Unit chair

Abstract

To provide a unit chair in which an angle of a headrest may be adjusted in a forward direction, while durability of a supporting structure can be ensured when force is applied in a reverse direction.SOLUTION: A link unit includes a first ratchet member constraining motion of a second link member so that the second link member is rotatable only in one direction about a central axis line of a first hinge pin. The first ratchet member may include; a first ratchet base portion with a plurality of saw teeth formed on one surface and shaped to be arranged in a ring shape about the central axis line of the first hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, where the first ratchet base portion has an opposite surface fixed to the first link member; and a first ratchet rotating portion with a plurality of saw teeth formed on one surface and engaged with the saw teeth of the first ratchet base portion, where the first ratchet rotating portion has an opposite surface fixed to the second link member.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a unit chair. [Background technology]

[0002] A unit chair is equipment for accommodating patients in dental clinics, etc., and generally includes a backrest to support the patient's back and a seat to support the patient's buttocks and legs. It may also include a headrest to support the patient's head, a doctor's table for placing dental treatment tools such as handpieces, a cuspidor, a water dispenser, etc.

[0003] The seat is supported by a base disposed on a floor of a dental treatment space, and at least one of the base and the seat may be provided with a drive unit capable of adjusting the height of the seat.

[0004] The backrest is connected to one end of the seat and can be tilted relative to the seat. By tilting the backrest forward to stand up, the patient can be placed in a sitting position, and by tilting the backrest backward to lie down, the patient can be placed in a lying position, allowing the patient to obtain a posture suitable for the medical treatment situation.

[0005] The headrest is preferably formed at the top of the backrest and the angle can be adjusted according to the purpose of the treatment, the patient's body shape, and the convenience of the medical staff. When considering a treatment situation requiring the headrest angle adjustment, the medical staff often holds the treatment tool in one hand and cannot use both hands freely, or the patient's head puts weight on the headrest.

[0006] Therefore, when the patient wants to adjust the angle or posture of the headrest in a direction in which the patient's head moves forward or down, it is preferable that the angle can be adjusted by only lightly pushing the headrest with one hand, without operating a separate button or lever. Conversely, adjusting the angle in a direction in which the patient's head returns to its original position (in the opposite direction) is possible only by operating a separate button or lever, and otherwise it is preferable that the head is firmly supported.

[0007] The design of the button or lever is very important. Reliability must be guaranteed so that the angle can be adjusted in the reverse direction only when the button or lever is pressed with an appropriate force. In addition, due to the nature of dental treatment, the doctor's hands are often near the headrest, so care must be taken because if the doctor's hands touch the button or lever and cause a malfunction, it may lead to injury to the patient. Therefore, it is necessary to take safety measures that can effectively prevent malfunction.

[0008] However, as described above, the angle can be adjusted in only one direction, and it is not easy to ensure the durability of the structure that supports the patient's head in the opposite direction.

[0009] In addition to ensuring durability, it is necessary to propose a structure that allows for more precise adjustment of the headrest position, resolves side effects such as parts of the structure sticking together, and is easy to manufacture.

[0010] In addition, it is necessary to provide a headrest support structure that can adjust the angle in only one direction and can accommodate postures of patients of various heights, including very short patients such as children. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention has been developed in consideration of the above-mentioned problems, and aims to provide a unit chair in which the headrest can be adjusted in the forward direction and the durability of the supporting structure is ensured when a force is applied in the reverse direction.

[0012] Another object of the present invention is to provide a headrest support structure that allows precise adjustment of the headrest position while eliminating side effects caused thereby.

[0013] Another object of the present invention is to provide a headrest support structure which can be manufactured easily by injection molding while simplifying the number of parts.

[0014] It is still another object of the present invention to provide a headrest support structure that can assume a posture corresponding to the body shapes of patients of various heights accommodated in the unit chair.

[0015] It is still another object of the present invention to provide a two-joint headrest support structure that is capable of independently releasing the movement restraint state of two joints and that allows for one-way angle adjustment.

[0016] It is yet another object of the present invention to provide a unit chair that allows the headrest to be adjusted in a forward position and has a structure that supports and fixes the headrest when a force is applied in the reverse direction.

[0017] Yet another object of the present invention is to provide a safety device for a unit chair that prevents malfunction of the function that releases the headrest from being supported and fixed as needed when a force in the opposite direction is applied. [Means for solving the problem]

[0018] According to one aspect of the present invention, there is provided a unit chair including a link portion for adjusting a posture of a headrest, the link portion including a first link member that can be fixed to a backrest portion of the unit chair, a second link member having one end hingedly connected to the first link member by a first hinge pin, and a first ratchet member that is formed on one surface of at least one of the first link member and the second link member and restricts the movement of the second link member so that the second link member can rotate in only one direction about a central axis of the first hinge pin, the first ratchet member including a first ratchet base portion having a plurality of sawtooth members arranged in an annular shape about the central axis of the first hinge pin, protruding in the direction of the central axis, and having sawtooth members formed on one surface having a shape inclined in only one direction, the first ratchet base portion having a first ratchet rotation portion having a plurality of sawtooth members formed on one surface, at least a portion of which engages with at least a portion of the sawtooth members of the first ratchet base portion, and having a first ratchet rotation portion having a first ratchet rotation portion formed on one surface and fixed to the second link member.

[0019] The seat belt may further include a third link member, one end of which is hinged to the other end of the second link member by a second hinge pin and has one surface to which the headrest is fixed, and a second ratchet member formed on one surface of at least one of the second link member and the third link member, and constraining movement of the third link member so that the third link member can rotate only in one direction around a central axis of the second hinge pin.

[0020] In addition, the second link member may include a first release portion capable of transmitting an external force to the first ratchet member to release the movement constrained state of the second link member, and a second release portion that operates independently of the first release portion and is capable of transmitting an external force to the second ratchet member to release the movement constrained state of the third link member.

[0021] In addition, the second link member includes a first release portion capable of transmitting an external force to the first ratchet member to release the restricted state of movement of the second link member, and the first ratchet member restricts the movement of the second link member so that the second link member can rotate in only one direction around the central axis of the first hinge pin by meshing between the sawtooth of the first ratchet base portion and the sawtooth of the first ratchet pivot portion, and when an external force is applied, the first release portion can release the meshing of the first ratchet member to release the restricted state of movement of the second link member.

[0022] In addition, the second ratchet member may include a second ratchet base portion having a plurality of sawtooth members arranged in a ring shape centered on a central axis of the second hinge pin, protruding in the direction of the central axis, and having one surface formed with sawtooth members having a shape inclined in only one direction, and an opposite surface fixed to the third link member; and a second ratchet rotating portion having a plurality of sawtooth members formed on one surface, at least a portion of which engages with at least a portion of the sawtooth members of the second ratchet base portion, and an opposite surface fixed to the second link member.

[0023] The second link member includes a first release portion capable of transmitting an external force to the first ratchet member to release the movement constraint state of the second link member, and the first release portion may include a first button protrudingly formed on one outer side of the second link member and to which an external force is applied, and a first operating member formed inside the second link member and supported by a first elastic member, having the first button and the first ratchet rotating portion fixed to one surface, and moving together with the first button and the first ratchet rotating portion when an external force is applied to the first button to separate the first ratchet rotating portion from the first ratchet base portion.

[0024] Also, the sawtooth of each of the first ratchet base portion and the first ratchet rotation portion may form an inclination angle of 40 degrees or more and 50 degrees or less in only one direction with respect to the surface on which the respective sawtooth is formed.

[0025] The inclination angle may also be 45 degrees.

[0026] In addition, one of the number of saw teeth of the first ratchet base portion and the number of saw teeth of the first ratchet rotation portion may be a multiple of the other one, the multiple being two or more.

[0027] Also, the number of saw teeth on the first ratchet rotation portion may be twice the number of saw teeth on the first ratchet base portion.

[0028] Also, the sawtooth of the first ratchet rotation portion may be arranged in a ring shape with a plurality of sawtooth members spaced at equal angular intervals.

[0029] In addition, the second link member has its movement constrained by the first ratchet member and can only rotate in a direction toward the seat surface of the backrest portion, and the third link member has its movement constrained by the second ratchet member and can only rotate in the direction opposite to the direction in which the second link member can rotate.

[0030] In addition, the second release portion may include a second button protruding from one outer side surface of the second link member to which an external force is applied, and a second operating member formed inside the second link member and supported by a second elastic member, with the second button and the second ratchet rotating portion fixed to one surface, and moving integrally with the second button and the second ratchet rotating portion to separate the second ratchet rotating portion from the second ratchet base portion when an external force is applied to the second button.

[0031] In addition, among the outer surfaces of the second link member, a surface that becomes a leading end when the second link member rotates in one direction may be formed into a concave shape when observed in the central axis direction of the first hinge pin.

[0032] In addition, when the first link member is fixed to the backrest portion, it is preferable that the rotation of the second link member in one direction enables the other end of the second link member, rather than the one end, to come into contact with the seat surface of the backrest portion.

[0033] According to another aspect of the present invention, there is provided a unit chair including a link portion for adjusting the posture of a headrest, the link portion including a first link member that can be fixed to a backrest portion of the unit chair, a second link member having one end hinged to the first link member by a first hinge pin, a third link member having one end hinged to the other end of the second link member by a second hinge pin and having the headrest fixed to one surface thereof, and a first link member that is formed on one surface of at least one of the first link member and the second link member, and has an inclined sawtooth engagement with the second link member by facing each other. and a second ratchet member that constrains the movement of the third link member so that the third link member can rotate in only one direction around the central axis of the second hinge pin by meshing of inclined sawtooth shapes formed on one surface of at least one of the second link member and the third link member and arranged to face each other, and the second link member may include a release portion that can transmit an external force to the first ratchet member to release the constrained state of the movement of the second link member.

