Internal thread forming device and forming process of threaded elbow

Abstract

The invention relates to the technical field of elbow pipe fitting machining, in particular to an internal thread forming device and technology for a threaded elbow. The multiple punched threaded elbows are placed at the designated positions of a combining and clamping device side by side; matched forging balls are placed at ports of the upper ends of the threaded elbows; the clamping device is correspondingly adjusted and combined according to the size of the threaded elbow; the combined clamping device is driven to extrude, and meanwhile, the multiple threaded elbows are subjected to ball forging and internal thread machining through automatic angle adjustment; the preparation method has the beneficial effects that the problems that in the prior art, independent processing and preparation are generally needed, batch preparation cannot be carried out at the same time, and the efficiency is low are solved; and meanwhile, the threaded elbow to be machined cannot be detected and subjected to sphere forging before machining.

Description

Technical Field

[0001] The present invention relates to the technical field of elbow pipe processing, and more particularly to an internal thread forming device and forming process for a threaded elbow. Background Art

[0002] Existing threaded elbows are usually a kind of pipe connector with internal or external threads, which are used to change the direction of the fluid (usually 45° or 90°) and realize detachable connection; its processing technology involves a variety of processes, which depend on the material, size, precision requirements and production batch, and usually the thread is processed after stamping; a 90-degree elbow stainless steel internal thread processing device similar to patent number CN202410800696.X includes a device frame, a clamping mechanism for adaptively clamping the 90-degree elbow is provided on the upper part of the device frame, and a clamping mechanism for adaptively clamping the 90-degree elbow is provided on the device frame. The invention is a tapping mechanism for synchronously processing the internal threads of the two pipe openings of the stainless steel 90-degree elbow. The invention adopts a moving component to drive the clamping block and the V-shaped block to cooperate, so that the clamping block and the V-shaped block only need to clamp the stainless steel 90-degree elbow once, and the two pipe openings of the stainless steel 90-degree elbow can be processed with the tapping mechanism at the same time, thereby improving the processing efficiency of the internal threads, avoiding the error of the secondary clamping, and ensuring the effect of the internal thread processing. In addition, when the clamping mechanism clamps the stainless steel 90-degree elbow, the pipe openings of the stainless steel 90-degree elbow can be made to face downward, which is conducive to the discharge of metal debris.

[0003] However, when processing the internal threads of the threaded elbows, the device usually needs to process and prepare them individually, and cannot prepare them in batches at the same time, which is inefficient. At the same time, it is impossible to detect and spherically forge the threaded elbows to be processed before processing. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the prior art usually requires individual processing and preparation, and cannot be prepared in batches at the same time, resulting in low efficiency; at the same time, it is impossible to detect and spherically forge the threaded elbows to be processed before processing.

[0005] To this end, the technical solution adopted is that the present invention provides an internal thread forming device and forming process for a threaded elbow, including a fixed base, on which a plurality of snap-fit ​​driving cylinders are symmetrically fixed, the upper ends of the snap-fit ​​driving cylinders are fixed on a snap-fit ​​extrusion table, one end of the snap-fit ​​extrusion table is hinged to one end of the fixed base, and a pushing processing table for inserting a forged sphere into the fixed threaded elbow is fixed on the snap-fit ​​extrusion table, and the threaded elbow is clamped and fixed in an adaptive angle adjustment base for sphere forging and internal thread forming.

[0006] Preferably, the upper end of the fixed base is connected to the lifting platform via a stable lifter, and the stable lifter drives the lifting platform to slide stably longitudinally on the fixed base.

[0007] Preferably, the stable lifter includes two lifting cylinders, both of which are fixed between a fixed base and a lifting platform, and the fixed base and the lifting platform are slidably connected to each other through two rack sockets, and the two rack sockets are transmitted by meshing the transverse transmission gear shaft and the longitudinal transmission gear shaft.

[0008] Preferably, the pushing processing table includes an upper fixed table, an extrusion tap driver and an extrusion arc seat. The upper fixed table is fixed to the lower end of the buckled extrusion table. Multiple extrusion tap drivers are evenly fixed side by side on the upper fixed table. An extrusion arc seat that fits the forged sphere for driving is fixed on the extrusion tap driver; a processing tap is fixed on the transmission shaft of the extrusion tap driver.

[0009] Preferably, the adaptive angle adjustment base is arranged on the lifting platform, and the adaptive angle adjustment base includes an angle tilting driver, which is fixed to the side end of the arc-shaped propulsion sliding base through a motor base, and the lower end of the arc-shaped propulsion sliding base slides back and forth on the lifting platform through a limited sliding.

