A plunger pump

Abstract

This utility model relates to the field of fluid transport technology, and in particular to a plunger pump, including a pump housing assembly, a plunger rod assembly, a first sealing assembly, and a sealing disc; the pump housing assembly includes a first inner cavity, a second inner cavity, and a third inner cavity arranged sequentially along the axial direction, the first inner cavity having a discharge port communicating with the outside, and the third inner cavity having a feed port; the first inner cavity is isolated into a first sub-cavity and a second sub-cavity by a valve seat formed on the plunger rod assembly, the first sub-cavity and the second sub-cavity being selectively connected through the valve seat formed on the plunger rod assembly, with the discharge port located in the second sub-cavity; the first sealing assembly is slidably sleeved on the plunger rod assembly and located in the second inner cavity, and follows the axial movement of the plunger rod assembly to block or open the communication between the second inner cavity and the third inner cavity; the sealing disc is disposed at the end of the plunger rod assembly and located at the feed port, and follows the axial movement of the plunger rod assembly to block or open the feed port; the plunger pump provided by this utility model has good sealing performance and reduces fluid leakage.

Description

Technical Field

[0001] This utility model relates to the field of fluid transport technology, and in particular to a plunger pump for transporting viscous fluids (such as glue). Background Technology

[0002] In the transportation of viscous fluids such as adhesives, plunger pumps are commonly used equipment. Traditional plunger pumps typically use a ball as a sealing component at the lower end, employing a passive sealing method. This relies on fluid pressure or the ball's own weight to achieve a seal with the sealing surface. While this passive sealing structure meets basic sealing requirements for transporting conventional fluids, it becomes problematic when dealing with high-density, high-viscosity adhesives. The poor flowability of the adhesive and insufficient thrust on the ball make it difficult to push the ball tightly against the sealing surface, resulting in a loose seal and frequent leaks. Leaks not only waste adhesive but also pollute the working environment, affecting the normal operation and transportation efficiency of the equipment, causing numerous inconveniences to production. Utility Model Content

[0003] This invention provides a plunger pump that can improve sealing performance and reduce fluid leakage.

[0004] This utility model provides a plunger pump, comprising:

[0005] The pump housing assembly includes a first inner cavity, a second inner cavity, and a third inner cavity arranged sequentially along the axial direction. The first inner cavity has a discharge port communicating with the outside on the side away from the second inner cavity, and the third inner cavity has a feed port on the end away from the second inner cavity.

[0006] A plunger rod assembly is inserted into the first inner cavity, the second inner cavity, and the third inner cavity. The first inner cavity is isolated into a first sub-cavity and a second sub-cavity by a valve seat formed on the plunger rod assembly. The first sub-cavity and the second sub-cavity are selectively connected through the valve seat formed on the plunger rod assembly. The discharge port is located in the second sub-cavity.

[0007] The first sealing component is slidably sleeved on the plunger rod assembly and located in the second inner cavity, and follows the axial movement of the plunger rod assembly to seal or open the communication between the second inner cavity and the third inner cavity;

[0008] A sealing disc is disposed at the end of the plunger rod assembly and located at the feed inlet, and moves axially with the plunger rod assembly to block or open the feed inlet.

[0009] In one embodiment of the present invention, a second sealing component and a third sealing component are provided between the pump housing assembly and the plunger rod assembly. The second sealing component is located at the end of the second sub-cavity away from the first sub-cavity, and the third sealing component is located between the first sub-cavity and the second sub-cavity. The first sealing component, the second sealing component, and / or the third sealing component are sealing structures with adjustable sealing performance.

[0010] In one embodiment of the present invention, the first sealing assembly includes:

[0011] The sealing sleeve is a sleeve-shaped structure. One end of the sealing sleeve is used to block or open the channel between the second inner cavity and the third inner cavity as the plunger rod assembly moves axially.

[0012] The first sealing ring is threadedly connected to the inner wall of the other end of the sealing sleeve;

[0013] The first sealing ring includes at least two and is disposed inside the sealing sleeve, and the inner wall of the first sealing ring is in contact with and sealed to the outer wall of the plunger rod assembly;

[0014] A first isolation ring is disposed inside the sealing sleeve, and at least one first isolation ring is located between two adjacent first sealing rings;

[0015] The first plug ring is configured such that the axial compression of the first sealing ring can be adjusted by rotation to change the sealing performance of the first sealing assembly.

[0016] In one embodiment of the present invention, one end face of the axial cross-section of the first sealing ring is an inverted V shape or an inverted W shape.

[0017] In one embodiment of the present invention, one end face of the axial cross-section of the first isolation ring is arched, and when the first isolation ring and the first sealing ring are in contact along the axial direction, the axial faces of the two form a gap area.

[0018] In one embodiment of the present invention, the pump housing assembly includes:

[0019] Upper pump housing; the discharge port is located on the upper pump housing;

[0020] The lower pump housing is detachably connected to the upper pump housing in the axial direction, and the feed inlet is located at the end of the lower pump housing away from the upper pump housing;

[0021] The second sealing assembly is used to seal the gap between the plunger rod assembly and the upper pump housing.

[0022] In one embodiment of the present invention, the third inner cavity includes a threaded sleeve that is threadedly connected to the pump housing assembly. The third inner cavity and the second inner cavity have a stepped structure. An annular isolation plate is provided at the stepped structure for limiting. The through hole in the middle of the annular isolation plate is a channel connecting the second inner cavity and the third inner cavity. The annular isolation plate is detachably fixed by the threaded sleeve.

[0023] In one embodiment of the present invention, the second sealing assembly includes:

[0024] The second sealing ring is disposed at the end of the second sealing assembly away from the first inner cavity and is threadedly connected to the pump housing assembly;

[0025] The second limiting ring is coaxially arranged with the second blocking ring and is limitedly connected to the pump housing assembly;

[0026] The second sealing ring includes at least two and is disposed between the second plugging ring and the second limiting ring within the pump housing assembly, wherein the inner wall of the second sealing ring is fitted and sealed to the outer wall of the plunger rod assembly;

[0027] A second isolation ring is disposed within the pump housing assembly, and at least one second isolation ring is located between two adjacent second sealing rings;

[0028] The second sealing ring is configured such that the axial compression of the second sealing ring can be adjusted by rotation to change the sealing performance of the second sealing assembly.

