Patent Description:
A unit chair is a device for accommodating an examinee at the dentist's office, etc., and generally includes a backrest for supporting the examinee's back and a seat (leg rest) for supporting the buttocks and legs. In addition, the unit chair may further include a headrest for supporting the examinee's head, a doctor table (i.e., an instrument tray) for holding dental tools such as a handpiece for the examinee's treatment, or a cuspidor, a watering table, etc..

The seat is supported by a base placed on a floor surface of a dental treatment space. At least one of the base and the seat may include a driving unit for adjusting a height of the seat.

The backrest may be coupled to one end of the seat and perform a tilting operation with respect to the seat. By tilting the backrest to stand forward, the examinee may be placed in a seated state, and by tilting the backrest to be reversed backward, the examinee may be placed in a lying state, thereby obtaining the suitable posture of the examinee for medical treatment situations.

The headrest is formed at an upper end of the backrest and an angle thereof may be adjusted according to the purpose of a treatment, a body type of a patient, and the convenience of medical staff. In a situation of a treatment that requires adjustment of the angle of the headrest, the medical staff is holding a treatment tool in one hand so that he/she may not use both hands freely or the examinee's head is applying a load to the headrest in many cases.

Therefore, in the case of adjusting the angle or posture of the headrest in a direction in which the examinee bows or advances his/her head, it is preferred for the angle to be adjusted by lightly pushing the headrest with one hand without operating a separate button or lever. Or, conversely, the angle may be adjusted in a direction in which the examinee's head is erected (reverse direction) only by operating a separate button or lever, and otherwise, it is better to firmly support the head.

The design of the button or lever is very important. Reliability should be ensured so that the angle may be adjusted in the reverse direction only when the button or lever is pressed with an appropriate force. In addition, in that the doctor's hand motions are often made near the headrest in terms of the characteristics of dental treatment, a malfunction caused as a hand touches the button or lever may lead to an injury of the examinee, which, thus, requires attention. Therefore, there is a need for a safety measure capable of effectively preventing a malfunction.

However, as described above, it is not easy to ensure durability in a structure that allows angle adjustment in only one direction and supports the examinee's head in the reverse direction.

Further, in addition to guaranteeing durability, it is necessary to propose a structure that may adjust a posture of a headrest more precisely, may solve side effects such as sticking between the parts constituting the structure, and may be easy to manufacture.

In addition, it is necessary to provide a support structure for the headrest that may take postures corresponding to body types of examinees of various heights, including very short examinees such as children, while adopting the structure in which the angle may be adjusted only in one direction.

An aspect of the present disclosure provides a unit chair in which an angle of a headrest may be adjusted in a forward direction, while durability of a structure is supported when a force is applied in a reverse direction.

Another aspect of the present disclosure provides a support structure of a headrest that may precisely adjust a posture of the headrest and solve side effects thereof.

Another aspect of the present disclosure provides a support structure for a headrest that is easy to manufacture through injection molding, while simplifying the number of parts.

Another aspect of the present disclosure provides a support structure for a headrest that may take a posture corresponding to a body type of an examinee of various heights accommodated in a unit chair.

Another aspect of the present disclosure provides a support structure for a two-joint headrest that may adjust an angle in one direction, while independently releasing a motion constraint state of the two joints, and may adjust the angle in one direction.

Another aspect of the present disclosure provides a unit chair having a structure that enables adjustment of a forward posture of a headrest and supports and fixes the headrest when a force is applied in a reverse direction.

Another aspect of the present disclosure provides a safety device for a unit chair, which prevents a malfunction of a function of releasing, as needed, a state in which a headrest is supported and fixed when a force in the reverse direction is applied.

According to an embodiment of the present disclosure, a unit chair includes a link unit for adjusting a posture of a headrest, wherein the link unit includes: a first link member fixed to a backrest portion of the unit chair; a second link member having one end portion hinged to the first link member by a first hinge pin; and a first ratchet member formed on one surface of at least one of the first link member and the second link member and constraining motion of the second link member so that the second link member is rotatable only in one direction based on a central axis line of the first hinge pin, wherein the first ratchet member includes a first ratchet base portion including a plurality of saw teeth formed on one surface, arranged in a ring shape based on the central axis line of the first hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the first link member; and a first ratchet rotating portion including a plurality of saw teeth formed on one surface and at least partially engaged with at least some of the saw teeth of the first ratchet base portion and having an opposite surface fixed to the second link member.

The unit chair may further include: a third link member having one end portion hinged to the other end portion of the second link member by a second hinge pin and allowing the headrest to be fixed to one surface thereof; 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 motion of the third link member so that the third link member is rotatable only in one direction based on a central axis line of the second hinge pin.

The second link member may include a first release portion transmitting an external force to the first ratchet member to release the motion constraint state of the second link member; and a second release portion operating independently from the first release portion and transmitting an external force to the second ratchet member to release a motion constraint state of the third link member.

The second link member may include a first release portion transmitting an external force to the first ratchet member to release the motion constraint state of the second link member, wherein the first ratchet member constrains motion of the second link member so that the second link member is rotatable only in one direction based on the central axis line of the first hinge pin as the saw teeth of the first ratchet base portion are engaged with the saw teeth of the first ratchet rotating portion, and the first release portion releases the motion constraint state of the second link member by releasing the engagement of the first ratchet member when an external force is applied.

The second ratchet member may include: a second ratchet base portion including a plurality of saw teeth formed on one surface, arranged in a ring shape based on a central axis line of the second hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the third link member; and a second ratchet rotating portion including a plurality of saw teeth formed on one surface and at least partially engaged with at least some of the saw teeth of the second ratchet base portion and having an opposite surface fixed to the second link member.

The second link member may include a first release portion transmitting an external force to the first ratchet member to release the motion constraint state of the second link member, wherein the first release portion may include: a first button protruding from an external side surface of the second link member and receiving an external force applied thereto; and a first operating member formed inside the second link member and supported by a first elastic member, having one surface to which the first button and the first ratchet rotating portion are fixed, and integrally moving together with the first button and the first ratchet rotating portion to separate the first ratchet rotating portion from the first ratchet base portion when an external force is applied to the first button.

Each saw tooth of each of the first ratchet base portion and the first ratchet rotating portion may be at an inclination angle of <NUM> degrees to <NUM> degrees only in one direction with respect to a surface on which each saw tooth is formed.

The inclination angle may be <NUM> degrees.

Any 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 may be a multiple of <NUM> or greater of the other.

The number of saw teeth of the first ratchet rotating portion may be twice the number of saw teeth of the first ratchet base portion.