[0010] Preferably, the front end of the arc-shaped propulsion sliding base is fixed on the telescopic shaft of the base propulsion cylinder; the base propulsion cylinder is fixed to the front end of the lifting base through a side fixing platform.

[0011] Preferably, the transmission shaft of the angle tilt driver is fixed to the middle end of the half-fan propulsion platform, and the half-fan propulsion platform slides in an arc shape on the arc end surface of the arc propulsion sliding base through an arc-shaped sliding groove for angle tilt adjustment.

[0012] Preferably, two tilting rods are symmetrically arranged on the half-door propulsion platform, and both tilting rods are provided with tilting grooves. Both tilting rods are fixed with clamping propulsion cylinders, and the clamping propulsion cylinders drive the clamping propulsion plate to slide in the two tilting grooves.

[0013] Preferably, a marking point is provided on the half-fan pushing platform; the clamping pushing plate is clamped tightly on the bending angle of the threaded elbow.

[0014] A process for forming an internal thread of a threaded elbow comprises the following steps:

[0015] S1: Place multiple stamped threaded elbows side by side at designated positions on the combined clamping device;

[0016] S2: Place suitable forged balls at the ports at the upper ends of multiple threaded elbows;

[0017] S3: Adjust and combine the clamping device according to the size of the threaded elbow;

[0018] S4: Drives the combined clamping device to squeeze and simultaneously perform forging balls and internal thread processing on multiple threaded elbows with automatic angle adjustment.

[0019] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in this application document.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 It is a schematic structural diagram of the internal thread forming device of the threaded elbow of the present invention in the first direction;

[0023] Figure 2 2. It is a schematic diagram of the overall structure of the internal thread forming device of the threaded elbow of the present invention in the second direction;

[0024] Figure 3 It is a partial structural diagram of the present invention;

[0025] Figure 4 It is a structural schematic diagram of the propulsion processing table of the present invention;

[0026] Figure 5 It is a structural schematic diagram of the stable lifter of the present invention;

[0027] Figure 6 This is a schematic diagram of the structure of the angle adjustment base of the present invention. Figure 1 ;

[0028] Figure 7 This is a schematic diagram of the structure of the angle adjustment base of the present invention. Figure 2 ;

[0029] Figure 8 This is a schematic diagram of the structure of the angle adjustment base of the present invention. Figure 3 ;

[0030] Figure 9 This is a schematic diagram of the structure of the angle adjustment base of the present invention. Figure 4 ;

[0031] Figure 10This is a schematic diagram of the structure of the angle adjustment base of the present invention. Figure 5 ;

[0032] Figure 11 It is a schematic flow diagram of the process of the present invention.

[0033] In the figure: fixed base 1, lifting base 2, stable lifter 3, snap-fit ​​extrusion platform 4, snap-fit ​​drive cylinder 5, advance processing platform 6, adaptive angle adjustment base 7, threaded elbow 8, forging sphere 9, upper fixed platform 10, extrusion tap driver 11, extrusion arc seat 12, lifting cylinder 13, horizontal transmission gear shaft 14, longitudinal transmission gear shaft 15, rack socket 16, angle tilt driver 17, half-fan advance platform 18, arc tilt drive slide 19, arc advance slide base 20, base advance cylinder 21, side fixed platform 22, clamping advance cylinder 23, clamping advance plate 24, processing tap 25. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] In the description of this application, it should be understood that the terms "middle", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. The terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0036] In addition, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0037] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0038] Example 1:

[0039] like Figure 1 — Figure 11 As shown, it includes a fixed base 1, on which are symmetrically fixed a plurality of snap-fit ​​drive cylinders 5, the upper ends of which are fixed on a snap-fit ​​extrusion platform 4, one end of which is hinged to one end of the fixed base 1, and a pushing processing platform 6 for inserting a forged sphere 9 into a fixed threaded elbow 8 is fixed on the snap-fit ​​extrusion platform 4, and the threaded elbow 8 is clamped and fixed in an adaptive angle adjustment base 7 for sphere forging and internal thread forming.

[0040] The working principle and beneficial effects of this embodiment are as follows: by clamping and fixing multiple threaded elbows 8 in the adaptive angle adjustment base 7, it is convenient for them to be processed side by side; then, by overall driving and controlling the snap-on driving cylinder 5, the pushing processing table 6 on the snap-on extrusion table 4 is aligned with the forging ball 9 on the threaded elbow 8, and the preset value of the frequency converter can make the pushing processing table 6 always adapt and adjust the angle of the adaptive angle adjustment base 7 during the falling arc process, so that the pushing processing table 6 always enters the multiple threaded elbows 8 vertically to perform the extrusion ball forging of the forging ball 9, and then naturally taps the inner wall of the threaded elbow 8 to process the internal thread.

