Chair

Abstract

This utility model relates to the furniture industry, specifically to chair design. The chair comprises a seat, a backrest, and a supporting frame comprising front legs, rear legs, and a seat section. The supporting frame elements are made of plywood. The seat section is formed by two side crossbars, a front crossbar, and a rear crossbar, connected to each other to form a quadrangular frame contour by means of threaded fasteners. Each rear leg is extended above the seat level and simultaneously forms a support post for the backrest. The supporting frame elements are made of plywood with a thickness of 8 to 36 mm. The technical result consists in increasing the rigidity, reliability, and manufacturability of the connection of the legs with the crossbars under the seat. 9 cl., 4 fig.

Description

[0001] This utility model relates to the furniture industry, specifically to the design of chairs comprising a seat, backrest, and supporting frame made of plywood elements. The utility model can be used in the manufacture of household, interior, dining, cafe-restaurant, and other chairs requiring a rigid, technologically advanced, and repairable connection between the legs and the seat without the use of complex tenon, adhesive, or hidden joints. Various chair designs are known from the prior art, comprising a seat, backrest, legs, and frame elements designed to connect the legs together and support the loads of the seat.

[0002] A chair patented by RU2124856C1 is known. It comprises a tubular metal frame, the legs of which are fastened in pairs by crossbars, a seat support, and a backrest on uprights connected by crossbars. In this solution, structural rigidity is provided by the metal tubular elements, crossbars, and backrest uprights. This chair is one of a type of design in which the legs are connected by crossbars, and the seat support is connected to the supporting frame.

[0003] A disadvantage of the aforementioned alternative to the claimed utility model is that it is based on a metal tubular frame and does not disclose the chair's design, in which the supporting frame elements are made of plywood. This alternative lacks a rectangular seat section formed by plywood side, front, and rear crossbars connected by threaded fasteners. It also fails to disclose the arrangement in which the front and rear legs are attached to the outer side of the side crossbars, and the front and rear crossbars are attached to the inner side of the same side crossbars. Consequently, this known solution does not provide the claimed technical result of increasing the rigidity, reliability, and ease of connection between the legs and the seat section in the plywood chair frame.

[0004] Also known is a chair patented by RU13463U1, comprising a tubular metal frame with side legs joined in pairs by arched crossbars, a seat support, and a semicircular backrest supported by rear-facing uprights. In this solution, the rear leg uprights form the backrest, and the frame elements are connected by tubular and arched crossbars.

[0005] A drawback of this alternative is that it also uses metal tubular structures and does not reveal the chair's plywood supporting frame. The frame elements in this solution are connected using a different design, in which the side legs are fastened in pairs with arched crossbars, rather than using a rectangular seat section made of plywood crossbars. This alternative does not utilize the side crossbar as a common base element, with the front and rear legs attached to its outer side and the front and rear crossbars attached to its inner side. Therefore, this existing solution does not address the challenge of creating a technologically advanced plywood frame with detachable threaded connections and increased rigidity of the leg-to-seat attachment points.

[0006] A technical solution, also known from publication WO2006061669A1, relates to a reinforcing element for a wooden chair or armchair frame. This solution proposes a metal C-shaped reinforcing element that is installed inside the wooden seat frame and connects the front, side, and rear crossbars. The reinforcing element is secured with screws and is designed to increase the mechanical strength of the wooden frame in the leg area, as these areas are subject to increased operational loads.

[0007] The stated solution is closer to the claimed utility model, as it addresses the problem of increasing the rigidity of a wooden chair frame in the area of ​​the seat and legs. However, its drawback is the need for an additional metal reinforcement, made separately from the main frame elements. The rigidity of the known design is achieved not by the relative positioning and direct connection of the plywood elements of the chair, but by introducing a separate metal component into the wooden frame. However, the known solution does not disclose the seat section, which is formed by a rectangular frame contour made of plywood crossbars, where the side crossbars simultaneously serve as longitudinal frame elements and as basic connecting elements for attaching the legs and crossbars.

[0008] The closest technical solution to the claimed utility model is WO2006061669A1, as it aims to increase the strength and rigidity of the wooden chair frame in the seat and leg area. In this known solution, the wooden chair frame is reinforced with a metal C-shaped element, which is placed inside the frame and connected to the front, side, and rear crossbars.

[0009] A drawback of the prototype is that it does not provide for the chair's supporting frame to be constructed of plywood, forming a quadrangular seat section connected by threaded fasteners. The prototype lacks a structural design in which the front and rear crossbars are positioned between the side crossbars and attached to their inner sides, while the front and rear legs are attached to the outer sides of the side crossbars. Furthermore, in the prototype, the side crossbar does not simultaneously function as the main longitudinal element of the seat section and as the base element for attaching the front leg, rear leg, front crossbar, and rear crossbar. The prototype also does not disclose the rear leg being constructed as a single, elongated plywood piece that simultaneously serves as the chair's support leg and backrest support post.

[0010] Due to the aforementioned shortcomings, known solutions do not fully improve the rigidity, reliability, and processability of the leg-to-seat connection in a plywood chair without the use of additional metal reinforcements and complex concealed joints. The claimed utility model eliminates these shortcomings by implementing a seat section consisting of a rectangular frame contour made of plywood crossbars connected by threaded fasteners. The side crossbars serve as the primary connecting elements: the front and rear legs are attached to them from the outside, and the front and rear crossbars are attached to them from the inside. This design allows for the creation of a compact, technologically advanced, and rigid plywood frame, in which the loads from the seat and backrest are distributed through the closed seat frame to the front and rear legs.