[0029] In one embodiment of the present invention, the plunger rod assembly includes:

[0030] The first rod has one end extending outside the first inner cavity and the other end located inside the first inner cavity.

[0031] The second rod passes through the second inner cavity and one end is located in the first inner cavity and is connected to the first rod; the second rod is provided with a first flow channel, and one end of the first flow channel is connected to the first sub-cavity;

[0032] A sphere is disposed in the receiving cavity between the first rod and the second rod, and is used to block or open the flow port of the first flow channel as the plunger rod assembly moves axially.

[0033] The third sealing assembly is disposed at the connection between the first rod and the second rod. The other end of the first flow channel passes through the second sealing assembly in the axial direction and communicates with the second sub-cavity. The close ends of the first rod and the second rod, the mating surfaces of the ball and the second sealing assembly form the valve seat.

[0034] In one embodiment of the present invention, the third sealing assembly includes:

[0035] The third sealing ring includes at least two and is disposed within the pump housing assembly, and the inner wall of the third sealing ring is in contact with and sealed to the outer wall of the plunger rod assembly;

[0036] A third isolation ring is disposed within the pump housing assembly, and at least one of the third isolation rings is located between two adjacent third sealing rings;

[0037] The first rod and the second rod are connected by internal and external threads. The first rod is provided with a first annular protrusion, and the second rod is provided with a second annular protrusion. The third sealing ring and the third isolation ring are both located between the first annular protrusion and the second annular protrusion. The sealing performance of the third sealing assembly is adjusted by the overlap length of the threaded connection between the first rod and the second rod.

[0038] The beneficial effects of this utility model are as follows: This utility model proposes a plunger pump that replaces the traditional passive sealing with an active sealing system. The sealing is achieved by actively driving the lower sealing disc through a cylinder or other driving components. This active sealing structure is unaffected by the density and viscosity of the adhesive, actively controlling the fit between the sealing disc and the sealing area. This ensures a tight seal when conveying various adhesives (including high-density, viscous adhesives), effectively preventing leakage. This not only saves adhesive raw materials and maintains a clean working environment, but also improves the pump's conveying efficiency and operational stability, broadening the application range of the plunger pump in the conveying of viscous fluids. Attached Figure Description

[0039] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0040] In the attached diagram:

[0041] Figure 1 This is a three-dimensional structural diagram of a fluid pump provided in an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of a side view of one embodiment of the present utility model;

[0043] Figure 3 for Figure 2 A structural cross-sectional view at point AA;

[0044] Figure 4 for Figure 3 Enlarged view of the structure at point A;

[0045] Figure 5 for Figure 3 Enlarged view of the structure at point B;

[0046] Figure 6 for Figure 3 Enlarged view of the structure at point C;

[0047] Figure 7 This is a schematic diagram of the flow direction of fluid in a fluid pump provided in one embodiment of the present invention;

[0048] The reference numerals in the attached drawings are as follows: Pump housing assembly 1, first inner cavity 101, second inner cavity 102, third inner cavity 103, discharge port 104, inlet port 105, upper pump housing 11, lower pump housing 12, threaded sleeve 13, stepped structure 14, annular isolation plate 15, plunger rod assembly 2, first rod 21, second rod 22, first flow channel 221, ball 23, receiving cavity 24, first annular protrusion 211, second annular protrusion 222, first sealing assembly 3, sealing sleeve 31, first plugging ring 32, first sealing ring 33, first isolation ring 34, sealing disc 4, second sealing assembly 5, second plugging ring 51, second limiting ring 52, second sealing ring 53, second isolation ring 54, third sealing assembly 6, third sealing ring 61, third isolation ring 62, first sub-cavity 1011, second sub-cavity 1012. Detailed Implementation

[0049] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0050] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0051] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the present invention.

[0052] like Figure 1-3 and Figure 7 As shown, this utility model provides a plunger pump, including a pump housing assembly 1, a plunger rod assembly 2, a first sealing assembly 3, and a sealing disc 4;

[0053] The pump housing assembly 1 includes a first inner cavity 101, a second inner cavity 102 and a third inner cavity 103 arranged sequentially along the axial direction. The first inner cavity 101 is provided with a discharge port 104 communicating with the outside on the side away from the second inner cavity 102, and the third inner cavity 103 is provided with a feed port 105 at the end away from the second inner cavity 102.

[0054] The plunger rod assembly 2 passes through the first inner cavity 101, the second inner cavity 102 and the third inner cavity 103, and the first inner cavity 101 is isolated into a first sub-cavity 1011 and a second sub-cavity 1012 by a valve seat formed on the plunger rod assembly 2. The first sub-cavity 1011 and the second sub-cavity 1012 are selectively connected through the valve seat formed on the plunger rod assembly 2, and the discharge port 104 is located in the second sub-cavity 1012.

[0055] The first sealing component 3 is slidably sleeved on the plunger rod assembly 2 and located in the second inner cavity 102, and follows the axial movement of the plunger rod assembly 2 to block or open the communication between the second inner cavity 102 and the third inner cavity 103;

[0056] The sealing disc 4 is disposed at the end of the plunger rod assembly 2 and located at the feed inlet 105, and moves axially with the plunger rod assembly 2 to block or open the feed inlet 105.

[0057] It should be noted that the pump housing assembly 1, as the basic structure of the plunger pump, is provided with a first inner cavity 101, a second inner cavity 102, and a third inner cavity 103 sequentially along the axial direction. These inner cavities can be formed integrally within the same housing, or they can be assembled from multiple separate housings. For example, an upper pump housing 11, a middle pump housing, and a lower pump housing 12 can be combined using bolts or threads to facilitate the installation and maintenance of the internal components. The first inner cavity 101 has an outlet 104 connected to the outside on the side away from the second inner cavity 102, used to transport the fluid inside the pump to an external pipeline. The third inner cavity 103 has an inlet 105 on the end away from the second inner cavity 102, used to receive external fluids to be transported, such as viscous substances like glue.

