CN114393106A

CN114393106A - Stamping manufacturing process method and process system of rope retainer

Info

Publication number: CN114393106A
Application number: CN202111446390.1A
Authority: CN
Inventors: 曹一枢; 段玉霞
Original assignee: Wuxi Shuguang Precision Industry Co ltd
Current assignee: Wuxi Shuguang Precision Industry Co ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-04-26
Anticipated expiration: 2041-11-30
Also published as: CN114393106B

Abstract

The invention discloses a punching manufacturing process method of a rope retainer and a process system thereof, wherein a punching die is driven by a press to punch a positioning hole; then, rib pressing is carried out through a rib pressing module; then cutting off the outline shape through the trimming module; then bending through a bending module; finally, cutting off redundant plate waste materials through a waste cutting die; and then, carrying out multi-directional synchronous punching on the piece to be punched after the processing of the above process through a bracket punching die. According to the invention, the continuous stamping die is used for stamping forming, so that a plurality of processes are synchronously carried out, and then the support punching die is used for synchronously carrying out multidirectional punching, so that the production efficiency is effectively improved; the lower guide ruler, the elastic guide assembly, the embedded block group, the material pressing assembly and the like are arranged to play a role in limiting, guiding, fixing and buffering, so that the quality of a product is ensured; through the installation setting of the classification mould of adopting the multimode, the effective life of utilization mould that can be abundant reduces the replacement cost.

Description

Stamping manufacturing process method and process system of rope retainer

Technical Field

The invention relates to the field of stamping processes, in particular to a method and a system for stamping and manufacturing a rope retainer.

Background

The winch is applied to the self-protection and traction devices of some special vehicles and ships, a common mechanical winch has stronger torque and very good toughness and durability because of directly taking power from an engine, but has the defects of large volume, heavy weight and quite limited applicable vehicle types, so that a cable retainer formed by punching and forming a metal plate is most suitable for being applied to the mechanical winch, the cable retainer has simple and light structure, but the cable retainer has multiple processing procedures and needs to be punched in multiple directions, so that the problems of low production efficiency, low service life of a die, high maintenance cost of the die and the like in production are caused.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a method and a system for stamping and manufacturing a rope retainer, which have high production efficiency and low cost.

The technical scheme is as follows: in order to achieve the above object, the present invention provides a method and a system for manufacturing a rope retainer by stamping, wherein the method for manufacturing a rope retainer by stamping through a system comprises the following steps:

step A, punching: punching a positioning hole by driving a punching die through a press;

step B, ribbing: rib pressing is carried out through a rib pressing module, specifically, rib pressing is carried out upwards at first, and then rib pressing is carried out downwards;

step C, trimming: cutting off the outline shape through the trimming module, wherein the outline shape specifically comprises an inner trimming and an outer trimming, and the part with the positioning hole is reserved;

step D, bending: bending through a bending module, and bending the cut plate for multiple times according to the preset shape of a finished product, wherein multiple positions at the front end are bent upwards, multiple positions at the tail end are bent downwards, and finally one position at the middle part is bent upwards;

step E, cutting waste: cutting off redundant plate waste materials through a waste cutting die;

step F, punching: and carrying out multi-directional synchronous punching on the piece to be punched after the processing of the above process through a bracket punching die.

Further, step a, step B, step C, step D and step E are all completed by a continuous press die.

Further, the rope retainer comprises an annular plate-shaped body, the plate-shaped body is bent into an S shape, the upper half ring of the plate-shaped body is provided with a continuous convex rib, the lower half ring of the plate-shaped body is provided with a segmented convex rib, and the continuous convex rib and the segmented convex rib are both protruded towards the bent inner part of the plate-shaped body; two sides of the lower half ring are respectively provided with an ear side;

two through holes are formed in the ear sides, two mounting holes are formed in two sides of the continuous convex rib respectively, and welding threaded plugs are arranged in the mounting holes;

the edge of the upper semi-ring extends towards the bending inner part of the plate-shaped body to form an arc curved surface.