[0034] The release portion may include a first release portion capable of transmitting an external force to the first ratchet member to release the movement constrained state of the second link member, and a second release portion that operates independently of the first release portion and is capable of transmitting an external force to the second ratchet member to release the movement constrained state of the third link member.

[0035] When an external force is applied, the first release portion can release the engagement of the sawtooth of the first ratchet member to release the movement restricted state of the second link member, and when an external force is applied, the second release portion can release the engagement of the sawtooth of the second ratchet member to release the movement restricted state of the third link member.

[0036] The first ratchet member includes a first ratchet base portion having a plurality of sawtooths arranged in an annular shape around the central axis of the first hinge pin, protruding in the direction of the central axis, and having one surface formed with sawtooths having a shape inclined in only one direction, and an opposite surface fixed to the first link member, and a first ratchet rotating portion having a plurality of sawtooths formed on one surface, at least a portion of which engages with at least a portion of the sawtooths of the first ratchet base portion, and an opposite surface fixed to the second link member, and the second ratchet member includes a second ratchet base portion having a plurality of sawtooths arranged in an annular shape around the central axis of the second hinge pin, protruding in the direction of the central axis, and having one surface formed with sawtooths having a shape inclined in only one direction, and an opposite surface fixed to the third link member, and a second ratchet rotating portion having a plurality of sawtooths formed on one surface, at least a portion of which engages with at least a portion of the sawtooths of the second ratchet base portion, and an opposite surface fixed to the second link member.

[0037] It is preferable that the sawtooths of each of the first ratchet base portion, the first ratchet rotation portion, the second ratchet base portion and the second ratchet rotation portion form an inclination angle of 40 degrees or more and 50 degrees or less in only one direction with respect to the surface on which each of the sawtooths is formed.

[0038] More preferably, the inclination angle is 45 degrees.

[0039] Either the number of saw teeth of the first ratchet base portion or the number of saw teeth of the first ratchet rotating portion may be a multiple of the other that is two or more, or either the number of saw teeth of the second ratchet base portion or the number of saw teeth of the second ratchet rotating portion may be a multiple of the other that is two or more.

[0040] The number of saw teeth of the first ratchet rotation portion may be twice the number of saw teeth of the first ratchet base portion, and the number of saw teeth of the second ratchet rotation portion may be twice the number of saw teeth of the second ratchet base portion.

[0041] The saw teeth of the first ratchet rotating portion and the saw teeth of the second ratchet rotating portion may each be arranged in a circular shape at equal angular intervals.

[0042] The second link member has its movement constrained by the first ratchet member and can only rotate in a direction toward the seat surface of the backrest portion, and the third link member has its movement constrained by the second ratchet member and can only rotate in the direction opposite to the direction in which the second link member can rotate.

[0043] The first release portion includes a first button protruding from one outer side surface of the second link member and receiving an external force, and a first operating member formed inside the second link member and supported by a first elastic member, having the first button and the first ratchet rotating part fixed to one surface, and moving integrally with the first button and the first ratchet rotating part to separate the first ratchet rotating part from the first ratchet base portion when an external force is applied to the first button. The second release portion includes a second button protruding from one outer side surface of the second link member and receiving an external force, and a second operating member formed inside the second link member and supported by a second elastic member, having the second button and the second ratchet rotating part fixed to one surface, and moving integrally with the second button and the second ratchet rotating part to separate the second ratchet rotating part from the second ratchet base portion when an external force is applied to the second button.

[0044] Among the outer surfaces of the second link member, a surface that becomes a leading end when the second link member rotates in one direction may be formed into a concave shape when observed in a central axial direction of the first hinge pin.

[0045] The second link member may be formed in a "C" shape.

[0046] When the first link member is fixed to the backrest portion, it is preferable that the rotation of the second link member in the one direction enables the other end of the second link member to come into contact with a seat surface of the backrest portion.

[0047] At least one of the first release portion and the second release portion may include a button that moves along a trajectory including a central axis of the first hinge pin or a central axis of the second hinge pin when an external force is applied.

[0048] The second release portion may include a second button that, when an external force is applied, moves while pressing at least a portion of the second ratchet member along a trajectory including a central axis of the first hinge pin to release the engagement of the saw teeth of the second ratchet member and release the movement constraint state of the third link member.

[0049] The first release portion may include a first button that is protruded from an outer side surface of the second link member and that moves along a path that does not include a central axis of the first hinge pin and is parallel to the central axis of the first hinge pin when an external force is applied, and a first operating member that is formed inside the second link member and supported by a first elastic member and that moves integrally with the first button when an external force is applied to release the engagement of the sawtooth of the first ratchet member to release the movement constraint state of the second link member.

[0050] According to yet another aspect of the present invention, there is provided a unit chair including a link portion for adjusting the posture of a headrest, the link portion including a first link member that can be fixed to a backrest portion of the unit chair, a second link member having one end hingedly connected to the first link member by a first hinge pin, and a first ratchet member that is formed on one surface of at least one of the first link member and the second link member and that constrains the movement of the second link member so that the second link member can rotate only in one direction around the central axis of the first hinge pin, the second link member including a first release portion that can transmit an external force to the first ratchet member to release the constrained state of the movement of the second link member, the first release portion including a first deformable member that changes in shape or position when an external force is applied thereto, and that can transmit the applied external force to the first ratchet member only when the amount of change in shape or position of the first deformable member exceeds a predetermined first reference amount.

[0051] In addition, the first release portion further includes a first actuating member formed inside the second link member and supported by a 1-1 elastic member, and the first deformation member includes a first button protrudingly formed on one outer side of the second link member and supported by a 1-2 elastic member, and the first actuating member can transmit the applied external force to the first ratchet member only when the first button moves beyond a first reference displacement due to an external force being applied to the first button.

[0052] When an external force is applied to the first button to move beyond the first reference displacement, the first actuation member may come into contact with and move in conjunction with the first button.

[0053] In addition, a first raised portion is formed on the inside of the housing of the second link member, which penetrates a hole formed in the first actuating member, and the outer wall of the first raised portion can guide the movement direction of the first actuating member.

[0054] In addition, a first guide groove for guiding a moving direction of the first button may be formed in the first protuberance.

[0055] In addition, the first-second elastic member has one end connected to the first protrusion and the other end connected to the first button to support the first button and can be deformed according to the movement of the first button.

[0056] In addition, the first ratchet member includes a first ratchet base portion, a plurality of which are arranged in a ring shape around the central axis of the first hinge pin, protruding in the direction of the central axis, with sawtooth on one surface having a shape inclined in only one direction, and an opposite surface fixed to the first link member, and a first ratchet rotating portion, a first ratchet base portion having sawtooth on one surface which engages with the sawtooth of the first ratchet base portion, and an opposite surface fixed to the first actuating member, and when an external force is applied to the first button, the first actuating member can move together with the first button and the first ratchet rotating portion to separate the first ratchet rotating portion from the first ratchet base portion.

[0057] In addition, the link portion further includes a third link member, one end of which is hinged to the other end of the second link member by a second hinge pin and one surface of which the headrest is fixed, and a second ratchet member formed on one surface of at least one of the second link member and the third link member and constraining the movement of the third link member so that the third link member can rotate only in one direction around the central axis of the second hinge pin, and the second link member further includes a second release portion that operates independently of the first release portion and is capable of transmitting an external force to the second ratchet member to release the constrained state of the movement of the third link member, and the second release portion includes a second deformable member whose shape or position changes when an external force is applied thereto, and can transmit the applied external force to the second ratchet member only when the amount of change in shape or position of the second deformable member exceeds a predetermined second reference amount.

[0058] In addition, the second release portion further includes a second actuating member formed inside the second link member and supported by a 2-1 elastic member, and the second deformation member includes a second button protrudingly formed on one outer side of the second link member and supported by a 2-2 elastic member, and the second actuating member can transmit the applied external force to the second ratchet member only when the second button moves beyond a second reference displacement due to an external force being applied to the second button.

[0059] In addition, when an external force is applied to the second button and the second actuating member moves beyond the second reference displacement, the second actuating member comes into contact with and moves in conjunction with the second button, and the second ratchet member includes a second ratchet base portion, a plurality of which are arranged in an annular shape around the central axis of the second hinge pin, protrude in the direction of the central axis, have sawtooth shapes having a shape inclined in only one direction formed on one surface, and have an opposite surface fixed to the third link member, and a second ratchet rotating portion, a sawtooth shape engaging with the sawtooth of the second ratchet base portion formed on one surface, and have an opposite surface fixed to the second actuating member, and when an external force is applied to the second button, the second actuating member can move together with the second button and the second ratchet rotating portion to separate the second ratchet rotating portion from the second ratchet base portion.

[0060] In addition, the second link member has its movement constrained by the first ratchet member and can only rotate in a direction toward the seat surface of the backrest portion, and the third link member has its movement constrained by the second ratchet member and can only rotate in a direction opposite to the direction in which the second link member can rotate. Effect of the Invention

[0061] According to various embodiments of the present invention, the forward angle adjustment of the headrest of the unit chair can be freely performed with one hand, and a strong support structure can be provided when a force is applied in the reverse direction.

[0062] In addition, according to various embodiments of the present invention, the headrest can be adjusted in the forward position, and the durability of the structure that supports and fixes the headrest can be ensured when a force is applied in the reverse direction.

[0063] In addition, according to various embodiments of the present invention, it is possible to effectively prevent malfunction of the function that releases the headrest from being supported and fixed as needed when a force in the opposite direction is applied.

[0064] In addition, according to various embodiments of the present invention, the position of the headrest can be precisely adjusted to accommodate the various body shapes of patients accommodated in the unit chair, and side effects such as parts of the headrest support structure sticking together can be eliminated.

