A centrifuge basket floating hoisting platform

Abstract

The application discloses a floating hoisting platform of a centrifuge basket, which comprises a floating support, an air spring, a floating pull rod, a fixed base, a movable base and a simulated lifting lug. The simulated lifting lug with the same size as the actual basket is installed to realize the positioning of the floating support platform in each direction, so that the position deviation between the basket mounting hole and the rotating arm mounting hole is as small as possible when the actual basket is installed. The air spring bears most of the load of the self weight of the basket, so that only a small load exists between the pin shaft and the basket mounting hole and the rotating arm mounting hole, and the possible damage of the pin shaft and the basket mounting hole and the rotating arm mounting hole is effectively avoided. The floating support of the basket in a small range is realized through the air spring. When the pin shaft is installed, the position deviation between the basket mounting hole and the rotating arm mounting hole is automatically corrected by the floating characteristic of the air spring, and the efficiency of the pin shaft installation is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hoisting devices, and particularly relates to a floating hoisting platform of a centrifuge basket. BACKGROUND

[0002] A hypergravity simulation centrifuge generates centrifugal force by high-speed rotation of a basket driven by a rotating arm to simulate the acceleration process of aerospace products or to reproduce the stress state of a geotechnical model through scale effect, and is important equipment for checking the anti-overload performance of aerospace equipment and predicting and verifying the structural properties of civil engineering. In order to adjust the direction of the centrifugal force on the test model, the basket loaded with the test model is usually connected with the rotating arm of the centrifuge through a pin shaft, and the basket can rotate relative to the rotating arm of the centrifuge around the pin shaft. In order to realize different functions, a centrifuge is usually matched with multiple baskets for use. Therefore, the disassembly and assembly of the basket, the rotating arm and the pin shaft need to be frequently performed.

[0003] Since the basket often needs to bear a huge load during the test, in order to ensure the bearing capacity of the pin shaft connection, the matching gap between the pin shaft and the connecting holes of the basket and the rotating arm needs to be set very small. At the same time, in order to be able to bear a large load, the weight of the basket itself is as high as several tons or even dozens of tons. During the installation of the basket, the rotating arm is usually pre-assembled and fixed, and the basket is usually hoisted to the position of the installation hole of the rotating arm by a crane. The basket installation hole is roughly aligned with the rotating arm installation hole by visual observation of the human eye and the movement of the crane, and the positioning accuracy cannot be guaranteed. Since the movement accuracy of the crane is limited, the deviation between the basket installation hole and the rotating arm installation hole cannot be adjusted to the ideal state. When the pin shaft is installed, due to the inevitable misalignment of the basket installation hole and the rotating arm installation hole, the pin shaft needs to overcome the huge self-weight load of the basket when being forcibly rotated into the installation hole, which easily causes the pin shaft to be stuck and damages the pin shaft and the installation hole matching surface. Therefore, in the traditional installation method, as the pin shaft is slowly assembled into the installation hole and enters the matching stage, on the one hand, the operator needs to judge the deviation direction and deviation amount between the two installation holes according to personal hand feeling experience combined with visual observation, and adjusts the position of the basket hoisted by the crane according to the feeling. On the other hand, the operator also needs to manually shake the suspended basket to make the basket installation hole position move back and forth around the ideal alignment position, so as to adjust the gap between the basket installation hole and the pin shaft, and avoid forcibly rotating the pin shaft into the installation hole to cause the pin shaft to be stuck or the matching surface to be damaged.

[0004] Therefore, the traditional method of adjusting the position of the basket by the crane during the installation of the centrifuge basket cannot guarantee the position accuracy requirement between the basket installation hole and the rotating arm installation hole; at the same time, the method of adjusting the gap between the basket installation hole and the pin shaft by shaking the lifting tool seriously depends on the work experience of the operator, and there is a certain safety hazard. The installation efficiency of the basket is low, and the installation quality is difficult to guarantee.

