CN222391519U - A four-pump-head plunger metering pump - Google Patents

Abstract

The utility model discloses a four-pump-head plunger metering pump, which relates to the technical field of metering pumps and is characterized by comprising a transmission shaft, wherein eccentric wheels are fixedly arranged at two ends of the transmission shaft, an eccentric shaft is eccentrically arranged on one side of the eccentric wheels, which is far away from the transmission shaft, two groups of connecting rods are rotatably arranged on a single eccentric shaft, the two groups of connecting rods are distributed on two sides of the eccentric shaft, a cross head is arranged at one end, which is far away from the eccentric shaft, of the connecting rods, one end, which is close to the connecting rods, of the cross head is hinged with the connecting rods through a cross head pin, and a cross head bushing is sleeved on the periphery of the cross head and used for guiding the cross head along the axial direction and limiting the cross head to reciprocate along the axial direction. The utility model uses one motor two to drive four pump heads, the flow and the discharge pressure of each pump head can be different, and the quantitative output of different media or the same injection point of the same media or different injection points can be completed.

Description

Four pump head plunger type metering pumps

Technical Field

The utility model relates to the technical field of metering pumps, in particular to a four-pump-head plunger metering pump.

Background

Metering pumps are fluid machines capable of delivering fluid media quantitatively, the biggest feature of which is that they are capable of delivering all the different media capable of flowing in a metered manner, the most widespread purpose of which is metering delivery of the delivered media. The plunger metering pump is a reciprocating volumetric pump, the size of the plunger stroke volume of which can be varied. The plunger stroke volume is changed in various ways, wherein the output flow of the pump is changed by changing the reciprocating stroke of the plunger, so that the metering and conveying of conveying media are realized, a metering pump is required to be provided with a unique plunger stroke adjusting mechanism capable of adjusting the plunger stroke, and the flow can be adjusted steplessly from 0-100% as required.

Due to the adjustable flow characteristic of the metering pump, the metering pump is widely applied to the aspects of chemical industry, petroleum, papermaking, food, plastics, pharmacy, daily chemical industry, water treatment and the like. Metering pumps are often used to deliver highly corrosive liquids, suspensions, molten fluids, radioactive feed liquids, flammable and explosive liquids, some toxic chemical liquids, and the like.

The metering pump generally consists of a motor one 100, a driving end, a hydraulic end mechanism one 600 and a base one 300, see fig. 1 and 2. The drive end is typically comprised of a reduction mechanism, a drive mechanism 400, a plunger travel adjustment mechanism, and the like. The first fluid end mechanism 600 is generally composed of a plunger, a plunger seal, a stuffing box, a fluid cylinder, a check valve of an inlet and an outlet, an inlet and an outlet connecting pipe, and the like.

In some processes, it is necessary to add different types of fluid chemicals together in different proportions or to deliver the same fluid chemical to different injection points in different parameters. Under the working condition, a plurality of metering pumps are usually required to be used for completing the work, but the driving ends of the motors of the metering pumps can be removed according to the structural characteristics of the metering pumps and connected in parallel, the middle is connected by a coupler 200 to form a pump group, one end of the pump group is connected with a motor A100 by the coupler, and the motor A100 is used for driving. Each of the transmission 400 and fluid end mechanism 600 comprise a unit, each having a separate stroke adjustment mechanism 500, which combines multiple units to form a multiple pump head pump, see fig. 3 and 4. The multi-pump head pump can meet the technological process requirements of the working conditions.

The utility model provides a four-pump-head plunger metering pump, which can be used for independently adjusting the pumping quantity.

Disclosure of Invention

The utility model provides a four-pump-head plunger type metering pump which has the advantage of being capable of independently adjusting the pumping capacity so as to solve the problems.