Further, the continuous stamping die comprises a press base, an upper beam frame is arranged right above the press base, the press base and the upper beam frame are rectangular and are aligned up and down, the upper beam frame and the press base are arranged in a relative movement mode through a plurality of guide assemblies, the guide assemblies are arranged vertically, and the upper beam frame is driven to move up and down through a press main cylinder; a stamping section is arranged between the base and the upper beam frame; a plurality of dies are continuously arranged in the stamping section along the length direction, and a lower guide ruler is arranged at the feeding end of the stamping section and fixed on the base; the plate enters the stamping section from the feeding end of the stamping section through the lower guide ruler;

the multiple dies are arranged according to the working procedure and sequentially comprise a punching die, a rib pressing die set, a trimming die set, a bending die set and a waste cutting die; the die comprises an upper die and a lower die, the upper die is fixed through an upper fixing plate, and the upper fixing plate is fixed on the lower end face of the upper beam frame; the lower die is correspondingly arranged right below the upper die, and the lower die is fixed on the upper end face of the press base through a lower fixing plate.

Furthermore, two sides of the upper end surface of the lower fixed plate are respectively arranged on a stop plate, the stop plates are elastically arranged on the lower fixed plate through an elastic guide assembly, the upper die and the lower die are positioned between the stop plates on the two sides, and the edges of the two sides of the plate are supported through the stop plates;

the elastic guide assembly comprises a guide part and an elastic part, the guide part comprises a small guide pillar and a small guide sleeve, the small guide pillar is vertically fixed on the upper end face of the lower fixing plate through the elastic part, the small guide sleeve is sleeved on the small guide pillar, the small guide sleeve is arranged in a sliding mode relative to the small guide pillar, and the small guide sleeve is fixedly arranged on the lower end face of the stop plate.

Furthermore, the plurality of moulds are respectively positioned in a plurality of modules, an empty station is arranged between the modules, and the moulds positioned in the same module share the same lower fixing plate and the same upper fixing plate; the punching die, the rib pressing die set and the trimming die set are positioned in the first die set; the bending module comprises a front end upward bending module, a tail end downward bending module and a middle portion upward bending module; the front end upward bending module is located in the second module, the tail end downward bending module is located in the third module, and the middle portion upward bending module is located in the fourth module.

Furthermore, the bracket punching die comprises a bracket base, wherein an insert block group is fixedly arranged on the upper end surface of the bracket base through a lower mounting plate, the upper end surface of the insert block group is a supporting surface, the piece to be punched is supported on the supporting surface, and the piece to be punched is tightly pressed and fixed through a pressing assembly; the piece to be punched comprises faces to be punched in multiple orientations, an upper punch, an inclined punch and two lateral punches are arranged on the faces to be punched, the upper punch and the inclined punch are fixed to the lower bottom face of an upper die plate through upper cushion blocks, the upper die plate is arranged on the upper end face of a support base through elastic guide pillar supports, the two lateral punches are located on two sides of the embedded block group respectively, and the lateral punches are fixedly mounted on the support base through punch mounting seats.

Furthermore, the embedded block group comprises a first embedded block and a second embedded block, the first embedded block and the second embedded block are arranged in a close fit manner, the upper surface of the first embedded block is connected with the upper surface of the second embedded block to form the supporting surface, and the shape of the supporting surface is fitted with that of the rope retainer; the upper end surface of the first embedded block, the inclined surface of the upper end of the second embedded block and two side surfaces are attached to the position of the surface to be punched, and female dies are correspondingly arranged; the ear sides are attached to the female die positioned on the two side faces of the embedded block.

Furthermore, the material pressing assembly comprises a material pressing plate, the material pressing plate is attached to the ear side and is driven to be compressed through an air cylinder, the material pressing plate is connected to the punch mounting seat through a plurality of elastic pieces, and a through hole for a lateral punch to pass through is formed in the material pressing plate; the elastic pieces are uniformly distributed around the through hole.

Has the advantages that: according to the stamping manufacturing process method and the stamping manufacturing process system of the rope retainer, stamping forming is carried out through the continuous stamping die, so that multiple processes are carried out synchronously, and then multidirectional punching is carried out synchronously through the bracket punching die, so that the production efficiency is effectively improved; the lower guide ruler, the elastic guide assembly, the embedded block group, the material pressing assembly and the like are arranged to play a role in limiting, guiding, fixing and buffering, so that the quality of a product is ensured; through the installation setting of the classification mould of adopting the multimode, the effective life of utilization mould that can be abundant reduces the replacement cost.

