Chair

Abstract

This utility model relates to the furniture industry, specifically to chair designs primarily made of sheet wood materials, in particular multilayer plywood. The chair comprises a seat, a backrest, and legs. The backrest elements are made of plywood. The legs are made of separate flat plywood elements. The backrest is secured to two parallel plywood posts. A central support plate made of plywood is mounted on the underside of the seat, to which the legs are radially attached. Each leg and backrest post are secured to the central support plate by means of threaded fasteners. The central support plate is provided with groove-shaped cutouts in which the inner ends of the legs and backrests are placed. The central support plate is secured to the underside of the seat by means of threaded fasteners. The technical result consists in increasing the rigidity and reliability of the chair. 8 clauses, 3 figs.

Description

[0001] This utility model relates to the furniture industry, specifically to chair designs intended for use in residential, public, administrative, and commercial spaces. The utility model can be used in the manufacture of furniture primarily from sheet wood materials, in particular, plywood.

[0002] The information search revealed technical solutions related to seating furniture, including the designs of chairs and stools with a seat, backrest and support elements.

[0003] A chair is known under Russian patent for utility model No. RU5322U1, "Chair." The chair comprises a seat, backrest, frame, and legs. The legs are T-shaped and mounted within T-shaped supports, allowing for discrete movement. This solution is primarily aimed at adjusting the seat height. A disadvantage of this solution, as applied to the claimed utility model, is the presence of a frame and guide supports, which complicate the design, as well as the chair's primary plywood construction and the lack of a central plywood radial leg attachment.

[0004] A piece of furniture is known under Russian Federation Patent for Utility Model No. RU34330U1, "Furniture Piece." The description describes a stool consisting of a seat, four legs, and a fastening device in the form of a square tie rod, the corners of which are bulged with screw sockets. A threaded stud is inserted into the upper end of each leg to engage with the tie rod socket. A disadvantage of this solution is the use of a separate tie rod with screw sockets and the lack of radial fastening of the flat plywood legs to the central plywood support plate attached to the underside of the seat.

[0005] An adjustable chair is known under Russian Patent No. RU2664662C2, "Adjustable Chair." This solution discloses the possibility of manufacturing chair components from a sheet of plywood using a CNC milling machine. The design comprises flat side panels with openings, seat plates, and footrests. A drawback of this solution is the different design of the support system: the chair is adjustable, contains side panels, and lacks a leg attachment point in the form of a central support platform to which the individual legs are radially attached.

[0006] A stool is known under Russian patent No. RU238907U1, "Stool." The stool consists of a round seat and two U-shaped uprights, which can be made of plywood. The seat has central intersecting grooves and cutouts, and the uprights are installed in the grooves with tension. The disadvantages of this design include the use of a grooved connection between the uprights and the seat, the lack of separate inclined legs, the absence of a backrest, and the absence of a central support platform to which the legs are attached with threaded elements.

[0007] A chair is known under Russian patent No. RU2124856C1, "Chair." The chair comprises a tubular metal frame, the legs of which are fastened in pairs with crossbars, a seat support, and a backrest on uprights. A drawback of this design is the construction of the supporting frame from tubular metal elements, the presence of crossbars, and the absence of a plywood central support platform with radial fastenings for the flat plywood legs.

[0008] The closest technical solution to the claimed utility model is the piece of furniture according to Russian Patent No. RU34330U1, as it comprises a seat, legs, and a fastener for connecting the legs to the seat using threaded elements. However, in the known solution, the fastener is a square coupler with screw sockets, and the legs interact with the coupler via studs.

[0009] The claimed utility model differs from the prototype in that the chair is made primarily of plywood, a central support platform made of plywood is installed on the underside of the seat, and each leg is made of a separate flat plywood blank and secured to the said central support platform by means of threaded fasteners, while the legs are located radially relative to the central support platform and are inclined outward relative to the vertical axis of the chair.

[0010] These distinctive features ensure increased spatial rigidity of the structure, simplified manufacturing, reduced weight of the product, a reduction in the number of metal and frame elements, as well as increased reliability of leg fastening due to load distribution through the central plywood support platform.

[0011] The proposed design provides increased rigidity and reliability of the chair.

[0012] The technical result is achieved due to the fact that the chair contains a seat, a backrest and legs, wherein the backrest elements are made of plywood, and the legs are made of separate flat plywood elements secured to the underside of the seat by means of fasteners, characterized in that a support platform made of plywood is installed on the underside of the seat, to which the legs are radially attached, and each leg is secured to the lower plane of the seat by means of threaded fasteners.