[0041] Example 2:

[0042] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, the upper end of the fixed base 1 is connected to the lifting base 2 through a stable lifter 3, and the stable lifter 3 drives the lifting base 2 to slide stably longitudinally on the fixed base 1.

[0043] The working principle and beneficial effects of this embodiment are as follows: the upper end of the fixed base 1 is connected to the lifting platform 2 through the stable lifter 3, and the lifting platform 2 is driven by the stable lifter 3 to slide stably longitudinally on the fixed base 1, so that the lifting and lowering of the lifting platform 2 on the fixed base 1 is more stable; thereby making it adaptable to threaded elbows 8 of different specifications for use, and thereby making it combined with the propulsion processing table 6 to always vertically enter the processing of multiple threaded elbows 8 to ensure the accuracy of the processing.

[0044] Example 3:

[0045] like Figure 1 — Figure 11 As shown, a device and process for forming an internal thread of a threaded elbow are provided. The stable lifter 3 includes two lifting cylinders 13. The two lifting cylinders 13 are fixed between a fixed base 1 and a lifting platform 2. The fixed base 1 and the lifting platform 2 are slidably connected to each other through two rack sockets 16. The two rack sockets 16 are driven by meshing the transverse transmission gear shaft 14 and the longitudinal transmission gear shaft 15.

[0046] The working principle and beneficial effects of this embodiment are as follows: the two lifting cylinders 13 simultaneously drive the lifting platform 2 to lift on the fixed base 1, and then during the lifting process of the lifting platform 2, the two rack sockets 16 can be synchronously driven to lift, and then the transmission is carried out by engaging the horizontal transmission gear shaft 14 and the longitudinal transmission gear shaft 15, so that multiple structures can be more connected and correlated during lifting, and the lifting is more stable to prevent the lifting tilt; at the same time, it is combined with the propulsion processing table 6 to always vertically enter the processing of multiple threaded elbows 8 to ensure the accuracy of the processing.

[0047] Example 4:

[0048] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, the pushing processing table 6 includes an upper fixed table 10, an extrusion tap driver 11 and an extrusion arc-shaped seat 12. The upper fixed table 10 is fixed to the lower end of the buckled extrusion table 4. A plurality of extrusion tap drivers 11 are evenly fixed side by side on the upper fixed table 10. The extrusion tap driver 11 is fixed with an extrusion arc-shaped seat 12 that fits the forged sphere 9 for driving; a processing tap 25 is fixed on the transmission shaft of the extrusion tap driver 11.

[0049] The working principle and beneficial effects of this embodiment are as follows: when the engagement drive cylinder 5 contracts and engages the extrusion platform 4 and the lifting base 2, the upper fixed platform 10, the extrusion tap driver 11 and the extrusion arc seat 12 are caused to move downward in an arc shape; thereby, the multiple extrusion tap drivers 11 and the extrusion arc seat 12 evenly fixed side by side on the upper fixed platform 10 are caused to descend, thereby facilitating the forging inspection and internal thread processing of the same batch of multiple threaded elbows 8.

[0050] Example 5:

[0051] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, the adaptive angle adjustment base 7 is arranged on the lifting base 2, and the adaptive angle adjustment base 7 includes an angle tilting driver 17, and the angle tilting driver 17 is fixed to the side end of the arc-shaped propulsion sliding base 20 through a motor base, and the lower end of the arc-shaped propulsion sliding base 20 slides back and forth on the lifting base 2 through a limited sliding.

[0052] The working principle and beneficial effects of this embodiment are as follows: the adaptive angle adjustment base 7 is arranged on the lifting base 2, which is convenient for adaptive adjustment in combination with the downward tilt angle of the propulsion processing table 6; because the angle tilting driver 17 is fixed to the side end of the arc-shaped propulsion sliding base 20 through the motor base, the lower end of the arc-shaped propulsion sliding base 20 slides back and forth on the lifting base 2 through the limit sliding, and then the arc-shaped propulsion sliding base 20 can drive the angle tilting driver 17 to slide back and forth synchronously with the limit sliding, and the data is collected and fed back to the frequency conversion device, thereby realizing automatic adjustment of the front and rear adaptation, and ensuring the accuracy of automatic processing.