The four-pump-head plunger metering pump is characterized by comprising a transmission shaft, eccentric wheels, a plunger stroke adjusting mechanism and a driving mechanism, wherein the two ends of the transmission shaft are fixedly provided with eccentric wheels, one side, far away from the transmission shaft, of each eccentric wheel is eccentrically provided with an eccentric shaft, two groups of connecting rods are rotatably arranged on a single eccentric shaft, the two groups of connecting rods are distributed on two sides of the eccentric shaft, the cross head is arranged at one end, far away from the eccentric shaft, of each connecting rod, the cross head is hinged with the connecting rod through a cross head pin, a cross head bushing is sleeved on the periphery of the cross head and used for guiding the cross head in the axial direction and used for limiting the cross head to reciprocate in the axial direction, the hydraulic end is positioned at one side, far away from the connecting rod, of the cross head is internally provided with a hydraulic cylinder cavity, a plunger stroke adjusting mechanism is arranged in the hydraulic cylinder cavity and used for connecting the cross head and the plunger, the plunger stroke adjusting mechanism can be used for adjusting the distance between the plunger and the plunger to change the position in the hydraulic cylinder cavity, so that the output flow of the pump is changed, and the driving mechanism is connected with the transmission shaft and is used for driving the transmission shaft to rotate.

The plunger stroke adjusting mechanism comprises a stroke adjusting screw rod, a stroke adjusting piston and a piston, wherein an internal threaded hole is formed in one end of the cross head, which is close to a plunger, the stroke adjusting screw rod is connected with one end of the stroke adjusting screw rod in a threaded mode, the stroke adjusting piston is installed in the stroke adjusting screw rod, a boss is arranged at one end of the stroke adjusting piston, which is close to a cross head pin, the outer circle of the boss is larger than the inner hole of the stroke adjusting screw rod, the limiting effect is achieved, the other end of the stroke adjusting piston is fixedly connected with the plunger, and the distance between the stroke adjusting piston and the cross head can be adjusted by adjusting the position of the stroke adjusting screw rod in the internal threaded hole so as to change the position of the plunger in a liquid cylinder cavity.

As a preferable technical scheme of the utility model, the hydraulic end is arranged on the stand and is coaxial with the cross head, one end of the stand is used for supporting the cross head bushing and the cross head, the other end of the stand is used for supporting the hydraulic end, and a liquid collecting tank is arranged in a region, opposite to the plunger, of the stand and is used for collecting leakage liquid.

As a preferable technical scheme of the utility model, the upper surface of the base is provided with a scale which is used as a comparison line for adjusting the length of the stroke adjusting piston.

The driving mechanism comprises a worm wheel shaft, a worm wheel, a motor II and a motor II, wherein the worm wheel shaft is a straight cylinder shaft with a cavity, the transmission shaft is positioned in the worm wheel shaft and rotates synchronously with the worm wheel shaft, the worm wheel is fixedly arranged on the periphery of the worm wheel shaft, one side of the worm wheel is meshed with a worm, and the motor II is arranged on one side of the worm and used for driving the worm to rotate.

As a preferable technical scheme of the utility model, the worm wheel is fixedly connected with the worm wheel shaft through the flat key so as to enable the worm wheel and the worm wheel shaft to synchronously rotate.

The utility model also comprises a second base, wherein a transmission case is arranged outside the worm and fixed on the second base, one end of the worm extends out of the transmission case, an axial worm hole is formed in the axis part of the extending end of the worm, a key slot is formed in the worm hole, a second shaft head of the motor is inserted into the worm hole and transmits torque through a key, the second motor is fixed on a motor bracket through a bolt, the motor bracket is fixedly connected with the transmission case through a bolt, two ends of the worm wheel shaft are supported on rolling bearing seats, and the rolling bearing seats are mounted on the transmission case through bolts.

As a preferable technical scheme of the utility model, one end of the eccentric shaft, which is close to the eccentric wheel, is provided with external threads, a threaded hole is arranged at the eccentric position of the end surface of the eccentric wheel, and the eccentric shaft is fixed on the eccentric wheel through the external threads and the threaded hole.

Compared with the prior art, the utility model provides a four-pump-head plunger type metering pump, which has the following beneficial effects:

the four-pump-head plunger metering pump drives four pump heads by one motor two, the flow and the discharge pressure of each pump head can be different, and quantitative output of different media or the same injection point of the same media or different injection points can be completed. The whole structure is compact, the speed reducing structure is arranged at the middle position of the pump, two ends of the transmission shaft are output, and the four hydraulic end mechanisms II of the pump are arranged at four corners of the base. The equipment space is reduced, and the operation and maintenance are convenient. The pump has good economic benefit after being put into use, and is mainly applied to the petroleum exploitation department as a chemical agent injection pump.