The saw teeth of the first ratchet rotating portion may be provided in plurality, and the plurality of saw teeth may be arranged in a ring shape at equiangular intervals.

The second link member is constrained in motion by the first ratchet member and is rotatable only in a direction toward a seat surface of the backrest portion, and the third link member may be constrained in motion by the second ratchet member so that the third link member is rotatable only in a direction opposite to a direction in which the second link member is rotatable.

The second release portion include: a second button protruding from an external side surface of the second link member and receiving an external force applied thereto; and a second operating member formed inside the second link member and supported by a second elastic member, having one surface to which the second button and the second ratchet rotating portion are fixed, and integrally moving together 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.

A surface becoming a front end when the second link member rotates in one direction, in an external surface of the second link member is recessed when observed in a direction of a central axial line of the first hinge pin.

When the first link member is fixed to the backrest portion, the other end portion of the second link member, rather than the one end portion of the second link member, contacts a seat surface of the backrest portion.

According to another embodiment of the present disclosure, a unit chair includes a link unit for adjusting a posture of a headrest, wherein the link unit includes: a first link member fixed to a backrest portion of the unit chair; a second link member having one end portion hinged to the first link member by a first hinge pin; a third link member having one end portion hinged to the other end portion of the second link member and allowing the headrest to be fixed to one surface thereof; a first ratchet member formed on one surface of at least one of the first link member and the second link member, constraining motion of the second link member so that the second link member is rotatable only in one direction based on a central axis line of the first hinge pin according to engagement of saw teeth having an inclined shape and facing each other; 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 motion of the third link member so that the third link member is rotatable only in one direction based on a central axis line of the second hinge pin according to engagement of the saw teeth having an inclined shape and facing each other, and wherein the second link member includes a release portion releasing the motion constraint state of the second link member by transmitting an external force to the first ratchet member.

The release portion includes: a first release portion releasing the motion constraint state of the second link member by transmitting an external force to the first ratchet member; and a second release portion operating independently from the first release portion and releasing the motion constraint state of the third link member by transmitting an external force to the second ratchet member.

The first release portion releases the motion constraint state of the second link member by releasing the engagement of the saw teeth of the first ratchet member when an external force is applied, and the second release portion releases the motion constraint state of the third link member by releasing the engagement of the saw teeth of the second ratchet member when an external force is applied.

The first ratchet member includes: a first ratchet base portion including a plurality of saw teeth formed on one surface, arranged in a ring shape based on the central axis line of the first hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the first link member; and a first ratchet rotating portion including a plurality of saw teeth formed on one surface and at least partially engaged with at least some of the saw teeth of the first ratchet base portion and having an opposite surface fixed to the second link member, and the second ratchet member includes: a second ratchet base portion including a plurality of saw teeth formed on one surface, arranged in a ring shape based on a central axis line of the second hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the third link member; and a second ratchet rotating portion including a plurality of saw teeth formed on one surface and at least partially engaged with at least some of the saw teeth of the second ratchet base portion and having an opposite surface fixed to the second link member.

Each saw tooth of each of the first ratchet base portion, the first ratchet rotating portion, the second ratchet base portion, and the second ratchet rotating portion is at an inclination angle of <NUM> degrees to <NUM> degrees only in one direction with respect to a surface on which each saw tooth is formed.

Any 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 <NUM> or greater of the other, or any 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 <NUM> or greater of the other.

The number of saw teeth of the first ratchet rotating portion may be double the number of saw teeth of the first ratchet base portion, and the number of saw teeth of the second ratchet rotating portion is double the number of saw teeth of the second ratchet base portion.

The saw teeth of the first ratchet rotating portion and the saw teeth of the second ratchet rotating portion may be provided in plurality, and the plurality of saw teeth may be arranged in a ring shape at equiangular intervals.

The second link member is constrained in motion by the first ratchet member and is rotatable only in a direction toward a seat surface of the backrest portion, and the third link member is constrained in motion by the second ratchet member so that the third link member is rotatable only in a direction opposite to a direction in which the second link member is rotatable.

The first release portion includes: a first button protruding from an external side surface of the second link member and receiving an external force applied thereto; and a first operating member formed inside the second link member and supported by a first elastic member, having one surface to which the first button and the first ratchet rotating portion are fixed, and integrally moving together with the first button and the first ratchet rotating portion to separate the first ratchet rotating portion from the first ratchet base portion when an external force is applied to the first button, and the second release portion includes: a second button protruding from an external side surface of the second link member and receiving an external force applied thereto; and a second operating member formed inside the second link member and supported by a second elastic member, having one surface to which the second button and the second ratchet rotating portion are fixed, and integrally moving together 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.

A surface becoming a front end when the second link member rotates in one direction, in an external surface of the second link member, is recessed when observed in a direction of a central axial line of the first hinge pin.

When the first link member is fixed to the backrest portion, the other end portion of the second link member may contact a seat surface of the backrest portion.

At least one of the first release portion and the second release portion includes a button moving along a trace including the central axis line of the first hinge pin or the central axis line of the second hinge pin when an external force is applied.

The second release portion includes a second button moving, while pushing at least a portion of the second ratchet member, along a trace including the central axis line of the first hinge pin to release the engagement of the saw teeth of the second ratchet member to release the motion constraint state of the third link member, when an external force is applied.

The first release portion may include: a first button protruding from one external side surface of the second link member and moving along a trace not including the central axis line of the first hinge pin and in parallel with the central axis line of the first hinge pin, when an external force is applied; and a first operating member formed inside the second link member, supported by a first elastic member, and integrally moving with the first button to release the engagement of the first ratchet member to release the motion constraint state of the second link member when an external force is applied.

According to another embodiment of the present disclosure, a unit chair includes a link unit for adjusting a posture of a headrest, wherein the link unit includes: a first link member fixed to a backrest portion of the unit chair; a second link member having one end portion hinged to the first link member by a first hinge pin; and a first ratchet member formed on one surface of at least one of the first link member and the second link member and constraining motion of the second link member so that the second link member is rotatable only in one direction based on a central axis line of the first hinge pin, wherein the second link member includes a first release portion releasing the motion constraint state of the second link member by transmitting an external force to the first ratchet member, and the first release portion includes a first deformation member changed in shape or position as an external force is applied, and the external force applied to the first ratchet member is transmitted only when a change amount of the shape or position of the first deformation member exceeds a predetermined first reference amount.

The first release portion further includes a first operating member formed inside the second link member and supported by a (<NUM>-<NUM>)-th elastic member, wherein the first deformation member includes a first button protruding from one external side surface of the second link member and supported by a (<NUM>-<NUM>)-th elastic member, and wherein the first operating member may transmit the applied external force to the first ratchet member only when the first button moves more than a first reference displacement as an external force is applied to the first button.