[0065] In addition, according to various embodiments of the present invention, by eliminating complex parts such as gas springs and leaf springs, it is possible to simplify the number of parts and provide a headrest support structure that is easy to manufacture by injection molding.

[0066] Furthermore, according to various embodiments of the present invention, the headrest can be positioned to accommodate patients of various heights accommodated in the unit chair.

[0067] Furthermore, according to various embodiments of the present invention, it is possible to realize a two-joint headrest support structure that is capable of independently releasing the movement restraint state of two joints and allowing one-way angle adjustment. [Brief description of the drawings]

[0068] [Figure 1] FIG. 1 is a perspective view of a unit chair according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram for explaining the configuration of a unit chair according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a block diagram for explaining a configuration of a link unit according to an embodiment of the present invention. [Figure 4]FIG. 4 is a right side view of the link portion according to the embodiment of the present invention. [Diagram 5] 5A to 5C are diagrams illustrating the structure of a first ratchet member according to an embodiment of the present invention. [Figure 6] 5A to 5C are diagrams for explaining the structure and operation of a release unit according to the present invention. [Figure 7] 5A and 5B are a front view and a right side view, respectively, for illustrating an assembled external shape of a second link member of the present invention. [Figure 8] 5A to 5C are diagrams illustrating the shape of a second link member of the present invention. [Figure 9] FIG. 4 is a right side view of the link portion according to the embodiment of the present invention. [Figure 10] 4A and 4B are a right side view and a rear view of a link portion according to an embodiment of the present invention. [Figure 11] 5A to 5C are diagrams for explaining the structure and operation of a release unit according to the present invention. [Figure 12] 5A to 5C are diagrams for explaining the structure of a release portion according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] The following merely illustrates the principles of the present invention. Thus, those skilled in the art can invent various devices that embody the principles of the present invention and are within the concept and scope of the present invention, even though they are not explicitly described or illustrated herein. In addition, all conditional terms and embodiments listed in this specification are intended expressly for the purpose of making the concept of the present invention understandable in principle, and should not be limited to the embodiments and conditions specifically listed in this specification.

[0070] Moreover, all detailed descriptions reciting specific embodiments, as well as principles, aspects, and embodiments of the invention, are intended to include both structural and functional equivalents of such items, and such equivalents should be understood to include not only currently known equivalents, but also equivalents developed in the future, i.e., all elements invented that perform the same function, regardless of structure.

[0071] The above-mentioned objects, features and advantages will become more apparent from the following detailed description in conjunction with the accompanying drawings, which will enable those skilled in the art to easily implement the technical ideas of the present invention. In addition, in describing the present invention, if it is determined that a detailed description of known techniques related to the present invention may obscure the gist of the present invention, the detailed description will be omitted.

[0072] Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0073] The unit chair 10 according to an embodiment of the present invention is a device that is installed on the floor of a dental treatment space and on which a patient sits or lies during treatment. The unit chair 10 can be shaped to fit the patient's body shape so that the patient does not feel uncomfortable during treatment.

[0074] FIG. 1 is a perspective view of a unit chair according to an embodiment of the present invention, and FIG. 2 is a block diagram for explaining the configuration of the unit chair according to an embodiment of the present invention.

[0075] As shown in these drawings, a unit chair 10 according to an embodiment of the present invention basically includes a seat portion 200 on which the patient's legs are placed, and a backrest portion 300 on which the patient rests.

[0076] In addition, the unit chair 10 may include a headrest unit 600 for supporting the head of the patient, a base unit 700 for supporting the seat unit 200, a driving unit 400 for driving at least one of the backrest unit 300 and the seat unit 200, and a control unit 100 for controlling the driving unit 400. At least one side surface of the backrest unit 300 and the seat unit 200 may be formed with an armrest on which the patient's arm is placed.

[0077] The unit chair 10 may also include an associated device. For example, it may include a treatment table unit 800 on which treatment tools and treatment charts for the patient are placed or which has an interface for operating tools. In addition, it may include at least one of a lighting unit (not shown) for illuminating the patient, a water supply unit (not shown) for supplying a gargle for rinsing the patient's mouth, a control unit (not shown), a display unit (not shown), a foot control unit (not shown), and a power supply unit (not shown).

[0078] The seat unit 200 may be a portion that comes into contact with the lower body including the buttocks of the patient. The seat unit 200 may be supported by a base unit 700. A leg rest (not shown) that supports the legs of the patient may be coupled to an end of the seat unit 200. The angle and / or distance of the leg rest (not shown) coupled to the seat unit 200 may be adjusted as necessary.

[0079] For the convenience of the clinician and patient, some portions of the unit chair 10 can operate separately from other portions.

[0080] The backrest portion 300 may be a portion that comes into contact with the back of a patient. A headrest portion 600 may be connected to an upper side of the backrest portion 300. The angle of the headrest portion 600 connected to the backrest portion 300 may be adjusted as necessary. The angle of the headrest portion 600 may be adjusted electrically and / or manually. The backrest portion 300 may be coupled to the seat portion 200 and / or the base portion 700.

[0081] The head rest portion 600 may include a head rest 610 that comes into contact with the head of the patient. At least a portion of the head rest 610 may be processed into a concave shape so as to correspond to the shape of the head.

[0082] The armrests may be located on both sides of the seat unit 200 or the backrest unit 300. The armrests may be provided at positions corresponding to the natural positions of both arms of a patient seated on the seat unit 200 so that the patient can be examined in a stable posture.

[0083] The treatment table 800 may be a cradle on which various dental instruments are placed for use in diagnosis and / or treatment of the unit chair 10. At least one of electricity, air pressure, and hydraulic pressure used for operating the dental instruments may be supplied to the treatment table 800. For example, this means that an oral cavity light, which is one of the dental instruments, may be turned on by the supplied electricity.

[0084] The treatment table 800 may include various switches. Considering the position of the practitioner, the treatment table 800 may be located at a distance that the practitioner can easily reach out and touch. Therefore, the treatment table 800 may have various switches for controlling each part of the unit chair 10.

[0085] The lighting unit (not shown) may be positioned at a position where the inside of the examiner's oral cavity is not visible due to the practitioner's torso, etc. For example, when the examiner moves his / her upper body to examine the inside of the examinee's oral cavity, the lighting unit may be positioned at an upper position where the inside of the oral cavity is not darkened.

[0086] The lighting units (not shown) can emit different lights as needed, meaning that the brightness and / or wavelength can be adjusted according to the surrounding brightness and / or examination content.

[0087] In one embodiment, the control unit 100 can control the luminance of the lighting unit (not shown) in response to the adjustment of the position of the headrest 610 by the operation of the link unit 900 of the present invention.

[0088] The water supply unit (not shown) may be used by the examinee for performing a procedure such as cleaning the inside of the oral cavity, etc. The water supply unit (not shown) may include a drainage device and / or a spitting receptacle for spitting.

[0089] The display unit (not shown) can display various information required for the examination. For example, an X-ray image of the oral cavity of the examinee, an image of the inside of the oral cavity of the examinee, etc. can be displayed in real time. The position / angle of the display unit 207 can be adjusted up, down, left, right, etc. as necessary to reduce fatigue of the examinee.

[0090] A foot control unit (not shown) can be used to adjust the operation of at least one dental treatment tool, allowing the examinee to use both hands freely while controlling the treatment tool by operating the foot control unit (not shown) with his / her feet.

[0091] The control unit 100 can control the operation of each part of the unit chair 10. The control unit 100 can make each part of the unit chair 10 operate organically.

[0092] The control unit 100 can be distributed in multiple locations. For example, the base unit 800 can be controlled by a first control unit, and the treatment table unit 800 can be controlled by a second control unit. The first and second control units can transmit signals between one or both of them so that the unit chair 10 operates in a well-balanced manner as a whole.

[0093] The control unit 100 can perform a control operation on an associated device of the unit chair 10. For example, when the control unit 100 is located on the base unit 800, it can perform a control operation on all or a part of the components of the unit chair 10 used together with the base unit 800 during a medical examination. For example, it can perform an activation or deactivation control operation on the associated device.

[0094] The power supply unit (not shown) can be a device that supplies power to the unit chair 10. The power supply unit (not shown) can include a converter for AC / DC power and / or a voltage / current converter appropriate for each component.

[0095] As shown in FIG. 2, according to one embodiment of the present invention, the headrest portion 600 may include a headrest 610 that supports the head of the patient, and a link portion 900 that links the headrest 610 and one end of the backrest portion 300.

[0096] The link unit 900 can perform an operation for adjusting the posture of the headrest 610. That is, the link unit 900 basically has a function of connecting the headrest 610 to one end of the backrest unit 300 and supporting the weight of the patient's head, and can perform an angle adjustment operation of lowering or widening the headrest 310 in the front-rear direction of the patient's head or a posture adjustment operation of moving the headrest 310 forward or backward according to convenience during treatment.

[0097] A user (medical staff) can adjust the angle or posture by holding the headrest 610 with one hand and applying an external force.

[0098] The configuration of the link unit 300 of the present invention will be described in more detail below with reference to the drawings.

[0099] Fig. 3 is a block diagram illustrating a configuration of a link unit according to an embodiment of the present invention. Fig. 4 is a right side view of the link unit according to an embodiment of the present invention. As shown in Figs. 3 and 4, the link unit 900 may include a series of a first link member 910 and a second link member 920. Depending on the embodiment, the link unit 900 may further include a third link member 930.

[0100] The first link member 910 can be fixed to the backrest portion 300 of the unit chair 10 .

[0101] In an embodiment of the present invention, the first link member 910 may be coupled to one end of the backrest portion 300 and fixed semi-permanently.

[0102] In another embodiment of the present invention, the first link member 910 may be formed long and slidably coupled to an insertion hole at one end of the backrest portion 300 .

