Adjustable dumbbell and production method thereof

Abstract

Provided are a flow filling adjustable dumbbell and a production method thereof. The adjustable dumbbell includes a handle structure and two counterweight structures respectively arranged at two ends of the handle structure. The counterweight structure includes multiple detachable counterweight units. The counterweight units includes a counterweight plate. The counterweight plate is provided with a closed chamber inside. The enclosed chamber is filled with flowable filling material. The present disclosure uses a thin-walled accommodation housing structure formed by blow molding to carry low-cost flowable filling materials such as iron sand, obtaining a low-cost counterweight plate. The low-cost counterweight plate is then used for modular design of dumbbells. Multiple counterweight units based on flowable filling materials can be disassembled and stacked along an axial direction, allowing the weight of dumbbells to flexibly switch between multiple preset gears. Without relying on complex mechanical adjustment mechanisms, rapid weight adjustment is achieved.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Chinese Patent Application No. 202610192906.0, filed on Feburary 10, 2026, which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to the field of exercise equipment technologies, and in particular, to a flowable filling adjustable dumbbell and a production method thereof.BACKGROUND

[0003] Dumbbells, as one of the most common equipment in strength training, are widely used in home fitness, rehabilitation training, and professional fitness venues. The existing dumbbell products can usually be divided into two categories: fixed weight dumbbells and weight adjustable dumbbells. Fixed weight dumbbells often use metal counterweight structures that are cast or machined as a whole. They have a simple structure and high strength, but due to their nonadjustable weight, users often need to purchase multiple sets of dumbbells of different weight specifications, resulting in large equipment space occupation, high procurement and maintenance costs, and difficulty in meeting the flexible weight adjustment needs of different training stages or users.

[0004] To address the aforementioned issues, various weight adjustable dumbbell solutions have been proposed in existing technology. A common approach is to use integrated dumbbell pads for graded combination, and install metal counterweights of different weights at two ends of the handle through structures such as threads, buckles, or pins, thereby achieving grade adjustment of the overall weight of the dumbbell. Although this type of scheme improves the flexibility of weight adjustment to a certain extent, its counterweight unit usually still adopts a solid metal structure, with high material consumption, complex manufacturing process, and high single piece cost. When multiple weight levels need to be covered, a large number of metal counterweights still need to be configured, which makes it difficult to effectively reduce the overall cost and is not conducive to the promotion and application in mass and family fitness scenarios.

[0005] Besides that, the above-mentioned adjustable dumbbells based on integrated metal counterweights often rely on threaded tightening or simple clamping in structural design to achieve connection between adjacent counterweights. Under long-term use or high-frequency vibration and impact loads, the connecting parts are prone to looseness, abnormal noise, and even detachment, thereby posing certain safety hazards during use. At the same time, in order to ensure the connection strength, the relevant structures usually require high assembly pretension, rendering the disassembly process laborious and the operation inconvenient, making it difficult to balance the stability of the connection and the need for quick disassembly.

[0006] On the other hand, there are still dumbbell solutions in existing technology that use fillers such as iron sand, steel balls, or liquids as the source of counterweights. This type of solution has certain advantages in material cost compared to solid metal counterweights by loading the flowable filling material into a container to achieve the target weight. However, existing dumbbells that use flowable filling bodies are mostly integral or fixed structures, and their weight is difficult to adjust in stages once filled, rendering it impossible to achieve modular weight adjustment. Therefore, it is still difficult to adapt to the needs of switching between different training intensities.

[0007] At the same time, due to the fact that flowable filling bodies usually rely on thin-walled containers for packaging, the related counterweight structures are prone to local deformation, shaking, or displacement after assembly to the dumbbell shell due to the thin wall thickness and insufficient structural rigidity of the container. During the movement, the above problems may further cause collisions, abnormal noises, and even structural damage between the counterweight units, affecting the user experience and safety. The existing technology is relatively insufficient in terms of multi-directional limit and stable fit design between the flowable filling counterweight and the external load-bearing structure, making it difficult to achieve long-term reliable use while ensuring assembly convenience.

[0008] In summary, there are still contradictions in the existing dumbbell technology that are difficult to balance in terms of weight adjustability, manufacturing cost, structural stability, and reliability of use. On the one hand, low-cost flow filling and balancing schemes are difficult to achieve modular gear adjustment. On the other hand, the adjustable dumbbell scheme commonly relies on high-cost integrated metal counterweights, and there is a trade-off between connection stability and disassembly convenience. Therefore, it is still necessary to propose a new technical solution that reduces the cost of weight distribution while ensuring adjustable weight grading and effectively improves the structural stability and safety of the internal and adjacent counterweight units.

[0009] The purpose of the present disclosure is to provide a flow filling adjustable dumbbell and a production method thereof.

[0010] In a first aspect, the present disclosure provides an adjustable dumbbell, including: a handle structure and two counterweight structures respectively provided at two ends of the handle structure; where the counterweight structures include multiple detachable counterweight units; the counterweight units include a counterweight plate; the counterweight plate is provided with a closed chamber inside; the enclosed chamber is filled with a flowable filling material.