When the first button moves more than the first reference displacement as an external force is applied, the first operating member may be in contact and interwork with the first button.

A first uplift portion penetrating a hole formed in the first operating member is formed on an inner side of a housing of the second link member, and an outer wall of the first uplift portion guides a motion direction of the first operating member.

The first uplift portion has a first guide recess guiding a motion direction of the first button.

One end of the (<NUM>-<NUM>)-th elastic member is connected to the first uplift portion and the other end of the (<NUM>-<NUM>)-th elastic member is connected to the first button to support the first button and may be deformed according to a motion operation of the first button.

The first ratchet member includes a first ratchet base portion including a plurality of saw teeth formed on one surface, arranged in a ring shape based on the central axis line of the first hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the first link member; and a first ratchet rotating portion including saw teeth formed on one surface and engaged with the saw teeth of the first ratchet base portion and having an opposite surface fixed to the first operating member, and wherein the first operating member is moved together with the first button and the first ratchet rotating portion to separate the first ratchet rotating portion from the first ratchet base portion when an external force is applied to the first button.

The link unit further includes: a third link member having one end portion hinged to the other end portion of the second link member by a second hinge pin and allowing the headrest to be fixed to one surface thereof; 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 motion of the third link member so that the third link member is rotatable only in one direction based on a central axis line of the second hinge pin, wherein the second link member further includes a second release portion operating independently from the first release portion and transmitting an external force to the second ratchet member to release a motion constraint state of the third link member, and wherein the second release portion includes a second deformation member changed in shape or position as an external force is applied, and the external force applied to the second ratchet member is transmitted only when a change amount of the shape or position of the second deformation member exceeds a predetermined second reference amount.

The second release portion further includes a second operating member formed inside the second link member and supported by a (<NUM>-<NUM>)-th elastic member, wherein the second deformation member includes a second button protruding from one external side surface of the second link member and supported by a (<NUM>-<NUM>)-th elastic member, and wherein the second operating member may transmit the applied external force to the second ratchet member only when the second button moves more than a second reference displacement as an external force is applied to the second button.

When the second button moves more than the second reference displacement as an external force is applied, the second operating member is in contact and interwork with the second button, wherein the second ratchet member includes: a second ratchet base portion including a plurality of saw teeth formed on one surface, arranged in a ring shape based on a central axis line of the second hinge pin, uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the third link member; and a second ratchet rotating portion including saw teeth formed on one surface and engaged with the saw teeth of the second ratchet base portion and having an opposite surface fixed to the second operating member, and wherein the second operating member is moved together 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.

According to various embodiments of the present disclosure, a structure in which an angle of a headrest of a unit chair can be easily adjusted with one hand in a forward direction and the headrest is firmly supported when a force is applied in a reverse direction may be provided.

In addition, according to various embodiments of the present disclosure, durability of the structure in which a posture of the headrest in the forward direction is adjustable and the headrest may be supported and fixed when a force is applied in the reverse direction may be secured.

In addition, according to various embodiments of the present disclosure, a malfunction of a function of releasing a state in which the headrest is supported and fixed, as needed, when a force in the reverse direction is applied may be effectively prevented.

In addition, according to various embodiments of the present disclosure, it is possible to precisely adjust the posture of the headrest in response to a body shape of various examinees accommodated in the unit chair, while side effects such as sticking between parts constituting a support structure of the headrest may be addressed.

In addition, according to various embodiments of the present disclosure, it is possible to provide a support structure of the headrest that is easy to manufacture through injection molding, while simplifying the number of parts by excluding complicated parts such as a gas spring or a leaf spring.

In addition, according to various embodiments of the present disclosure, it is possible to take the posture of the headrest in response to a body type of the examinee of various heights accommodated in the unit chair.

In addition, according to various embodiments of the present disclosure, it is possible to implement a support structure of a two-joint headrest capable of adjusting an angle in one direction, while independently releasing a motion constraint state of the two joints.

The following description illustrates only a principle of the present disclosure.

The above-mentioned objects, features, and advantages will become obvious from the following detailed description provided in relation to the accompanying drawings. Therefore, those skilled in the art to which the present disclosure pertains may easily practice a technical idea of the present disclosure. Further, in describing the present disclosure, in the case in which it is judged that a detailed description of a well-known technology associated with the present disclosure may unnecessarily make unclear the gist of the present disclosure, it will be omitted.

Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

A unit chair <NUM> according to an embodiment of the present disclosure is a device that is installed on the floor of a dental treatment space and allows an examinee to sit on or lie down during treatment. The unit chair <NUM> may have a shape corresponding to a body shape so that the examinee does not feel discomfort during treatment.

<FIG> is a perspective view of a unit chair according to an embodiment of the present disclosure, and <FIG> is a block diagram illustrating a configuration of a unit chair according to an embodiment of the present disclosure.

As shown in these drawings, the unit chair <NUM> according to an embodiment of the present disclosure basically includes a seat portion <NUM> on which the examinee's legs are mounted and a backrest portion <NUM> on which the examinee's backrests.

In addition, the unit chair <NUM> may include a headrest portion <NUM> supporting the examinee's head, a base portion <NUM> supporting the seat portion <NUM>, a driving unit <NUM> driving at least one of the backrest portion <NUM> and the seat portion <NUM>, and a controller <NUM> controlling the driving unit <NUM>. An armrest on which an examinee's arm is mounted may be formed on a side surface of at least one of the backrest portion <NUM> and the seat portion <NUM>.

In addition, the unit chair <NUM> may include an associated device. For example, the associated device may include a treatment table portion <NUM> having an interface for operating an instrument or holding a treatment instrument, treatment chart, and the like for the examinee's treatment. In addition, the associated device may include at least one of a lighting unit (not shown) for illuminating the examinee, a water supply unit (not shown) for supplying gargle water for rinsing the examinee'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).

The seat portion <NUM> may be a portion in contact with the examinee's lower body including the buttocks. The seat portion <NUM> may be supported by the base portion <NUM>. A leg rest (not shown) supporting the examinee's foot may be coupled to the end of the seat portion <NUM>. The leg rest (not shown) coupled to the seat portion <NUM> may have an angle and/or distance adjusted as needed.

For the convenience of medical practitioners and examinees, one portion of the unit chair <NUM> may operate separately from other portions.