Drawings

FIG. 1 is a front view of a metering pump of the prior art;

FIG. 2 is a side view of a metering pump of the prior art;

FIG. 3 is a front view of a pump unit of the prior art;

FIG. 4 is a side view of a pump unit of the prior art;

FIG. 5 is a schematic diagram of the internal structure of the front view of the present utility model;

FIG. 6 is a schematic top view of the internal structure of the present utility model;

FIG. 7 is an enlarged view of area A of FIG. 6 in accordance with the present utility model;

fig. 8 is an enlarged view of region B of fig. 6 in accordance with the present utility model.

100 Parts of a motor I, 200 parts of a coupling, 300 parts of a base I, 400 parts of a transmission mechanism, 500 parts of a stroke adjusting mechanism, 600 parts of a hydraulic end mechanism I;

1. The motor II comprises a motor bracket, a worm hole, a transmission case, a worm, a connecting rod, an eccentric wheel, a cross pin, a cross head bush, a cross head 11, a sealing ring, a cross head 12, a cross head 13, a locking nut, a hydraulic end 14, a hydraulic end 15, a liquid collecting groove 17, a stroke adjusting piston 18, a stroke adjusting screw rod 19, a machine base 20, a worm bearing 21, an eccentric shaft 22, a retainer ring 23, a transmission shaft 25, a worm wheel shaft 26, a rolling bearing seat 27, a scale 28, a worm wheel 29, a flat key 30, a plunger 31, a hydraulic cylinder cavity 32, a key II, a T-shaped groove 33, a T-shaped groove 34, a machine base II and a bolt 35.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The four pump head plunger metering pump provided by the embodiment of the utility model is described below according to fig. 5 to 8.

The utility model discloses a four-pump-head plunger metering pump which comprises a second base 34, a driving mechanism, a transmission shaft 23, a crank connecting rod mechanism, a stroke adjusting mechanism and a second hydraulic end mechanism, wherein the driving mechanism is used for driving the transmission shaft 23 to rotate, the crank connecting rod mechanism is used for converting the rotation force of the transmission shaft 23 into the reciprocating force required by the reciprocating operation of the second hydraulic end mechanism, and the stroke adjusting mechanism is used for adjusting the pumping capacity of the second hydraulic end mechanism.

1. A driving mechanism:

The driving mechanism consists of a motor II 1 and a first-stage worm and gear speed reducing structure. The primary worm gear speed reducing mechanism comprises a motor bracket 2, a transmission case 4, a worm 5, a worm bearing 20, a worm wheel 28, a flat key 29, a worm wheel shaft 25 and a rolling bearing seat 26.

The worm wheel shaft 25 is a straight cylinder shaft with a cavity, the transmission shaft 23 is a stepped shaft which is arranged in the cavity of the worm wheel shaft 25 and is matched with the worm wheel shaft 25, the worm wheel shaft 25 and the transmission shaft 23 are connected through a second key 32, the worm wheel 28 is fixed on the periphery of the transmission shaft 23, the worm 5 is arranged on the upper part of the worm wheel 28 and horizontally arranged, one end of the worm 5 extends out of the transmission box 4, an axial worm hole 3 is arranged at the axial center part of one end of the worm 5 extending out of the transmission box 4, a key slot is arranged in the worm hole 3, a second motor 1 is positioned at one end of the worm 5 far away from a hydraulic end mechanism, a shaft head of the second motor 1 is inserted into the worm hole 3 of the worm 5, torque is transmitted through a key, the second motor 1 is fixed on a motor bracket 2 through a bolt, the motor bracket 2 is fixedly connected with the transmission box 4 through a bolt, the second motor 1 rotates through the key to drive the worm 5, the worm wheel 28 is meshed with the worm wheel 28, the two ends of the worm wheel 25 are supported on a rolling bearing 26, and the rolling bearing 26 is mounted on the transmission box 4 through a bolt. The worm wheel 28 rotates to drive the worm wheel shaft 25 to rotate through the flat key 29.