[0058] The plunger rod assembly 2 passes through the first inner cavity 101, the second inner cavity 102, and the third inner cavity 103. It can be manufactured from a single rod or formed by combining multiple rod segments through threaded connections, welding, or flange connections to adapt to the structural requirements of different inner cavities. The first inner cavity 101 is isolated into a first sub-cavity 1011 and a second sub-cavity 1012 by a valve seat formed on the plunger rod assembly 2. The valve seat allows selective communication between the first sub-cavity 1011 and the second sub-cavity 1012; that is, when the valve seat is open, the two sub-cavities are interconnected, and fluid can flow between them; when the valve seat is closed, the two sub-cavities are isolated, preventing fluid flow. Selective communication of the valve seat can be achieved through the axial movement of the plunger rod assembly 2. For example, the valve seat may be equipped with an axially movable sealing element, such as a ball 23 or a conical valve core. Under the action of the plunger rod assembly 2, the sealing element may engage or disengage with the valve port, thereby controlling the flow. The discharge port 104 is located in the second sub-cavity 1012, so that the fluid in the second sub-cavity 1012 can be smoothly discharged through the discharge port 104.

[0059] The first sealing assembly 3 is slidably sleeved on the plunger rod assembly 2 and located in the second inner cavity 102. It can move axially with the plunger rod assembly 2 to block or open the connection between the second inner cavity 102 and the third inner cavity 103. The sealing assembly may include a sealing sleeve 31 and a sealing ring disposed on the inner side of the sleeve. The sealing ring is made of an elastic material, such as nitrile rubber or fluororubber, to ensure sealing performance with the outer wall of the plunger rod assembly 2. One end of the sealing sleeve 31 may be provided with a sealing end face for blocking the connection. When the plunger rod assembly 2 drives the sealing sleeve 31 to move axially, the sealing end face fits or separates from the mating surface of the connection, realizing the closure or opening of the passage. In addition, the first sealing assembly 3 may also adopt a piston structure, and the sealing and on / off control are achieved by the sliding fit between the piston and the inner wall of the second inner cavity 102.

[0060] The sealing disc 4 is disposed at the end of the plunger rod assembly 2 and located at the inlet 105. Its shape is adapted to the sealing surface of the inlet 105, and it can adopt a circular, square, or other structure. The material can be selected according to the characteristics of the fluid being transported. For example, for viscous adhesives, polyurethane or polytetrafluoroethylene with a certain degree of elasticity can be selected to ensure the sealing effect. The sealing disc 4 can move axially with the plunger rod assembly 2. When the plunger rod assembly 2 moves towards the inlet 105, the sealing disc 4 is tightly fitted with the sealing surface of the inlet 105, thus sealing the inlet 105. When the plunger rod assembly 2 moves away from the inlet 105, the sealing disc 4 separates from the sealing surface, the inlet 105 opens, and the external fluid can enter the third inner cavity 103.

[0061] The principle behind this invention's solution to the technical problem lies in the following: Traditional plunger pumps use a ball for passive sealing, where the sealing effect relies on the fluid's own pressure to push the ball against the sealing surface. For adhesives with high density and viscosity, the fluid cannot provide sufficient thrust, resulting in the ball failing to seal tightly and causing leakage. This solution, by setting a sealing disc 4 that moves axially with the plunger rod assembly 2, changes the passive sealing to an active sealing. The axial driving force of the plunger rod assembly 2 drives the sealing disc 4 to actively contact the sealing surface of the inlet 105, applying sufficient sealing pressure to ensure a tight seal even when conveying viscous adhesives, effectively preventing leakage. Simultaneously, through the selective communication control of the first sub-cavity 1011 and the second sub-cavity 1012 by the valve seat, and the on / off control of the connection between the second inner cavity 102 and the third inner cavity 103 by the first sealing assembly 3, the coordinated movement of all components achieves orderly fluid delivery.

[0062] like Figure 3-6 As shown, in an optional embodiment of this case, a second sealing component 5 and a third sealing component 6 are provided between the pump housing assembly 1 and the plunger rod assembly 2. The second sealing component 5 is located at the end of the second sub-cavity 1012 away from the first sub-cavity 1011, and the third sealing component 6 is located between the first sub-cavity 1011 and the second sub-cavity 1012. The first sealing component 3, the second sealing component 5 and / or the third sealing component 6 are sealing structures with adjustable sealing performance.

[0063] It should be noted that the placement of a second sealing assembly 5 and a third sealing assembly 6 between the pump housing assembly 1 and the plunger rod assembly 2 further enhances the overall sealing performance of the plunger pump, effectively preventing fluid leakage from the gap between the pump housing and the plunger rod during transport. Specifically, the second sealing assembly 5 is located at the end of the second sub-cavity 1012 furthest from the first sub-cavity 1011, effectively preventing fluid in the second sub-cavity 1012 from permeating to the outside of the plunger pump or non-working areas. The third sealing assembly 6 is located between the first sub-cavity 1011 and the second sub-cavity 1012, strengthening the isolation between the two sub-cavities and preventing unintended fluid communication between them, thus ensuring the effectiveness of the valve seat's control over the communication state between the two sub-cavities.

[0064] The specific structures of the second sealing component 5 and the third sealing component 6 can be flexibly designed according to actual sealing requirements. For example, the second sealing component 5 can adopt a structure in which multiple sealing rings and isolation rings are alternately stacked. The sealing rings can be made of wear-resistant rubber or polytetrafluoroethylene with self-lubricating properties, while the isolation rings can be made of metal or hard plastic to maintain the stable shape of the sealing rings. The third sealing component 6 can also adopt a similar multi-layer sealing structure, or, depending on the pressure characteristics of its location, a combined sealing element can be selected, such as a combined structure including a U-ring and a support ring.

[0065] The first sealing assembly 3, the second sealing assembly 5, and / or the third sealing assembly 6 employ an adjustable sealing structure, enabling the plunger pump to adapt to sealing requirements under different operating conditions. The adjustable sealing can be achieved in various ways. For example, the sealing assembly may include a threaded adjusting member; rotating the adjusting member changes the axial compression of the sealing ring, thereby adjusting the tightness of the sealing surface. Alternatively, the sealing assembly and the plunger rod assembly 2 may be connected by a movable limiting structure; changing the limiting position adjusts the preload of the sealing assembly. Furthermore, an elastic adjustment structure may be used, such as incorporating a spring in the sealing assembly, utilizing the spring force to dynamically adjust the sealing pressure to adapt to fluctuations in fluid pressure.