[0013] Preferably, the central support platform is provided with groove-shaped cutouts in which the inner ends of the legs and backs are placed.

[0014] Preferably, the central support platform is secured to the bottom surface of the seat by means of threaded fasteners.

[0015] The legs are preferably made of multi-layer birch plywood with a thickness of 15 to 30 mm.

[0016] Each leg is preferably made in the form of an L-shaped solid figure.

[0017] Preferably the legs are located in pairs at the front and back of the seat.

[0018] Preferably the backrest is fixed on two parallel plywood posts.

[0019] Preferably, the backrest posts extend through the seat area and are additionally connected to its supporting part.

[0020] The seat and backrest are preferably equipped with soft elements.

[0021] The legs are preferably mounted in a detachable manner.

[0022] The stated combination of design features is aimed at achieving a synergistic technical result, resulting in a significant increase in the chair's rigidity and reliability through the creation of an integrated spatial load-bearing system, in which each element and its connection contribute to the redistribution and absorption of stress. The chair's assembly, comprising the seat, backrest, and legs, forms a basic closed load-bearing structure, where external loads from the user's weight and dynamic impacts are transmitted along predictable trajectories, a fundamental condition for the overall increase in rigidity and reliability.

[0023] The plywood construction of the backrest elements, combined with the legs made from individual flat plywood elements secured to the underside of the seat with fasteners, provides the foundation for increased chair rigidity and reliability thanks to the anisotropic strength and stability of laminated wood. Unlike solid wood, plywood exhibits high resistance to delamination and warping under changing humidity and temperature conditions. Fastening the flat elements to the underside of the seat creates additional stiffening ribs that effectively counteract torsional and deflective deformations, directly enhancing the chair's rigidity and reliability.

[0024] The plywood support platform on the underside of the seat, to which the legs are radially attached, is central to increasing the chair's rigidity and reliability, as this platform functions as a distribution unit. The radial connection of the legs to the platform transforms the point loads supported by each leg into membrane stresses distributed over a large area of ​​the seat, preventing stress concentration at critical fastening points and significantly reducing the risk of fatigue failure of the load-bearing panel material, thereby increasing the chair's rigidity and reliability.

[0025] Securing each leg to the underside of the seat with threaded fasteners plays a key role in increasing the chair's rigidity and reliability, as it creates a controlled tightening force that ensures the connection remains secure during operation under alternating loads. The threaded fastener pair creates a powerful frictional bond between the mating surfaces, eliminating play and micro-movements that are the main causes of loss of geometric stability, thereby guaranteeing long-term increased rigidity and reliability.

[0026] To enhance this effect, the design preferably incorporates groove-shaped cutouts on the central support surface, which accommodate the inner ends of the legs and backrests. This further enhances the chair's rigidity and reliability through geometric locking. This groove-shaped locking prevents the mating parts from absorbing bending moments and shear forces, transmitting them not only through friction in the threaded connection but also through the compression and thrust forces of the groove's side surfaces. This dramatically increases the resistance of the assembly to alternating loads and enhances the rigidity and reliability of the chair as a whole.

[0027] Furthermore, securing the central support pad to the underside of the seat with threaded fasteners ensures secure integration of the entire frame with the seat's supporting surface, directly increasing the chair's rigidity and reliability. The multi-point threaded connection uniformly tightens the pad across the entire contact surface, transforming the seat and substructure into a single box-shaped system that effectively resists both vertical shear deformations and tangential shear forces generated when the user sits, thereby enhancing the chair's rigidity and reliability.

[0028] The preferred choice of multi-layer birch plywood legs, 15 to 30 mm thick, plays a critical role in increasing the chair's rigidity and reliability, owing to the exceptional physical and mechanical properties of this material. Birch plywood of this thickness range has high specific static bending strength and elasticity, allowing the legs to withstand significant eccentric loads without residual deformation or the risk of brittle fracture. The increased thickness ensures a significant moment of inertia in the cross-section of the uprights, which directly translates into increased rigidity and reliability when used on uneven floor surfaces and when the occupant's center of gravity shifts.

[0029] The L-shaped, one-piece construction of each leg significantly increases the chair's rigidity and reliability due to the absence of mechanical joints in the transition area from the vertical support to the horizontal support. The monolithic structure of the L-shaped plywood element eliminates the formation of a "hinge" at the point of application of the maximum bending moment, which inevitably weakens prefabricated structures. The integrity of the fibers and adhesive layers during bending allows for smooth transfer of forces to the floor, ensuring an elastic response to dynamic movements and thereby significantly increasing the chair's rigidity and reliability without increasing its weight.