[0011] In some embodiments of the present disclosure, iron sand is filled in the closed chamber as the flowable filling material.

[0012] In some embodiments of the present disclosure, the counterweight unit further includes a counterweight housing; the counterweight plate is provided inside the counterweight housing; the counterweight plate includes an accommodation shell, a sealing plug, and a flowable filling material; the accommodation shell is provided with a filling port; the flowable filling material is filled in the accommodation shell; the sealing plug is provided on the filling port of the accommodation shell, thereby forming the closed chamber inside the accommodation shell.

[0013] In some embodiments of the present disclosure, the accommodation shell is formed by blow molding. The filling port of the accommodation shell corresponds to a blow molding port.

[0014] In some embodiments of the present disclosure, the counterweight housing located at an innermost end of the same counterweight structure is integrally formed with one end of the handle structure, and an arc-shaped transition structure is provided at a connection position.

[0015] In some embodiments of the present disclosure, an inner wall of the counterweight housing is provided with one or more limit strips; an outer peripheral surface of the accommodation shell is provided with a limit depression that matches the limit strip.

[0016] In some embodiments of the present disclosure, adjacent two counterweight housings in the same counterweight structure are connected by a rotary joint structure; the rotary joint structure includes positioning protrusions and positioning recesses respectively arranged on opposite sides of adjacent counterweight housings and matched with each other; the positioning recesses are provided with a curved clamp slot; the curved convex strip is provided on the positioning protrusions; the curved convex strip is screwed into the corresponding curved clamp slot; the curved convex strip and the curved clamp slot are provided with mutually matching inclined surface structures.

[0017] In some embodiments of the present disclosure, an elastic locking structure is provided between adjacent two counterweight housings connected by the rotary joint structure; the elastic locking structure includes an elastic protrusion structure and a lock recess; the elastic protrusion structure and the lock recess are respectively provided on opposite sides of two adjacent counterweight housings; in a state where two adjacent counterweight housings are tightened by the rotary joint structure, the elastic protrusion structure on one of the counterweight housings is inserted into the lock recess of the other counterweight housing; the mating surface of the elastic protrusion structure and / or lock recess is curved.

[0018] In some embodiments of the present disclosure, the elastic protrusion structure includes a lock installation slot, a spring, and a lock block; the lock installation slot is provided inside the counterweight housing; one side of the connection cover body is provided with a locking through-hole aligned with the locking installation groove; the lock block extends beyond the outer peripheral surface of the counterweight housing through the locking through-hole and is limited by the locking through-hole; the spring is provided between the lock block and the lock installation slot.

[0019] In some embodiments of the present disclosure, a bottom surface of the lock installation slot is provided with a limit column; one end of the spring facing away from the lock block is sleeved onto the limit column.

[0020] In some embodiments of the present disclosure, an inner wall of the counterweight housing is provided with a convex platform structure; an outer peripheral surface of the accommodation shell is provided with a concave structure that matches the convex platform structure; the convex platform structure on an inner wall of the housing body is hollow, thereby forming the lock installation slot.

[0021] In some embodiments of the present disclosure, the elastic locking structure further includes a circular recess; the circular recess is provided on the counterweight housing and passes through all lock recess; a depth of the circular recess is smaller than a depth of the lock recess.

[0022] In some embodiments of the present disclosure, in a state of being tightened by the rotary joint structure, opposite side edges of adjacent two counterweight housings are aligned; a cross-section of the counterweight housing is a circular or non-circular rotationally symmetric shape; in a case where a cross-section of the counterweight housing is a non-circular rotational symmetric shape, the symmetry order n of the non-circular rotational symmetric shape is a positive integer multiple of the number m of curved clamp slot on the same positioning recess, so that adjacent two counterweight housings can be rotated in multiple different relative orientations.

[0023] In some embodiments of the present disclosure, an inner wall of the counterweight housing is provided with a limit recess; the limit recess and the positioning protrusion are provided at inner and outer sides of the same structure on the counterweight housing; a center position of one side of the accommodation shell is provided with a limit protrusion; the limit protrusion is clamped into the limit recess.

[0024] In some embodiments of the present disclosure, the counterweight housing includes a housing body and a closed cover; the housing body is provided with an opening configured to insert the counterweight plate; the closed cover is provided at the opening of the housing body.

[0025] In some embodiments of the present disclosure, the opening of the housing body is located on one side of the housing body away from the handle structure; in two adjacent counterweight unit, the housing body of the counterweight unit located on the inner side is detachably connected to the closed cover of the counterweight unit located on an outer side. Therefore, the rotary joint structure is provided on the closed cover of an inner side counterweight unit and the housing body of an outer side counterweight unit in adjacent two counterweight units.