[0103] The first link member 910 allows the headrest 610 to slide away from the one end of the backrest portion 300 and be fixed in a specific position when the unit chair 10 must accommodate a tall patient.

[0104] When the unit chair 10 needs to accommodate a patient with a somewhat short back, the first link member 910 allows the headrest 610 to slide closer to the one end of the backrest portion 300 and be fixed in a specific position.

[0105] One end of the second link member 920 may be hinged to the first link member 910 by a first hinge pin 911 .

[0106] One end of the third link member 930 may be hinged to the other end of the second link member 920 by a second hinge pin 931, instead of the one end of the second link member 920.

[0107] As shown in FIG. 4, a headrest 610 may be fixed to one surface of the third link member.

[0108] The link part 900 may further include a first ratchet member 940 formed on one surface of at least one of the first link member 910 and the second link member 920.

[0109] The first ratchet member 940 may include two sub-members that contact each other and are rotatable relative to each other in only one direction.

[0110] The two sub-members may be a first ratchet base portion 941 and a first ratchet rotating portion 945 of the present invention, which will be described later.

[0111] By using a ratchet structure rather than a structure such as a gas spring or a leaf spring, it is possible to further simplify the structure of the headrest portion 300.

[0112] The first ratchet member 940 can constrain the movement of the second link member 920 to unidirectional rotational movement.

[0113] The first ratchet member 940 can constrain the movement of the second link member 920 so that the second link member 920 can rotate only in one direction (the direction indicated by the dotted arrow at the bottom of Figure 4) around the central axis of the first hinge pin 911 (the center of the "+" shape at the bottom of Figure 4).

[0114] The second link member 920 may include a release portion 960 capable of transmitting an external force to the first ratchet member 940 to release the motion constraint state of the second link member 920 .

[0115] The link unit 900 of the present invention may further include a second ratchet member 950 formed on one surface of at least one of the second link member 920 and the third link member 930.

[0116] The second ratchet member 950 may be structurally similar to the first ratchet member 940 .

[0117] The second ratchet member 950 can constrain the movement of the third link member 930 to unidirectional rotational movement.

[0118] The second ratchet member 950 can constrain the movement of the third link member 930 so that the third link member 930 can rotate only in one direction (the direction indicated by the upper dotted arrow in Figure 4) around the central axis of the second hinge pin 931 (the center of the upper "+" shape in Figure 4).

[0119] In an embodiment further including a second ratchet member 950, the release portion 960 may transmit an external force to the second ratchet member 950 to release the movement restriction state of the third link member 930.

[0120] The first ratchet member 940 may be formed on one surface of at least one of the first link member 910 and the second link member 920.

[0121] The second ratchet member 950 may be formed on one surface of at least one of the second link member 920 and the third link member 930 .

[0122] FIG. 5 is a diagram for explaining the structure of the first ratchet member according to one embodiment of the present invention.

[0123] As shown in FIG. 5(a) and an enlarged view of a portion thereof in FIG. 5(b), the first ratchet member 940 can restrict the movement of the second link member 920 so that the second link member 920 can rotate in only one direction around the central axis of the first hinge pin 911 by the meshing of inclined sawtooth shapes arranged to face each other.

[0124] The first ratchet member 940 may include two sawtooth groups, each of which is made up of a plurality of sawtooth that are inclined in only one direction.

[0125] The two sawtooth groups may refer to a group of sawtooth 942 formed on part 941 shown in the upper part of FIG. 5 and a group of sawtooth 946 formed on part 945 shown in the lower part of FIG.

[0126] The first ratchet member 940 can constrain the movement of the second link member 920 by the interconnection of the two sawtooth groups so that the second link member 920 can rotate in only one direction around the central axis of the first hinge pin 911.

[0127] The second ratchet member 950 may be formed in the same structure as the first ratchet member 940 .

[0128] The second ratchet member 950 can also restrict the movement of the third link member 930 by the interlocking of inclined sawtooth shapes arranged facing each other, so that the third link member 930 can rotate in only one direction around the central axis of the second hinge pin 931.

[0129] The second ratchet member 950 may include two sawtooth groups, each of which is composed of a plurality of sawtooth inclined in only one direction.

[0130] The second ratchet member 950, by the interconnection of the two sawtooth groups, can constrain the movement of the third link member 930 so that the third link member 930 can rotate in only one direction around the central axis of the second hinge pin 931.

[0131] When an external force is applied, the first release portion 970 may release the mutual connection between the two sawtooth groups of the first ratchet member 940, thereby releasing the movement restriction state of the second link member 920.

[0132] When an external force is applied, the second release portion 980 may release the mutual connection between the two sawtooth groups of the second ratchet member 950, thereby releasing the movement restriction state of the third link member 930.

[0133] More specifically, the first ratchet member 940 may include a first ratchet base portion 941 and a first ratchet rotating portion 945. When the first ratchet base portion 941 and the first ratchet rotating portion 945 are interconnected, they may form a clutch configuration for transmitting force, i.e., a one-way clutch system may be realized.

[0134] The second ratchet member 950 may include a second ratchet base portion 951 and a second ratchet rotating portion 955. When the second ratchet base portion 951 and the second ratchet rotating portion 955 are interconnected, they may form a clutch configuration for transmitting force.

[0135] The first ratchet base portion 941 may have a surface formed with a plurality of sawtooth members 942 arranged in an annular shape around the central axis of the first hinge pin 911, protruding in the direction of the central axis, and inclined in only one direction. The opposite surface of the surface may be fixed to the first link member 910.

[0136] The second ratchet base portion 951 may have a surface formed with a plurality of sawtooth members 952 arranged in an annular shape around the central axis of the second hinge pin 931, protruding in the direction of the central axis, and inclined in only one direction. The opposite surface of the surface may be fixed to the third link member 930.

[0137] The first ratchet rotation portion 945 may have a plurality of sawtooth 946 formed on one surface thereof, at least a portion of which engages with at least a portion of the sawtooth 942 of the first ratchet base portion 941. The opposite surface of the one surface may be fixed to the second link member 920.

[0138] The second ratchet rotation part 955 may have a plurality of sawtooth 956 formed on one surface thereof, at least a portion of which engages with at least a portion of the sawtooth 952 of the second ratchet base part 951. The opposite surface of the one surface may be fixed to the second link member 920.

[0139] By configuring the sawtooth arranged in an annular shape to mesh with each other, the force transmitted between the first ratchet rotation part 945 and the first ratchet base part 941 and the force transmitted between the second ratchet rotation part 955 and the second ratchet base part 951 can be dispersed by the number of sawtooths. This makes it possible to support the patient's head with a stronger force, prolong the life of the ratchet member, and ensure its durability.

[0140] Furthermore, by forming the first ratchet rotation portion 945 and the first ratchet base portion 941 from a synthetic resin material rather than metal and manufacturing them by injection molding, it is possible to reduce costs for materials and processing.

[0141] The sawtooth 946 may also be formed in a shape inclined in only one direction. Therefore, when a force is transmitted to the inclined surfaces of the sawtooth 942 and 946, the sawtooth 942 and 946 can slide, but when a pushing force is transmitted to the perpendicular surfaces, the sawtooth 942 and 946 cannot slide, and therefore the first ratchet base part 941 and the first ratchet rotation part 945 cannot rotate relative to each other.

[0142] Generally, the sawtooth of a gear is formed with an inclined surface corresponding to both directions of rotation. However, the sawtooth 942, 946, 952, 956 of the present invention may be formed with an inclined surface in one direction and a right angle in the other direction, as shown in Figures 5(a) and 5(b).

[0143] The right angle of the present invention may mean a right angle in a substantial sense, not a geometric sense.

[0144] If the inclined surface is too gentle, the ratchet base parts 941, 951 and the corresponding ratchet rotation parts 945, 955 may easily be released from their mutually restricted movement. In this case, the headrest 610 may fall backwards while treating a patient, causing inconvenience and danger.

[0145] If the inclined surface is too steep, it is difficult to rotate the ratchet base parts 941, 951 and the corresponding ratchet rotation parts 945, 955 in one direction, which makes it difficult to achieve the purpose of changing the position and posture of the headrest to a state required for treatment with one hand.

[0146] It is preferable that the sawtooths 942, 946 of the first ratchet base portion 941 and the first ratchet rotation portion 945 form an inclination angle (CL in (b) of Figure 5) of 40 degrees or more and 50 degrees or less in only one direction with respect to the surface on which the respective sawtooths 942, 946 are formed.

[0147] More preferably, the inclination angle CL is 45 degrees.

[0148] It is preferable that the sawtooths 952, 956 of the second ratchet base portion 951 and the second ratchet rotation portion 955 form an inclination angle of 40 degrees or more and 50 degrees or less in only one direction with respect to the surface on which the sawtooths 952, 956 are formed.

[0149] More preferably, the inclination angle is 45 degrees.

[0150] Either one of the number of the saw teeth 942 of the first ratchet base portion 941 and the number of the saw teeth 946 of the first ratchet rotating portion 945 may be a multiple of the other one, which is two or more.

[0151] Either one of the number of the saw teeth 952 of the second ratchet base portion 951 and the number of the saw teeth 956 of the second ratchet rotating portion 955 may be a multiple of the other one, which is two or more.

[0152] In this way, configuring the number of saw teeth on one of the ratchet base portions 941, 951 and the corresponding ratchet rotation portions 945, 955 to be different from the number of saw teeth on the other, and further designing them to be multiples or divisors of each other, has various advantages.

[0153] First, by omitting some of the sawtooth for parts having shapes that are more difficult to injection mold among the ratchet base portions 941, 951 and the corresponding ratchet rotation portions 945, 955, there is an advantage that injection molding becomes easier.