Drawings

FIG. 1 is a flow chart of a stamping process;

FIG. 2 is a block diagram of a rope retainer;

FIG. 3 is a view showing the structure of a continuous stamping die;

FIG. 4 is a schematic view of a stopper and an elastic guide member;

FIG. 5 is a diagram of a module and empty station distribution;

FIG. 6 is a view of the structure of the bracket punching die;

FIG. 7 is a side view of a bracket punching die;

FIG. 8 is a block diagram;

fig. 9 is a structural view of the swaging assembly.

Detailed Description

The present invention will be further described with reference to the accompanying drawings.

The method for manufacturing the rope retainer by stamping and the process system thereof as shown in fig. 1 to 9 specifically include the following steps:

The step A, the step B, the step C, the step D and the step E are all completed through a continuous stamping die.

The rope retainer comprises an annular plate-shaped body 1, the plate-shaped body 1 is bent into an S shape, an upper half ring 1-1 of the plate-shaped body 1 is provided with a continuous convex rib 2, a lower half ring 1-2 of the plate-shaped body 1 is provided with a segmented convex rib 3, and the continuous convex rib 2 and the segmented convex rib 3 are both protruded towards the bent inner part of the plate-shaped body 1; two sides of the lower half ring 1-2 are respectively provided with an ear side 4;

two through holes are formed in the ear sides 4, two mounting holes 5 are formed in two sides of the continuous convex rib 2 respectively, and welding threaded plugs 6 are arranged in the mounting holes 5;

the edge of the upper half ring 1-1 extends towards the bending of the plate-shaped body 1 and is provided with an arc curved surface 7.

The continuous stamping die comprises a press base 8, wherein an upper beam frame 9 is arranged right above the press base 8, the press base 8 and the upper beam frame 9 are rectangular and are aligned up and down, the upper beam frame 9 and the press base 8 are arranged in a relatively moving mode through a plurality of guide assemblies 10, the guide assemblies 10 are arranged vertically, and the upper beam frame 9 is driven to move up and down through a press main cylinder; a stamping section 11 is arranged between the base 8 and the upper beam frame 9; multiple dies 12 are continuously arranged in the stamping area 11 along the length direction, a lower guide rule 13 is arranged at the feed end of the stamping area 11, the lower guide rule 13 is fixed on the base 8, the lower guide rule 13 comprises a support plate and two side baffles, the support plate is horizontally fixed on the base through a cushion block, the two side baffles are respectively vertically arranged on two sides of the support plate to form a U-shaped guide groove, the width of the U-shaped guide groove is consistent with that of the plate, and the upper end surface of the support plate is flush with that of the lower die; the sheet material 20 enters the stamping section 11 from the feeding end of the stamping section 11 through the lower guide ruler 13;

the multiple dies 12 are arranged according to working procedures and sequentially comprise a punching die, a rib pressing die set, an edge cutting die set, a bending die set and a waste cutting die; the die 12 comprises an upper die 14 and a lower die 15, the upper die 14 is fixed by an upper fixing plate 16, and the upper fixing plate 16 is fixed on the lower end surface of the upper beam frame 9; the lower die 15 is correspondingly arranged right below the upper die 14, and the lower die 15 is fixed on the upper end surface of the press base 8 through a lower fixing plate 17;

the feeding machine conveys the plate in the stamping interval by the preset feeding amount, the plate is fed once by each stamping, the guide limiting effect is achieved through the lower guide ruler, the plate advances in the preset feeding direction, the punching, rib pressing, trimming, bending and waste cutting are sequentially performed, multiple processes are performed synchronously, the punching operation is orderly and efficiently completed quickly, and the working efficiency is improved.