Preferably, the transmission case 4 is fixed on the second base 34.

2. Crank link mechanism:

The crank-link mechanism comprises two eccentric wheels 8, two eccentric shafts 21, four connecting rods 6, four cross heads 12 and four cross head pins 9.

The eccentric wheels 8 are arranged at two ends of the transmission shaft 23, the inner holes of the eccentric wheels 8 are matched with the transmission shaft 23, the end parts of the eccentric shafts 21 are provided with threads, the end surfaces of the eccentric wheels 8 are provided with threaded holes, and the threaded end parts of the two eccentric shafts 21 are respectively screwed into the corresponding threaded holes of the end surfaces of the eccentric wheels 8. The four connecting rods 6 are distributed on the two eccentric wheels 8, namely, one eccentric wheel 8 is provided with two groups of connecting rods 6, the two groups of connecting rods 6 are symmetrical along the center of a transmission shaft 23, one end (big head end) of each connecting rod 6 is sleeved on the corresponding eccentric shaft 21, the connecting rods 6 can rotate on the eccentric shafts 21, and the two connecting rods 6 on the same eccentric wheel 8 are distributed on two sides of the eccentric shafts 21.

Preferably, a retainer ring 22 for separating the two connecting rods 6 is provided on the eccentric shaft 21.

The other end (small head end) of the connecting rod 6 is provided with a cross head 12, a cross head pin 9 is arranged in a pin hole of the cross head 12, the small head end of the connecting rod is arranged on the cross head pin 9, the pin hole on the small head end is matched and hinged with the cross head pin 9, the center distance between the center of the eccentric shaft 21 and the center of the transmission shaft 23 is not only the crank radius of a crank connecting rod mechanism, but also one half of the reciprocating motion stroke of the cross head 12, a cross head bushing 10 is also arranged, and the cross head bushing 10 is sleeved outside the cross head 12 and used for guiding the cross head 12 along the axial direction, so that the cross head 12 is limited to be capable of reciprocating motion along the axial direction only.

Preferably, sealing rings 11 are provided in the region where both ends of the inside of the crosshead bushing 10 are in contact with the crosshead 12.

Preferably, a housing 19 is also provided, and the cross-head bushing 10 is bolted into a bore in the housing 19.

In this embodiment, when the transmission shaft 23 rotates along with the worm wheel shaft 25, the eccentric wheel 8 is also driven to rotate together, the eccentric wheel 8 rotates to drive the eccentric shaft 21 thereon to rotate around the axis of the transmission shaft 23, the diameter of a circle formed by the rotation of the eccentric shaft 21 around the axis of the transmission shaft 23 is the stroke of the reciprocating motion of the cross head 12 of the pump, and the big end of the connecting rod 6 moves along with the eccentric shaft 21 in a circular motion, and at the same time, the small end of the connecting rod 6 drives the cross head 12 to move together through the cross head pin 9, so that the cross head 12 is installed in the cross head bushing 10, and the cross head 12 can only move along the axial direction. The eccentric shaft 21 moves around the center of the transmission shaft 23 for one circle, and the cross head 12 completes one reciprocating motion in the cross head bushing 10. The maximum stroke of one reciprocation of the cross-head 12 is the maximum stroke of the pump plunger 30.

3. And a hydraulic end mechanism II:

The second hydraulic end mechanism comprises a hydraulic end 14, the hydraulic end 14 is positioned on one side of the cross head 12 away from the connecting rod 6, a hydraulic cylinder cavity 31 is formed in the hydraulic end 14, a plunger 30 is arranged in the hydraulic cylinder cavity 31, and when the plunger 30 moves reciprocally along the hydraulic cylinder cavity 31, liquid can be sucked in and pumped out.

The plunger 30 reciprocates in the cylinder chamber 31, and when the plunger 30 sucks the medium to be conveyed into the cylinder chamber 31 through the suction valve in the suction stroke, and when the plunger 30 discharges the medium from the cylinder chamber 31 to the outside of the pump through the discharge valve in the discharge stroke, the conveying of the medium by the pump fluid end is completed.