[0011] The objective of the utility model is to create a chair design in which the connection of the legs to the seat crossbars is carried out in a simple, technological and reliable way without the need for complex hidden connections.

[0012] The technical result is to increase the rigidity, reliability and manufacturability of the connection of the legs with the crossbars under the seat.

[0013] The specified technical result is achieved in that the chair contains a seat, a backrest and a supporting frame including front legs, rear legs and a seat section, characterized in that the elements of the supporting frame are made of plywood, the seat section is formed by two side crossbars, a front crossbar and a rear crossbar, connected to each other to form a quadrangular frame contour by means of threaded fasteners, wherein the corresponding front leg and rear leg are attached to the outer side of each side crossbar, and the front crossbar and rear crossbar are attached to the inner side of each side crossbar, wherein each rear leg is made elongated above the level of the seat and at the same time forms a support post for the backrest, the elements of the supporting frame are made of plywood with a thickness of 8 to 36 mm.

[0014] In a preferred embodiment, the connection of each leg to the seat part is made by means of a groove formed in the upper connecting section of the leg, into which the corresponding crossbar of the seat part is inserted.

[0015] In the preferred embodiment, the side bars, front bar and rear bar of the seat section have a height of 40 to 160 mm and a thickness of 8 to 30 mm.

[0016] In the preferred embodiment, the front legs and the rear legs are made of flat plywood pieces with a thickness of 8 to 30 mm, and the width of the upper connecting section of each leg is 40 to 180 mm.

[0017] In the preferred embodiment, the overall height is from 650 to 950 mm, the overall width is from 350 to 650 mm, the overall depth is from 350 to 700 mm, the height of the seat from the supporting surface is from 350 to 550 mm, while the width of the seat is from 300 to 550 mm, and the depth of the seat is from 280 to 500 mm.

[0018] In the preferred embodiment, the side crossbars, front crossbar and rear crossbar of the seat section are made in the form of flat plywood parts.

[0019] In the preferred embodiment, the front legs and rear legs are made in the form of flat plywood pieces.

[0020] In a preferred embodiment, each side crossbar has an outer side surface to which the upper connecting sections of the front and rear legs are attached on the outside.

[0021] In a preferred embodiment, each side crossbar has an inner side surface to which the end sections of the front and rear crossbars are attached from the inside.

[0022] In a preferred embodiment, the connection of the front leg with the corresponding side crossbar is made by means of at least two threaded fasteners spaced apart from each other in the connection area.

[0023] In a preferred embodiment, the connection of the rear leg with the corresponding side crossbar is made by means of at least two threaded fasteners spaced apart from each other in the connection area.

[0024] In a preferred embodiment, the upper portions of the front legs and the rear legs overlap in height at least a portion of the side crossbars of the seat portion.

[0025] In a preferred embodiment, the backrest is secured to the upper portions of the rear legs that form the backrest support posts by means of threaded fasteners.

[0026] In the preferred embodiment, the back is made of plywood in the form of a panel element with a rounded outline.

[0027] In a preferred embodiment, the seat is mounted on a quadrangular seat post and secured thereto with the ability to transfer the load from the seat through the seat post to the front and rear legs.

[0028] In the preferred embodiment, the connections of the supporting frame elements are detachable.

[0029] In the preferred embodiment, the threaded fasteners are in the form of screws, bolts, furniture ties, confirmats, or a combination thereof.

[0030] In a preferred embodiment, in the areas where the front and rear legs are connected to the side crossbars, the fastening elements are arranged to form a unit that prevents the leg from rotating relative to the corresponding side crossbar.

[0031] This chair, comprising a seat, backrest, and supporting frame, including front legs, rear legs, and a seat post, features a design that supports the user's operating loads not through separate, disparate elements, but through a single spatial system. The seat post between the seat and legs creates an intermediate load-bearing unit through which vertical loads, lateral forces, tipping moments, and variable loads during sitting are more evenly transferred to the front and rear legs. This increases the rigidity, reliability, and ease of connection between the legs and the crossbars under the seat, as the connection not only secures the leg to the seat but also integrates the legs, crossbars, and frame contour.

[0032] Making the supporting frame elements from plywood increases rigidity, reliability, and processability of the leg-to-seat crossbar connections due to a combination of sufficient bending rigidity, dimensional stability, and the ease of machining flat blanks. The plywood's multilayer structure ensures a more uniform stress distribution in the fastening area, reduces the risk of localized material crushing when tightening threaded fasteners, and allows for the formation of flat mating surfaces with high repeatability. This allows the connecting sections of the legs and crossbars to fit precisely together, reducing gaps, play, and distortion in the assembly.

[0033] The seat post is formed by two side crossbars, a front crossbar, and a rear crossbar, connected to form a rectangular frame using threaded fasteners. This ensures increased rigidity, reliability, and ease of connection between the legs and the crossbars under the seat by creating a closed frame. This rectangular frame supports not only the vertical loads from the seat but also the horizontal thrust forces that arise from user movement, chair tilt, and uneven loads on the legs. The framed seat post prevents the legs from moving closer together or further apart, limits frame twisting, and creates a stable base for the seat.