[0154] In addition, when rotating in one direction, the angle between two connected sawtooths in a part with a large number of sawtooths is maintained at the minimum angle of rotation, allowing for more precise operation, and by reducing the friction surface, the ratchet base parts 941, 951 and the corresponding ratchet rotating parts 945, 955 can be prevented from sticking to each other.

[0155] More preferably, the number of saw teeth 946 of the first ratchet pivot portion 945 may be twice the number of saw teeth 942 of the first ratchet base portion 941. The number of saw teeth 956 of the second ratchet pivot portion 955 may be twice the number of saw teeth 952 of the second ratchet base portion 951 (see FIG. 5).

[0156] The sawtooth 946 of the first ratchet rotating portion 945 and the sawtooth 956 of the second ratchet rotating portion 955 may each be arranged in a circular shape at equal angular intervals.

[0157] Meanwhile, as shown in FIG. 4, the second link member 920 is restricted in movement by the first ratchet member 940 and can rotate only in a direction toward the seat surface 310 of the backrest portion 300 .

[0158] The seat surface 310 may refer to a surface of the outer surface of the backrest portion 300 that contacts the patient's back.

[0159] As shown in FIG. 4, the third link member 930 is constrained in movement by the second ratchet member 950 and can only rotate in the opposite direction to the direction in which the second link member 920 is rotatable (the direction of rotation indicated by the dotted arrow at the bottom of FIG. 4).

[0160] FIG. 6 is a diagram for explaining the structure and operation of the release unit of the present invention.

[0161] As shown in FIG. 6( a ), the release unit 960 may include a first release unit 970 and a second release unit 980 that operates independently of the first release unit 970 .

[0162] As shown in FIG. 6(b), the first release portion 970 can transmit an external force (acting in the direction of the arrow on the right side of FIG. 6(b)) to the first ratchet member 940 to release the movement restriction state of the second link member 920.

[0163] The second release portion 980 can transmit an external force (acting in the direction of the arrow on the left side of FIG. 6B) to the second ratchet member 950 to release the motion restriction state of the third link member 930.

[0164] FIG. 7(a) is a front view and (b) is a right side view for explaining the assembled external shape of the second link member of the present invention.

[0165] As shown in FIG. 7, the first release portion 970 may include a first button 971 and a first actuation member 972 .

[0166] The first button 971 may be formed to protrude from one outer side of the second link member 920 and configured to receive an external force applied by a user.

[0167] The first operating member 972 may be formed inside the second link member 920 .

[0168] The first operating member 972 may be supported by a first elastic member 973. The first elastic member 973 may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

[0169] One end of the first elastic member 973 may be fixed to the first operating member 972 , and the other end of the first elastic member 973 may be fixed to a housing 921 forming the outer shape of the second link member 920 .

[0170] The first elastic member 973 can return the first operating member 972 to its original position when the external force applied to the first button 971 is removed.

[0171] The first button 971 and the first ratchet rotating part 945 may be fixed to one surface of the first operating member 972. When an external force is applied to the first button 971, the first operating member 972 may move integrally with the first button 971 and the first ratchet rotating part 945 to separate the first ratchet rotating part 945 from the first ratchet base part 941. When the separation occurs in this manner, the restriction on the movement of the second link member 920 in one direction is released.

[0172] The second release portion 980 may be structurally similar to the first release portion 970 .

[0173] The second release portion 980 may include a second button 981 and a second actuation member 982 .

[0174] The second button 981 may be formed to protrude from one outer side of the second link member 920 and configured to receive an external force applied by a user.

[0175] The second operating member 982 may be formed inside the second link member 920 .

[0176] The second operating member 982 may be supported by a second elastic member 983. The second elastic member 983 may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

[0177] One end of the second elastic member 983 may be fixed to the second operating member 982 , and the other end of the second elastic member 983 may be fixed to a housing 921 forming the outer shape of the second link member 920 .

[0178] The second elastic member 983 can return the second operating member 982 to its original position when the external force applied to the second button 981 is removed.

[0179] The second button 981 and the second ratchet rotating part 955 may be fixed to one surface of the second operating member 982. When an external force is applied to the second button 981, the second operating member 982 may move integrally with the second button 981 and the second ratchet rotating part 955 to separate the second ratchet rotating part 955 from the second ratchet base part 951. When the separation occurs in this manner, the restriction on the movement of the third link member 930 in one direction is released.

[0180] Fig. 8 is a view for explaining the shape of the second link member of the present invention. As shown in Fig. 8, a surface 925 of the outer surface of the second link member 920, which becomes a leading end when the second link member 920 rotates in one direction, may be formed in a concave shape when observed in the direction of the central axis of the first hinge pin 911. That is, the leading end surface 925 may be formed in a concave shape toward a surface that becomes a rear end when viewed from a side of the headrest part 600.

[0181] Preferably, the tip surface 925 may be formed in a "C" shape when viewed from the side, and more preferably, the tip surface 925 may be formed in an arc shape when viewed from the side.

[0182] The second link member 920 may have an overall C-shaped external shape. Preferably, the second link member 920 is formed in an arc shape.

[0183] The second link member 920 formed in a curved shape as described above allows the headrest 610 to be easily moved to a position suitable for even very short patients such as children.

[0184] 9 is a right side view of a link unit according to an embodiment of the present invention, which may represent the state where the headrest is in a position suitable for a child, as described above.

[0185] In the embodiment of FIG. 9, each of the first link member 920 and the third link member 930 can be in a fully rotated state.

[0186] In FIG. 9, the head rest 610 is in a position adjusted to fit the child's back.

[0187] The curved shape of the second link member 920 as described above makes it possible to realize a posture mode that can effectively support the head of a short patient such as a child.

[0188] As shown in FIG. 8, when the second link member 920 is realized simply in a straight line, the distance d' between the end to which the third link member 930 is connected and the first link member 910 becomes large.

[0189] In this case, when a very short patient such as a child is accommodated, the patient's head is lowered excessively forward, making the device unsuitable as a head support table.

[0190] However, when the second link member 920 is formed in a curved shape as in the present invention, the distance d between the end to which the third link member 930 is connected and the first link member 910 can be appropriately maintained according to the child's body shape.

[0191] 9, when the first link member 910 is fixed to the backrest portion 300, it is preferable that the other end of the second link member 920, i.e., the end to which the third link member 930 is coupled, can contact the seat surface 310 of the backrest portion 300 by the rotation of the second link member 920 in the one direction. More preferably, it is preferable that the other end can advance so as to deform the seat surface 310 after contacting the seat surface 310 by the rotation of the second link member 920 in the one direction. In other words, it is embedded in the seat surface 310. This allows the height (thickness) of the headrest 610 to be further reduced so as to be suitable for placing a child's head thereon.

[0192] The seat surface 310 may refer to a surface of the outer surface of the backrest portion 300 that contacts the patient's back.

[0193] If the second link member 920 were simply realized in a straight line, the end of the second link member 920 to which the third link member 930 is connected would not be structurally able to contact the seat surface 310 of the backrest portion 300.

[0194] On the other hand, as shown in FIG. 4, the movement of the second link member 920 is restricted by the first ratchet member 940 and can only rotate in a direction toward the seat surface 310 of the backrest portion 300 .

[0195] The seat surface 310 may refer to a surface of the outer surface of the backrest portion 300 that contacts the patient's back.

[0196] As shown in FIG. 4, the third link member 930 is constrained in movement by the second ratchet member 950 and can only rotate in the opposite direction to the direction in which the second link member 920 is rotatable (the direction of rotation indicated by the dotted arrow at the bottom of FIG. 4).

[0197] As described above, by setting the direction in which the second link member 920 and the third link member 930 can each freely rotate, together with the shape of the concave tip of the second link member 920, even if a user such as a doctor takes the headrest 610 with only one hand, it is possible to easily switch from the headrest position mode for an adult (see Figure 4) to the headrest position mode for a child (see Figure 6).

[0198] Furthermore, by operating the release portion 960, the movement constraint state of each of the second link member 920 and the third link member 930 can be released, thereby easily returning to the headrest posture mode for adults (see Figure 4).

[0199] FIG. 10 is a right side view and a rear view of a link portion according to an embodiment of the present invention.

[0200] As shown in FIG. 10, at least one of the first release portion 970 and the second release portion 980 according to an embodiment of the present invention may include a button 981 that moves (see the direction of the arrow in FIG. 10(b)) along a trajectory including the central axis of the first hinge pin 911 or the central axis of the second hinge pin 931 when an external force is applied.

[0201] According to an embodiment of the present invention, the first release part 970 may include a first button 971 that releases the motion constrained state of the second link member 920 when an external force is applied. When an external force is applied, the second button may move while pressing at least a part of the first ratchet member 940 along a trajectory including a central axis of the first hinge pin 911. While moving as described above, the first button 971 may release the engagement of the saw teeth 942, 946 of the first ratchet member 940, thereby releasing the motion constrained state of the second link member 920.

[0202] More specifically, the first button 971 may be integrally formed with the first ratchet rotating part 945. When an external force is applied to the first button 971, the first button 971 and the first ratchet rotating part 945 may move together, and the first ratchet rotating part 945 may separate from the first ratchet base part 941. When the separation occurs in this manner, the restriction on the movement of the second link member 920 in one direction is released.

[0203] According to an embodiment of the present invention, the second release part 980 may include a second button 981 that releases the motion constrained state of the third link member 930 when an external force is applied. When an external force is applied, the second button may move while pressing at least a part of the second ratchet member 950 along a trajectory including a central axis of the first hinge pin 911. While moving as described above, the second button 981 may release the engagement of the saw teeth 952, 956 of the second ratchet member 950, thereby releasing the motion constrained state of the third link member 930.

[0204] More specifically, the second button 981 may be formed integrally with the second ratchet rotating part 955. When an external force is applied to the second button 981, the second button 981 and the second ratchet rotating part 955 may move integrally, and the second ratchet rotating part 955 may separate from the second ratchet base part 951. When the separation occurs in this manner, the restriction on the movement of the third link member 930 in one direction is released.