[0066] The principle behind this structure's solution to the technical problem lies in the fact that traditional plunger pumps often have fixed sealing components, making it difficult to adjust their sealing performance after assembly. When faced with adhesives of varying viscosities or slight wear on the seals, insufficient sealing force can easily lead to leakage. This solution, however, utilizes a strategically positioned second and third sealing components 5 and an adjustable sealing structure. This allows for flexible adjustment of the sealing strength based on actual operating conditions such as adhesive viscosity and delivery pressure. For example, for higher viscosity adhesives, the pre-tightening force of the sealing components can be increased to ensure a tight seal. When seals wear down due to prolonged use, the structure can be adjusted to compensate for the wear, maintaining an effective seal and preventing leakage due to seal failure.

[0067] The technical effects achieved are as follows: First, it significantly improves the sealing adaptability of the plunger pump, enabling it to stably handle the delivery of adhesives of different densities and viscosities, ensuring good sealing performance under various working conditions; second, it extends the service life of the sealing components, compensating for wear through an adjustable structure and reducing the number of downtime maintenance caused by seal failure; third, it further optimizes the flow control of the fluid inside the pump, making the fluid delivery path more precise by strengthening the isolation between sub-cavities and between sub-cavities and the outside, thereby improving the working stability and efficiency of the plunger pump.

[0068] like Figure 3 and Figure 4 As shown, as an optional embodiment of this case, the first sealing assembly 3 includes a sealing sleeve 31, a first plugging ring 32, a first sealing ring 33, and a first isolation ring 34;

[0069] The sealing sleeve 31 has a sleeve-shaped structure. One end of the sealing sleeve 31 is used to block or open the channel between the second inner cavity 102 and the third inner cavity 103 as the plunger rod assembly 2 moves axially.

[0070] The first plugging ring 32 is threadedly connected to the inner wall of the other end of the sealing sleeve 31;

[0071] The first sealing ring 33 includes at least two and is disposed inside the sealing sleeve 31, and the inner wall of the first sealing ring 33 is in contact with and sealed to the outer wall of the plunger rod assembly 2;

[0072] The first isolation ring 34 is disposed inside the sealing sleeve 31, and at least one first isolation ring 34 is located between two adjacent first sealing rings 33;

[0073] The first sealing ring 32 is configured to adjust the axial compression of the first sealing ring 33 by rotation to change the sealing performance of the first sealing assembly 3.

[0074] It should be noted that in the first sealing assembly 3, the sealing sleeve 31 is a sleeve-shaped structure, which can be made of metal or high-strength engineering plastic to ensure structural strength and wear resistance. One end of the sealing sleeve 31 is used to move axially with the plunger rod assembly 2, thereby blocking or opening the channel between the second inner cavity 102 and the third inner cavity 103. This end can be set as a planar structure or a tapered structure that cooperates with the channel. By fitting or separating from the channel port, the flow control is achieved to ensure the orderly flow of fluid between the second inner cavity 102 and the third inner cavity 103.

[0075] The first plugging ring 32 is threadedly connected to the inner wall of the other end of the sealing sleeve 31. This threaded connection not only facilitates the installation and removal of the first plugging ring 32, but also allows for precise control of its axial position within the sealing sleeve 31 through the thread engagement depth. Besides threaded connections, other detachable connection methods with axial adjustment functions can also be used, such as snap-fit ​​adjustments with axial scales, but threaded connections offer advantages in adjustment accuracy and stability.

[0076] The first sealing ring 33 comprises at least two rings, both disposed within the sealing sleeve 31, with their inner walls fitting against the outer wall of the plunger rod assembly 2 to achieve a seal. The first sealing ring 33 can be made of materials with good sealing and wear resistance, such as oil-resistant rubber or polytetrafluoroethylene. The arrangement of multiple sealing rings can form a multi-stage seal, significantly improving the sealing effect. Its cross-sectional shape can be O-shaped, U-shaped, or V-shaped, etc. Sealing rings with different cross-sectional shapes can be combined according to actual sealing requirements to further enhance sealing reliability.

[0077] The first isolation ring 34 is disposed within the sealing sleeve 31, and at least one is located between two adjacent first sealing rings 33. Its function is to separate adjacent first sealing rings 33, preventing the sealing rings from sticking together or deforming and interfering with each other under pressure, and ensuring that each sealing ring independently performs its sealing function. The first isolation ring 34 can be a metal ring or a rigid plastic ring, and its axial thickness can be adapted according to the size of the sealing ring. A shallow groove structure can also be provided on the surface of the isolation ring to accommodate the slight deformation of the sealing ring under pressure.

[0078] The first plugging ring 32 is configured to adjust the axial compression of the first sealing ring 33 by rotation, thereby changing the sealing performance of the first sealing assembly 3. Specifically, when the first plugging ring 32 is rotated, it moves axially through its threaded engagement with the sealing sleeve 31, generating a thrust on the adjacent first sealing ring 33. This thrust is transmitted to other sealing rings through the first isolation ring 34, causing multiple first sealing rings 33 to be axially compressed simultaneously. The tightness of the seal rings against the outer wall of the plunger rod assembly 2 changes accordingly, thereby adjusting the sealing performance. This adjustment method is simple to operate and allows for flexible adjustment of the sealing strength according to the viscosity of the adhesive being delivered. For example, for adhesives with higher viscosity, the compression can be increased to enhance the sealing force and ensure reliable sealing.

[0079] The principle behind this structure's solution to the technical problem lies in the fact that traditional sealing components have a fixed sealing force. When conveying adhesives of different viscosities, this fixed sealing force struggles to balance sealing reliability with component wear. For viscous adhesives, insufficient sealing force may lead to leakage, while for thinner adhesives, excessive sealing force may exacerbate wear. However, the first sealing component 3, through the rotation of the first sealing ring 32, adjusts the compression of the first sealing ring 33, dynamically adapting to the characteristics of different adhesives. This ensures that the sealing force matches the adhesive viscosity, fundamentally solving the problem of unreliable sealing.