[0034] Connecting each stem to the seat post via a groove formed in the upper connection section of the stem, into which the corresponding seat post crossbar is inserted, increases the rigidity, reliability, and ease of connection between the stems and the seat posts by creating not only a fastening but also a geometrically locking connection. In this design, the seat post crossbar is not simply applied to the surface of the stem and held in place by threaded fasteners, but is partially inserted into the upper connection section of the stem, creating a grooved fit between the stem and the crossbar, mutually embracing the mating parts.

[0035] This design significantly increases the resistance of the assembly to shear, rotation, and loosening, as the operating loads are supported not only by the fastener rods but also by the sidewalls of the groove, the supporting surface of the groove, and the crossbar inserted into it. Under a vertical load from the seat, the force is transferred through the underseat section to the legs more precisely and stably, as the crossbar has a predetermined position in the groove and cannot move freely relative to the leg in the plane of the connection. This increases the rigidity, reliability, and ease of manufacture of the connection between the legs and the crossbars under the seat, as the strength of the assembly is less dependent on the tightening force of the threaded fasteners alone.

[0036] The groove in the upper leg connection area also increases rigidity, reliability, and ease of assembly by improving the precision of the relative positioning of the parts during assembly. The groove serves as a mounting base, determining the height, direction, and depth of the crossbar. This reduces the likelihood of crossbar misalignment relative to the leg, simplifies alignment of mounting holes, and ensures consistent frame geometry during serial production. This is especially important for collapsible plywood structures, where the precise relative positioning of flat parts directly impacts the stability of the chair, uniform leg support, and the absence of play.

[0037] Sliding the corresponding seat post crossbar into the groove of the upper leg connection increases the rigidity, reliability, and ease of use of the leg-to-seat crossbar connection, also because it creates an additional mechanical lock preventing the leg from rotating relative to the crossbar. When the chair is subjected to a lateral load, the user shifts, or a torque from the backrest, the leg tends to rotate relative to the seat frame. However, the crossbar inserted into the groove interacts with the side walls of the groove, preventing such rotation. As a result, the threaded fasteners primarily act as clamps and secure the components, rather than bearing the entire shear and bending load, increasing the durability of the connection.

[0038] Furthermore, the tongue-and-groove joint enhances the rigidity, reliability, and ease of manufacture of the leg-to-seat crossbar connection by increasing the contact area between the leg and crossbar. With a planar connection, where the crossbar is inserted into the groove, the load is distributed over a larger area of ​​the plywood, reducing localized stress concentration around the mounting holes, and reducing the risk of crushing, cracking, or gradual loosening of the plywood in the mounting area. This distribution of forces is especially important for elements made of plywood sheets, as it allows for more efficient use of the material's multilayer structure and its resistance to compression, shear, and bending.

[0039] From a manufacturing standpoint, the groove in the upper leg connection section increases rigidity, reliability, and ease of manufacture when connecting the legs to the crossbars under the seat. The groove can be formed using standard milling, cutting, CNC machining, or material removal during the production of a flat plywood part. During assembly, the crossbar is inserted into a pre-prepared seat, reducing the need for complex fixtures, templates, and manual adjustments. The assembler obtains a predetermined crossbar position relative to the leg, after which the connection is secured with threaded fasteners, speeding up assembly and reducing the likelihood of errors.

[0040] Taken together, this feature enhances the performance of the entire seat post assembly, as the connection between the leg and the crossbar takes on a combined character: the groove provides geometric alignment and resistance to displacement, while the threaded fasteners provide pressure and final fixation of the mating parts. This increases the rigidity, reliability, and processability of the leg-to-crossbar connection under the seat, resulting in reduced play, increased resistance to leg rotation, more uniform load transfer from the seat to the supports, simplified assembly, and increased geometric stability of the chair's supporting frame.

[0041] A seatpost height of 40 to 160 mm for the side crossbars, front crossbar, and rear crossbar directly impacts the rigidity, reliability, and ease of connection between the legs and the crossbars under the seat, as this range ensures sufficient vertical crossbar ...Therefore, the range from 40 to 160 mm is technically feasible, as it allows for the formation of a sufficiently rigid frame contour under the seat while simultaneously maintaining the technological efficiency of manufacturing plywood parts.

[0042] The thickness of the side crossbars, front crossbar, and rear seat crossbar, ranging from 8 to 30 mm, ensures increased rigidity, reliability, and ease of manufacture of the connection between the legs and the crossbars under the seat. This plywood thickness is selected to withstand the loads from the seat, fasteners, and legs without failure or excessive deformation. Thicknesses less than 8 mm do not provide sufficient resistance to crushing and tearing of fasteners, especially in grooved or overlapped joints. Such thin thicknesses reduce the contact area between the parts and reduce the crossbar's ability to withstand shear and bending loads. Conversely, thicknesses greater than 30 mm unnecessarily increase weight, material consumption, and processing labor, and may complicate the use of standard furniture fasteners.Thus, the range from 8 to 30 mm provides a rational balance between strength, weight and manufacturing efficiency.

[0043] Making the front and rear legs from flat plywood pieces with a thickness of 8 to 30 mm improves rigidity, reliability, and the ease of connection to the crossbars under the seat. This thickness ensures sufficient load-bearing capacity for the legs and stability of their upper attachment points where they connect to the seat post. Legs with thicknesses less than 8 mm may have insufficient resistance to bending, twisting, and localized failure at the fastener installation points or where grooves are formed. Thicknesses greater than 30 mm make the structure excessively bulky, increase the weight of the chair, complicate cutting and processing the plywood, and may reduce the cost-effectiveness of serial production. This range allows for the use of standard plywood sheets and ensures compatibility with typical milling, drilling, and assembly operations.