Two sides of the upper end surface of the lower fixing plate 17 are respectively provided with a stop plate 18, the stop plates 18 are elastically arranged on the lower fixing plate 17 through an elastic guide assembly 19, the upper die 14 and the lower die 15 are positioned between the stop plates 18 at two sides, and two side edges of the plate 20 are supported by the stop plates 18;

the elastic guide assembly 19 comprises a guide part and an elastic part, the guide part comprises a small guide post 21 and a small guide sleeve 22, the small guide post 21 is vertically fixed on the upper end surface of the lower fixing plate 17 through the elastic part, the small guide sleeve 22 is sleeved on the small guide post 21, the small guide sleeve 22 is arranged in a sliding manner relative to the small guide post 21, the small guide sleeve 22 is fixedly arranged on the lower end surface of the stop plate 18, the elastic part adopts a nitrogen spring 21-1, the top end of the small guide post 21 is fixedly provided with a buffer spring 21-2, and the buffer spring 21-2 contacts the lower end surface of the stop plate 18 in the punching process;

support panel through backstop board and elastic guide subassembly for panel is located the top of lower mould, and leaves an elasticity space between the lower mould, and in the stamping process, make panel be close to the lower mould through last mould push down, has accomplished the punching press, and this in-process plays the effect of direction and buffering with the elastic guide subassembly, and after the punching press is ended, panel just can be lifted by the backstop board, breaks away from the lower mould once more, has two advantages like this: firstly, make things convenient for panel and the waste material separation after cutting the punching press to the clearance of the waste material of being convenient for, secondly, for the structural configuration of lower mould is different, the plane that both sides backstop board constitutes is more level and smooth, the feeding of the panel of being convenient for.

The plurality of moulds 12 are respectively positioned in a plurality of modules, an empty station 27 is arranged between the modules, and the moulds 12 positioned in the same module share the same lower fixing plate 17 and the same upper fixing plate 16; the punching die, the rib pressing die set and the trimming die set are positioned in the first module 23; the bending module comprises a front end upward bending module, a tail end downward bending module and a middle portion upward bending module; the front end upward bending module is positioned in the second module 24, the tail end downward bending module is positioned in the third module 25, and the middle portion upward bending module is positioned in the fourth module 26;

according to the working procedures, the whole stamping process is divided into a plurality of modules, more continuous and similar processing processes are placed in the same module, and empty stations are arranged among the modules, namely, a certain distance is reserved for the installation of the dies at the position where the dies are not arranged in one feeding amount, so that the mutual influence is avoided;

the working procedures in the first module are finished in a plane, the purpose is to cut the plate into the approximate outline of a target product, the second module, the third module and the fourth module are bending working procedures, in order to ensure better bending effect, a processing sequence of bending two ends firstly and then bending the middle part is adopted, and due to different bending directions, the plate is classified according to the steps that the front end is bent upwards at multiple positions, the tail end is bent downwards at multiple positions and the middle part is bent upwards at one time, and then the corresponding dies are respectively corresponding to the second module, the third module and the fourth module;

the mould in same module is fixed through same fixed plate, leave the distance of an idle station between the mould close on the adjacent fixed plate, because whole stamping process contains multiple punching press type, the mould also has the difference greatly, the type of punching press is different, the degree of wear that causes is different, if it is not cost-effective to change all moulds because of a comparatively serious wearing and tearing of department, with the mould of close type install on same mounting panel, they have similar degree of wear in the certain limit, when changing the mould, then can change according to the module, the cost has been practiced thrift, the speed of changing has been guaranteed again, and the efficiency is improved.

The support punching die comprises a support base 28, a block group 30 is fixedly arranged on the upper end face of the support base 28 through a lower mounting plate 29, the upper end face of the block group 30 is a supporting face 31, the piece to be punched is supported on the supporting face 31, and the piece to be punched is pressed and fixed through a pressing assembly 39; the piece to be punched comprises faces to be punched in various directions, an upper punch 32, an inclined punch 33 and two lateral punches 34 are arranged right opposite to the faces to be punched, the upper punch 32 and the inclined punch 33 are fixed on the lower bottom surface of an upper template 36 through an upper cushion block 35, the upper template 36 is supported and arranged on the upper end surface of the bracket base 28 through an elastic guide pillar 37, the two lateral punches 34 are respectively positioned on two sides of the embedded block group 30, and the lateral punches 34 are fixedly arranged on the bracket base 28 through punch mounting seats 38;

the punches are correspondingly arranged at the positions corresponding to the positions to be punched through the support structure, and the punches are respectively controlled through a plurality of air cylinders supplied with air through the same air path so as to complete the synchronous multi-directional punching, thereby effectively improving the working efficiency.