[0030] The leg configuration, with pairs placed at the front and back of the seat, optimizes the static performance of the frame to enhance the chair's rigidity and reliability. The paired, symmetrical placement of the supports at the dominant weight-bearing points (under the hips and in the ischial tuberosity area) ensures uniform loading of all structural elements, preventing distortion and twisting of the frame base. This increases the chair's rigidity and reliability and prevents progressive loosening of the components.

[0031] Mounting the backrest on two parallel plywood posts effectively increases the chair's rigidity and reliability by creating a symmetrical bio-support structure that absorbs the horizontal loads from the user's back. This design eliminates asymmetric moments at the backrest-seat attachment point, acting as a spatial truss, where both posts evenly distribute bending stresses across the seat plane and then onto the radially attached legs, ensuring a systematic increase in the chair's rigidity and reliability.

[0032] Additionally, the backrest supports extend through the seat area and are connected to its supporting structure, implementing the principle of continuous force transmission, which is critical for increasing the chair's rigidity and reliability. Extending the supports below the seat level and firmly securing them to the support surface or directly to the base elements creates a continuous force connection, ensuring that the moment that tilts the backrest backward is absorbed by the entire seat and legs as a single unit, greatly increasing the system's resistance and ensuring increased rigidity and reliability under prolonged cyclic loading.

[0033] The use of soft elements on the seat and backrest, in addition to their ergonomic function, indirectly enhances the rigidity and reliability of the chair as an engineering structure. The soft, pliable layer dampens peak dynamic loads that occur during a sudden landing, converting some of the kinetic energy into deformation of the upholstery and padding. This reduces the amplitude of impact impulses transmitted to the plywood frame and, consequently, to the threaded fasteners, preventing their fatigue loosening and thereby ensuring long-term improvement in the rigidity and reliability of the chair under real-world conditions.

[0034] Finally, the preferred method of disassembling the legs using threaded connections ensures the chair's rigidity and reliability are maintained throughout its lifespan. The technological ability to repeatedly assemble and disassemble the components without losing their load-bearing capacity, characteristic of controlled threaded connections within the plywood, allows for periodic tightening of the fasteners, compensating for natural shrinkage and stress relaxation in the wood, thereby restoring and consistently maintaining the chair's high level of rigidity and reliability.

[0035] Fig. 1 shows a general view of the chair from the front.

[0036] Fig. 2 shows a general view of the chair from the back.

[0037] Fig. 3 shows a bottom view of the leg mounting unit.

[0038] The chair is made primarily of multi-layer plywood and comprises a seat, a backrest, support legs, a central support platform formed on the underside of the seat, and fasteners for connecting the said parts together.

[0039] The chair's main supporting elements are made of multi-layer plywood, primarily birch. The thickness of the plywood used can range from 12 to 30 mm, with 15 to 24 mm being preferred. The use of multi-layer plywood ensures high bending strength, resistance to cracking at the fastening points, reduced weight, and the ability to fabricate parts using milling or other mechanical processing of the sheet material.

[0040] The seat is a flat supporting element, preferably round or oval in plan. It can also be rectangular, trapezoidal, or have other rounded corners. The seat width can range from 320 to 520 mm, preferably from 380 to 460 mm. The seat depth can range from 300 to 500 mm, preferably from 360 to 440 mm. The thickness of the seat base can range from 12 to 30 mm, preferably from 15 to 21 mm.

[0041] The upper surface of the seat can be fitted with a soft pad made of polyurethane foam, foam rubber, latex, or other elastic material. The thickness of the soft pad can range from 10 to 80 mm, preferably from 20 to 50 mm. The outer surface of the soft pad can be covered with fabric, leather, faux leather, or other furniture upholstery.

[0042] A central support plate is installed on the underside of the seat. It is designed to support the seat's load and transfer it to the legs. The central support plate is a separate element made of multi-layer plywood. The plate can be round, oval, polygonal, or other shaped. A round plate is preferred.

[0043] The diameter of the central support plate can be between 160 and 380 mm, preferably between 200 and 320 mm. The thickness of the plate can be between 12 and 30 mm, preferably between 15 and 24 mm. The central support plate can be secured to the underside of the seat using screw connections, adhesive bonding, furniture fasteners, dowels, or a combination of these.