[0044] The width of the upper connection section of each leg, ranging from 40 to 180 mm, ensures increased rigidity, reliability, and ease of manufacture when connecting the legs to the crossbars under the seat, as this section is where the main load transfer from the seat post to the supports occurs. Widths less than 40 mm reduce the contact area between the leg and the crossbar, making it difficult to place two or more spaced fasteners, reducing the resistance to rotation of the leg relative to the side crossbar, and increasing the risk of loosening the connection. Widths greater than 180 mm make the upper connection section structurally redundant, increasing plywood consumption, degrading the product's appearance, and potentially interfering with other seat frame components. Therefore, this range allows for a large support surface for tongue-and-groove, overlap, or combined connections while maintaining a compact design.

[0045] A chair height of 650 to 950 mm indirectly improves the rigidity, reliability, and processability of the leg-to-seat crossbar connection. This range corresponds to a reasonable overall height for the chair, where the rear legs, extended above seat level and forming the backrest pillars, maintain sufficient rigidity without excessively increasing the bending arm. A chair height of less than 650 mm may have insufficient backrest height and limited user functionality. A chair height of over 950 mm increases the length of the rear pillars, increasing the bending moments exerted on the backrest, which may require reinforcing the connections and increasing the cross-sections of the elements. A height range of 650 to 950 mm maintains structural stability and ensures efficient load transfer from the backrest through the rear legs to the seat.

[0046] A chair width of 350 to 650 mm improves the rigidity, reliability, and ease of connection between the legs and the crossbars under the seat, as it determines the distance between the side frame elements and, consequently, the dimensions of the seat frame. Widths less than 350 mm reduce the chair's lateral stability and reduce the seat support area. Widths greater than 650 mm increase the span of the front and rear crossbars, which can lead to increased bending loads and the need to increase the crossbar ...

[0047] A chair depth of 350 to 700 mm influences the rigidity, reliability, and technological effectiveness of the connection between the legs and the crossbars under the seat, as it determines the distance between the front and rear legs and the length of the side crossbars of the seat section. A depth of less than 350 mm reduces the chair's longitudinal stability and increases the risk of tipping when the user leans back or forward. A depth greater than 700 mm increases the length of the side crossbars, increases their bending load, and may reduce the compactness of the chair. The range from 350 to 700 mm provides a rational balance between longitudinal stability, frame rigidity, and seat section manufacturing efficiency.

[0048] A seat height from the support surface of 350 to 550 mm ensures increased rigidity, reliability, and ease of connection between the legs and the crossbars under the seat, as it determines the effective height of the legs and the length of the load path from the seat to the floor. A seat height below 350 mm makes the product low-profile and less versatile. A seat height above 550 mm increases the leg length and bending moment at the connection to the seat post, which increases the rigidity requirements of the mounting assembly. This range allows for an ergonomic seat height while maintaining sufficient resistance to bending and loosening.

[0049] A seat width of 300 to 550 mm improves the rigidity, reliability, and technological effectiveness of the seatpost-to-seatpost connection, as it determines the area where the user's load is absorbed and the area where this load is transferred to the rectangular seatpost. A seat width of less than 300 mm reduces comfort and reduces the seat's contact area with the frame. A seat width greater than 550 mm increases the seatpost width and crossbar length, which can increase deflection and require reinforcing the connections. A seat width of 300 to 550 mm provides sufficient seating area while maintaining a compact and rigid frame structure.

[0050] A seat depth of 280 to 500 mm improves the rigidity, reliability, and ease of connection between the legs and the crossbars under the seat, as it determines the longitudinal dimension of the supported load and its distribution between the front and rear crossbars. A seat depth of less than 280 mm limits the seat's support surface, which reduces the product's performance. A seat depth greater than 500 mm increases the load-bearing leverage relative to the front and rear legs, increasing the bending moment in the side crossbars and their connections. This range allows for the user load to be distributed between the front, rear, and side crossbars without excessively increasing the overall dimensions or stressing the connections.

[0051] Taken together, these size ranges ensure increased rigidity, reliability, and processability of the leg-to-seat crossbar connection, as they define rational limits for the cross-sections of the supporting plywood elements, the contact area at the joints, the dimensions of the under-seat frame contour, and the overall dimensions of the product. These limits help avoid insufficient strength and rigidity with excessively small dimensions, as well as excess weight, increased material consumption, and assembly complications with excessively large dimensions. This ensures that the leg-to-seat crossbar connection remains resistant to shear, rotation, loosening, and localized failure, and the chair structure remains suitable for mass production from flat plywood parts using standard threaded fasteners.

[0052] Attaching the corresponding front and rear footrests to the outer side of each side crossbar, while simultaneously attaching the front and rear footrests to the inner side of each side crossbar, increases the rigidity, reliability, and ease of connection of the footrests to the seat crossbars by separating the attachment zones and rationally arranging the mating parts. In this assembly, the side crossbar serves as the main load-bearing connecting element, to which the support elements are attached on the outside and the crossbars of the frame contour on the inside. This arrangement avoids overlapping attachment zones, simplifies drilling and assembly, improves the accuracy of footrest positioning relative to the frame, and ensures a more favorable transfer of forces from the seat post to the supports.