The inclined punch 33 is connected to the cylinder through an inclined punch mounting block 45, a guide groove 46 is formed in the side wall of the inclined punch mounting block 45, the inclined punch mounting block 45 is arranged in a sliding mode along an inclined guide block 47 through the guide groove 46, and the inclined guide block 47 is supported and fixed on the upper end face of the support base 28 through a lower cushion block 48;

the inclined punch is always kept right to the direction of the surface to be punched through the matching of the inclined guide block and the guide groove.

The insert block group 30 comprises an insert block I30-1 and an insert block II 30-2, the insert block I30-1 and the insert block II 30-2 are arranged in a close fit manner, the upper surface of the insert block I30-1 is connected with the upper surface of the insert block II 30-2 to form the supporting surface 31, and the shape of the supporting surface 31 is fitted to the shape of the piece to be punched; the upper end surface of the first embedded block 30-1, the inclined surface of the upper end of the second embedded block 30-2 and two side surfaces are attached to the position of the surface to be punched, and female dies 40 are correspondingly arranged; the ear sides 4 are attached to the female die 40 positioned on the side face of the second embedded block 30-2;

the punching die has the advantages that the punching die is convenient to attach to a supporting surface better, positioning and certain fixing effects are achieved, the processing difficulty of the embedded blocks is high due to the fact that the shape is special and the concave dies need to be arranged at multiple positions, and the embedded blocks are manufactured in a mode that the two embedded blocks are spliced.

The pressing assembly 39 comprises a pressing plate 41, the pressing plate 41 is attached to the ear, the pressing plate 41 is driven to be pressed through an air cylinder, the pressing plate 41 is connected to the punch mounting seat 38 through a plurality of elastic pieces 42, and a through hole 43 for the lateral punch 34 to pass through is formed in the pressing plate 41; the elastic pieces 42 are uniformly distributed around the through hole 43;

after on will waiting to punch a hole and place lower module, compress tightly the ear side through cylinder drive pressure plate from both sides, the side direction drift then passes through the through-hole in the middle of pressing the flitch, punches a hole to the ear side, and the elastic component then plays certain cushioning effect, avoids the side direction to punch a hole and causes the influence to the ear side structure, has guaranteed the strand and has kept off-the-shelf quality of ware.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention described above, and such modifications and adaptations are intended to be within the scope of the invention.

Claims

1. The method for manufacturing the rope retainer by stamping is characterized by comprising the following steps of:

2. The method of claim 1, wherein the method comprises the steps of: the step A, the step B, the step C, the step D and the step E are all completed through a continuous stamping die.

3. A process system in a method of manufacturing a hoist rope holder according to any of claims 1-2, characterised in that: the rope retainer comprises an annular plate-shaped body (1), the plate-shaped body (1) is bent into an S shape, an upper half ring (1-1) of the plate-shaped body (1) is provided with a continuous convex rib (2), a lower half ring (1-2) of the plate-shaped body (1) is provided with a segmented convex rib (3), and the continuous convex rib (2) and the segmented convex rib (3) are both protruded towards the bent inner part of the plate-shaped body (1); two sides of the lower half ring (1-2) are respectively provided with an ear side (4);

two through holes are formed in the ear sides (4), two mounting holes (5) are formed in two sides of the continuous convex rib (2), and welding threaded plugs (6) are arranged in the mounting holes (5);

the edge of the upper half ring (1-1) extends towards the bending of the plate-shaped body (1) and is provided with an arc curved surface (7).

4. A process system in a method of manufacturing a strand holder according to claim 2, wherein: the continuous stamping die comprises a press base (8), wherein an upper beam frame (9) is arranged right above the press base (8), the press base (8) and the upper beam frame (9) are rectangular and are aligned up and down, the upper beam frame (9) is arranged in a relative movement mode with the press base (8) through a plurality of guide assemblies (10), the guide assemblies (10) are vertically arranged, and the upper beam frame (9) is driven to move up and down through a press main cylinder; a stamping section (11) is arranged between the base (8) and the upper beam frame (9); a plurality of dies (12) are continuously arranged in the stamping section (11) along the length direction, a lower guide ruler (13) is arranged at the feed end of the stamping section (11), and the lower guide ruler (13) is fixed on the base (8); the plate (20) enters the stamping area (11) from the feeding end of the stamping area (11) through the lower guide ruler (13);

the multiple dies (12) are arranged according to working procedures and sequentially comprise a punching die, a rib pressing die set, a trimming die set, a bending die set and a waste cutting die; the die (12) comprises an upper die (14) and a lower die (15), the upper die (14) is fixed through an upper fixing plate (16), and the upper fixing plate (16) is fixed on the lower end face of the upper beam frame (9); the lower die (15) is correspondingly arranged right below the upper die (14), and the lower die (15) is fixed on the upper end face of the press base (8) through a lower fixing plate (17).