[0044] The peripheral sections of the central support platform are cut out in the form of grooves designed to accommodate the inner ends of the legs. The number of grooves corresponds to the number of chair legs. For a four-legged version, four grooves are made around the circumference of the platform.

[0045] Each groove is open on the outer edge of the central support surface and is formed by two side walls and a bottom surface. The groove width can range from 12 to 35 mm, preferably from 15 to 25 mm. The groove depth can range from 20 to 120 mm, preferably from 35 to 80 mm.

[0046] The inner ends of the legs are partially positioned within the corresponding grooves. The side surfaces of the legs interact with the side surfaces of the grooves, providing additional mechanical fixation of the legs relative to the central support surface. This design allows some of the resulting loads to be absorbed directly by the walls of the grooves, reducing the load on the fasteners.

[0047] The legs are made from individual flat plywood blanks. Each leg can be straight, curved, or broken. Leg thickness can range from 12 to 30 mm, preferably from 15 to 24 mm. Leg width can range from 35 to 120 mm, preferably from 45 to 80 mm.

[0048] The height of the legs is selected depending on the intended use of the product and can range from 300 to 520 mm. The height of the seating surface from the floor can range from 380 to 550 mm, with a preferred height of 430 to 480 mm.

[0049] The legs are installed at an angle relative to the vertical axis of the product. The angle can range from 3 to 25°, preferably from 5 to 15°. The front legs can be tilted forward and to the sides, while the rear legs can be tilted backward and to the sides. This arrangement increases the support surface area and improves the product's stability.

[0050] The legs are secured to the grooves of the central support platform using threaded fasteners. These fasteners can include furniture screws, bolts, dowels, Euro screws, studs with nuts, screws with threaded bushings, or other detachable fasteners. The diameter of the fasteners can range from 4 to 10 mm, with 5 to 8 mm being preferred. Each leg can be secured with one, two, three, or more fasteners.

[0051] The backrest is made of plywood and has a predominantly curved shape with rounded side sections. The backrest width can range from 250 to 550 mm, preferably from 320 to 450 mm. The backrest height can range from 150 to 450 mm, preferably from 200 to 350 mm. The plywood base thickness of the backrest can range from 12 to 30 mm.

[0052] The front of the backrest can also feature a soft element with decorative upholstery. The thickness of the soft element can range from 10 to 70 mm.

[0053] The backrest is connected to the seat by two vertical plywood posts. The posts can be straight or shaped like elongated planks. The thickness of the posts can range from 12 to 30 mm, preferably from 15 to 24 mm. The width of the posts can range from 20 to 100 mm, preferably from 30 to 60 mm. The distance between the posts can range from 50 to 250 mm.

[0054] The posts can be attached to the seat and backrest using screws, bolts, furniture fasteners, dowels, adhesive joints, or a combination of these.

[0055] During operation, the user's load is supported by the seat and transferred to the central support plate. The load is then distributed among all legs through their slots and fasteners. The slots in the central support plate limit lateral movement of the legs and increase the connection's resistance to torsional and bending loads.

[0056] The radial arrangement of the legs relative to the central support platform ensures even load distribution between the supports and creates a rigid spatial structure. This results in increased leg security, increased rigidity, reduced joint loosening, and a longer service life.

Claims

1. A chair comprising a seat, a backrest and legs, wherein the backrest elements are made of plywood and the legs are made of separate flat plywood elements, characterized in that the backrest is secured to two parallel plywood posts, and a central support platform made of plywood is mounted on the underside of the seat, to which the legs are radially attached, wherein each leg and backrest post are secured to the central support platform by means of threaded fasteners.

2. A chair according to paragraph 1, characterized in that the central support platform has cutouts in the form of grooves in which the inner ends of the legs and backs are placed.

3. A chair according to item 1, characterized in that the central support platform is secured to the lower surface of the seat by means of threaded fasteners.

4. A chair according to paragraph 1, characterized in that the legs are made of multilayer birch plywood with a thickness of 15 to 30 mm.

5. A chair according to item 1, characterized in that each leg is made in the form of an L-shaped solid figure.

6. A chair according to item 1, characterized in that the legs are located in pairs at the front and back of the seat.

7. A chair according to item 6, characterized in that the backrest posts pass through the seat area and are additionally connected to its supporting part.

8. A chair according to item 1, characterized in that the seat and back are equipped with soft elements.

9. A chair according to item 1, characterized in that the leg fastening is detachable.

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