[0026] In some embodiments of the present disclosure, the closed cover is connected to an opening of the chamber of the housing body through a buckle connection structure; the buckle connection structure includes a clamp slot and a clamp convex block; the clamp slot is provided on one of the closed cover or the housing body; the clamp convex block is provided on another one of the closed cover or the housing body; the clamp convex block and the clamp slot match each other to form a buckle connection.

[0027] In some embodiments of the present disclosure, the buckle connection structure further includes a limit protrusion; the limit protrusion is provided on the closed cover or the housing body, and is located in a connection gap between the closed cover and the housing body, thereby maintaining stability by constraining a relative maintenance between the closed cover and the housing body.

[0028] In some embodiments of the present disclosure, anti slip stripes are provided on an outer peripheral surface of the handle structure.

[0029] In a second aspect, the present disclosure provides a method for producing a dumbbell, which is used for producing the aforementioned flowable filling adjustable dumbbell, and the method includes:

[0030] preparing the accommodation shell through blow molding process; preparing the handle structure, housing body, closed cover, and sealing plug through injection molding process;

[0031] after loading the flowable filling material into the accommodation shell, installing the sealing plug on the filling port of the accommodation shell to obtain the counterweight plate;

[0032] assembling the housing body, counterweight plate, and closed cover together to obtain the counterweight units;

[0033] stacking and assembling multiple counterweight units and connecting the handle structure to obtain the adjustable dumbbell.

[0034] In some embodiments of the present disclosure, the volume of the accommodation shell is calculated based on a target weight difference of the dumbbell, such that a sum of weights of the housing body, closed cover, and the counterweight plate formed by filling the accommodation shell with iron sand is equal to the target weight difference of the dumbbell.

[0035] The present disclosure has the following beneficial effects.

[0036] 1. The flowable filling type counterweight plate provided by the present disclosure combines low-cost iron sand filling and modular weight adjustable design with dumbbells. Specifically, the present disclosure uses a thin-walled accommodation shell structure formed by blow molding to support low-cost flowable filling bodies such as iron sand, resulting in a low-cost counterweight plate. The low-cost counterweight plate is then used for modular design of dumbbells. Multiple weight units based on flowable filling bodies can be disassembled and stacked along an axial direction, allowing the weight of dumbbells to flexibly switch between multiple preset gears. Without relying on complex mechanical adjustment mechanisms, rapid weight adjustment is achieved, thereby significantly improving the flexibility and adaptability of product use.

[0037] 2. The present disclosure improves the installation stability and reliability of the counterweight plate of the blow molded shell inside the housing body through the collaborative setting of multiple limit fitting structures. Specifically, the present disclosure provides outward convex structures, inward concave structures, and limit depressions around the edges of the accommodation shell of the counterweight plate, and a limit convex platform at the center position of the side surface. A matching concave convex structure is further provided on the housing body, so that the blow molded accommodation shell with low structural strength and easy deformation forms a multi-directional limit and elastic fit inside the counterweight housing. On the premise of ensuring low assembly resistance, it effectively avoids problems such as deformation, shaking, displacement, and abnormal noise of the counterweight plate inside the housing body, ensuring the stability and safety of the dumbbell during training.

[0038] 3. The present disclosure utilizes a combination design of a rotary joint structure and an elastic locking structure to significantly enhance the connection stability between adjacent counterweight units while maintaining the detachable nature of the counterweight units. Specifically, the present disclosure forms a reliable tightening connection through a curved convex strip and an arc-shaped rotary joint slot, and uses the elastic locking structure to achieve automatic locking, effectively preventing loosening problems caused by vibration or impact during use, thereby ensuring quick disassembly and improving the reliability and service life of the overall structure.BRIEF DESCRIPTION OF DRAWINGS

[0039] FIG. 1 is a perspective view of embodiment 1 of the present disclosure.

[0040] FIG. 2 is an explosion schematic diagram of embodiment 1 of the present disclosure.

[0041] FIG. 3 is a schematic diagram of a first axial cross-section of embodiment 1 of the present disclosure.

[0042] FIG. 4 is an exploded schematic diagram of a counterweight unit in embodiment 1 of the present disclosure.

[0043] FIG. 5 is a back schematic diagram of a counterweight housing in embodiment 1 of the present disclosure.

[0044] FIG. 6 is a back schematic diagram of an accommodation shell in embodiment 1 of the present disclosure.

[0045] FIG. 7 is a schematic cross-sectional view of the counterweight unit in embodiment 1 of the present disclosure.

[0046] FIG. 8 is a schematic diagram of a second axial cross-section of embodiment 1 of the present disclosure.

[0047] FIG. 9 is a schematic diagram of an elastic locking structure in embodiment 1 of the present disclosure (i.e., a partially enlarged view of part A in FIG. 8).