[0053] Extending each rear leg above the seat height while simultaneously forming a support post for the backrest increases rigidity, reliability, and the ease of connection between the legs and the crossbars under the seat. The rear leg becomes a continuous load-bearing element connecting the seat frame, seat frame, and backrest. When the user exerts force on the backrest, the bending moment is transferred directly through the extended rear leg to the seat frame and then to the side crossbars, rather than through an additional insert or a separate transition piece. This reduces the number of connections, reduces the likelihood of loosening, and improves the overall dimensional stability of the chair.

[0054] Constructing the side crossbars, front crossbar, and rear seat crossbar as flat plywood pieces increases rigidity, reliability, and ease of assembly between the legs and the crossbars under the seat by creating wide support and contact surfaces at the joints. The flat shape of the pieces ensures a tight fit between the crossbars and the legs, increases the contact area at the joint, and reduces stress concentration around the mounting holes. Furthermore, these pieces are easily manufactured by cutting them from plywood sheets, improving dimensional repeatability and simplifying serial assembly.

[0055] Making the front and rear legs as flat plywood pieces also increases rigidity, reliability, and ease of assembly between the legs and the crossbars under the seat, as the upper connecting sections of the legs can be designed with a developed contact area with the side crossbars. Unlike point or linear contact, a flat connection allows the fasteners to work in concert with the friction forces between the adjacent surfaces, increasing the resistance of the assembly to rotation, shear, and loosening. Flat legs are also easier to position during assembly, as they have distinct reference surfaces.

[0056] The outer surface of each side crossbar, onto which the upper connecting sections of the front and rear legs are attached externally, increases rigidity, reliability, and ease of connection between the legs and the crossbars under the seat by directly applying the load-bearing sections of the legs to the longitudinal member of the seat frame. With this arrangement, the load from the side crossbar is transferred to the leg through a flat contact, rather than through the fastener pin alone. This reduces the load on each individual fastener, reduces the risk of holes becoming loose, and ensures a stable mutual alignment of the parts during operation.

[0057] The internal surface of each side crossbar, to which the end sections of the front and rear crossbars are attached from the inside, increases rigidity, reliability, and ease of connection between the legs and the crossbars under the seat. This internal connection creates a more compact and efficient assembly, with the front and rear crossbars acting as spacers, preventing lateral deformation of the frame. At the same time, the outer surfaces of the side crossbars remain accessible for leg attachment, simplifying the fastener layout.

[0058] Connecting the front leg to the corresponding side crossbar using at least two threaded fasteners spaced apart within the connection zone increases the rigidity, reliability, and manufacturability of the connection between the legs and the crossbars under the seat by creating a torque-resistant connection. Spaced apart, the fasteners support not only the shear load but also the torque that tends to rotate the front leg relative to the side crossbar. The greater the distance between the fasteners within the permissible connection zone, the greater the resistance to rotation of the joint and the less likely it is to develop play under repeated loading cycles.

[0059] Connecting the rear leg to the corresponding side crossbar using at least two threaded fasteners spaced apart at the connection area increases the rigidity, reliability, and adaptability of the connection between the legs and the crossbars under the seat, especially at the rear of the chair, where additional loads from the backrest occur. The rear leg bears not only the vertical loads from the seat but also the bending moments caused by the user leaning on the backrest. Therefore, the spaced fastening reduces stress concentration, prevents the leg from rotating, and increases the durability of the connection.

[0060] Overlapping the upper sections of the front and rear legs with at least a portion of the seatpost crossbars increases the rigidity, reliability, and ease of connection between the legs and the seatpost crossbars, as it increases the area of ​​mutual contact between the parts and allows for adequate spacing between the fasteners. This overlap creates a developed overlap zone, where the load is transferred across a large mating area rather than a small, localized area. This reduces the risk of fastener failure, plywood collapse, and the accumulation of deformations during use.

[0061] Securing the backrest to the upper sections of the rear legs, which form the backrest support posts, using threaded fasteners increases rigidity, reliability, and the ease of connection between the legs and the crossbars under the seat. This design connects the backrest to the same load-bearing elements that support the load from the seatpost. This eliminates the need for separate intermediate posts or additional brackets, reduces the number of parts and connections, and ensures the transfer of forces from the backrest to the rear legs and then to the side crossbars of the seatpost.

[0062] The plywood backrest, constructed as a panel element with a rounded contour, provides increased rigidity, reliability, and indirectly improves the stability of the rear power unit by connecting the legs to the crossbars under the seat. The plywood panel backrest, mounted on extended rear legs, acts as an additional connecting element between the uprights, reducing their relative displacement and increasing the resistance of the rear frame to distortion. The rounded contour reduces the presence of sharp stress concentrators and improves the operational safety of the product.

[0063] Mounting the seat on a rectangular seatpost with a mounting system that allows the load from the seat to be transferred through the seatpost to the front and rear legs increases rigidity, reliability, and the technological effectiveness of the connection between the legs and the crossbars under the seat. This design distributes the user load along the frame contour rather than relying on individual mounting points. This design allows the seat to rest on a closed seatpost frame, reducing localized deformation, increasing resistance to deflection, and ensuring the coordinated operation of the front and rear legs.

[0064] Detachable connections between the supporting frame elements enhance rigidity, reliability, and ease of manufacture, allowing for precise assembly, tightening, repair, and replacement of individual components without destroying the frame. Detachable connections allow for controlled fastener tightening, eliminate potential play, and ensure stable clamping of mating plywood components. Furthermore, this design is convenient for transportation and mass production, as the components can be supplied flat and assembled using standard fasteners.