The backrest portion <NUM> may be a portion in contact with the examinee's back part. A headrest portion <NUM> may be connected to an upper side of the backrest portion <NUM>. An angle of the headrest portion <NUM> connected to the backrest portion <NUM> may be adjusted as needed. The angle of the headrest portion <NUM> may be electrically and/or manually adjusted. The backrest portion <NUM> may be coupled to the seat portion <NUM> and/or the base portion <NUM>.

The headrest portion <NUM> may include a headrest <NUM> that is in contact with the examinee's head part. At least a portion of the headrest <NUM> may be machined into a concave shape to correspond to a shape of the head.

The armrest may be located on both sides of the seat portion <NUM> or the backrest portion <NUM>. The armrest may be provided at a position corresponding to a portion in which both arms of the examinee seated on the seat portion <NUM> are naturally positioned so that the examinee may be examined in a stable posture.

The treatment table portion <NUM> may be a cradle on which various dental instruments are disposed to use the unit chair <NUM> for medical treatment and/or care. At least one of electricity, pneumatic pressure, and hydraulic pressure to be used for an operation of a surgical instrument may be supplied to the treatment table portion <NUM>. For example, it means that an oral light, one of the surgical instruments, may be turned on with the supplied electricity.

The treatment table portion <NUM> may include various switches. Considering a location of an operator, the treatment table portion <NUM> may be located at a distance for the operator to easily reach with his or her hand. Accordingly, various switches for controlling each portion of the unit chair <NUM> may be located in the treatment table portion <NUM>.

A lighting unit (not shown) may be at a position in which the inside of the examinee's oral cavity is not covered by the operator's body or the like. For example, when the operator moves his upper body to examine the inside of the examinee's oral cavity, the lighting unit is positioned at an upper position in which the inside of the oral cavity is not darkened.

The lighting unit (not shown) may emit different lights as needed. For example, it means that brightness and/or a wavelength may be adjusted according to ambient brightness and/or the contents of the examination.

In an embodiment, it is possible to control a luminous intensity of illumination of the lighting unit (not shown) by the controller <NUM> in response to a posture adjustment of the headrest <NUM> according to an operation of a link unit <NUM> of the present disclosure.

The water supply unit (not shown) may be used for procedures such as cleaning the inside of the oral cavity of the examinee. The water supply unit (not shown) may include a drainage device and/or a cuspidor for spitting.

The display unit (not shown) may display various types of information required for examination. For example, it means that an X-ray image of the examinee's oral condition and an image of the inside of the examinee's mouth may be displayed in real time. The position/angle of the display unit may be adjusted up, down, left and right as needed so that the examinee feels less fatigue.

The foot control unit (not shown) may be used to control the operation of at least one dental instrument. The examinee may freely use both hands, while controlling the surgical instrument by operating the foot control unit (not shown) with the foot.

The controller <NUM> may perform a control operation on each portion of the unit chair <NUM>. The controller <NUM> may cause each portion of the unit chair <NUM> to be organically operated.

The controller <NUM> may be distributed in a plurality of locations. For example, the base portion <NUM> may be controlled by a first controller, and the treatment table portion <NUM> may be controlled by a second controller. The first and second controllers may transmit signals in one direction or in both directions so that the unit chair <NUM> as a whole operates harmoniously.

The controller <NUM> may perform a control operation on the associated device of the unit chair <NUM>. For example, when the controller <NUM> is located in the base portion <NUM>, the controller <NUM> may perform a control operation on all or some of the components of the unit chair <NUM> together with the base portion <NUM> during the examination. For example, it means that an activation or deactivation control operation is performed on the associated device.

The power supply unit (not shown) may be a device for supplying power to the unit chair <NUM>. The power supply unit (not shown) may include a converter for AC/DC power and/or a voltage/current converter suitable for each component.

As shown in <FIG>, according to an embodiment of the present disclosure, the headrest portion <NUM> may include a headrest <NUM> supporting the examinee's head and a link unit <NUM> linking the headrest <NUM> and one end of the backrest portion <NUM>.

The link unit <NUM> may perform an operation for adjusting a posture of the headrest <NUM>. That is, basically having a function of connecting the headrest <NUM> to one end of the backrest portion <NUM> and supporting a load of the examinee's head, the link unit <NUM> may perform an angle adjustment operation of bending or unfolding in forward and backward directions of the examinee's head or move forward or backward the headrest <NUM> to adjust a posture for convenience during treatment.

A user (medical staff) may adjust the angle or posture by holding the headrest <NUM> with one hand and applying an external force.

Hereinafter, a configuration of the link unit <NUM> of the present disclosure will be described in more detail with reference to the drawings.

<FIG> is a block diagram illustrating a configuration of a link unit according to an embodiment of the present disclosure. <FIG> is a right view of a link unit according to an embodiment of the present disclosure. As shown in <FIG> and <FIG>, the link unit <NUM> may include a series of first link member <NUM> and a second link member <NUM>. Also, according to an embodiment, the link unit <NUM> may further include a third link member <NUM>.

The first link member <NUM> may be fixed to the backrest portion <NUM> of the unit chair <NUM>.

In an embodiment of the present disclosure, the first link member <NUM> may be coupled to one end of the backrest portion <NUM> to be semi-permanently fixed.

In another embodiment of the present disclosure, the first link member <NUM> may be elongated and may be slidably coupled to an insertion hole of one end of the backrest portion <NUM>.

When the unit chair <NUM> needs to accommodate a tall examinee, the first link member <NUM> may slide so that the headrest <NUM> is away from one end of the backrest <NUM> and is fixed to a specific position.

When the unit chair <NUM> needs to accommodate a rather short examinee, the first link member <NUM> may slide so that the headrest <NUM> approaches the one end of the backrest portion <NUM> and is fixed to a specific position.

One end portion of the second link member <NUM> may be hinged to the first link member <NUM> by a first hinge pin <NUM>.

One end portion of the third link member <NUM> may be hinged to the other end portion of the second link member <NUM>, not the one end portion thereof, by a second hinge pin <NUM>.

As shown in <FIG>, the headrest <NUM> may be fixed to one surface of the third link member.

The link unit <NUM> may further include a first ratchet member <NUM> formed on one surface of at least one of the first link member <NUM> and the second link member <NUM>.

The first ratchet member <NUM> may include two sub-members rotatable in only one direction relative to each other in contact with each other.

The two sub-members may be a first ratchet base portion <NUM> and a first ratchet rotating portion <NUM> of the present disclosure to be described below.

It is possible to further simplify a structure of the headrest portion <NUM> by using a structure of a ratchet, without using a structure such as a gas spring or a leaf spring.

The first ratchet member <NUM> may constrain the motion of the second link member <NUM> to a unidirectional rotational motion.