[0005] Therefore, a centrifuge basket floating hoisting platform needs to be developed to solve the above problems. SUMMARY

[0006] The centrifuge basket floating hoisting platform is designed to solve the above problems.

[0007] The centrifuge basket floating hoisting platform is designed to solve the above problems.

[0008] The centrifuge basket floating hoisting platform comprises:

[0009] The floating support;

[0010] The air spring;

[0011] The floating pull rod comprises an upper cylindrical segment one, an intermediate disc segment and a lower cylindrical segment connected in sequence from top to bottom, the upper end of the upper cylindrical segment one is connected with the floating support, two groups of threaded clearance holes are vertically arranged on the intermediate disc segment, the threaded clearance hole on the inner side is used for being connected with the simulated lifting lug through bolts, and the threaded clearance hole on the outer side is used for being connected with the movable base through bolts;

[0012] The fixed base comprises a base plate and two positioning conical tables, the base plate is connected with the rotating arm; a plurality of threaded holes are vertically arranged on the fixed base, one group of threaded holes is used for being connected with the movable base upward through bolts, one group of threaded holes is used for being connected with the rotating arm downward through bolts, and one group of threaded holes is used for being connected with the positioning conical table upward through bolts; the positioning conical table is a conical table, a threaded clearance hole is arranged in the middle, and the threaded clearance hole is used for being connected with the base plate downward through bolts;

[0013] The movable base; the air spring is arranged between the floating support and the movable base, the upper end of the air spring is connected with the floating support, and the lower end of the air spring is connected with the movable base; the middle part of the movable base is provided with a stepped through hole, the intermediate disc segment of the floating pull rod is arranged in the large hole of the stepped through hole, and the lower cylindrical segment is arranged in the small hole of the stepped through hole; two taper holes are arranged on the lower surface of the movable base, and the two taper holes are positioned and matched with the two positioning conical tables respectively;

[0014] The simulated lifting lug comprises an upper cylindrical segment two and a lower trapezoidal support connected in sequence from top to bottom, a group of threaded holes are arranged above the upper cylindrical segment two, and the threaded holes are used for being connected with the floating pull rod upward through bolts; a semicylindrical arc surface is arranged at the bottom of the lower trapezoidal support, and is used for being matched with the pin shaft to be installed; a circular hole is arranged at the bottom of the lower cylindrical segment of the floating pull rod, the upper cylindrical segment two is arranged in the circular hole, and the upper cylindrical segment two is positioned and matched with the lower cylindrical segment.

[0015] Further, the lower end of the circular hole arranged at the bottom of the lower cylindrical segment is formed into a taper hole, and the taper hole is used for guiding and matching with the top conical table of the basket during assembly.

[0016] Specifically, the air spring comprises two bases, two air bags and two floating platforms, the two air bags are arranged on the same horizontal plane, upper ends of the two air bags are connected with the two floating platforms respectively, lower ends of the two air bags are connected with the two bases respectively, two first grooves are arranged below the floating support, two second grooves are arranged above the movable base, the two floating platforms are arranged in the two first grooves respectively and are connected with the bottom of the first grooves through bolts; the two bases are arranged in the two second grooves respectively and are connected with the bottom of the second grooves through bolts.

[0017] Further, a third groove is arranged below the floating support, the third groove is arranged at the center between the two first grooves, a group of threaded clearance holes are arranged at the bottom of the third groove, and the floating pull rod is connected with the third groove through bolts.

[0018] Preferably, a group of through holes are arranged on both sides of the third groove, and the connecting screws between the floating pull rod and the simulated lifting lugs are arranged in the through holes.

[0019] Preferably, the stepped through hole is arranged at the center between the two second grooves.

[0020] Further, the base plate is a plate structure with a slot in the middle, and a boss stop is arranged below the base plate, which is used for positioning with the rotating arm.