[0205] According to an embodiment of the present invention, the first release part 970 may include a first button 971 and a first operating member 972. The first button 971 is formed to protrude from one outer side surface of the second link member 920, and when an external force is applied, the first button 971 may move along a trajectory parallel to the central axis of the first hinge pin 911 without including the central axis of the first hinge pin 911. The first operating member 972 may be formed inside the second link member 920 and supported by a first elastic member 973. When an external force is applied, the first operating member 972 may move together with the first button 971 to release the engagement of the saw teeth 942 and 946 of the first ratchet member 940, thereby releasing the motion constraint state of the second link member 920.

[0206] According to an embodiment of the present invention, the second release part 980 may include a second button 981 and a second actuating member 982. The second button 981 is protruded from one outer side surface of the second link member 920 and may move along a trajectory parallel to the central axis of the second hinge pin 931 without including the central axis of the second hinge pin 931 when an external force is applied. The second actuating member 982 may be formed inside the second link member 920 and supported by a second elastic member 983. When an external force is applied, the second actuating member 982 may move together with the second button 981 to release the engagement of the saw teeth 952 and 956 of the second ratchet member 950, thereby releasing the motion restriction state of the third link member 930.

[0207] FIG. 11 is a diagram for explaining the structure and operation of the release unit of the present invention.

[0208] 11(a), the release unit 960 may include a first release unit 970. Also, according to an embodiment, the release unit 960 may further include a second release unit 980 that operates independently of the first release unit 970.

[0209] As shown in (b) of FIG. 11, the first release portion 970 can transmit an external force (acting in the direction of the arrow shown in the upper left corner of (b) of FIG. 11) to the first ratchet member 940 to release the movement restriction state of the second link member 920.

[0210] The second release portion 980 can transmit an external force to the second ratchet member 950 to release the movement restriction state of the third link member 930.

[0211] The first ratchet member 940 may include a first ratchet base portion 941 and a first ratchet rotating portion 945 .

[0212] The first ratchet base portion 941 may have a surface formed with a plurality of sawtooth members 942 arranged in an annular shape around the central axis of the first hinge pin 911, protruding in the direction of the central axis, and inclined in only one direction. The opposite surface of the surface may be fixed to the first link member 910.

[0213] Generally, the sawtooth of a gear is formed on an inclined surface corresponding to both directions of rotation, but the sawtooth 942 of the present invention may be formed with an inclined surface in one direction and a right angle in the other direction, as shown within the dotted oval in Fig. 11(c).

[0214] The right angle of the present invention may mean a right angle in a substantial sense, not a geometric sense.

[0215] The first ratchet rotation part 945 may have sawtooth 946 formed on one surface thereof to be engaged with the sawtooth 942 of the first ratchet base part 941. The opposite surface of the one surface may be fixed to the second link member 920.

[0216] By configuring the sawtooth arranged in an annular shape to mesh with each other, the force transmitted between the first ratchet rotation part 945 and the first ratchet base part 941 can be dispersed by the number of sawtooth, which makes it possible to support the patient's head with a stronger force, and to extend the life span and ensure the durability of the first ratchet rotation part 945 and the first ratchet base part 941.

[0217] Furthermore, by forming the first ratchet rotation portion 945 and the first ratchet base portion 941 from a synthetic resin material rather than metal and manufacturing them by injection molding, it is possible to reduce costs for materials and processing.

[0218] The sawtooth 946 may also be formed in a shape inclined in only one direction. Therefore, when a force is transmitted to the inclined surfaces of the sawtooth 942 and 946, the sawtooth can slide, but when a pushing force is transmitted to the surfaces at right angles, the sawtooth cannot slide, and therefore the first ratchet base part 941 and the first ratchet rotating part 945 cannot rotate relative to each other.

[0219] The second ratchet member 950 may be structurally similar to the first ratchet member 940 .

[0220] The second ratchet member 950 may include a second ratchet base portion 951 and a second ratchet rotating portion 955 .

[0221] The second ratchet base portion 951 may have a surface on which sawtooth teeth 952 are arranged in a ring shape around the central axis of the second hinge pin 931 (the center of the upper “+” shape in FIG. 4), protrude in the direction of the central axis, and have a shape inclined in only one direction.

[0222] The second ratchet rotation part 955 may have sawtooth 953 formed on one surface thereof to engage with the sawtooth 952 of the second ratchet base part 951 , and may have an opposite surface fixed to the second link member 920 .

[0223] The first release part 970 may include a first deformable member that changes shape or position when an external force is applied to the first release part 970. The applied external force may be transmitted to the first ratchet member 940 only when the change in shape or position of the first deformable member exceeds a first reference amount.

[0224] The first reference amount may be a positive numerical reference for the change of the first deformable member. In one embodiment, when the position of the first deformable member changes, it may mean a specific reference displacement value (distance). In another embodiment, when the shape of the first deformable member changes, it may be a reference volume corresponding to the degree of change of the shape.

[0225] The first reference amount can be appropriately designed within a range smaller than the positive maximum value at which the first deformable member changes. For example, it can be determined to a value not reaching half of the maximum value. It can be preferably set to a value corresponding to 70% to 80%. More preferably, it can be set to 75%.

[0226] In this way, when the first reference amount is set to a value that does not reach half of the maximum value, the effect of preventing the malfunction of the first release unit 970 is increased.

[0227] The first release portion 970 may include a first button 971 and a first actuating member 972 .

[0228] The first button 971 may be formed to protrude from one outer side of the second link member 920 and configured to receive an external force applied by a user.

[0229] The first operating member 972 may be formed inside the second link member 920 .

[0230] The first operating member 972 may be supported by a first-1 elastic member 973. The first elastic member 973 may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

[0231] One end of the first-1 elastic member 973 may be fixed to the first operating member 972 , and the other end of the first elastic member 973 may be fixed to a housing 921 forming the outer shape of the second link member 920 .

[0232] The first-1st elastic member 973 can return the first operating member 972 to its original position when the external force applied to the first button 971 is removed.

[0233] The first release portion 970 further includes a first operating member 972 formed inside the second link member 920 and supported by a first-1 elastic member 973, and the first deformable member may include a first button 971 formed to protrude from one outer side surface of the second link member 920 and supported by a first-2 elastic member 974 (see FIG. 11 (a) to (c)).

[0234] The first operating member 972 can transmit the applied external force to the first ratchet member 940 only when an external force is applied to the first button 971, causing the first button 971 to move by more than a first reference displacement 975 (see (c) of FIG. 11).

[0235] When the first button 971 is moved by more than the first reference displacement 975 due to application of an external force, the first operating member 972 may come into contact with and move in conjunction with the first button 971 .

[0236] In this way, if the amount of movement of the first button 971 does not reach the first reference displacement 975, no external force is transmitted to the first ratchet member 940, and the movement constraint state of the second link member 920 continues.

[0237] This can prevent malfunctions such as releasing the movement restriction state when a user such as a doctor accidentally touches the button and applies a certain amount of external force.

[0238] In addition, a first raised portion 922 that penetrates a hole formed in the first operating member 972 is formed on the inside of the housing 921 of the second link member 920, and the outer wall of the first raised portion 922 can guide the movement direction of the first operating member 972.

[0239] In addition, the first protrusion 922 may be formed with a first guide groove 923 for guiding the moving direction of the first button 971 .

[0240] By configuring the first protuberance 922 in this manner, the first protuberance 922 can guide the movement of both the first operating member 972 and the first button 971 along accurate trajectories.

[0241] In addition, the first-2 elastic member 974 has one end connected to the first protrusion 922 and the other end connected to the first button 971 to support the first button 971 and can be deformed in response to the movement of the first button 971.

[0242] When the external force is removed, the first-second elastic member 974 deviates from the deformed state and returns the first button 971 to its original position.

[0243] When an external force is applied to the first button 971, the first operating member 972 may move together with the first button 971 and the first ratchet rotating portion 945 to move the first ratchet rotating portion 945 away from the first ratchet base portion 941.

[0244] When separation occurs in this way, the restriction on the movement of the second link member 920 in one direction is released.

[0245] The second link member 920 may further include a second release portion 980 that operates independently of the first release portion 970 and transmits an external force to the second ratchet member 950 to release the movement constraint state of the third link member 930.

[0246] The second release part 980 may be formed to have the same structure as the first release part 970 according to an embodiment of the present invention.

[0247] The second release part 980 may include a second deformable member whose shape or position changes when an external force is applied.

[0248] The second release portion 980 may be configured to transmit the applied external force to the second ratchet member 950 only when the change in shape or position of the second deformation member exceeds a predetermined second reference amount.

[0249] The second reference amount may have the same properties as the first reference amount and may be determined to be an equivalent value.

[0250] The second release portion 980 may further include a second operating member 982 formed inside the second link member 920 and supported by a second-1 elastic member 983 .

[0251] The second operating member 982 may be formed inside the second link member 920 .

[0252] The second operating member 982 may be supported by a 2-1 elastic member 983. The 2-1 elastic member 983 may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

[0253] One end of the 2-1 elastic member 983 may be fixed to the second operating member 982 , and the other end of the 2-1 elastic member 983 may be fixed to a housing 921 forming the outer shape of the second link member 920 .

[0254] The 2-1 elastic member 983 can return the second operating member 982 to its original position when the external force applied to the second button 981 is removed.

[0255] The second deformation member may include a second button 981 protruding from one outer side surface of the second link member 920 and supported by a second-second elastic member 984 .

[0256] The second button 981 may be configured to receive an external force applied by a user.

[0257] The second operating member 982 can transmit the applied external force to the second ratchet member 950 only when an external force is applied to the second button 981 causing the second button 981 to move beyond a second reference displacement.