The first ratchet member <NUM> may constrain the motion of the second link member <NUM> so that the second link member <NUM> may rotate only in one direction (a direction indicated by the dotted arrow at a lower portion in <FIG>) based on a central axis line (the center having a "+" shape at the lower portion in <FIG>) of the first hinge pin <NUM>.

The second link member <NUM> may include a release portion <NUM> capable of releasing the motion constraint state of the second link member <NUM> by transmitting an external force to the first ratchet member <NUM>.

The link unit <NUM> of the present disclosure may further include a second ratchet member <NUM> formed on one surface of at least one of the second link member <NUM> and the third link member <NUM>.

The second ratchet member <NUM> may be structurally formed to be the same as that of the first ratchet member <NUM>.

The second ratchet member <NUM> may constrain a motion of the third link member <NUM> to a unidirectional rotational motion.

The second ratchet member <NUM> may constrain a motion of the third link member <NUM> so that the third link member <NUM> may rotate only in one direction (a direction indicated by the dotted arrow at an upper portion in <FIG>) based on a central axis line (the center having a "+" shape at an upper portion in <FIG>) of the second hinge pin <NUM>.

In an embodiment further including the second ratchet member <NUM>, the release portion <NUM> may release the motion constraint state of the third link member <NUM> by transmitting an external force to the second ratchet member <NUM>.

The first ratchet member <NUM> may be formed on one surface of at least one of the first link member <NUM> and the second link member <NUM>.

The second ratchet member <NUM> may be formed on one surface of at least one of the second link member <NUM> and the third link member <NUM>.

<FIG> are views illustrating a structure of the first ratchet member according to an embodiment of the present disclosure.

As shown in <FIG>, which is an enlarged view of a portion thereof, the first ratchet member <NUM> may constrain the motion of the second link member <NUM> so that the second link member <NUM> is rotatable only in one direction based on a central axis line of the first hinge pin <NUM> as saw teeth having an inclined shape and facing each other are engaged with each other.

The first ratchet member <NUM> may include two saw teeth groups each including a plurality of saw teeth inclined in only one direction.

The two saw teeth groups may refer to a group of the saw teeth <NUM> formed in a component <NUM> illustrated in an upper portion of <FIG> and a group of saw teeth <NUM> formed in a component <NUM> illustrated in a lower portion of <FIG>.

The first ratchet member <NUM> may constrain the motion of the second link member <NUM> so that the second link member <NUM> is rotatable only in one direction based on the central axis line of the first hinge pin <NUM> through an interconnection of the two saw teeth groups.

The second ratchet member <NUM> may have a structure equivalent to that of the first ratchet member <NUM>.

The second ratchet member <NUM> may also constrain the motion of the third link member <NUM> so that the third link member <NUM> is rotatable only in one direction based on the central axis line of the second hinge pin <NUM> as the saw teeth having an inclined shape and facing each other are engaged with each other.

The second ratchet member <NUM> may include two saw teeth groups each including a plurality of saw teeth inclined in only one direction.

The second ratchet member <NUM> may constrain the motion of the third link member <NUM> so that the third link member <NUM> is rotatable based on the central axis line of the second hinge pin <NUM> through an interconnection of the two saw teeth groups.

The first release portion <NUM> may release the interconnection of the two saw teeth groups of the first ratchet member <NUM> to release the motion constraint state of the second link member <NUM>, when an external force is applied.

When an external force is applied, the second release portion <NUM> may release the interconnection of the two saw teeth groups of the second ratchet member <NUM> to release the motion constraint state of the third link member <NUM>.

More specifically, the first ratchet member <NUM> may include a first ratchet base portion <NUM> and a first ratchet rotating portion <NUM>. The first ratchet base portion <NUM> and the first ratchet rotating portion <NUM> may form a clutch configuration to transmit a force when interconnected. That is, a one-way-clutch system may be implemented.

The second ratchet member <NUM> may include a second ratchet base portion <NUM> and a second ratchet rotating portion <NUM>. The second ratchet base portion <NUM> and the second ratchet rotating portion <NUM> may form a clutch configuration to transmit a force when interconnected.

A plurality of saw teeth <NUM> arranged in a ring shape based on the central axis line of the first hinge pin <NUM>, uplifted in a direction toward the central axis line, and inclined in only one direction may be formed on one surface of the first ratchet base portion <NUM>. A surface opposite to the one surface may be fixed to the first link member <NUM>.

A plurality of saw teeth <NUM> arranged in a ring shape based on the central axis line of the second hinge pin <NUM>, uplifted in a direction toward the central axis line, and inclined in only one direction may be formed on one surface of the second ratchet base portion <NUM>. A surface opposite to the one surface may be fixed to the third link member <NUM>.

A plurality of saw teeth <NUM>, which are at least partially engaged with at least some of the saw teeth <NUM> of the first ratchet base portion <NUM>, may be formed on one surface of the first ratchet rotating portion <NUM>. A surface opposite to the one surface may be fixed to the second link member <NUM>.

A plurality of saw teeth <NUM>, which are at least partially engaged with at least some of the saw teeth <NUM> of the second ratchet base portion <NUM>, may be formed on one surface of the second ratchet rotating portion <NUM>. A surface opposite to the one surface may be fixed to the second link member <NUM>.

Through the configuration of the annularly arranged saw teeth to be engaged with each other, a force mutually transmitted by the first ratchet rotating portion <NUM> and the first ratchet base portion <NUM> and a force mutually transmitted by the second ratchet rotating portion <NUM> and the second ratchet base portion <NUM> may be distributed. Accordingly, it is possible to support the examinee's head with a stronger force and it is possible to ensure durability by extending a lifespan of the ratchet members.

In addition, the first ratchet rotating portion <NUM> and the first ratchet base portion <NUM> are formed of a synthetic resin-based material, rather than a metal, and manufactured through injection molding, costs for materials and machining may be reduced.

The saw teeth <NUM> may also be formed to be inclined only in one direction. Therefore, when a mutual force is transmitted to the inclined surface of each of the saw teeth <NUM> and <NUM>, sliding is possible, but when a mutual pushing force is transmitted to a perpendicular surface, sliding is impossible, so mutual rotation of the first ratchet base portion <NUM> and the first ratchet rotating portion <NUM> is also impossible.

In general, the saw teeth of a gear wheel are formed as inclined planes corresponding to both directions of rotation. However, the saw teeth <NUM>, <NUM>, <NUM>, and <NUM> of the present disclosure may be formed with an inclined plane in one direction and may be formed at a right angle in the other direction as shown in <FIG>.

The right angle in the present disclosure may refer to a right angle in a practical sense rather than a geometric meaning.