[0021] The beneficial effects of the present application are as follows:

[0022] The simulated lifting lugs with the same size as the actual hanging basket are installed to realize the pre-positioning of the floating support platform in all directions, so that the position deviation between the hanging basket mounting hole and the rotating arm mounting hole is as small as possible when the actual hanging basket is installed; the air spring bears most of the load of the self-weight of the hanging basket, so that only a small load exists between the pin shaft and the hanging basket mounting hole and the rotating arm mounting hole, and the possible damage of the pin shaft and the hanging basket mounting hole and the rotating arm mounting hole is effectively avoided; the floating support of the hanging basket in a small range is realized through the air spring, and when the pin shaft is installed, the position deviation between the hanging basket mounting hole and the rotating arm mounting hole is automatically corrected by the floating characteristic of the air spring, and the efficiency of the pin shaft installation is improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The figure is a structural schematic diagram of the present application;

[0024] Figure 2 The figure is a partial cross-section of the present application after installation Figure One ;

[0025] Figure 3 The figure is a partial cross-section of the present application after installation Figure Two ;

[0026] Figure 4 The figure is a structural schematic diagram of the floating support in the present application;

[0027] Figure 5 It is a structural schematic diagram of the floating pull rod in the present application;

[0028] Figure 6 It is a structural schematic diagram of the movable base in the present application;

[0029] Figure 7 It is a structural schematic diagram of the fixed base in the present application;

[0030] Figure 8 It is a structural schematic diagram of the simulated lifting lug in the present application.

[0031] Legend: 1-floating support; 2-air spring; 3-floating pull rod; 4-fixed base; 4-1-base flat plate; 4-2-positioning cone; 5-movable base; 6-simulated lifting lug; 7-slewing arm; 8-pivot. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

[0034] It should be noted that: similar numbers and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0035] In the description of the present application, it is understood that the terms "upper", "lower", "inner", "outer", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the present application is used, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0036] In addition, the terms "first", "second" and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance.

[0037] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms such as "arranged", "connected" and the like should be interpreted in a broad sense, for example, "connected" can be fixedly connected, or detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium, or can be internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0039] As Figures 1-8 shown, a centrifuge basket floating hoisting platform, comprising:

[0040] Floating bracket 1;

[0041] Air spring 2;

[0042] Floating pull rod 3; floating pull rod 3 includes upper cylindrical segment one, middle disc segment and lower cylindrical segment connected in turn from top to bottom, the upper end of upper cylindrical segment one is connected with floating bracket 1, two groups of threaded clearance holes are vertically arranged on middle disc segment, the threaded clearance hole on the inner side is used for connecting with the simulated lifting lug 6 through bolts, and the threaded clearance hole on the outer side is used for connecting with the movable base 5 through bolts;

[0043] Fixed base 4; fixed base 4 includes base plate 4-1 and two positioning conical frustums 4-2, base plate 4-1 is connected with rotating arm 7; a plurality of threaded holes are vertically arranged on fixed base 4, one group of threaded holes is used for connecting with movable base 5 upward through bolts, one group of threaded holes is used for connecting with rotating arm 7 downward through bolts, and one group is used for connecting with positioning conical frustum 4-2 upward through bolts; positioning conical frustum 4-2 is a conical frustum, a threaded clearance hole is arranged in the middle, and is used for connecting with base plate 4-1 downward through bolts;

[0044] The movable base 5 is provided with an air spring 2 between the floating support 1 and the movable base 5, and the upper end of the air spring 2 is connected with the floating support 1, and the lower end of the air spring 2 is connected with the movable base 5; the middle part of the movable base 5 is provided with a stepped through hole, the middle disc segment of the floating pull rod is arranged in the large hole of the stepped through hole, and the lower cylindrical segment is arranged in the small hole of the stepped through hole and is in small gap fit, so as to limit the horizontal movement range of the floating pull rod 3; the lower surface of the movable base 5 is provided with two taper holes, and the two taper holes are respectively positioned and matched with two positioning conical tables 4-2; a plurality of installation grooves are formed in the side wall of the large hole of the stepped through hole, screw holes are arranged at the bottom of the installation grooves, the large hole of the stepped through hole is formed in a petal shape, and correspondingly, the side wall of the middle disc segment is also formed with a plurality of petal-shaped ears, the plurality of petal-shaped ears can slide up and down in the plurality of installation grooves, and the petal-shaped ears and the installation grooves can be connected through bolts.