[0080] like Figure 3 and Figure 4 As shown, as an optional embodiment of this case, one end face of the axial cross-section of the first sealing ring 33 is an inverted V shape or an inverted W shape.

[0081] It should be noted that one end face of the axial cross-section of the first sealing ring 33 is an inverted V-shape or an inverted W-shape. An inverted V-shape refers to an end face with a triangular notch structure, while an inverted W-shape refers to an end face with a double-triangular notch structure. In addition to the above shapes, similar polygonal structures, such as a V-shape with a rounded transition, can also be used. Through the multi-angled or multi-faceted end face shape, directional deformation occurs under axial pressure, allowing the inner wall of the first sealing ring 33 to fit more tightly against the outer wall of the plunger rod assembly 2. This also enhances the elastic recovery capability of the sealing ring itself, adapting to the slight radial runout during the axial movement of the plunger rod assembly 2.

[0082] The principle behind the above structural design is as follows: the end face of traditional sealing rings is mostly flat or simple curved, and the deformation direction is dispersed under axial compression, which easily leads to the problem of poor sealing surface fit in some areas. Especially when conveying viscous glue, the viscosity resistance of the glue will aggravate the gap leakage of the sealing surface. However, the inverted V-shaped or inverted W-shaped end face of the first sealing ring 33 can concentrate the sealing force through the directional deformation of the bend under pressure, thereby enhancing the tightness of the fit with the outer wall of the plunger rod assembly 2.

[0083] like Figure 3 and Figure 4 As shown, in an optional embodiment of this case, one end face of the axial cross-section of the first isolation ring 34 is arched, and when the first isolation ring 34 and the first sealing ring 33 are in contact along the axial direction, the axial faces of the two form a gap area.

[0084] It should be noted that one end face of the axial cross-section of the first isolation ring 34 is arched, which can be either circular or elliptical, and its curvature can be designed to fit the end face shape of the first sealing ring 33. When the first isolation ring 34 and the first sealing ring 33 are in contact along the axial direction, the gap area formed by their axial faces provides a buffer space for the deformation of the first sealing ring 33 under pressure. This gap area can prevent the first sealing ring 33 from being excessively compressed and losing its elasticity, while also accommodating excess material when the sealing ring deforms, ensuring that each first sealing ring 33 independently and stably performs its sealing function.

[0085] The principle behind the above structural design is that the end faces of traditional isolation rings and sealing rings are mostly in planar contact. When the sealing ring is compressed, it lacks deformation buffer space and is prone to elastic failure or local wear due to excessive compression, affecting the sealing effect. However, the gap area formed by the arched end face of the first isolation ring 34 and the first sealing ring 33 can guide the deformation direction of the sealing ring, providing it with sufficient deformation space, while avoiding mutual interference between the sealing rings.

[0086] like Figure 3 As shown, as an optional embodiment of this case, the pump housing assembly 1 includes an upper pump housing 11 and a lower pump housing 12;

[0087] The discharge port 104 of the upper pump housing 11 is located on the upper pump housing 11; the lower pump housing 12 is detachably connected to the upper pump housing 11 in the axial direction, and the inlet 105 is located at the end of the lower pump housing 12 away from the upper pump housing 11;

[0088] The second sealing component 5 is used to seal the gap between the plunger rod assembly 2 and the upper pump housing 11.

[0089] It should be noted that the pump housing assembly 1 includes an upper pump housing 11 and a lower pump housing 12. The upper pump housing 11 and the lower pump housing 12 are detachably connected in the axial direction. This connection method facilitates the installation, maintenance, and replacement of internal components of the pump housing. Specifically, bolted connections or threaded connections can be used. The discharge port 104 is located on the upper pump housing 11, allowing it to directly form a fluid passage with the second sub-cavity 1012, ensuring the smooth discharge of fluid from the second sub-cavity 1012. The inlet port 105 is located at the end of the lower pump housing 12 away from the upper pump housing 11, facilitating the receipt of fluids to be transported from the outside, such as viscous substances like glue.

[0090] The second sealing assembly 5 is used to seal the gap between the plunger rod assembly 2 and the upper pump housing 11. It can adopt a multi-layer sealing structure similar to the first sealing assembly 3, such as consisting of alternating sealing rings and isolation rings. The sealing rings can be made of materials such as rubber or polytetrafluoroethylene to adapt to the characteristics of different fluids. By setting the second sealing assembly 5, the fluid in the second sub-cavity 1012 can be effectively prevented from leaking from the gap between the upper pump housing 11 and the plunger rod assembly 2, further enhancing the overall sealing performance of the pump body.

[0091] like Figure 3 As shown, in an optional embodiment of this case, the third inner cavity 103 includes a threaded sleeve 13 that is threadedly connected to the pump housing assembly 1. There is a stepped structure 14 between the third inner cavity 103 and the second inner cavity 102. An annular isolation plate 15 is provided at the stepped structure 14 for limiting. The through hole in the middle of the annular isolation plate 15 is a channel connecting the second inner cavity 102 and the third inner cavity 103. The annular isolation plate 15 is detachably fixed by the threaded sleeve 13.

[0092] It should be noted that the third inner cavity 103 includes a threaded sleeve 13 that is threadedly connected to the pump housing assembly 1. The threaded connection allows the threaded sleeve 13 to be adjusted in the axial direction, facilitating changes in the effective volume of the third inner cavity 103 according to actual needs, or enabling the compression and release of internal components. A stepped structure 14 exists between the third inner cavity 103 and the second inner cavity 102. This stepped structure 14 provides a limiting base for the annular isolation plate 15, ensuring that the annular isolation plate 15 can be stably installed in a preset position.

[0093] The annular isolation plate 15 is positioned at the stepped structure 14, with its central through-hole forming a channel connecting the second inner cavity 102 and the third inner cavity 103, allowing fluid to flow orderly between the two cavities. The annular isolation plate 15 is detachably fixed via a threaded sleeve 13. Specifically, the axial pressure generated when the threaded sleeve 13 is tightened presses the annular isolation plate 15 against the limiting surface of the stepped structure 14. This fixing method ensures the stability of the connection and facilitates the disassembly and replacement of the annular isolation plate 15. If the channel diameter needs to be adjusted, only an annular isolation plate 15 with a different through-hole size needs to be replaced.