[0258] The second reference displacement may be determined to be equal to the first reference displacement.

[0259] In addition, when the second button 981 is moved by more than the second reference displacement 975 due to application of an external force, the second operating member 982 can come into contact with and move in conjunction with the second button 971 .

[0260] In this manner, when the amount of movement of the second button 981 does not reach the second reference displacement, no external force is transmitted to the second ratchet member 950, and the movement constraint state of the third link member 930 continues.

[0261] This can prevent malfunctions such as releasing the movement restriction state when a user such as a doctor accidentally touches the button and applies a certain amount of external force.

[0262] In addition, a second raised portion 926 that penetrates a hole formed in the second operating member 982 is formed on the inside of the housing 921 of the second link member 920, and the outer wall of the second raised portion 926 can guide the movement direction of the second operating member 982.

[0263] In addition, the second protuberance 926 may be formed with a second guide groove 927 for guiding the moving direction of the second button 981 .

[0264] By configuring the second protuberance 926 in this manner, the second protuberance 926 can guide the movement of both the second operating member 982 and the second button 981 along accurate trajectories.

[0265] In addition, the 2-2 elastic member 984 has one end connected to the second protrusion 926 and the other end connected to the second button 981 to support the second button 981 and can be deformed according to the movement of the second button 981.

[0266] When the external force is removed, the second-2 elastic member 984 deviates from the deformed state and serves to return the second button 981 to its original position.

[0267] When an external force is applied to the second button 981 , the second operating member 982 moves together with the second button 981 and the second ratchet rotating part 955 , and can move the second ratchet rotating part 955 away from the second ratchet base part 951 .

[0268] When separation occurs in this way, the restriction on the movement of the third link member 930 in one direction is released.

[0269] The first-1 elastic member 973 may be formed of a coil spring that wraps around the outer wall of the first protruding portion 922 (see FIG. 11).

[0270] The first-second elastic member 974 can be inserted into the first button 971. Also, the first-second elastic member 974 can be formed of a coil spring (see FIG. 11).

[0271] The 2-1 elastic member 983 may be formed of a coil spring that wraps around the outer wall of the second protruding portion 922 (see FIG. 11).

[0272] The second-second elastic member 984 can be inserted into the first button 981. Also, the second-second elastic member 984 can be formed of a coil spring (see FIG. 11).

[0273] FIG. 12 is a diagram for explaining the structure of the release portion according to one embodiment of the present invention.

[0274] As shown in FIG. 12(a), the 1-1, 1-2, 2-1, and 2-2 elastic members may be formed at positions different from those in the embodiment shown in FIG.

[0275] That is, the 1-1 and 2-1 elastic members may be formed at positions that do not completely surround the corresponding protuberances 922 and 926, respectively.

[0276] The first-second elastic member 974 may be inserted into the first guide groove 923 of the first protruding portion 922. Also, the first-second elastic member 974 may be formed of a coil spring.

[0277] The second-2 elastic member 984 may be inserted into a second guide groove 927 formed in the second protruding portion 926. Also, the second-2 elastic member 984 may be formed of a coil spring.

[0278] Also, at least one of the first operating member 972 and the second operating member 982 may be hinged to the housing 921. Fig. 12(a) illustrates an embodiment in which the first operating member 972 and the second operating member 982 share a third hinge pin 961.

[0279] In this manner, in an embodiment in which at least one of the first actuating member 972 and the second actuating member 982 is hingedly connected to the housing 921, it is preferable that the shape of the first protrusion 922 or the second protrusion 926 is also formed into a shape corresponding to the movement trajectory of the first actuating member 972 and the second actuating member 982.

[0280] As yet another embodiment, as shown in FIG. 12(b), one end of each of the first operating member 972 and the second operating member 982 may be configured to be integrally fixed to the housing 921.

[0281] In such an embodiment, the first actuating member 972 and the second actuating member 982 may be integrally formed to form a single actuating member.

[0282] Also, it may be formed of a material having elasticity (e.g., carbon steel, plastic, etc.) and may function without the 1-1 elastic member 973 and the 2-1 elastic member 983. In such an embodiment, the structure may be simplified and costs may be reduced.

[0283] Whereas, in this specification and claims, terms such as "first," "second," "third," and "fourth" are used to distinguish between similar components and are used to describe, but not necessarily, a particular sequential or occurring order. The terms used therewith can be understood to be interchangeable, under appropriate circumstances, such that the embodiments of the invention described herein operate in other sequences than those illustrated or described herein, for example. Similarly, when a method is described herein as including a series of steps, the order of such steps presented herein is not necessarily the order in which such steps may be performed, and any described step can / is omitted, or any other step not described herein can be added to the method.

[0284] Terms such as "left", "right", "front", "rear", "top", "floor", "upper", "lower" and the like in this specification and claims are used for purposes of explanation and not necessarily to describe fixed relative positions. Terms used in this manner are understood to be interchangeable under appropriate circumstances such that the embodiments of the invention described herein may, for example, be operated in other orientations than those shown or described herein. As used herein, the term "coupled" is defined as directly or indirectly connected in an electrical or non-electrical manner. Herein, objects described as "adjacent" to one another may be in physical contact with one another, in close proximity to one another, or in the same general area or region of one another, as appropriate for the context in which the phrase is used. Herein, the presence of the phrase "in one embodiment" refers to the same embodiment, although this is not necessarily the case.

[0285] In addition, in this specification and claims, the terms "connected," "couple," "fastened," "fasten," "coupled," "join," and various variations of such expressions are used to mean either directly connected to another component or indirectly connected via another component.

[0286] In addition, the suffixes "module" and "section" for components used in this specification are given or mixed together solely for the convenience of drafting the specification, and do not have any distinct meanings or roles in themselves.

[0287] In addition, the terms used in the present specification are for describing the embodiments and are not intended to limit the present invention. In the present specification, the singular form includes the plural form unless otherwise specified in the text. When used in the specification, "comprise" and / or "comprising" refer to a referenced component, step, operation, and / or element, the term does not exclude the presence or addition of one or more other components, steps, operations, and / or elements.

[0288] Furthermore, although the above illustrates and describes preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, and it goes without saying that various modifications can be made by a person having ordinary skill in the art to which the invention pertains without departing from the gist of the present invention as claimed in the claims, and such modifications should not be understood separately from the technical ideas and perspectives of the present invention.

Claims

1. A unit chair including a link part having one end connected to a backrest part and another end connected to a headrest for adjusting the posture of the headrest, The link portion is A first link member fixed to the backrest portion; a second link member, one end of which is hingedly connected to the first link member by a first hinge pin; a first ratchet member formed on one surface of at least one of the first link member and the second link member, and restricting the movement of the second link member such that the second link member is rotatable in only one direction around a central axis of the first hinge pin; The first ratchet member is a first ratchet base portion, the first ratchet base portion being arranged in an annular shape around a central axis of the first hinge pin, protruding in a direction of the central axis, the first ratchet base portion having a sawtooth shape inclined in only one direction formed on one surface thereof, and the opposite surface thereof being fixed to the first link member; a first ratchet rotation part, the first ratchet rotation part being arranged in an annular shape around a central axis of the first hinge pin, the first ratchet rotation part having a surface on which a plurality of sawtooths are formed, at least a portion of which meshes with at least a portion of the sawtooths of the first ratchet base part, and the opposite surface of the first ratchet rotation part being fixed to the second link member, a surface of an outer surface of the second link member that becomes a distal end when the second link member rotates in the one direction is formed in a concave shape when observed in a central axis direction of the first hinge pin, When the second link member rotates in the one direction, the other end of the second link member comes into contact with the seat surface of the backrest portion, instead of the one end of the second link member, This unit chair is characterized in that the other end portion is movable so as to be embedded in the seat surface by further rotating the second link member in the one direction to deform the seat surface, and by rotating the first ratchet member only in the direction toward the seat surface.

2. One end of the second link member is hinged to the other end of the second link member by a second hinge pin, a third link member to one surface of which the headrest is fixed; The unit chair as described in claim 1, further comprising a second ratchet member formed on one surface of at least one of the second link member and the third link member, which restricts the movement of the third link member so that the third link member can rotate only in one direction around the central axis of the second hinge pin.

3. The second link member is a first release portion capable of transmitting an external force to the first ratchet member to release the motion restraint state of the second link member; The unit chair as described in claim 2, characterized in that it includes a second release portion that operates independently of the first release portion and is capable of transmitting an external force to the second ratchet member to release the movement constraint state of the third link member.

4. the second link member includes a first release portion capable of transmitting an external force to the first ratchet member to release the movement constraint state of the second link member, the first ratchet member restricts movement of the second link member such that the second link member can rotate in only one direction around a central axis of the first hinge pin by meshing between the sawtooth of the first ratchet base portion and the sawtooth of the first ratchet pivot portion; The unit chair according to claim 1, wherein the first release portion releases the engagement of the first ratchet member to release the motion constraint state of the second link member when an external force is applied.

5. The second ratchet member is a second ratchet base portion, the second ratchet base portion being arranged in an annular shape around a central axis of the second hinge pin, protruding in the direction of the central axis, the second ratchet base portion having a sawtooth shape inclined in only one direction formed on one surface, and the second ratchet base portion having an opposite surface fixed to the third link member; The unit chair described in claim 3, characterized in that it includes a second ratchet rotating part having a plurality of sawtooths arranged in a ring shape around the central axis of the second hinge pin, at least a portion of which engages with at least a portion of the sawtooths of the second ratchet base part formed on one side, and an opposite side fixed to the second link member.