[0048] Numeral reference: 1, handle structure; 2, counterweight unit; 2-1, housing body; 2-1-1, convex platform structure; 2-1-2, limit recess; 2-1-3, limit strip; 2-2, counterweight plate; 2-2-1, accommodation shell; 2-2-2, sealing plug; 2-2-3, flowable filling material; 2-2-4, external convex structure; 2-2-5, limit protrusion; 2-2-6, concave structure; 2-2-7, limit depression; 2-3, closed cover; 2-3-1, connection cover body; 2-3-2, end cover body; 3, buckle connection structure; 3-1, limit protrusion; 3-2, clamp slot; 3-3, clamp convex block; 4, rotary joint structure; 4-1, positioning protrusion; 4-2, positioning recess; 4-3, curved clamp slot; 4-4, avoidance slot; 4-5, curved convex strip; 5, elastic locking structure; 5-1, circular recess; 5-2, lock recess; 5-3, lock installation slot; 5-4, limit column; 5-5, spring; 5-6, lock block.DESCRIPTION OF EMBODIMENTS

[0049] The present disclosure will be further explained in combination with the accompanying drawings.Embodiment 1

[0050] As shown in FIGS. 1 and 2, a flow filled adjustable dumbbell includes a handle structure 1 and two symmetrical counterweight structures arranged at two ends of the handle structure 1. Each counterweight structure includes multiple counterweight units 2 that can be disassembled and connected in sequence along an axial direction. An innermost counterweight unit 2 in each counterweight structure is fixed to a corresponding end of the handle structure 1.

[0051] As shown in FIGS. 2 and 3, the counterweight unit 2 includes counterweight housing and a counterweight plate 2-2. The counterweight housing includes a housing body 2-1 and a closed cover 2-3. The housing body 2-1 is provided with an accommodation chamber that is open at one end and closed at the other end. An opening of the accommodation chamber is located on one side of the housing body 2-1 away from the handle structure 1. The counterweight plate 2-2 is provided in the accommodation chamber of the housing body 2-1. The closed cover 2-3 can be detachably fixed at an opening of the accommodation chamber, thereby constraining the counterweight plate 2-2 within the accommodation chamber of the housing body 2-1.

[0052] As shown in FIGS. 4 and 5, the closed cover 2-3 is detachably connected to the opening of the housing body 2-1 through a buckle connection structure 3. The buckle connection structure 3 between the closed cover 2-3 and the housing body 2-1 includes a limit protrusion 3-1, a clamp slot 3-2, and a clamp convex block 3-3. The limit protrusion 3-1 and the clamp slot 3-2 are provided on an outer peripheral surface of the closed cover 2-3. The clamp convex block 3-3 is provided at a position near the opening of the housing body 2-1 of the accommodation chamber. The position of the limit protrusion 3-1 is offset from a position of the clamp convex block 3-3. A position of the clamp slot 3-2 is aligned with the clamp convex block 3-3, and their shapes match each other. An outer side of the clamp convex block 3-3 is provided with a guiding slope, so that during an insertion of the closed cover 2-3 into the opening of the housing body 2-1, the clamp convex block 3-3 can smoothly pass over an edge of the clamp slot 3-2 and be inserted into an interior of the clamp slot 3-2, thereby achieving a reliable connection between the closed cover 2-3 and the housing body 2-1.

[0053] The limit protrusion 3-1 is configured to tightly adhere to an inner wall of the accommodation chamber of the housing body 2-1, avoiding a gap between the closed cover 2-3 and the housing body 2-1 and reducing a connection tightness between the closed cover 2-3 and the housing body 2-1. In this embodiment, a cross-section of the counterweight unit 2 is a rounded rectangle. There are eight clamp slots 3-2 on the closed cover 2-3. All eight clamp slots 3-2 are located near rounded corners of the closed cover 2-3. Four edges of the closed cover 2-3 are each provided with one or more limit protrusions 3-1.

[0054] As shown in FIGS. 6 and 7, the counterweight plate 2-2 includes an accommodation shell 2-2-1, a sealing plug 2-2-2, and a flowable filling material 2-2-3. The accommodation shell 2-2-1 is formed using blow molding technology and has a unique filling port. The flowable filling material 2-2-3 is filled in the accommodation shell 2-2-1. The filling port is configured to insert the flowable filling material 2-2-3 into the accommodation shell 2-2-1. The sealing plug 2-2-2 can be detachably connected to the filling port of the accommodation shell 2-2-1, configured to seal an inner chamber of the accommodation shell 2-2-1 and prevent the leakage of the flowable filling material 2-2-3.

[0055] An outer periphery surface of the accommodation shell 2-2-1 is provided with multiple external convex structures 2-2-4. The external convex structures 2-2-4 are attached to an inner wall of the chamber of the housing body 2-1. A position of the external convex structures 2-2-4 are offset from a position of the clamp convex block 3-3 to avoid the clamp convex block 3-3 blocking the installation of the counterweight plate 2-2 into the housing body 2-1. By setting an external convex structures 2-2-4 around an outer periphery of the thin-walled accommodation shell 2-2-1, a contact area between the accommodation shell 2-2-1 and an inner wall of the chamber of the housing body 2-1 can be reduced, and the resistance of the accommodation shell 2-2-1 being assembled into the housing body 2-1 can be lowered. At the same time, an elastic deformation of the external convex structures 2-2-4 can tightly adhere to an inner wall of the accommodation chamber, thereby avoiding an overall deformation of the accommodation shell 2-2-1, ensuring the connection tightness between the counterweight plate 2-2 and the housing body 2-1, avoiding the shaking of the counterweight plate 2-2 in the housing body 2-1, and reducing the user experience of the dumbbell.