[0065] The use of threaded fasteners such as screws, bolts, furniture ties, dowels, or a combination of these enhances the rigidity, reliability, and ease of assembly between the legs and the crossbars under the seat. This allows for a choice of fasteners depending on the plywood thickness, required clamping force, load direction, and assembly conditions. Screws and dowels are convenient for joining plywood elements, furniture ties ensure a neat, detachable connection and the ability to be reassembled multiple times, and bolted connections provide increased tightening force. The use of such standard fasteners reduces manufacturing labor and improves repairability.

[0066] The placement of fasteners at the junction of the front and rear legs with the side crossbars, forming a joint that prevents the leg from rotating relative to the corresponding side crossbar, increases the rigidity, reliability, and ease of use of the leg-to-seat crossbar connection by transforming a conventional fastening into a stable, anti-rotation joint. In this joint, the fasteners work in conjunction with the planar contact of the plywood components, absorbing shear, tearing, and torque. This is especially important during chair use, as the legs are constantly subjected to variable loads associated with sitting, standing, lateral movement of the user, and possible tilting of the chair.

[0067] Taken together, these features create a design in which increased rigidity, reliability, and processability of the leg-to-seat crossbar connection are achieved not by a single isolated element, but by the coordinated interaction of flat plywood parts, a rectangular frame underseat contour, external leg connections to the side crossbars, internal connections of the front and rear crossbars, spaced threaded fastenings, and the use of extended rear legs as backrest supports. This design ensures stable load transfer, reduces the likelihood of loosening of the connections, simplifies the fabrication of sheet metal parts, and improves the chair's suitability for disassembly, transportation, and mass production.

[0068] Fig. 1 shows a general view of the chair from the front.

[0069] Fig. 2 shows a general side view of the chair.

[0070] Fig. 3 shows a general view of the chair from the back.

[0071] Fig. 4 shows a bottom view of the chair showing the quadrangular seat section.

[0072] The chair consists of a seat, a backrest, and a supporting frame. The supporting frame is made of plywood and includes front legs, rear legs, two side crossbars, a front crossbar, and a rear crossbar. Manufactured from plywood, the frame elements allow for easy manufacturing using sheet metal cutting, the ability to achieve repeatable geometry, reduced labor intensity, and ease of serial assembly.

[0073] The seat section of the chair forms a rectangular frame contour. This contour is formed by two side crossbars located on the sides under the seat, as well as front and rear crossbars, located at the front and rear of the seat area, respectively. The front and rear crossbars are located between the side crossbars and are attached to the inner sides of the side crossbars using threaded fasteners. As a result, the side crossbars form the outer longitudinal elements of the frame contour, and the front and rear crossbars form transverse elements connecting the side crossbars together.

[0074] Each side crossbar has an outer side facing the corresponding side surface of the chair and an inner side facing the inside of the rectangular frame contour. The front leg and rear leg are attached to the outer side of each side crossbar. The end sections of the front and rear crossbars are attached to the inner side of each side crossbar. Thus, the side crossbar serves as a common load-bearing element that connects the legs to the seat frame and connects the longitudinal and transverse elements of the seat post to each other.

[0075] The front leg is constructed from plywood, comprising a lower support section, an intermediate load-bearing section, and an upper connection section. The upper connection section of the front leg is attached to the outer side of the corresponding side crossbar and connected to it with threaded fasteners. Preferably, the connection between the front leg and the side crossbar is achieved by at least two threaded fasteners spaced apart at the connection point. This spacing of the fasteners prevents rotation of the front leg relative to the side crossbar and increases the rigidity of the connection under vertical and lateral loads.

[0076] The rear leg is also made of plywood, but it is elongated and extends above the seat level. This allows the rear leg to simultaneously support the backrest. The middle or lower attachment section of the rear leg is secured to the outer side of the corresponding side crossbar under the seat, while the upper section of the rear leg serves to mount and secure the backrest. This design allows the rear support and backrest support to be combined in a single plywood piece, reducing the number of individual frame components, simplifying assembly, and enhancing the chair's structural integrity.

[0077] The front seat post is positioned between the side posts in the forward area under the seat. Its ends are adjacent to the inner sides of the side posts and are connected to them with threaded fasteners. The rear seat post is positioned between the side posts in the rear area under the seat and is similarly connected at its ends to the inner sides of the side posts. This arrangement of the front and rear posts within a rectangular contour allows for a compact frame system, leaving the outer surfaces of the side posts accessible for mounting the footpegs.

[0078] Threaded fasteners can be screws, bolts, furniture ties, confirmat screws, screws and nuts, threaded bushings, or other fasteners that provide a detachable or partially detachable connection between plywood components. Preferred fasteners pass through the side crossbar into the end section of the front or rear crossbar, and through the top section of the leg into the side crossbar. Pre-drilled mounting holes, recesses for fastener heads, washers, bushings, or cage nuts are permitted.

[0079] In one embodiment, the front and rear legs are attached to the outer side of the side rail using two fasteners positioned one above the other. In another embodiment, the fasteners may be spaced apart along the length of the side rail. In yet another embodiment, the fasteners may be arranged diagonally or in a triangular pattern. In all of these cases, the spacing of the fasteners at the connection area allows for the absorption of moment loads that occur when the chair tilts, the user sits down, or when subjected to lateral movement or rocking.

[0080] The seat is mounted on a rectangular seatpost. The seat may comprise a rigid base and a soft, upholstered upper section. The rigid seat base may be attached to the seatpost with screws, bolts, ties, or other fasteners. The seatpost supports the load from the seat and transfers it through the side crossbars to the front and rear legs.