[0053] Example 6:

[0054] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, the front end of the arc-shaped pushing sliding base 20 is fixed on the telescopic shaft of the base pushing cylinder 21; the base pushing cylinder 21 is fixed to the front end of the lifting base 2 through the side fixing platform 22.

[0055] The working principle and beneficial effects of this embodiment are as follows: because the front end of the arc-shaped propulsion sliding base 20 is fixed on the telescopic shaft of the base propulsion cylinder 21; the base propulsion cylinder 21 is fixed to the front end of the lifting base 2 through the side fixed platform 22, and the control program of the base propulsion cylinder 21 is set to a frequency conversion program, and then the arc-shaped propulsion sliding base 20 and the angle tilt driver 17 are driven to move forward and backward through the base propulsion cylinder 21, thereby driving multiple threaded elbows 8 to move forward and backward during the processing process.

[0056] Example 7:

[0057] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, the transmission shaft of the angle tilting driver 17 is fixed to the middle end of the half-fan propulsion platform 18, and the half-fan propulsion platform 18 slides in an arc shape on the arc end surface of the arc propulsion sliding base 20 through an arc-shaped slide groove for angle tilt adjustment.

[0058] The working principle and beneficial effects of this embodiment are as follows: the transmission shaft of the angle tilting driver 17 is fixed to the middle end of the half-fan propulsion platform 18, so that it drives the half-fan propulsion platform 18 to rotate, because the half-fan propulsion platform 18 slides in an arc shape on the arc end surface of the arc-shaped propulsion sliding base 20 through the arc-shaped slide groove, so that it can be used for angle tilting, thereby realizing the adjustment of the angle tilt of the half-fan propulsion platform 18, and thus the angle tilt of the multiple threaded elbows 8 arranged side by side in the half-fan propulsion platform 18 is also adjusted, so that it is adapted to be combined with the propulsion processing table 6 to always enter the multiple threaded elbows 8 vertically for processing, so as to ensure the accuracy of the processing.

[0059] Example 8:

[0060] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, two tilting rods are symmetrically arranged on the half-fan propulsion platform 18, both tilting rods are provided with tilting grooves, and both tilting rods are fixed with a clamping propulsion cylinder 23, which drives the clamping propulsion plate 24 to slide in the two tilting grooves.

[0061] The working principle and beneficial effects of this embodiment are as follows: two tilting rods are symmetrically arranged on the half-door propulsion platform 18 for extension, and inclined grooves are provided on both tilting rods. Clamping propulsion cylinders 23 are fixed on both tilting rods, so that the clamping propulsion cylinders 23 can drive the clamping propulsion plate 24 to slide within the two inclined grooves, and then the two clamping propulsion cylinders 23 can drive the clamping propulsion plate 24 to clamp the multiple threaded elbows 8 arranged in the half-door propulsion platform 18, and cooperate with the spherical forging and internal thread processing.

[0062] Example 9:

[0063] like Figure 1 — Figure 11 As shown, an internal thread forming device and forming process of a threaded elbow, the half-fan pushing platform 18 is provided with a marking point; the clamping pushing plate 24 is clamped and fitted tightly at the bending angle of the threaded elbow 8.

[0064] The working principle and beneficial effects of this embodiment are as follows: marking points are provided on the half-fan pushing platform 18 to ensure the placement of each threaded elbow 8; the clamping pushing plate 24 is clamped tightly on the bending angle of the threaded elbow 8, making it convenient to clamp each threaded elbow 8 on the half-fan pushing platform 18 for simultaneous forging and internal thread processing of multiple threaded elbows 8.

[0065] Example 10:

[0066] A process for forming an internal thread of a threaded elbow comprises the following steps:

[0067] S1: placing multiple stamped threaded elbows 8 side by side at designated positions of a combined clamping device;

[0068] S2: Place matching forged balls 9 at the ports on the upper ends of multiple threaded elbows 8;

[0069] S3: Adjust and combine the clamping device according to the size of the threaded elbow 8;

[0070] S4: driving the combined clamping device to extrude and simultaneously process the forged spheres 9 and internal threads of the plurality of threaded elbows 8 so as to automatically adjust the angles.

[0071] The working principle and beneficial effects of this embodiment are as follows: multiple stamped threaded elbows 8 are placed side by side at designated positions of the combined clamping device; suitable forged balls 9 are placed at the ports at the upper ends of the multiple threaded elbows 8; the combined clamping device is adjusted accordingly according to the size of the threaded elbows 8; the combined clamping device is driven to extrude the forged balls 9 and automatically adjust the angles of the multiple threaded elbows 8 at the same time, and the internal threads are processed; thereby achieving the effect of adaptively and automatically forging and processing the internal threads of the multiple threaded elbows 8.