[0094] The principle behind the above structural design is that the traditional connection between the third and second inner cavities lacks an adjustable isolation structure. When conveying adhesives of different viscosities, a fixed channel diameter may lead to excessive fluid resistance or unreliable sealing. However, by using the threaded sleeve 13 in conjunction with the annular isolation plate 15, the channel diameter can be controlled through the through-hole of the annular isolation plate 15, and the position adjustment of the threaded sleeve 13 can reliably fix the annular isolation plate 15. At the same time, it is easy to replace the annular isolation plate 15 according to the fluid characteristics to optimize the channel parameters.

[0095] like Figure 3 and Figure 5 As shown, in an optional embodiment of this case, the second sealing assembly 5 includes a second plugging ring 51, a second limiting ring 52, a second sealing ring 53, and a second isolation ring 54;

[0096] The second sealing ring 51 is disposed at one end of the second sealing assembly 5 away from the first inner cavity 101 and is threadedly connected to the pump housing assembly 1;

[0097] The second limiting ring 52 is coaxially arranged with the second blocking ring 51 and is limitedly connected to the pump housing assembly 1;

[0098] The second sealing ring 53 includes at least two and is disposed between the second plugging ring 51 and the second limiting ring 52 within the pump housing assembly 1. The inner wall of the second sealing ring 53 is in contact with and sealed to the outer wall of the plunger rod assembly 2.

[0099] The second isolation ring 54 is disposed within the pump housing assembly 1, and at least one second isolation ring 54 is located between two adjacent second sealing rings 53;

[0100] The second sealing ring 51 is configured to adjust the axial compression of the second sealing ring 53 by rotation to change the sealing performance of the second sealing assembly 5.

[0101] It should be noted that the second sealing assembly 5 includes a second plugging ring 51, a second limiting ring 52, a second sealing ring 53, and a second isolation ring 54. The second plugging ring 51 is located at the end of the second sealing assembly 5 away from the first inner cavity 101 and is threadedly connected to the pump housing assembly 1. The threaded connection facilitates precise adjustment of its axial position by rotation and provides a stable connection. Alternative connection methods may include snap-fit ​​connections with axial graduations, but the threaded connection has advantages in adjustment accuracy and locking stability, ensuring the fixed position after adjustment.

[0102] The second limiting ring 52 is coaxially arranged with the second blocking ring 51 and is limitedly connected to the pump housing assembly 1. The limiting connection can be achieved by using an annular step on the inner wall of the pump housing assembly 1 or by using a radial pin to cooperate with the pin hole of the pump housing assembly 1. Its function is to fix its own position and prevent it from rotating with the second blocking ring 51, while providing an axial support reference for the second sealing ring 53.

[0103] The second sealing ring 53 includes at least two rings, each disposed between the second plugging ring 51 and the second limiting ring 52 within the pump housing assembly 1. Its inner wall is fitted against the outer wall of the plunger rod assembly 2 to achieve a seal. The second sealing ring 53 can be made of materials such as oil-resistant rubber or polytetrafluoroethylene (PTFE). Rubber has good elastic recovery capabilities, while PTFE is suitable for applications requiring high wear resistance. Its cross-sectional shape can be O-shaped or U-shaped. The arrangement of multiple sealing rings forms a multi-stage seal, improving sealing redundancy.

[0104] The second isolation ring 54 is disposed inside the pump housing assembly 1, and at least one is located between two adjacent second sealing rings 53. Its material can be metal or high-strength engineering plastic. The metal isolation ring has high strength, while the plastic isolation ring has a certain buffering capacity. Its function is to separate adjacent second sealing rings 53, prevent the sealing rings from sticking together or deforming and interfering with each other when under pressure, and ensure that each sealing ring can independently and stably perform its sealing function.

[0105] The second plugging ring 51 is configured to adjust the axial compression of the second sealing ring 53 by rotation, thereby changing the sealing performance of the second sealing assembly 5. Specifically, when the second plugging ring 51 is rotated, it moves axially towards the second limiting ring 52 through its threaded engagement with the pump housing assembly 1, compressing the second sealing ring 53 and increasing the tightness of the seal ring against the outer wall of the plunger rod assembly 2, thus enhancing the sealing performance. When rotated in the opposite direction, the compressive effect weakens, and the sealing performance decreases accordingly, thereby achieving flexible adjustment of the sealing performance.

[0106] The principle behind the above structural design is as follows: Traditional second sealing components have a fixed sealing force. When conveying adhesives of varying viscosities, this fixed sealing force is difficult to match actual needs. For viscous adhesives, insufficient sealing force may lead to leakage, while for thinner adhesives, excessive sealing force may exacerbate wear on the sealing ring. This structure, however, adjusts the compression of the second sealing ring 53 by rotating the second plug ring 51. This allows for dynamic adjustment of the sealing force based on the adhesive characteristics, ensuring reliable sealing while reducing unnecessary wear.

[0107] like Figure 3 As shown, in an optional embodiment of this case, the plunger rod assembly 2 includes a first rod 21, a second rod 22, and a ball 23;

[0108] One end of the first rod 21 extends out of the first inner cavity 101, and the other end is located inside the first inner cavity 101.

[0109] The second rod 22 passes through the second inner cavity 102 and one end is located in the first inner cavity 101 and is connected to the first rod 21; the second rod 22 is provided with a first flow channel 221, and one end of the first flow channel 221 is connected to the first sub-cavity 1011.

[0110] The ball 23 is disposed in the receiving cavity 24 between the first rod 21 and the second rod 22, and is used to block or open the flow port of the first flow channel 221 by following the axial movement of the plunger rod assembly 2.

[0111] The third sealing assembly 6 is disposed at the connection between the first rod 21 and the second rod 22. The other end of the first flow channel 221 passes through the second sealing assembly 5 in the axial direction and communicates with the second sub-cavity 1012. The valve seat is formed by the close-proximity ends of the first rod 21 and the second rod 22, the mating surface of the ball 23 and the second sealing assembly 5.