6. the second link member includes a first release portion capable of transmitting an external force to the first ratchet member to release the movement constraint state of the second link member, The first release unit is a first button protruding from an outer side of the second link member to which an external force is applied; 2. The unit chair as described in claim 1, further comprising: a first actuating member formed inside the second link member and supported by a first elastic member, having the first button and the first ratchet rotating part fixed to one surface thereof, and moving integrally with the first button and the first ratchet rotating part to separate the first ratchet rotating part from the first ratchet base part when an external force is applied to the first button.

7. The unit chair as described in claim 1, characterized in that the sawtooth of each of the first ratchet base portion and the first ratchet rotating portion forms an inclination angle of 40 degrees or more and 50 degrees or less in only one direction with respect to the surface on which each of the sawtooth is formed.

8. The unit chair according to claim 7, characterized in that the inclination angle is 45 degrees.

9. The unit chair according to claim 7, wherein one of the number of saw teeth of the first ratchet base portion and the number of saw teeth of the first ratchet rotating portion is a multiple of the other one, the multiple being two or more.

10. The unit chair according to claim 9, wherein the number of saw teeth of the first ratchet rotation portion is twice the number of saw teeth of the first ratchet base portion.

11. The unit chair according to claim 10, wherein the sawtooth of the first ratchet rotation portion is arranged in a ring shape at equal angular intervals.

12. the second link member is restricted in movement by the first ratchet member and is rotatable only in a direction toward a seat surface of the backrest portion, 3. The unit chair according to claim 2, wherein the third link member is constrained in movement by the second ratchet member and can only rotate in a direction opposite to a direction in which the second link member can rotate.

13. The second release unit is a second button protruding from an outer side of the second link member to which an external force is applied; 6. The unit chair as described in claim 5, further comprising: a second actuating member formed inside the second link member and supported by a second elastic member, having the second button and the second ratchet rotating part fixed to one surface thereof, and moving integrally with the second button and the second ratchet rotating part to separate the second ratchet rotating part from the second ratchet base part when an external force is applied to the second button.

14. The second link member includes a first release portion capable of transmitting an external force to the first ratchet member to release the motion constraint state of the second link member, The first release unit is a first deformable member whose shape or position changes when an external force is applied thereto, and the applied external force is transmitted to the first ratchet member only when a change in shape or position of the first deformable member exceeds a first reference amount; a first actuating member formed inside the second link member and supported by a first-1 elastic member, The first deformable member is a first button protruding from an outer side of the second link member and supported by a first-second elastic member; the first operating member transmits an applied external force to the first ratchet member only when the first button is moved beyond a first reference displacement by the application of the external force to the first button; A first protrusion is formed on the inside of the housing of the second link member and passes through a hole formed in the first operating member, an outer wall of the first raised portion guides the movement direction of the first operating member; The unit chair described in claim 1, characterized in that the first-2 elastic member has one end connected to the first raised portion and the other end connected to the first button to support the first button and is deformed in response to the movement of the first button.

15. A unit chair including a link portion for adjusting the posture of a headrest, The link portion is A first link member fixed to a backrest portion of the unit chair; a second link member, one end of which is hingedly connected to the first link member by a first hinge pin; a third link member, one end of which is hinged to the other end of the second link member by a second hinge pin and one surface of which is fixed to the headrest; a first ratchet member that is formed on one surface of at least one of the first link member and the second link member and restricts movement of the second link member such that the second link member can rotate in only one direction around the central axis of the first hinge pin by meshing of inclined sawtooth members that are arranged to face each other; a second ratchet member that restricts movement of the third link member so that the third link member can rotate in only one direction around the central axis of the second hinge pin by meshing of inclined sawtooth members that are formed on one surface of at least one of the second link member and the third link member and are arranged to face each other; The second link member is a release portion capable of transmitting an external force to the first ratchet member to release the motion restraint state of the second link member, a surface of an outer surface of the second link member that becomes a distal end when the second link member rotates in the one direction is formed in a concave shape when observed in a central axis direction of the first hinge pin, When the second link member rotates in the one direction, the other end of the second link member comes into contact with a seat surface of the backrest portion, This unit chair is characterized in that the other end portion is movable so as to be embedded in the seat surface by further rotating the second link member in the one direction to deform the seat surface, and by rotating the first ratchet member only in the direction toward the seat surface.

16. The unit chair described in claim 15, characterized in that the release portion includes a first release portion capable of transmitting an external force to the first ratchet member to release the movement constraint state of the second link member, and a second release portion that operates independently of the first release portion and is capable of transmitting an external force to the second ratchet member to release the movement constraint state of the third link member.

17. The first release unit is When an external force is applied, the sawtooth of the first ratchet member is released from engagement, thereby releasing the motion restriction state of the second link member; The second release unit is The unit chair according to claim 16, characterized in that, when an external force is applied, the engagement of the sawtooth of the second ratchet member is released, thereby releasing the movement restriction state of the third link member.

18. The first ratchet member is a first ratchet base portion, the first ratchet base portion being arranged in an annular shape around a central axis of the first hinge pin, protruding in a direction of the central axis, the first ratchet base portion having a sawtooth shape inclined in only one direction formed on one surface thereof, and the opposite surface thereof being fixed to the first link member; a first ratchet rotation portion having a plurality of sawtooths arranged in an annular shape around a central axis of the first hinge pin, at least a portion of which engages with at least a portion of the sawtooths of the first ratchet base portion on one surface thereof, and an opposite surface thereof fixed to the second link member; The second ratchet member is a second ratchet base portion, the second ratchet base portion being arranged in an annular shape around a central axis of the second hinge pin, protruding in the direction of the central axis, the second ratchet base portion having a sawtooth shape inclined in only one direction formed on one surface, and the second ratchet base portion having an opposite surface fixed to the third link member; The unit chair according to claim 16 or claim 17, characterized in that it includes a second ratchet rotating part having a plurality of sawtooths arranged in a ring shape around the central axis of the second hinge pin, at least a portion of which engages with at least a portion of the sawtooths of the second ratchet base part formed on one side, and an opposite side fixed to the second link member.

19. The unit chair described in claim 18, characterized in that the sawtooth of each of the first ratchet base portion, the first ratchet rotating portion, the second ratchet base portion and the second ratchet rotating portion forms an inclination angle of 40 degrees or more and 50 degrees or less in only one direction with respect to the surface on which each of the sawtooths is formed.

20. 20. The unit chair of claim 19, wherein the inclination angle is 45 degrees.

21. Either one of the number of saw teeth of the first ratchet base portion and the number of saw teeth of the first ratchet rotation portion is a multiple of the other one, the multiple being 2 or more; The unit chair according to claim 18, wherein one of the number of saw teeth of the second ratchet base portion and the number of saw teeth of the second ratchet rotating portion is a multiple of the other one, the multiple being two or more.

22. the number of saw teeth of the first ratchet rotation portion is twice the number of saw teeth of the first ratchet base portion, The unit chair according to claim 21, characterized in that the number of saw teeth of the second ratchet pivot part is twice the number of saw teeth of the second ratchet base part.

23. The unit chair according to claim 22, wherein the sawtooth of the first ratchet rotating part and the sawtooth of the second ratchet rotating part are each arranged in a ring at equal angular intervals.

24. the second link member is restricted in movement by the first ratchet member and is rotatable only in a direction toward a seat surface of the backrest portion, The unit chair according to claim 15, characterized in that the third link member is constrained in movement by the second ratchet member and can only rotate in a direction opposite to the direction in which the second link member can rotate.

25. The first release unit is a first button protruding from an outer side of the second link member to which an external force is applied; a first operating member formed inside the second link member and supported by a first elastic member, the first button and the first ratchet rotating part being fixed to one surface thereof, and moving together with the first button and the first ratchet rotating part when an external force is applied to the first button to separate the first ratchet rotating part from the first ratchet base part, The second release unit is a second button protruding from an outer side of the second link member to which an external force is applied; and a second actuating member formed inside the second link member and supported by a second elastic member, having the second button and the second ratchet rotating part fixed to one surface thereof, and moving integrally with the second button and the second ratchet rotating part to separate the second ratchet rotating part from the second ratchet base part when an external force is applied to the second button.

26. The unit chair according to claim 15, wherein the second link member is formed in a "C" shape.

27. The unit chair according to claim 16, wherein at least one of the first release part and the second release part includes a button that moves along a trajectory including a central axis of the first hinge pin or a central axis of the second hinge pin when an external force is applied.

28. The second release unit is The unit chair described in claim 27, further comprising a second button that, when an external force is applied, pushes and moves at least a portion of the second ratchet member along a path including the central axis of the first hinge pin to release the engagement of the saw teeth of the second ratchet member and release the movement constraint state of the third link member.

29. The first release unit is a first button that is protruded from an outer side surface of the second link member and moves along a path that does not include a central axis of the first hinge pin and is parallel to the central axis of the first hinge pin when an external force is applied; The unit chair as described in claim 28, further comprising a first operating member formed inside the second link member and supported by a first elastic member, which moves integrally with the first button when an external force is applied, thereby releasing the engagement of the sawtooth of the first ratchet member and releasing the movement restriction state of the second link member.

30. The release unit, a first deformable member whose shape or position changes when an external force is applied thereto, and the applied external force is transmitted to the first ratchet member only when a change in shape or position of the first deformable member exceeds a first reference amount; a first actuating member formed inside the second link member and supported by a first-1 elastic member, The first deformable member is a first button protruding from an outer side of the second link member and supported by a first-second elastic member; the first operating member transmits an applied external force to the first ratchet member only when the first button is moved beyond a first reference displacement by the application of the external force to the first button; A first protrusion is formed on the inside of the housing of the second link member and passes through a hole formed in the first operating member, an outer wall of the first raised portion guides the movement direction of the first operating member; The unit chair described in claim 15, characterized in that the first-2 elastic member has one end connected to the first raised portion and the other end connected to the first button to support the first button and is deformed in response to the movement of the first button.

Images