[0072] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention also fall within the scope of protection of the present invention.

Claims

1. An internal thread forming device for a threaded elbow, characterized in that: The invention comprises a fixed base (1), a plurality of snap-on driving oil cylinders (5) are symmetrically fixed on the fixed base (1), the upper ends of the snap-on driving oil cylinders (5) are fixed on a snap-on extrusion platform (4), one end of the snap-on extrusion platform (4) is hinged to one end of the fixed base (1), a pushing processing platform (6) for inserting a forged sphere (9) into a fixed threaded elbow (8) is fixed on the snap-on extrusion platform (4), and the threaded elbow (8) is clamped and fixed in an adaptive angle adjustment base (7) to perform sphere forging and internal thread forming.

2. The internal thread forming device of a threaded elbow according to claim 1, characterized in that: The upper end of the fixed base (1) is connected to the lifting platform (2) via a stable lifter (3), and the stable lifter (3) drives the lifting platform (2) to slide stably longitudinally on the fixed base (1).

3. The internal thread forming device of a threaded elbow according to claim 2, characterized in that: The stable lifter (3) includes two lifting cylinders (13), both of which are fixed between a fixed base (1) and a lifting platform (2). The fixed base (1) and the lifting platform (2) are slidably connected to each other through two rack sockets (16), and the two rack sockets (16) are driven by meshing a transverse transmission gear shaft (14) and a longitudinal transmission gear shaft (15).

4. The internal thread forming device of a threaded elbow according to claim 1, characterized in that: The pushing processing table (6) includes an upper fixed table (10), an extrusion tap driver (11) and an extrusion arc seat (12). The upper fixed table (10) is fixed to the lower end of the buckled extrusion table (4). A plurality of extrusion tap drivers (11) are evenly fixed side by side on the upper fixed table (10). The extrusion tap driver (11) is fixed with an extrusion arc seat (12) that fits the forged sphere (9) for driving. A processing tap (25) is fixed on the transmission shaft of the extrusion tap driver (11).

5. The internal thread forming device of a threaded elbow according to claim 2, characterized in that: The adaptive angle adjustment base (7) is arranged on the lifting base (2), and the adaptive angle adjustment base (7) includes an angle tilting driver (17). The angle tilting driver (17) is fixed to the side end of the arc-shaped propulsion sliding base (20) through a motor base, and the lower end of the arc-shaped propulsion sliding base (20) slides back and forth on the lifting base (2) through a limit sliding.

6. The internal thread forming device of a threaded elbow according to claim 5, characterized in that: The front end of the arc-shaped propulsion sliding base (20) is fixed on the telescopic shaft of the base propulsion oil cylinder (21); the base propulsion oil cylinder (21) is fixed to the front end of the lifting base (2) through the side fixing platform (22).

7. The internal thread forming device of a threaded elbow according to claim 5, characterized in that: The transmission shaft of the angle tilting driver (17) is fixed to the middle end of the half-fan propulsion platform (18), and the half-fan propulsion platform (18) slides in an arc shape on the arc end surface of the arc propulsion sliding base (20) through an arc chute for angle tilting adjustment.

8. The internal thread forming device of a threaded elbow according to claim 7, characterized in that: Two tilting rods are symmetrically arranged on the half-door propulsion platform (18), and both tilting rods are provided with tilting slots. Both tilting rods are fixed with clamping propulsion cylinders (23), and the clamping propulsion cylinders (23) drive the clamping propulsion plate (24) to slide within the two tilting slots.

9. The internal thread forming device of a threaded elbow according to claim 8, characterized in that: The half-fan pushing platform (18) is provided with a marking point; the clamping pushing plate (24) is clamped and fitted tightly at the bending angle of the threaded elbow (8).

10. A process for forming an internal thread of a threaded elbow, suitable for an internal thread forming device of a threaded elbow according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1: placing a plurality of stamped threaded elbows (8) side by side at designated positions of a combined clamping device; S2: placing matching forged balls (9) at the ports at the upper ends of the plurality of threaded elbows (8); S3: Adjust and combine the clamping device according to the size of the threaded elbow (8); S4: driving the combined clamping device to squeeze and simultaneously process the forged spheres (9) for automatically adjusting the angles of the plurality of threaded elbows (8) and the internal threads.

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