5. A process system in a method of a press manufacturing process of a rope holder according to claim 4, characterized in that: two sides of the upper end surface of the lower fixing plate (17) are respectively arranged on a stop plate (18), the stop plates (18) are elastically arranged on the lower fixing plate (17) through elastic guide assemblies (19), the upper die (14) and the lower die (15) are located between the stop plates (18) on the two sides, and the edges of the two sides of the plate (20) are supported through the stop plates (18);

the elastic guide assembly (19) comprises a guide part and an elastic part, the guide part comprises a small guide pillar (21) and a small guide sleeve (22), the small guide pillar (21) is vertically fixed on the upper end face of the lower fixing plate (17) through the elastic part, the small guide sleeve (22) is sleeved on the small guide pillar (21), the small guide sleeve (22) is arranged in a sliding mode relative to the small guide pillar (21), and the small guide sleeve (22) is fixedly arranged on the lower end face of the stop plate (18).

6. A process system in a method of a press manufacturing process of a rope holder according to claim 5, characterized in that: the moulds (12) are respectively positioned in a plurality of modules, an empty station (27) is arranged between the modules, and the moulds (12) positioned in the same module share the same lower fixing plate (17) and the same upper fixing plate (16); the punching die, the rib pressing die set and the trimming die set are positioned in the first module (23); the bending module comprises a front end upward bending module, a tail end downward bending module and a middle portion upward bending module; the front end upward bending module is located in the second module (24), the tail end downward bending module is located in the third module (25), and the middle portion upward bending module is located in the fourth module (26).

7. A process system in a method of manufacturing a strand holder according to claim 1, characterized in that: the support punching die comprises a support base (28), a block group (30) is fixedly arranged on the upper end face of the support base (28) through a lower mounting plate (29), the upper end face of the block group (30) is a supporting face (31), the piece to be punched is supported on the supporting face (31), and the piece to be punched is pressed and fixed through a pressing assembly (39); the piece to be punched comprises faces to be punched in multiple orientations, an upper punch (32), an inclined punch (33) and two lateral punches (34) are arranged on the faces to be punched, the upper punch (32) and the inclined punch (33) are fixed on the lower bottom surface of an upper template (36) through an upper cushion block (35), the upper template (36) is supported and arranged on the upper end surface of a bracket base (28) through an elastic guide pillar (37), the two lateral punches (34) are respectively located on two sides of an embedded block group (30), and the lateral punches (34) are fixedly mounted on the bracket base (28) through punch mounting seats (38).

8. A process system in a method of manufacturing a strand holder according to claim 1, characterized in that: the embedded block group (30) comprises a first embedded block (30-1) and a second embedded block (30-2), the first embedded block (30-1) and the second embedded block (30-2) are arranged in a clinging manner, the upper surface of the first embedded block (30-1) is connected with the upper surface of the second embedded block (30-2) to form the supporting surface (31), and the shape of the supporting surface (31) is attached to the shape of the stranded cable retainer; the upper end surface of the first embedded block (30-1), the inclined surface of the upper end of the second embedded block (30-2) and the positions of the two side surfaces which are attached to the surface to be punched are correspondingly provided with female dies (40); the ear sides (4) are attached to the concave die (40) located on the side face of the second insert block (30-2).

9. A process system in a method of manufacturing a strand holder according to claim 1, characterized in that: the material pressing assembly (39) comprises a material pressing plate (41), the material pressing plate (41) is attached to the ear, the material pressing plate (41) is driven to be pressed through a cylinder, the material pressing plate (41) is connected to the punch mounting seat (38) through a plurality of elastic pieces (42), and a through hole (43) for the lateral punch (34) to pass through is formed in the material pressing plate (41); the elastic pieces (42) are uniformly distributed around the through hole (43).