[0056] One side wall of the accommodation chamber of the housing body 2-1 is provided with a convex platform structure 2-1-1. One side edge of the accommodation shell 2-2-1 is provided with a concave structure 2-2-6. The convex platform structure 2-1-1 matches a shape of the concave structure 2-2-6. The convex platform structure 2-1-1 inside the housing body 2-1 is inserted into the concave structure 2-2-6 of the accommodation shell 2-2-1, improving the connection tightness between the counterweight plate 2-2 and the accommodation shell 2-2-1.

[0057] The remaining three side walls of the accommodating chamber of the housing body 2-1 are provided with limit strips 2-1-3. The other three side walls of the accommodation shell 2-2-1 are provided with limit depression 2-2-7. The shape of the limit strip 2-1-3 matches that of the limit depression 2-2-7. The limit strip 2-1-3 inside the housing body 2-1 is inserted into the limit depression 2-2-7 of the accommodation shell 2-2-1, improving the connection tightness between the counterweight plate 2-2 and the accommodation shell 2-2-1. The limit depression 2-2-7 is formed between two adjacent external convex structures 2-2-4.

[0058] A center position of one side of the accommodation shell 2-2-1 is provided with a limit protrusion 2-2-5. The housing body 2-1 is provided with a limit recess 2-1-2 at a center position of a bottom surface of the accommodation chamber. The limit protrusion 2-2-5 is inserted into the limit recess 2-1-2, thereby further improving the connection tightness between the counterweight plate 2-2 and the accommodation shell 2-2-1.

[0059] The flowable filling material 2-2-3 is configured to provide a predetermined weight for the counterweight unit 2. In this embodiment, the flowable filling material 2-2-3 adopts a granular structure filling body, preferably iron sand. Compared to conventional integrated counterweight structures such as iron cakes, the weight of the counterweight plate 2-2 in this embodiment mainly comes from discrete iron sand. The cost of iron sand is much lower than that of integrated counterweight structures such as iron cakes, so the dumbbell provided in this embodiment not only meets the requirement of adjustable weight, but also significantly reduces the production cost of dumbbells.

[0060] Compared to the iron cake type counterweights that require integral casting or machining, the iron sand used in this embodiment has a wide range of sources, low prices, and simple processing technology, and its unit cost is much lower than that of conventional solid metal counterweights. Combined with the thin-walled containment shell structure formed by blow molding, it significantly reduces the amount of metal materials used while meeting weight and strength requirements, fundamentally reducing raw material and manufacturing costs.

[0061] Volume V of the accommodation chamber is designed based on a target weight G of the counterweight plate 2-2. V=G / ρ, where, ρ is the density after filling with iron sand. The target weight G of the counterweight plate 2-2 and a sum of weights of the housing body 2-1 and the counterweight plate 2-2 are the design weights of the counterweight unit.

[0062] In some other embodiments, the flowable filling material 2-2-3 may also use a liquid filling body, such as water or other density liquids.

[0063] The closed cover 2-3 is divided into two types, namely a connection cover body 2-3-1 located between the two housing bodies 2-1, and an end cover body 2-3-2 located at an outermost end. The connection cover body 2-3-1 is provided with a rotary joint structure 4 that matches the housing body 2-1 of the adjacent counterweight unit 2. An outer side of the end cover body 2-3-2 has no connecting structure, and a decorative structure can be provided to improve the aesthetic appearance of the dumbbell end face. In this embodiment, the decorative structure is a wave shaped stepped convex platform structure 2-1-1 that gradually protrudes outward from an outer periphery of the end cover body 2-3-2 towards a center.

[0064] As shown in FIGS. 4 and 5, two adjacent counterweight units 2 in the same counterweight structure are detachably and fixedly connected through the rotary joint structure 4. Specifically, the rotary joint structure 4 includes positioning protrusions 4-1 and positioning recess 4-2 that are matched with each other. The positioning recess 4-2 is provided on an outer side of the closed cover 2-3. The positioning protrusion 4-1 is provided on an outer peripheral surface of a closed end of the housing body 2-1. An inner peripheral side wall of the positioning recess 4-2 and an outer peripheral surface of the positioning protrusion 4-1 are both cylindrical or conical in shape. An outer side of the closed cover 2-3 is specifically one side of the closed cover 2-3 facing away from the counterweight plate 2-2 in the same counterweight unit 2. A closed end outer surface of the housing body 2-1 is specifically one end face of the housing body 2-1 facing the handle structure 1.