[0045] The simulation lifting lug 6 includes an upper cylindrical segment two and a lower trapezoidal support connected in sequence from top to bottom, a group of threaded holes are arranged above the upper cylindrical segment two, and the upper cylindrical segment two is connected with the floating pull rod 3 upward through bolts; the lower trapezoidal support is provided with a semicylindrical arc surface at the bottom, and is matched with a to-be-installed pin shaft; the lower cylindrical segment of the floating pull rod is provided with a circular hole, and the upper cylindrical segment two is arranged in the circular hole and is positioned and matched with each other.

[0046] In some embodiments, the lower end of the circular hole arranged at the bottom of the lower cylindrical segment is formed into a taper hole, and the taper hole is used for guiding and matching with the top conical table of the hanging basket during assembly.

[0047] In some embodiments, the air spring 2 includes two bases, two air bags and two floating tables, the two air bags are arranged on the same horizontal plane, the upper ends of the two air bags are respectively connected with the two floating tables, the lower ends of the two air bags are respectively connected with the two bases, the lower part of the floating support 1 is provided with two first grooves, the upper part of the movable base 5 is provided with two second grooves, the two floating tables are respectively arranged in the two first grooves and connected with the bottom of the first grooves through bolts; the two bases are respectively arranged in the two second grooves and connected with the bottom of the second grooves through bolts.

[0048] In some embodiments, the air spring 2 further includes a height adjusting valve and a pressure adjusting valve. The air spring 2 can adjust the height of the floating table through the height adjusting valve, and adjust the gas pressure entering the air bag through the pressure adjusting valve, so as to adjust the carrying capacity. After the air spring 2 reaches the balance under the load, it can elastically float in the horizontal direction and the numerical direction within a small range under the action of additional external load.

[0049] In some embodiments, the floating support 1 is provided with a third groove below, the third groove is arranged at the center between the two first grooves, a group of threaded gap holes are arranged at the bottom of the third groove, and the floating pull rod 3 is connected through bolts.

[0050] In some embodiments, a set of through holes are arranged on both sides of the third groove, for mounting the connecting screw between the floating pull rod 3 and the simulation lifting lug 6.

[0051] In some embodiments, a stepped through hole is arranged at the center between the two second grooves.

[0052] In some embodiments, the base plate 4-1 is a middle-slotted plate structure, with a boss stopper below for cooperating with the rotating arm 7 for positioning.

[0053] In some embodiments, two weight-reducing grooves are arranged on both sides of the third groove on the floating support 1.

[0054] When the application is in operation: the fixed base 4 is installed on the centrifuge rotating arm 7, the movable base 5 is installed on the fixed base 4 and positioned by the positioning cone 4-2, a set of air springs 2 are installed on the fixed base 5, the floating support 1 is installed on the air springs, and the floating pull rod 3 is installed below the floating support 1. The positioning cone 4-2 is placed in the corresponding installation position of the base plate 4-1, but not fixed by screws.

[0055] The positions of the threaded mounting interface and the pin shaft mounting hole on the top of the simulation lifting lug are basically consistent with those of the basket. Before installing the basket, the simulation lifting lug is installed below the floating pull rod 3, the horizontal position of the semi-cylindrical arc surface axis below the simulation lifting lug is adjusted by adjusting the relative position between the movable base 5 and the fixed base 4 in the horizontal direction, and the vertical position of the semi-cylindrical arc surface axis below the simulation lifting lug is adjusted by adjusting the height adjustment valve and the pressure adjustment valve of the air spring, so that the semi-cylindrical surface is tightly fitted with the pin shaft 8, and the movable base 5 is pre-positioned. At this time, the connection between the movable base 5 and the fixed base 4 is fastened by screws, and the positioning cone 4-2 is fixed and connected on the base plate 4-1 by screws.

