bending cavity (53) is provided at both ends of the second intermediate cavity (62). The second bending upper die (40) includes an upper die body (41), the bottom of which is configured as a curved surface structure that cooperates with the second intermediate cavity (62). The curved surface structure cooperates with the second intermediate cavity (62) to perform a second bending on the middle of the blank. Positioning blocks (42) are provided at both ends of the upper mold body (41), and an inclined surface (43) is provided at the bottom of the positioning block (42). A connecting block (44) is provided at the top of the positioning block (42). One end of the connecting block (44) is rotatably connected to the upper mold body (41) through a rotating shaft (45). An elastic corner piece (46) is provided on the side of the upper mold body (41), and one side of the elastic corner piece (46) is connected to the positioning block (42). The inclined surface (43) is used to fit the end surface of the blank. When the upper part of the connecting block (44) is subjected to downward pressure, it rotates around the rotating shaft (45). The elastic corner piece (46) supports the positioning block (42) to approach the upper mold body (41). When the downward pressure disappears, the elastic corner piece (46) makes the positioning block (42) return to its initial position. A guide groove (47) is provided in the middle of the inclined surface (43). The guide groove (47) is along the length direction of the inclined surface (43), and the guide groove (47) has the same structure as the first bending cavity (53). A pressure plate (11) is provided above the upper fixed plate (10). The bottom of the pressure plate (11) is engaged with the upper surface of the upper fixed plate (10). A pressure spindle (12) is provided in the middle of the pressure plate (11). A connecting seat (13) is installed on the pressure spindle (12). A plurality of pressure relief devices (80) are provided on the connecting seat (13). The pressure relief device (80) includes an electromagnetic drive unit (81) and a first guide rod (82). A through hole (83) is provided on the pressure plate (11) to cooperate with the first guide rod (82). A second guide rod (84) is provided above the through hole (83). An electromagnet is provided at the top of the second guide rod (84). A third guide rod (85) is connected to the bottom of the second guide rod (84). A guide hole (86) is provided in the axial direction of the first guide rod (82) to cooperate with the third guide rod (85). A pressure-bearing spring (87) is fitted on the rod body of the third guide rod (85). A first wedge (88) is provided at the bottom of the second guide rod (84) located on both sides of the upper mold body (41). A countersunk hole (89) is provided on the connecting block (44) on both sides of the upper mold body (41). A second wedge that cooperates with the first wedge (88) is provided in the countersunk hole (89). The first wedge (88) and the second wedge form a wedge surface transmission pair. The wedge-shaped transmission pair composed of the first wedge (88) and the second wedge drives the connecting block (44) to rotate around the rotating shaft (45).

2. The two-pass bending die according to claim 1, characterized in that, The end of the primary bending cavity (53) away from the first intermediate cavity (52) extends horizontally toward the side of the primary bending die (50) to form a positioning groove (54).

3. The two-pass bending die according to claim 1, characterized in that, Calibration holes (70) are provided on both sides of the first bending upper die (30), the first bending lower die (50), the second bending upper die (40), and the second bending lower die (60). The calibration holes (70) on the same side of the first bending upper die (30), the first bending lower die (50), the second bending upper die (40), and the second bending lower die (60) are collinear in the vertical direction.

4. The two-pass bending die according to claim 1, characterized in that, Before the pressure plate (11) contacts the upper fixed plate (10), the electromagnetic drive unit (81) is used to linearly increase the force on the electromagnet, so that the second guide rod (84) drives the first guide rod (82) to contact the upper fixed plate (10) through the third guide rod (85) under the action of the pressure spring (87).

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