If the inclined plane is too gentle, the mutual motion constraint state of the ratchet base portions <NUM> and <NUM> and the corresponding ratchet rotating portions <NUM> and <NUM> may be easily released. In this case, the headrest <NUM> may be turned to the rear of the examinee, while accommodating and treating the examinee, which may cause discomfort and risk.

If the inclined plane is excessively steep, it may be difficult to rotate the ratchet base portions <NUM> and <NUM> and the corresponding ratchet rotating portions <NUM> and <NUM> in one direction. In this case, it may be difficult to achieve the purpose of changing the position and posture of the headrest with one hand to a state necessary to perform medical treatment.

The saw teeth <NUM> and <NUM> of the first ratchet base portion <NUM> and the first ratchet rotating portion <NUM> are preferably at an inclination angle (CL of <FIG>) ranging from <NUM> degrees to <NUM> degrees only in one direction with respect to a plane on which the saw teeth <NUM> and <NUM> are formed.

More preferably, the inclination angle CL is <NUM> degrees.

The saw teeth <NUM> and <NUM> of the second ratchet base portion <NUM> and the second ratchet rotating portion <NUM> are preferably at an inclination angle ranging from <NUM> degrees to <NUM> degrees only in one direction with respect to a plane on which the saw teeth <NUM> and <NUM> are formed.

Any one of the number of saw teeth <NUM> of the first ratchet base portion <NUM> and the number of saw teeth <NUM> of the first ratchet rotating portion <NUM> may be a multiple of <NUM> or greater of the other.

Any one of the number of saw teeth <NUM> of the second ratchet base portion <NUM> and the number of saw teeth <NUM> of the second ratchet rotating portion <NUM> may be a multiple of two or greater of the other.

In this manner, configuring the number of saw teeth of one of the ratchet base portions <NUM> and <NUM> and the corresponding ratchet rotating portions <NUM> and <NUM> to be different from the number of the other saw teeth and designing to establish the relationship of multiples and divisors to each other have many advantages.

First, since a portion of saw teeth of a component having a shape difficult for injection molding, among the ratchet base portions <NUM> and <NUM> and the corresponding ratchet rotating portions <NUM> and <NUM>, is omitted, injection molding may be facilitated.

In addition, an angle at which two contiguous saw teeth in components having a large number of saw teeth during one-way rotation is maintained at a minimum angle or rotation, thereby enabling more precise operation, and since a frictional surface is reduced, the ratchet base portions <NUM> and <NUM> and the corresponding ratchet rotating portions <NUM> and <NUM> may be prevented from becoming stuck to each other.

More preferably, the number of saw teeth <NUM> of the first ratchet rotating portion <NUM> may be twice the number of saw teeth <NUM> of the first ratchet base portion <NUM>. The number of saw teeth <NUM> of the second ratchet rotating portion <NUM> may be twice the number of saw teeth <NUM> of the second ratchet base portion <NUM> (see <FIG>).

The plurality of saw teeth <NUM> of the first ratchet rotating portion <NUM> and the plurality of saw teeth <NUM> of the second ratchet rotating portion <NUM> may each be arranged in a ring shape at equal angular intervals.

Meanwhile, as shown in <FIG>, the motion of the second link member <NUM> is constrained by the first ratchet member <NUM> so that the second link member <NUM> may rotate only in a direction toward the seat surface <NUM> of the backrest portion <NUM>.

The seat surface <NUM> may refer to a surface that the examinee's back touches among the outer surfaces of the backrest portion <NUM>.

As shown in <FIG>, the motion of the third link member <NUM> is constrained by the second ratchet member <NUM> and is rotatable only in a direction opposite to a direction (a rotation direction indicated by the dotted line arrow at a lower portion in <FIG>) in which the second link member <NUM> is rotatable.

<FIG> are views illustrating a structure and operation of the release portion of the present disclosure.

As shown in <FIG>, the release portion <NUM> may include a first release portion <NUM> and a second release portion <NUM> that operates independently of the first release portion <NUM>.

As shown in <FIG>, the first release portion <NUM> may transmit an external force (acting in the direction of the right arrow in <FIG>) to the first ratchet member <NUM> to release a motion constraint state of the second link member <NUM>.

The second release portion <NUM> may transmit an external force (acting in the left arrow direction in <FIG>) to the second ratchet member <NUM> to release a motion constraint state of the third link member <NUM>.

<FIG> and <FIG> are respectively a front view and a right view illustrating an assembled outer appearance of a second link member of the present disclosure.

As shown in <FIG> and <FIG>, the first release portion <NUM> may include a first button <NUM> and a first operating member <NUM>.

The first button <NUM> may be configured to protrude from one outer side surface of the second link member <NUM>, to which an external force applied by a user is applied.

The first operating member <NUM> may be formed inside the second link member <NUM>.

The first operating member <NUM> may be supported by a first elastic member <NUM>. The first elastic member <NUM> may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

One end of the first elastic member <NUM> may be fixed to the first operating member <NUM>, and the other end of the first elastic member <NUM> may be fixed to a housing <NUM> forming an outer appearance of the second link member <NUM>.

When the external force applied to the first button <NUM> is removed, the first elastic member <NUM> may return the first operating member <NUM> to its original position.

The first button <NUM> and the first ratchet rotating portion <NUM> may be fixed to one surface of the first operating member <NUM>. When an external force is applied to the first button <NUM>, the first operating member <NUM> may integrally move with the first button <NUM> and the first ratchet rotating portion <NUM> to separate the first ratchet rotating portion <NUM> from the first ratchet base portion <NUM>. When the separation occurs, a motion constraint of the second link member <NUM> in one direction is released.

The second release portion <NUM> may be structurally formed to have the same configuration as that of the first release portion <NUM>.

The second release portion <NUM> may include a second button <NUM> and a second operating member <NUM>.

The second button <NUM> may be configured to protrude from one outer side surface of the second link member <NUM>, to which an external force applied by a user is applied.

The second operating member <NUM> may be formed inside the second link member <NUM>.

The second operating member <NUM> may be supported by the second elastic member <NUM>. The second elastic member <NUM> may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

One end of the second elastic member <NUM> may be fixed to the second operating member <NUM>, and the other end of the second elastic member <NUM> may be fixed to the housing <NUM> forming an outer appearance of the second link member <NUM>.

When the external force applied to the second button <NUM> is removed from the second elastic member <NUM>, the second elastic member <NUM> may return the second operating member <NUM> to its original position.