[0065] As shown in FIGS. 4 and 5, an inner peripheral wall of the positioning recess 4-2 is provided with four curved clamp slots 4-3 uniformly distributed along a circumferential direction. There is an avoidance slot 4-4 between adjacent curved clamp slots 4-3. The avoidance slot 4-4 is configured to provide space for the curved convex strip 4-5 to enter and exit the positioning recess 4-2. The outer peripheral surface of the positioning protrusion 4-1 is provided with four curved convex strips 4-5 uniformly distributed along a circumferential direction. The positioning protrusion 4-1 is inserted into the positioning recess 4-2, and the four curved convex strips 4-5 are respectively screwed into the curved clamp slots 4-3. The curved convex strips 4-5 and the curved clamp slot 4-3 are provided with mutually matching inclined surface structures, so that adjacent two counterweight units 2 can form a fastening friction force through relative rotation, thereby stably fixing the adjacent two counterweight units 2 together.

[0066] In this embodiment, the position and shape of the positioning protrusion 4-1 on an outer surface of the accommodation shell 2-2-1 and the limit recess 2-1-2 on an inner surface correspond to each other, while simultaneously satisfying the limiting function of the rotary joint counterweight plate 2-2 and maintaining the thin-walled structure at this position, reducing the loss of injection molding materials and further reducing costs.

[0067] As shown in FIGS. 8 and 9, in the same counterweight structure, there are elastic locking structure 5 between adjacent counterweight units 2. The elastic locking structure 5 includes a lock installation slot 5-3, a circular recess 5-1, a lock recess 5-2, a spring 5-5, and a lock block 5-6. The convex platform structure 2-1-1 on an inner wall of the housing body 2-1 is hollow, forming a lock installation slot 5-3. A bottom surface of the lock installation slot 5-3 is provided with a limit column 5-4. The connection cover body 2-3-1 is provided with a locking through-hole that is aligned with the limit column 5-4. The lock block 5-6 is located in the locking through-hole and partially extends beyond the locking through-hole. One end of the spring 5-5 is sleeved on the limit column 5-4, and the other end thereof is pressed against the lock block 5-6. The lock block 5-6 is spherical in shape. One end of an inner wall of the locking through-hole facing away from the lock installation slot 5-3 is provided with an annular limiting arc surface that matches the shape of the lock block 5-6. The lock block 5-6 is pressed against an annular limiting arc surface and cannot fully pass through the locking through-hole due to the limitation. The lock block 5-6 forms an elastic protrusion structure that can shrink inward after being compressed at a position offset from a center of the outer end surface of the counterweight unit 2.

[0068] The circular recess 5-1 is provided on an outer surface of a closed end of the housing body 2-1. The circular recess 5-1 is circular in shape, and its center coincides with the rotation center of the counterweight unit 2. The four lock recess 5-2 are all provided on the circular recess 5-1 and evenly distributed along a circumference of a rotation center of the counterweight unit 2. The positions of the circular recess 5-1 and the lock recess 5-2 match the positions of the lock block 5-6. A depth of the lock recess 5-2 is greater than a depth of the circular recess 5-1. The shape of the lock recess 5-2 matches the shape of the lock block 5-6.

[0069] When two adjacent counterweight units 2 are tightened and fixed by the rotary joint structure 4, the lock block 5-6 located in an inner side counterweight unit 2 is inserted into one of the lock recesses 5-2 located in an outer side counterweight unit 2.

[0070] The elastic locking structure 5 can provide locking force between adjacent two weight units 2, ensuring the connection stability the between adjacent counterweight units 2 while keeping a detachable of the two adjacent counterweight units 2.

[0071] In some other embodiments, the number of the curved convex strip 4-5 and the avoidance slot 4-4 is not four, but other feasible numbers, such as 1, 2, 3, and 5.

[0072] In this embodiment, the counterweight unit 2 located at an innermost end is integrally formed with the corresponding end of the handle structure 1, so the housing body 2-1 of the counterweight unit 2 located at the innermost end does not have the rotary joint structure 4.

[0073] In some other embodiments, the counterweight unit 2 located at the innermost end is detachably connected to the corresponding end of the handle structure 1. The connection methods for detachable connections include but are not limited to rotary connections, snap connections, bolt connections, and pin connections. In the case of using a rotary connection, a rotary joint structure 4 and an elastic locking structure 5 are provided between the housing body 2-1 of the innermost counterweight unit 2 and the handle structure 1. In other embodiments, the counterweight unit 2 located at the innermost end is non detachably fixedly connected to the corresponding end of the handle structure 1. The non removable fixed connection methods include but are not limited to bonding and welding.

[0074] In some embodiments, anti-slip stripes are provided on an outer peripheral surface of the handle structure 1.