[0081] The backrest is attached to the upper sections of the rear legs, which form the backrest's support posts. The backrest can be made of plywood as a panel element with a round, oval, rectangular shape with rounded corners, or any other ergonomic contour. The backrest can be attached to the rear legs using threaded fasteners that pass through the rear legs into the backrest body or through the backrest into the rear legs.

[0082] When assembling the chair, a rectangular seat section is first formed by connecting the side crossbars to the front and back crossbars. Then, the front and back legs are attached to the outer sides of the side crossbars. Next, the seat is installed on the seat section, and the backrest is attached to the upper sections of the back legs. This assembly sequence is efficient because the main connections are made from the exposed outer and inner sides of the plywood parts, requiring no complex tooling and allowing visual inspection of the fasteners.

[0083] In one embodiment, the front crossbar and rear crossbar are positioned between two side crossbars, with the end sections of the front and rear crossbars adjacent to the inner sides of the side crossbars. These elements are connected by threaded fasteners that pass through the side crossbars into the end sections of the front and rear crossbars. This design allows for the simple formation of a rectangular frame contour, in which the side crossbars serve as the outer longitudinal elements of the seat post, and the front and rear crossbars serve as transverse elements that connect the side crossbars together.

[0084] In another embodiment, the front and rear crossbars can be connected to the side crossbars using threaded fasteners extending through the front and rear crossbars into the body of the side crossbars. This option can be used with a different fastener orientation, when it is necessary to conceal the fastener heads on the outside of the side crossbars, or when using embedded threaded fasteners, bushings, or nuts in the side crossbars.

[0085] In the preferred embodiment, the connection between the underseat components is detachable or partially detachable. Threaded fasteners may include screws, wood screws, confirmat bolts, bolts, furniture fasteners, eccentric fasteners, cap screws, threaded bushings, or other fasteners suitable for joining plywood components. If necessary, pre-drill mounting holes, recesses for fastener heads, holes for embedded threaded bushings, or mating fastener components in the plywood components.

[0086] An option is available in which the front and rear crossbars are joined to the side crossbars in a butt joint. In this design, the end surfaces of the front and rear crossbars are connected to the inner surfaces of the side crossbars, after which the parts are tightened together with threaded fasteners. This option is technologically simple, as it does not require complex milling and can be implemented by cutting plywood parts and then drilling the mounting holes.

[0087] In another embodiment, the side crossbars can be provided with mounting grooves that accommodate the end sections of the front and rear crossbars. The mounting grooves ensure the preliminary positioning of the crossbars relative to the side crossbars, limit their displacement during assembly, and improve the accuracy of the rectangular frame contour. After inserting the end sections of the front and rear crossbars into the corresponding grooves, the connection is further secured with threaded fasteners. This design increases the rigidity of the corner joints of the seat post and reduces the likelihood of crossbar displacement under operating loads.

[0088] A tongue-and-groove connection is also possible, with projections at the ends of the front and rear crossbars fitting into corresponding grooves in the side crossbars. In this case, the tongue-and-groove connection serves as a guide and positioning element, while threaded fasteners provide a secure hold for the connected parts. By combining mechanical engagement and threaded tightening, the corner joint's resistance to shear, distortion, and loosening is increased.

[0089] In a specific embodiment, the connection of the seat section elements can be further reinforced with dowels. For this purpose, aligned holes are drilled in the plywood elements to be connected, into which wooden, polymer, or combination dowels are installed. The dowels ensure precise relative positioning of the front and rear crossbars relative to the side crossbars and absorb some of the shear loads, while threaded fasteners tighten the parts and prevent the connection from opening. This option is particularly useful for serial production of chairs, as it improves assembly repeatability and reduces stress on the threaded fasteners.

[0090] One or more threaded fasteners may be used at each corner joint of the seat post. Preferably, at least two threaded fasteners are installed at the junction of the end section of the front or rear crossbar with the side crossbar, spaced apart along the crossbar height or along the length of the connection area. Spaced apart, the fasteners create a connection that is resistant to rotation and distortion of the connected parts, since the load is supported not by a single fastening point, but by a system of fasteners forming a torque couple.

[0091] The front legs are made of plywood and are flat, load-bearing components. Each front leg has a lower support section designed to contact the supporting surface, an intermediate load-bearing section, and an upper connection section that connects the front leg to the seat section. The front legs can be positioned vertically or inclined outward and / or forward relative to the vertical, ensuring the required stability of the chair and the desired structural shape.

[0092] The rear legs are also made of plywood and have an elongated shape. Each rear leg extends above the seat level and simultaneously forms a backrest support. The lower section of the rear leg serves as the chair support, the middle section connects to the seat, and the upper section serves as the backrest mount. This design allows the rear leg and backrest support to be combined in a single plywood piece, reducing the number of individual frame elements and enhancing the chair's structural integrity.

[0093] The connection of the legs to the seat post can be accomplished in various ways within the scope of the claimed design. In one embodiment, the upper connecting sections of the front and rear legs are attached to the outer sides of the corresponding side bars and secured with threaded fasteners. Each side bar functions as a base longitudinal element, with the legs attached to the outer side and the front and rear seat bars attached to the inner side.

[0094] In another embodiment, a groove can be made in the upper connecting section of each leg, through which the leg is connected to the seat post. The corresponding side crossbar of the seat post, or the section of the assembly formed by the side crossbar and the adjacent front or rear crossbar, is inserted into this groove. After the side crossbar is inserted into the groove, the leg is additionally secured to the seat post with threaded fasteners. This design ensures not only a secure fastening but also a geometric fit around the seat post element, increasing the connection's resistance to displacement and rotation.