Preferably, the second fluid end mechanism is mounted in a bore in the housing 19, coaxial with the cross-head 12. The four stand 19 are fixed on the second base 34 by bolts 35 respectively, the four stand 19 plays a supporting role, one end of the stand 19 supports the cross head bush 10 and the cross head 12, and the other end supports the second hydraulic end mechanism of the pump. Each base 19 is provided with a liquid collecting tank 15 for collecting leakage liquid generated by reciprocating movement of the plunger 30 after sealing.

4. Plunger stroke adjustment mechanism:

The plunger stroke adjusting mechanism is used for connecting the cross head 12 and the plunger 30, and can adjust the distance between the plunger 30 and the cross head 12 so as to change the position of the plunger 30 in the hydraulic cylinder cavity 31, thereby changing the output flow of the pump, and the specific plunger 30 stroke adjusting mechanism consists of a stroke adjusting screw 18, a stroke adjusting piston 17, a lock nut 13 and a scale 27.

The outer circumference of the stroke adjusting screw 18 is an external thread, an internal thread hole is formed in one end of the cross head 12 close to the plunger 30, the external thread of the stroke adjusting screw 18 is matched with the internal thread of the cross head 12, the distance between the end face of the thread part of the stroke adjusting screw 18 and the end face of the bottom of the internal thread of the cross head 12 is changed by rotating the stroke adjusting screw 18, so that the relative position of the stroke adjusting screw 18 and the plunger 30 is adjusted, the stroke adjusting piston 17 is arranged between the cross head 12 and the stroke adjusting screw 18, a boss is arranged at the end part of the stroke adjusting piston 17, the outer circle of the boss is larger than the inner hole of the stroke adjusting screw 18, the limiting effect is achieved, the stroke adjusting piston 17 is prevented from being separated from the stroke adjusting screw 18, a T-shaped groove 33 is formed in the other end of the stroke adjusting piston 17, and a T-shaped block matched with the T-shaped groove 33 is arranged on the plunger 30, so that the two are embedded.

The stroke adjusting piston 17 can only move in the axial direction between the cross head 12 and the stroke adjusting screw 18, and by rotating the stroke adjusting screw 18 to adjust the relative distance between the stroke adjusting piston and the cross head 12, the position of the stroke adjusting piston 17 relative to the hydraulic end 14 can be changed, so that the position of the pump plunger 30 relative to the hydraulic cylinder cavity 31 can be changed, and the output flow of the pump can be changed. The distance change of the stroke adjusting piston 17 is marked with a scale 27 on the housing 19, which serves as a reference line for the length adjustment of the stroke adjusting piston 17.

In summary, the four-pump-head plunger metering pump drives four pump heads by one motor two 1, and the flow and the discharge pressure of each pump head can be different, so that the quantitative output of different media or the same injection point of the same media or different injection points can be completed. The whole structure is compact, the speed reducing structure is arranged at the middle position of the pump, two ends of the transmission shaft 23 are output, and four hydraulic end mechanisms II of the pump are arranged at four corners of the base II 34. The equipment space is reduced, and the operation and maintenance are convenient. The pump has good economic benefit after being put into use, and is mainly applied to the petroleum exploitation department as a chemical agent injection pump.

It should be noted that in this document, terms such as "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.

Although embodiments of the present utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the utility model, the scope of which is defined in the appended claims and their equivalents.

Claims (8)

1. A four-pump-head plunger metering pump, comprising:

The eccentric mechanism comprises a transmission shaft (23), wherein eccentric wheels (8) are fixedly arranged at two ends of the transmission shaft (23), an eccentric shaft (21) is eccentrically arranged on one side, far away from the transmission shaft (23), of the eccentric wheels (8), two groups of connecting rods (6) are rotatably arranged on a single eccentric shaft (21), and the two groups of connecting rods (6) are distributed on two sides of the eccentric shaft (21);

The cross head (12) is arranged at one end of the connecting rod (6) far away from the eccentric shaft (21), one end of the cross head (12) close to the connecting rod (6) is hinged with the connecting rod (6) through a cross head pin (9), and the periphery of the cross head (12) is sleeved with a cross head bushing (10) for guiding the cross head (12) along the axial direction and limiting the cross head (12) to reciprocate along the axial direction;

The hydraulic end (14) is positioned on one side of the cross head (12) far away from the connecting rod (6), a hydraulic cylinder cavity (31) is formed in the hydraulic end (14), and a plunger (30) is arranged in the hydraulic cylinder cavity (31);

The plunger stroke adjusting mechanism is used for connecting the cross head (12) and the plunger (30) and can adjust the distance between the plunger (30) and the cross head (12) so as to change the position of the plunger (30) in the hydraulic cylinder cavity (31) and change the output flow of the pump;

and the driving mechanism is connected with the transmission shaft (23) and is used for driving the transmission shaft (23) to rotate.