[0075] In this embodiment, the sum of the weight of the handle structure 1 and the two innermost non detachable counterweight units 2 is 2.2 pounds. The weight of detachable counterweight unit 2 is 0.7 pounds. By increasing or decreasing the number of counterweight units 2 in the two counterweight structures, the weight of the flow filling adjustable dumbbell can be switched between 2.2 pounds, 3.6 pounds, and 5 pounds. Holding a dumbbell in each hand can create a 10 pound of dual hand exercise weight.

[0076] In some other embodiments, the sum of the weight of the handle structure 1 and the two innermost non detachable counterweight units 2 is 4 pounds. The weight of detachable counterweight unit 2 is 1.5 pounds. By increasing or decreasing the number of counterweight units 2 in the two counterweight structures, the weight of the flow filling adjustable dumbbell can be switched between 4 pounds, 7 pounds, and 10 pounds. Holding a dumbbell in each hand can create 20 pounds of dual hand exercise weight.

[0077] Compared with conventional adjustable dumbbells, the flow filling adjustable dumbbell provided in this embodiment does not require the use of metal cast weight plates, but instead uses iron sand contained in the blow molded accommodation shell 2-2-1 to provide weight. At the same time, the solution of accommodation shell 2-2-1, which can be removed as a whole with the counterweight unit, realizes the quantitative increase or decrease of iron sand according to needs, and achieves the rapid adjustment of dumbbell weight grading.Embodiment 2

[0078] A flow filling adjustable dumbbell, a difference between this embodiment and embodiment 1 is that in the weight unit 2, the closed cover 2-3 is located on one side of the housing body 2-1 near the handle structure 1.Embodiment 3

[0079] A flow filling adjustable dumbbell, a difference between this embodiment and embodiment 1 is that the clamp slot 3-2 in the buckle connection structure 3 is located on the housing body 2-1, and the clamp convex block 3-3 is located on the closed cover 2-3.Embodiment 4

[0080] A flow filling adjustable dumbbell, a difference between this embodiment and embodiment 1 is that the positioning protrusion 4-1 in the rotary joint structure 4 is located on the closed cover 2-3, and the positioning recess 4-2 is located on the housing body 2-1. The accommodation shell 2-2-1 is provided with a recess structure corresponding to a position of the positioning recess 4-2.Embodiment 5

[0081] A production method for the flow filling adjustable dumbbells, including the following steps.

[0082] Step 1: according to weight grading requirements of dumbbells, setting a target weight difference (i.e. a difference between two adjacent two grade weights of dumbbells). Calculating the volume of the accommodation shell 2-2-1 so that it is filled with iron sand to form a counterweight plate with a predetermined weight. A sum of the weights of the counterweight plate filled with iron sand, the housing body 2-1, and the closed cover 2-3 is equal to M or 0.5M, where M is a target weight difference of the dumbbell. In this embodiment, since the counterweight units need to be added or removed in pairs to avoid weight imbalance during grip, m=0.5M. According to the volume of the accommodation shell 2-2-1, it involves the size of the accommodation shell 2-2-1.

[0083] Step 2: preparing the accommodation shell 2-2-1 through blow molding process. Preparing the handle structure 1, the housing body 2-1, the closed cover 2-3, and the sealing plug 2-2-2 through injection molding process.

[0084] Step 3: using a funnel to load iron sand into the accommodation shell 2-2-1, and then installing a sealing plug 2-2-2 on the filling port of the accommodation shell 2-2-1 to obtain a counterweight plate 2-2 with the target weight.

[0085] Step 4: installing the spring 5-5 and lock block 5-6 into the lock installation slot 5-3 of the housing body 2-1, and clamping and fixing the closed cover 2-3 at the opening of the housing body 2-1 to obtain the complete counterweight unit 2.

[0086] Step 5: stacking and assembling multiple weight units 2, and connecting the handle structure 1 to obtain a complete flow filling adjustable dumbbell.

Claims

1. An adjustable dumbbell, comprising: a handle structure and two counterweight structures respectively provided at two ends of the handle structure; wherein the counterweight structures comprise multiple detachable counterweight units; the counterweight units comprise a counterweight plate; the counterweight plate is provided with a closed chamber inside; the enclosed chamber is filled with a flowable filling material .

2. The adjustable dumbbell according to claim 1, wherein iron sand is filled in the closed chamber as the flowable filling material .

3. The adjustable dumbbell according to claim 1, wherein the counterweight unit further comprises a counterweight housing; the counterweight plate is provided inside the counterweight housing; the counterweight plate comprises an accommodation shell, a sealing plug, and a flowable filling material ; the accommodation shell is provided with a filling port; the flowable filling material is filled in the accommodation shell; the sealing plug is provided on the filling port of the accommodation shell, thereby forming the closed chamber inside the accommodation shell.

4. The adjustable dumbbell according to claim 3, wherein the accommodation shell is formed by blow molding.

5. The adjustable dumbbell according to claim 3, wherein the counterweight housing located at an innermost end of the same counterweight structure is integrally formed with one end of the handle structure, and an arc-shaped transition structure is provided at a connection position.