[0112] It should be noted that the plunger rod assembly 2 includes a first rod 21 and a second rod 22. One end of the first rod 21 extends out of the first inner cavity 101 and can be used to connect to an external drive device to obtain axial driving force. The other end is located inside the first inner cavity 101. Its material can be a high-strength metal or alloy to meet structural strength requirements. The second rod 22 passes through the second inner cavity 102, and one end is located inside the first inner cavity 101 and connected to the first rod 21. The connection method can be a threaded connection or a flange connection. The threaded connection is convenient for disassembly and length adjustment, while the flange connection can provide higher connection strength. The second rod 22 is provided with a first flow channel 221. This flow channel can be an axial through hole or a stepped hole structure. One end of it communicates with the first sub-cavity 1011 to ensure that the fluid in the first sub-cavity 1011 can enter the flow channel.

[0113] The ball 23 is disposed in the receiving cavity 24 between the first rod 21 and the second rod 22. The receiving cavity 24 can be formed by the concave portions at the opposite ends of the two rods. The ball 23 can block or open the flow channel opening of the first flow channel 221 by following the axial movement of the plunger rod assembly 2. The material of the ball 23 can be wear-resistant metal or high-strength engineering plastic to adapt to the long-term erosion of adhesives with different viscosity.

[0114] The third sealing component 6 is disposed at the connection between the first rod 21 and the second rod 22. It can adopt a structure with alternating sealing rings and isolation rings, or a combined sealing element, to seal the gap between the two rods and prevent fluid leakage from the connection. The other end of the first flow channel 221 passes through the second sealing component 5 in the axial direction and communicates with the second sub-cavity 1012. Here, a sealing structure adapted to the second sealing component 5 can be provided on the outer wall of the flow channel to ensure the sealing performance at the interface between the flow channel and the second sealing component 5, without affecting fluid flow.

[0115] The valve seat is formed by the close-proximity ends of the first rod 21 and the second rod 22, the mating surfaces of the ball 23 and the second sealing assembly 5. When the ball 23 is in contact with the flow channel opening and the mating surface under the action of axial force, the valve seat is sealed. When the ball 23 moves in the opposite direction with the plunger rod assembly 2 and separates from the mating surface, the valve seat is opened, and fluid can flow through the first flow channel 221 between the first sub-cavity 1011 and the second sub-cavity 1012.

[0116] The principle behind the above structural design is as follows: Traditional valve seat sealing relies on fluid pressure to passively press the sealing element together. For viscous adhesives, insufficient fluid thrust can easily lead to loose seals, and the seal at the rod connection often carries a risk of leakage due to its simple structure. In this structure, the ball 23 actively moves axially with the plunger rod assembly 2, enabling it to actively press against the mating surface. Combined with the third sealing assembly 6 sealing the rod connection, this ensures reliable sealing of both the valve seat and the connection when conveying viscous adhesives. The overall structure makes the flow of fluid between the first sub-cavity 1011 and the second sub-cavity 1012 more controllable, improving the operational stability and delivery efficiency of the plunger pump.

[0117] like Figure 3 and Figure 6 As shown, in an optional embodiment of this case, the third sealing assembly 6 includes a third sealing ring 61 and a third isolation ring 62;

[0118] The third sealing ring 61 includes at least two and is disposed within the pump housing assembly 1, and the inner wall of the third sealing ring 61 is in contact with and sealed to the outer wall of the plunger rod assembly 2;

[0119] The third isolation ring 62 is disposed within the pump housing assembly 1, and at least one of the third isolation rings 62 is located between two adjacent third sealing rings 61;

[0120] The first rod 21 and the second rod 22 are connected by internal and external threads. The first rod 21 is provided with a first annular protrusion 211, and the second rod 22 is provided with a second annular protrusion 222. The third sealing ring 61 and the third isolation ring 62 are both located between the first annular protrusion 211 and the second annular protrusion 222. The sealing performance of the third sealing assembly 6 is adjusted by the overlapping length of the threaded connection of the first rod 21 and the second rod 22.

[0121] It should be noted that the third sealing assembly 6 includes a third sealing ring 61 and a third isolation ring 62. At least two third sealing rings 61 are included, both disposed within the pump housing assembly 1, with their inner walls fitting against the outer wall of the plunger rod assembly 2 to achieve a seal. The third sealing rings 61 can be made of wear-resistant rubber or self-lubricating polytetrafluoroethylene (PTFE), and their cross-sectional shape can be O-shaped or V-shaped. The arrangement of multiple sealing rings can form a multi-stage seal, improving sealing redundancy.

[0122] The third isolation ring 62 is disposed within the pump housing assembly 1, and at least one is located between two adjacent third sealing rings 61. Its function is to separate adjacent third sealing rings 61, preventing the sealing rings from sticking together or deforming and interfering with each other under pressure, and ensuring that each sealing ring independently performs its sealing function. The third isolation ring 62 can be a metal ring or a high-strength plastic ring, and its axial thickness can be adapted according to the size of the sealing ring. Shallow grooves can also be provided on its surface to accommodate minor deformation of the sealing ring.

[0123] The first rod 21 and the second rod 22 are connected by internal and external threads. This connection method not only facilitates the assembly and disassembly of the two rods, but also allows adjustment of their relative positions by adjusting the thread engagement depth. The threads can be ordinary fine-pitch threads or trapezoidal threads. Fine-pitch threads are conducive to precise adjustment, while trapezoidal threads can withstand greater axial forces. The first rod 21 is provided with a first annular protrusion 211, and the second rod 22 is provided with a second annular protrusion 222. The protrusions can be integrally formed with the rod body or fixed by welding. Their radial dimension is larger than that of the rod body and is used to axially limit the third sealing ring 61 and the third isolation ring 62.

[0124] The third sealing ring 61 and the third isolation ring 62 are both located between the first annular protrusion 211 and the second annular protrusion 222. When the thread engagement length of the first rod 21 and the second rod 22 is adjusted, the axial distance between the two annular protrusions changes accordingly: as the engagement length increases, the two protrusions move closer together, generating greater axial pressure on the third sealing ring 61 and the third isolation ring 62, enhancing the tightness of the seal ring against the outer wall of the plunger rod assembly 2 and improving the sealing performance; as the engagement length decreases, the pressure decreases, and the sealing performance decreases accordingly. In this way, the sealing performance of the third sealing assembly 6 can be flexibly adjusted.