2. The four-pump head plunger metering pump of claim 1 wherein said plunger travel adjustment mechanism comprises:

The stroke adjusting screw (18) is arranged in one end of the cross head (12) close to the plunger (30), and one end of the stroke adjusting screw (18) is connected in the internal threaded hole in a threaded manner;

The stroke adjusting piston (17), stroke adjusting piston (17) is installed in stroke adjusting screw (18), and the one end that stroke adjusting piston (17) is close to cross head round pin (9) is equipped with the boss, and the boss excircle is greater than the hole of stroke adjusting screw (18), plays the limiting effect, the other end and the plunger (30) rigid coupling of stroke adjusting piston (17), can adjust the distance between stroke adjusting piston (17) and cross head (12) through adjusting stroke adjusting screw (18) internal thread hole's position to change the position of plunger (30) in hydraulic cylinder chamber (31).

3. A four-pump head plunger metering pump according to claim 2, further comprising a housing (19), said fluid end (14) being mounted on the housing (19) and coaxial with the crosshead (12);

One end of the machine base (19) is used for supporting the cross head bushing (10) and the cross head (12), the other end of the machine base (19) supports the hydraulic end (14), and the machine base (19) is provided with a liquid collecting groove (15) for collecting leakage liquid when the plunger (30) reciprocates.

4. A four-pump head plunger metering pump as claimed in claim 3, characterised in that the upper surface of the housing (19) is provided with a scale (27) for use as a control line for the length adjustment of the stroke adjusting piston (17).

5. A four-pump head plunger metering pump as claimed in any one of claims 1 to 4, wherein said drive mechanism comprises:

The worm wheel shaft (25), the worm wheel shaft (25) is a straight cylinder shaft with a cavity, and the transmission shaft (23) is positioned in the worm wheel shaft (25) and rotates synchronously with the worm wheel shaft (25);

The worm wheel (28), the said worm wheel (28) is fixedly set up in the periphery of worm wheel shaft (25), one side of worm wheel (28) engages with worm (5);

and the motor II (1) is arranged at one end of the worm (5) far away from the hydraulic end (14) and is used for driving the worm (5) to rotate.

6. A four-pump head plunger metering pump as claimed in claim 5, wherein the worm wheel (28) is fixedly connected with the worm wheel shaft (25) through a flat key (29) so as to enable the worm wheel (28) and the worm wheel shaft (25) to synchronously rotate.

7. The four-pump head plunger type metering pump according to claim 5, further comprising a second base (34), wherein a transmission case (4) is arranged outside the worm (5), and the transmission case (4) is fixed on the second base (34);

the worm (5) is horizontally arranged, one end of the worm (5) extends out of the transmission case (4), an axial worm hole (3) is formed in the axle center part of one end of the worm (5) extending out of the transmission case (4), a key slot is formed in the worm hole (3), and a shaft head of the second motor (1) is inserted into the worm hole (3) to transmit torque through a key;

The motor II (1) is fixed on the motor bracket (2) through bolts, and the motor bracket (2) is fixedly connected with the transmission case (4) through bolts;

the two ends of the worm wheel shaft (25) are supported on a rolling bearing seat (26), and the rolling bearing seat (26) is mounted on the transmission case (4) through bolts.

8. The four-pump-head plunger type metering pump of claim 7, wherein the eccentric shaft (21) is provided with external threads at one end close to the eccentric wheel (8), a threaded hole is arranged at the eccentric position of the end face of the eccentric wheel (8), and the eccentric shaft (21) is fixed on the eccentric wheel (8) through the external threads and the threaded hole.