[0056] When installing the basket, the dummy lug is removed from below the floating rod 3, the pressure in the air spring 2 is adjusted to make the floating platform of the air spring 2 descend, and the floating support 1 and the floating rod 3 as a whole descend until the bottom surface of the floating rod 3 contacts the middle groove in the movable base 5. At this time, the air spring does not bear a load. The basket is hoisted using a crane to be close to the bottom guiding conical hole of the floating rod 3 from below the floating rod 3, and continues to move upward along the guiding conical hole to the positioning cylindrical hole until it is attached to the bottom of the floating rod 3. At this time, the floating rod 3 and the basket are fixed together through screws. Since the basket mounting hole and the mounting hole of the rotating arm 7 are basically consistent in position in the horizontal direction due to the pre-positioning through the dummy lug, a high horizontal positioning accuracy can be ensured. Then, the connecting screw between the floating rod 33 and the movable base 55 is loosened, the pressure in the air spring 2 is adjusted according to the weight of the basket, and the floating platform of the air spring 2 rises. Since the position of the height adjustment valve has been calibrated through the dummy lug, the floating platform of the air spring 2 and the floating support 1 drive the floating rod 3 and the basket to move to the pre-positioned position and then stop moving and maintain stability. At this time, the position deviation of the basket mounting hole and the mounting hole of the rotating arm 7 in each direction is small.

[0057] Finally, the pin 8 is slowly loaded into the mounting hole of the rotating arm 7 and the mounting hole of the basket. Since the air spring 2 has a low dynamic stiffness, when the pin 8 moves to the mounting hole of the basket and forms a contact, a small additional load will push the floating rod 3, the floating support 1, and the floating platform of the air spring 2 as a whole to move a small distance in the corresponding direction, thereby further reducing the position deviation of the mounting hole of the basket and the mounting hole of the rotating arm 7. At this time, most of the load of the self-weight of the basket is still borne by the air spring 2, and only a small load is borne between the pin 8 and the mounting hole of the basket and the mounting hole of the rotating arm 7. Therefore, the pin 8, the mounting hole of the basket, and the mounting hole of the rotating arm 7 are all free from the risk of being damaged. At the same time, since the position deviation of the mounting hole of the basket and the mounting hole of the rotating arm 7 is further reduced, it is more conducive to the further installation of the pin 8.

[0058] After the pin 8 is installed, the connecting screw between the floating rod 3 and the basket is removed, and the movable base 5, the air spring 2, the floating support 1, and the floating rod 3 are integrally removed from above the rotating arm 7. However, the positioning conical platform 4-2 and the fixed base 4 are retained on the rotating arm 7.

[0059] When the basket needs to be disassembled, the pressure of the air spring 2 pressure regulating valve is adjusted to the set value in the reverse order of the above, and the movable base 5, the air spring 2, the floating support 1 and the floating pull rod 3 are integrally installed above the rotating arm 7. Since the positioning cone 4-2 is pre-installed on the fixed base 4 and the rotating arm 7, the movable base 5 can be conveniently positioned through the bottom tapered hole. After the movable base 5 is installed, the connecting screw between the floating pull rod 3 and the basket is installed, at this time, most of the self-weight load of the basket is again borne by the air spring 2. Therefore, only a small load exists between the pin shaft 8 and the basket mounting hole and the rotating arm 7 mounting hole, and the pin shaft 8 can be smoothly removed. After the pin shaft 8 is removed, the basket is lifted by a crane, the connecting screw between the floating pull rod 3 and the basket is removed, and the basket is lifted away from the rotating arm 7, so that the disassembly of the basket is realized.