6. The adjustable dumbbell according to claim 3, wherein an inner wall of the counterweight housing is provided with one or more limit strips; an outer peripheral surface of the accommodation shell is provided with a limit depression that matches the limit strip.

7. The adjustable dumbbell according to claim 3, wherein adjacent two counterweight housings in the same counterweight structure are connected by a rotary joint structure; the rotary joint structure comprises positioning protrusions and positioning recesses respectively arranged on opposite sides of adjacent counterweight housings and matched with each other; the positioning recesses are provided with a curved clamp slot; the curved convex strip is provided on the positioning protrusions; the curved convex strip is screwed into the corresponding curved clamp slot; the curved convex strip and the curved clamp slot are provided with mutually matching inclined surface structures.

8. The adjustable dumbbell according to claim 7, wherein an elastic locking structure is provided between adjacent two counterweight housings that are connected by the rotary joint structure; the elastic locking structure comprises an elastic protrusion structure and a lock recess; the elastic protrusion structure and the lock recess are respectively provided on opposite sides of two adjacent counterweight housings; in a state where two adjacent counterweight housings are tightened by the rotary joint structure, the elastic protrusion structure on one of the counterweight housings is inserted into the lock recess of the other counterweight housing; the mating surface of the elastic protrusion structure and / or lock recess is curved.

9. The adjustable dumbbell according to claim 8, wherein the elastic protrusion structure comprises a lock installation slot, a spring, and a lock block; the lock installation slot is provided inside the counterweight housing; one side of the connection cover body is provided with a locking through-hole that is aligned with the locking installation groove; the lock block extends beyond the outer peripheral surface of the counterweight housing through the locking through-hole and is limited by the locking through-hole; the spring is provided between the lock block and the lock installation slot.

10. The adjustable dumbbell according to claim 9, wherein a bottom surface of the lock installation slot is provided with a limit column; one end of the spring facing away from the lock block is sleeved onto the limit column.

11. The adjustable dumbbell according to claim 9, wherein an inner wall of the counterweight housing is provided with a convex platform structure; an outer peripheral surface of the accommodation shell is provided with a concave structure that matches the convex platform structure; the convex platform structure on an inner wall of the housing body is hollow, thereby forming the lock installation slot.

12. The adjustable dumbbell according to claim 9, wherein the elastic locking structure further comprises a circular recess; the circular recess is provided on the counterweight housing and passes through all lock recess; a depth of the circular recess is smaller than a depth of the lock recess.

13. The adjustable dumbbell according to claim 8, wherein in a state of being tightened by the rotary joint structure, opposite side edges of adjacent two counterweight housings are aligned; a cross-section of the counterweight housing is a circular or non-circular rotationally symmetric shape; in a case where a cross-section of the counterweight housing is a non-circular rotational symmetric shape, the symmetry order n of the non-circular rotational symmetric shape is a positive integer multiple of the number m of curved clamp slot on the same positioning recess.

14. The adjustable dumbbell according to claim 7, wherein an inner wall of the counterweight housing is provided with a limit recess; the limit recess and the positioning protrusion are provided at inner and outer sides of the same structure on the counterweight housing; a center position of one side of the accommodation shell is provided with a limit protrusion; the limit protrusion is clamped into the limit recess.

15. The adjustable dumbbell according to claim 3, wherein the counterweight housing comprises a housing body and a closed cover; the housing body is provided with an opening configured to insert the counterweight plate; the closed cover is provided at the opening of the housing body.

16. The adjustable dumbbell according to claim 15, wherein the opening of the housing body is located on one side of the housing body away from the handle structure; in two adjacent counterweight unit, the housing body of the counterweight unit located on the inner side is detachably connected to the closed cover of the counterweight unit located on an outer side.

17. The adjustable dumbbell according to claim 15, wherein the closed cover is connected to an opening of the chamber of the housing body through a buckle connection structure; the buckle connection structure comprises a clamp slot and a clamp convex block; the clamp slot is provided on one of the closed cover or the housing body; the clamp convex block is provided on another one of the closed cover or the housing body; the clamp convex block and the clamp slot match each other to form a buckle connection.

18. The adjustable dumbbell according to claim 17, wherein the buckle connection structure further comprises a limit protrusion; the limit protrusion is provided on the closed cover or the housing body, and is located in a connection gap between the closed cover and the housing body.

19. The adjustable dumbbell according to claim 1, wherein anti slip stripes are provided on an outer peripheral surface of the handle structure.

20. A method for producing dumbbells, wherein it is used for producing the adjustable dumbbell according to claim 15; and the method comprises:preparing the accommodation shell through blow molding process; preparing the handle structure, housing body, closed cover, and sealing plug through injection molding process;after loading the flowable filling material into the accommodation shell, installing the sealing plug on the filling port of the accommodation shell to obtain the counterweight plate;assembling the housing body, counterweight plate, and closed cover together to obtain the counterweight units;stacking and assembling multiple counterweight units and connecting the handle structure to obtain the adjustable dumbbell.

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