[0095] In a specific embodiment, the groove in the upper connecting section of the leg can embrace the side crossbar on at least two sides. The groove walls form support surfaces that interact with the side surfaces of the side crossbar. This connection reduces the load on the threaded fasteners, as some of the operating forces are absorbed through the groove contact surfaces. In this case, the threaded fasteners serve as a tightening and locking function, preventing the side crossbar from slipping out of the groove and causing the assembly to loosen.

[0096] In another embodiment, the groove can be designed to accommodate not only the side crossbar section, but also the connection area between the side crossbar and the front or rear crossbar. In this design, the upper connection section of the leg engages the corner joint of the seat post, allowing for additional connection of the leg to the rectangular frame contour. This design increases the spatial rigidity of the frame, since the load from the leg is transferred not to a single crossbar, but to the joint connecting several seat post elements.

[0097] The stem-to-seat connection can be additionally secured with two or more threaded fasteners spaced apart at the connection point. The fasteners can be spaced along the height of the upper stem connection, along the sidebar, or diagonally. This arrangement of fasteners prevents the stem from rotating relative to the sidebar and improves the connection's reliability under vertical, lateral, and rocking loads.

[0098] The seat is mounted on the seatpost and may comprise a rigid base and a soft top. The rigid seat base can be secured to the rectangular frame using screws, wood screws, furniture ties, or other fasteners. The load from the seat is transferred to the front, rear, and side crossbars of the seatpost, and then through the connecting points to the front and rear legs.

[0099] The backrest is attached to the upper sections of the rear legs, which also serve as the backrest support posts. The backrest can be made of plywood, wood, a soft element on a rigid base, or a combination of materials. In one embodiment, the backrest is a panel element with a rounded or smoothly curved contour and is connected to the upper sections of the rear legs using threaded fasteners. Because the rear legs are an extension of the backrest support posts, the force from the backrest is transferred directly to the rear legs and then to the seat post, increasing structural reliability.

[0100] The overall dimensions of the chair can be selected depending on the purpose of the product. The thickness of the plywood elements of the supporting frame is from 8 to 36 mm. The height of the side, front and rear crossbars of the seat part can be from 40 to 160 mm, and their thickness corresponds to the thickness of the plywood used or is determined by a set of plywood parts. The width of the upper connecting section of the leg can be from 40 to 180 mm, which ensures sufficient contact area with the seat part. The overall height of the chair can be from 650 to 950 mm, width - from 350 to 650 mm, depth - from 350 to 700 mm, seat height from the supporting surface - from 350 to 550 mm, seat width - from 300 to 550 mm, seat depth - from 280 to 500 mm.

[0101] The claimed design provides increased rigidity, reliability, and ease of connection between the legs and the seat section of the chair, as the side crossbars simultaneously function as longitudinal elements of the quadrangular frame contour and as basic load-bearing elements for attaching the front and rear legs. Externally attaching the legs to the side crossbars provides an increased contact area and ease of installation, while internally attaching the front and rear crossbars to the same side crossbars creates a closed frame system that prevents distortion, loosening, and mutual displacement of the frame elements.

Claims

1. A chair comprising a seat, a backrest and a supporting frame including front legs, rear legs and a seat section, characterized in that the supporting frame elements are made of plywood, the seat section is formed by two side crossbars, a front crossbar and a rear crossbar, connected to each other to form a quadrangular frame contour by means of threaded fasteners, wherein each rear leg is made elongated above the level of the seat and simultaneously forms a support post for the backrest, the supporting frame elements are made of plywood with a thickness of 8 to 36 mm.

2. A chair according to claim 1, characterized in that a corresponding front leg and a back leg are attached to the outer side of each side crossbar, and a front crossbar and a back crossbar are attached to the inner side of each side crossbar.

3. A chair according to paragraph 1, characterized in that the connection of each leg with the seat part is made by means of a groove formed in the upper connecting section of the leg, into which the corresponding crossbar of the seat part is inserted.

4. The chair according to item 1, characterized in that the side crossbars, the front crossbar and the rear crossbar of the seat section have a height of 40 to 160 mm and a thickness of 8 to 30 mm.

5. A chair according to paragraph 1, characterized in that the front legs and rear legs are made of flat plywood parts with a thickness of 8 to 30 mm, while the width of the upper connecting section of each leg is from 40 to 180 mm.

6. The chair according to paragraph 1, characterized in that the overall height is from 650 to 950 mm, the overall width is from 350 to 650 mm, the overall depth is from 350 to 700 mm, the height of the seat from the supporting surface is from 350 to 550 mm, while the width of the seat is from 300 to 550 mm, and the depth of the seat is from 280 to 500 mm.

7. A chair according to claim 1, characterized in that the connection of the rear leg with the corresponding side crossbar is made by means of at least two threaded fasteners spaced apart from each other in the connection area.

8. A chair according to claim 1, characterized in that the front crossbar and the rear crossbar are connected to the side crossbars by means of threaded fasteners passing through the side crossbars into the end sections of the front and rear crossbars.

9. The chair according to item 1, characterized in that the front crossbar and the rear crossbar are located between the side crossbars of the seat part.

10. The chair according to item 1, characterized in that the side crossbars are located outside the front and rear crossbars of the seat section.

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