The second button <NUM> and the second ratchet rotating portion <NUM> may be fixed to one surface of the second operating member <NUM>. When an external force is applied to the second button <NUM>, the second operating member <NUM> may integrally move together with the second button <NUM> and the second ratchet rotating portion <NUM> to separate the second ratchet rotating portion <NUM> from the second ratchet base portion <NUM>. When the separation occurs, the motion constraint the third link member <NUM> in one direction is released.

<FIG> is a view illustrating a shape of the second link member of the present disclosure. As shown in <FIG>, among the external surfaces of the second link member <NUM>, a surface <NUM>, which is a front end when the second link member <NUM> rotates in the one direction, may have a recessed shape when observed in the central axis line direction of the first hinge pin <NUM>. That is, when viewed from the side of the headrest portion <NUM>, the front end surface <NUM> may be recessed toward a rear end surface and formed to be concave.

Preferably, the front end surface <NUM> may be formed in a "C" shape when viewed from the side. More preferably, the front end surface <NUM> may be formed in an arc shape when viewed from the side surface.

The second link member <NUM> may have an overall 'C' shape. Preferably, the second link member <NUM> is preferably formed in an arc shape.

The second link member <NUM> formed in a curved shape as described above may easily move the headrest <NUM> to a position suitable for a very short examinee such as a child.

<FIG> is a right view of a link unit according to an embodiment of the present disclosure. <FIG> may mean a state in which the headrest is positioned at a location suitable for a child as described above.

In the embodiment of <FIG>, each of the first link member <NUM> and the third link member <NUM> may be in a fully rotated state.

In <FIG>, the headrest <NUM> is in a position adjusted to fit a child's height.

The curved shape of the second link member <NUM> enables realization of a posture mode that may effectively support a head of a short examinee, such as a child.

As can be seen in <FIG>, when the second link member <NUM> is simply implemented in a straight shape, a distance d' between the end portion to which the third link member <NUM> is connected and the first link member <NUM> is large.

In this case, when accommodating a very short examinee such as a child, the examinee's head is bent excessively forward, so it is not suitable as a headrest.

However, when the second link member <NUM> is formed in a curved shape as in the present disclosure, the distance d between the end portion to which the third link member <NUM> is connected and the first link member <NUM> may be appropriately maintained according to a body shape of the child body shape of the child.

As shown in <FIG>, when the first link member <NUM> is fixed to the backrest portion <NUM>, the other end portion of the second link member <NUM>, i.e., an end portion to which the third link member <NUM> is coupled, preferably contacts the seat surface <NUM> of the backrest portion <NUM> through rotation of the second link member <NUM> in one direction. More preferably, it is preferable that the other end portion may advance so as to deform the seat surface <NUM> after contacting the seat surface <NUM> through rotation of the second link member <NUM> in the one direction. That is, it is buried in the seat surface <NUM>. Through this, a height (thickness) of the headrest <NUM> may be further lowered to be suitable for mounting the head of a child.

If the second link member <NUM> is simply implemented in a straight shape, the end portion of the second link member <NUM> to which the third link member <NUM> is coupled cannot contact the seat surface <NUM> of the backrest portion <NUM> structurally.

Meanwhile, as shown in <FIG>, the motion of the second link member <NUM> is constrained by the first ratchet member <NUM> and is rotatable only in a direction toward the seat surface <NUM> of the backrest portion <NUM>.

The seat surface <NUM> may refer to a surface that the examinee's back contacts among the outer surfaces of the backrest portion <NUM>.

As shown in <FIG>, the motion of the third link member <NUM> is constrained by the second ratchet member <NUM> and is rotatable only in a direction opposite to a direction (rotation direction indicated by the dotted line arrow at a lower portion in <FIG>) in which the second link member <NUM> is rotatable.

With the shape of the recessed front end portion of the second link member <NUM> as described above, by setting the directions in which each of the second link member <NUM> and the third link member <NUM> may rotate freely, a user such as a doctor may easily switch a headrest posture mode for adults (see <FIG>) to a headrest posture mode for children (see <FIG>), while holding the headrest <NUM> only with one hand.

In addition, the headrest posture mode may be easily returned to the headrest posture mode (see <FIG>) for adults by releasing the motion constraint state of each of the second link member <NUM> and the third link member <NUM> by operating the release portion <NUM>.

<FIG> and <FIG> are respectively a right view and a rear view of a link unit according to an embodiment of the present disclosure.

As shown in <FIG> and <FIG>, at least one of the first release portion <NUM> and the second release portion <NUM> according to an embodiment of the present disclosure may include a button <NUM> moving (see the arrow direction of <FIG>) along a trace including a central axis line of the first hinge pin <NUM> or a central axis line of the second hinge pin <NUM> when an external force is applied.

According to an embodiment of the present disclosure, the first release portion <NUM> may include a first button <NUM> for releasing the motion constraint state of the second link member <NUM> when an external force is applied. When an external force is applied, the second button may move, while pushing at least a portion of the first ratchet member <NUM> along a trace including the central axis of the first hinge pin <NUM>. The first button <NUM> may release the engagement of the saw teeth <NUM> and <NUM> of the first ratchet member <NUM> while moving as described above, thereby releasing the motion constraint state of the second link member <NUM>.

More specifically, the first button <NUM> may be integrally formed with the first ratchet rotating portion <NUM>. When an external force is applied to the first button <NUM>, the first button <NUM> and the first ratchet rotating portion <NUM> may move integrally, and the first ratchet rotating portion <NUM> may be separated from the first ratchet base portion <NUM>. When the separation occurs, the motion constraint of the second link member <NUM> in one direction is released.

According to an embodiment of the present disclosure, the second release portion <NUM> may include a second button <NUM> for releasing the motion constraint state of the third link member <NUM> when an external force is applied. When an external force is applied, the second button may move, while pushing at least a portion of the second ratchet member <NUM> along a trace including the central axis line of the first hinge pin <NUM>. The second button <NUM>, while moving as described, may release the engagement of the saw teeth <NUM> and <NUM> of the second ratchet member <NUM>, thereby releasing the motion constraint state of the third link member <NUM>.

More specifically, the second button <NUM> may be integrally formed with the second ratchet rotating portion <NUM>. When an external force is applied to the second button <NUM>, the second button <NUM> and the second ratchet rotating portion <NUM> may move integrally, and the second ratchet rotating portion <NUM> may be separated from the second ratchet base portion <NUM>. When this separation occurs, the motion constraint of the third link member <NUM> in one direction is released.