[0060] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the technical principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A centrifuge basket float hoist platform, characterized by, The utility model relates to a floating support (1), air spring (2), floating pull rod (3), fixed base (4), movable base (5), simulation lifting lug (6) and rotating arm (7). The floating pull rod (3) comprises upper cylindrical segment one, middle disc segment and lower cylindrical segment connected in sequence from top to bottom, the upper end of the upper cylindrical segment one is connected with the floating support (1), two groups of threaded clearance holes are vertically arranged on the middle disc segment, the threaded clearance hole on the inner side is used for being connected with the simulation lifting lug (6) through bolts, and the threaded clearance hole on the outer side is used for being connected with the movable base (5) through bolts. The fixed base (4) comprises base flat plate (4-1) and two positioning conical tables (4-2), the base flat plate (4-1) is connected with the rotating arm (7), a plurality of threaded holes are vertically arranged on the fixed base (4), one group of threaded holes is used for being connected with the movable base (5) upward through bolts, one group of threaded holes is used for being connected with the rotating arm (7) downward through bolts, and one group of threaded holes is used for being connected with the positioning conical table (4-2) upward through bolts. The positioning conical table (4-2) is a conical table, a threaded clearance hole is arranged in the middle, and the threaded clearance hole is used for being connected with the base flat plate (4-1) downward through bolts. The movable base (5) is arranged between the floating support (1) and the air spring (2), the upper end of the air spring (2) is connected with the floating support (1), the lower end of the air spring (2) is connected with the movable base (5), the middle part of the movable base (5) is provided with a stepped through hole, the middle disc segment of the floating pull rod (3) is arranged in the large hole of the stepped through hole, and the lower cylindrical segment is arranged in the small hole of the stepped through hole. The lower surface of the movable base (5) is provided with two taper holes, and the two taper holes are positioned and matched with the two positioning conical tables (4-2) respectively. The simulation lifting lug (6) comprises upper cylindrical segment two and lower trapezoidal support connected in sequence from top to bottom, a group of threaded holes are arranged above the upper cylindrical segment two, and the upper cylindrical segment two is connected with the floating pull rod (3) upward through bolts.

2. A floating hoist platform for a centrifuge basket according to claim 1, wherein, The bottom of the lower cylindrical segment of the floating pull rod (3) is provided with a circular hole, the upper cylindrical segment two is arranged in the circular hole, and the upper cylindrical segment two is positioned and matched with the floating pull rod (3).

3. A floating hoist platform for a centrifuge basket according to claim 1, wherein, The lower end of the air spring (2) is connected with the movable base (5) through bolts.

4. A floating hoist platform for a centrifuge basket according to claim 3, wherein, The lower cylindrical segment bottom setting circular hole's lower opening is formed into a taper hole, and the taper hole is used for guiding and matching with the top conical table of the hanging basket during assembly. The air spring (2) comprises two bases, two air bags and two floating table surfaces, the two air bags are arranged on the same horizontal plane, the upper ends of the two air bags are connected with the two floating table surfaces respectively, the lower ends of the two air bags are connected with the two bases respectively, the lower part of the floating support (1) is provided with two first grooves, the upper part of the movable base (5) is provided with two second grooves, the two floating table surfaces are arranged in the two first grooves respectively and are connected with the bottom of the first groove through bolts, and the two bases are arranged in the two second grooves respectively and are connected with the bottom of the second groove through bolts. The lower part of the floating support (1) is provided with a third groove, the third groove is arranged at the center between the two first grooves, a group of threaded clearance holes are arranged on the bottom of the third groove, and the threaded clearance holes are used for being connected with the floating pull rod (3) through bolts.

5. A floating hoist platform for a centrifuge basket according to claim 4, wherein, A group of through holes are arranged on both sides of the third groove for mounting the connecting screw between the floating pull rod (3) and the simulated lifting lug (6).

6. A floating hoist platform for a centrifuge basket according to claim 3, wherein, The stepped through hole is arranged at the center between the two second grooves.

7. A floating hoist platform for a centrifuge basket according to claim 1, wherein, The base plate (4-1) is a plate structure with a slot in the middle, and a boss stop is arranged below for positioning with the rotating arm (7).

Images