[0125] The principle behind the above structural design is as follows: Traditional third sealing components have a fixed sealing force. When conveying adhesives of different viscosities or when the sealing ring wears down, the sealing performance cannot be compensated for by adjustment, easily leading to leakage at the connection. This structure, however, adjusts the spacing of the annular protrusions through the threaded connection of two rods, changing the compression of the third sealing ring 61. This allows the sealing force to dynamically adapt to actual working conditions, ensuring reliable sealing when conveying viscous adhesives, while simultaneously compensating for the wear of the sealing ring, thereby further improving the operational stability and adaptability of the plunger pump.

[0126] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit the scope of this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A piston pump characterized in that, include: The pump housing assembly includes a first inner cavity, a second inner cavity, and a third inner cavity arranged sequentially along the axial direction. The first inner cavity has a discharge port communicating with the outside on the side away from the second inner cavity, and the third inner cavity has a feed port on the end away from the second inner cavity. A plunger rod assembly is inserted into the first inner cavity, the second inner cavity, and the third inner cavity. The first inner cavity is isolated into a first sub-cavity and a second sub-cavity by a valve seat formed on the plunger rod assembly. The first sub-cavity and the second sub-cavity are selectively connected through the valve seat formed on the plunger rod assembly. The discharge port is located in the second sub-cavity. The first sealing component is slidably sleeved on the plunger rod assembly and located in the second inner cavity, and follows the axial movement of the plunger rod assembly to seal or open the communication between the second inner cavity and the third inner cavity; A sealing disc is disposed at the end of the plunger rod assembly and located at the feed inlet, and moves axially with the plunger rod assembly to block or open the feed inlet.

2. The piston pump of claim 1, wherein, A second sealing assembly and a third sealing assembly are provided between the pump housing assembly and the plunger rod assembly. The second sealing assembly is located at the end of the second sub-cavity away from the first sub-cavity, and the third sealing assembly is located between the first sub-cavity and the second sub-cavity. The first sealing assembly, the second sealing assembly, and / or the third sealing assembly are sealing structures with adjustable sealing performance.

3. The piston pump of claim 2, wherein, The first sealing assembly includes: The sealing sleeve is a sleeve-shaped structure. One end of the sealing sleeve is used to block or open the channel between the second inner cavity and the third inner cavity as the plunger rod assembly moves axially. The first sealing ring is threadedly connected to the inner wall of the other end of the sealing sleeve; The first sealing ring includes at least two and is disposed inside the sealing sleeve, and the inner wall of the first sealing ring is in contact with and sealed to the outer wall of the plunger rod assembly; A first isolation ring is disposed inside the sealing sleeve, and at least one first isolation ring is located between two adjacent first sealing rings; The first plug ring is configured such that the axial compression of the first sealing ring can be adjusted by rotation to change the sealing performance of the first sealing assembly.

4. The piston pump of claim 3, wherein, One end face of the axial cross-section of the first sealing ring is an inverted V shape or an inverted W shape.

5. The piston pump of claim 4, wherein, One end face of the axial cross-section of the first isolation ring is arched, and when the first isolation ring and the first sealing ring are in contact along the axial direction, the axial faces of the two form a gap area.

6. The piston pump of claim 2, wherein, The pump housing assembly includes: Upper pump housing; the discharge port is located on the upper pump housing; The lower pump housing is detachably connected to the upper pump housing in the axial direction, and the feed inlet is located at the end of the lower pump housing away from the upper pump housing; The second sealing assembly is used to seal the gap between the plunger rod assembly and the upper pump housing.

7. The piston pump of claim 1, wherein, The third inner cavity includes a threaded sleeve that is threadedly connected to the pump housing assembly. There is a stepped structure between the third inner cavity and the second inner cavity. An annular isolation plate is provided at the stepped structure for limiting. The through hole in the middle of the annular isolation plate is a channel connecting the second inner cavity and the third inner cavity. The annular isolation plate is detachably fixed by the threaded sleeve.

8. The piston pump of claim 2, wherein, The second sealing assembly includes: The second sealing ring is disposed at the end of the second sealing assembly away from the first inner cavity and is threadedly connected to the pump housing assembly; The second limiting ring is coaxially arranged with the second blocking ring and is limitedly connected to the pump housing assembly; The second sealing ring includes at least two and is disposed between the second plugging ring and the second limiting ring within the pump housing assembly, wherein the inner wall of the second sealing ring is fitted and sealed to the outer wall of the plunger rod assembly; A second isolation ring is disposed within the pump housing assembly, and at least one second isolation ring is located between two adjacent second sealing rings; The second sealing ring is configured such that the axial compression of the second sealing ring can be adjusted by rotation to change the sealing performance of the second sealing assembly.

9. The piston pump of claim 2, wherein, The plunger rod assembly includes: The first rod has one end extending outside the first inner cavity and the other end located inside the first inner cavity. The second rod passes through the second inner cavity and one end is located in the first inner cavity and is connected to the first rod; the second rod is provided with a first flow channel, and one end of the first flow channel is connected to the first sub-cavity; A sphere is disposed in the receiving cavity between the first rod and the second rod, and is used to block or open the flow port of the first flow channel as the plunger rod assembly moves axially. The third sealing assembly is disposed at the connection between the first rod and the second rod. The other end of the first flow channel passes through the second sealing assembly in the axial direction and communicates with the second sub-cavity. The close ends of the first rod and the second rod, the mating surfaces of the ball and the second sealing assembly form the valve seat.

10. The piston pump of claim 9, wherein, The third sealing assembly includes: The third sealing ring includes at least two and is disposed within the pump housing assembly, and the inner wall of the third sealing ring is in contact with and sealed to the outer wall of the plunger rod assembly; A third isolation ring is disposed within the pump housing assembly, and at least one of the third isolation rings is located between two adjacent third sealing rings; The first rod and the second rod are connected by internal and external threads. The first rod is provided with a first annular protrusion, and the second rod is provided with a second annular protrusion. The third sealing ring and the third isolation ring are both located between the first annular protrusion and the second annular protrusion. The sealing performance of the third sealing assembly is adjusted by the overlap length of the threaded connection between the first rod and the second rod.

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