According to an embodiment of the present disclosure, the first release portion <NUM> may include a first button <NUM> and a first operating member <NUM>. The first button <NUM> is formed to protrude from one outer side surface of the second link member <NUM>, and when an external force is applied, the first button <NUM> may move along a trace parallel to the central axis line of the first hinge pin <NUM>, without including the central axis line of the first hinge pin <NUM>. The first operating member <NUM> may be formed inside the second link member <NUM> and supported by the first elastic member <NUM>. When an external force is applied, the first operating member <NUM> may move integrally with the first button <NUM> and releases the engagement of the saw teeth <NUM> and <NUM> of the first ratchet member <NUM>, thereby releasing the motion constraint state of the link member <NUM>.

According to an embodiment of the present disclosure, the second release portion <NUM> may include a second button <NUM> and a second operating member <NUM>. The second button <NUM> is formed to protrude from one outer side surface of the second link member <NUM>, so that when an external force is applied, the second button <NUM> may move along a trace parallel to the central axis line of the second hinge pin <NUM>, without including the central axis line of the second hinge pin <NUM>. The second operating member <NUM> may be formed inside the second link member <NUM> and supported by the second elastic member <NUM>. When an external force is applied, the second operating member <NUM> may move integrally with the second button <NUM> and releases the engagement of the saw teeth <NUM> and <NUM> of the second ratchet member <NUM> to release the motion constraint state of the link member <NUM>.

<FIG> are views illustrating a structure and operation of a release portion of the present disclosure.

As shown in <FIG>, the release portion <NUM> may include a first release portion <NUM>. In addition, according to an embodiment, the release portion <NUM> may further include a second release portion <NUM> that operates independently of the first release portion <NUM>.

As shown in of <FIG>, the first release portion <NUM> may transmit an external force (acting in the arrow direction illustrated on upper left portion of <FIG>) to the first ratchet member <NUM> to release a motion constraint state of the second link member <NUM>.

The second release portion <NUM> may transmit an external force to the second ratchet member <NUM> to release the motion constraint state of the third link member <NUM>.

The first ratchet member <NUM> may include a first ratchet base portion <NUM> and a first ratchet rotating portion <NUM>.

The first ratchet base portion <NUM> may have a plurality of saw teeth <NUM> formed on one surface thereof, arranged in a ring shape based on the central axis line of the first hinge pin <NUM>, uplifted in the central axis direction, and having a shape inclined only in one direction. An opposite surface of the one surface may be fixed to the first link member <NUM>.

In general, the saw teeth of a gear wheel are formed as inclined planes corresponding to both directions of rotation. However, as indicated in the oval dotted line of <FIG>, the saw tooth <NUM> of the present disclosure may have an inclined plane in one direction and a right angle in the other direction.

The first ratchet rotating portion <NUM> may have saw teeth <NUM> engaged with the saw teeth <NUM> of the first ratchet base portion <NUM> on one surface thereof. An opposite surface of the one surface may be fixed to the second link member <NUM>.

Through the configuration of the annularly arranged saw teeth to be engaged with each other, a force transmitted by the first ratchet rotating portion <NUM> and the first ratchet base portion <NUM> may be distributed by the number of saw teeth. Accordingly, it is possible to support the examinee's head with a stronger force, and it is possible to increase a lifespan of the first ratchet rotating portion <NUM> and the first ratchet base portion <NUM> to ensure durability.

The second ratchet member <NUM> may include a second ratchet base portion <NUM> and a second ratchet rotating portion <NUM>.

The second ratchet base portion <NUM> may have a plurality of saw teeth <NUM> arranged in a ring shape based on the central axis line (the center of a '+' shape at an upper portion in <FIG>) of the second hinge pin <NUM>, uplifted in the central axis line direction, and having a shape inclined only in one direction. An opposite surface of the one surface may be fixed to the third link member <NUM>.

The second ratchet rotating portion <NUM> may have saw teeth <NUM> on one surface thereof and engaged with the saw teeth <NUM> of the second ratchet base portion <NUM>, and an opposite surface of the one surface of the second ratchet rotating portion <NUM> may be fixed to the second link member <NUM>.

The first release portion <NUM> may include a first deformable member whose shape or position is changed as an external force is applied. The applied external force may be transmitted to the first ratchet member <NUM> only when the amount of change in the shape or position of the first deformable member exceeds a predetermined first reference amount.

The first reference amount may be a determined numerical reference of the amount by which the first deformable member changes. In an embodiment, when the position of the first deformable member changes, it may mean a displacement value (distance) of a specific reference. In another embodiment, when the shape of the first deformable member changes, it may be a reference volume corresponding to the amount of change in shape.

The first reference amount may be appropriately designed in a range smaller than a maximum value of the amount by which the first deformable member changes. For example, the first reference amount may be set to a value less than half of the maximum value. Preferably, the first reference amount may be designated as a value corresponding to <NUM>% to <NUM>%, and more preferably, <NUM>%.

In this manner, when the first reference amount is set to a value less than half of the maximum value, the malfunction prevention effect of the first release portion <NUM> is increased.

The first release portion <NUM> may include a first button <NUM> and a first operating member <NUM>.

The first button <NUM> may be configured to protrude from one outer side surface of the second link member <NUM> and to which an external force applied by a user may be applied.

The first operating member <NUM> may be supported by the (<NUM>-<NUM>)-th elastic member <NUM>. The first elastic member <NUM> may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

One end of the (<NUM>-<NUM>)-th elastic member <NUM> may be fixed to the first operating member <NUM>, and the other end of the first elastic member <NUM> may be fixed to the housing <NUM>.

When an external force applied to the first button <NUM> is removed, the (<NUM>-<NUM>)-th elastic member <NUM> may return the first operating member <NUM> to its original position.

The first release portion <NUM> may further include a first operating member <NUM> formed inside the second link member <NUM> and supported by the (<NUM>-<NUM>)-th elastic member <NUM>, and the first deformable member may include a first button <NUM> protruding from one outer side surface of the second link member <NUM> and supported by a (<NUM>-<NUM>)-th elastic member <NUM> (see <FIG>).

When an external force is applied to the first button <NUM>, the first operating member <NUM> may transmit the applied external force to the first ratchet member <NUM> only when the first button <NUM> moves more than a first reference displacement <NUM> (see <FIG>).

When the first button <NUM> moves more than the first reference displacement <NUM> as an external force is applied, the first operating member <NUM> may contact and interwork with the first button <NUM>.

In this manner, when the amount of motion of the first button <NUM> is less than the first reference displacement <NUM>, an external force is not transmitted to the first ratchet member <NUM> and the motion constraint state of the second link member <NUM> continues.

Accordingly, a malfunction of releasing the motion constraint state when the user's hand such as a doctor's hand erroneously touches the button and a certain amount of external force is applied may be prevented.

In addition, a first uplift portion <NUM> penetrating through a hole formed in the first operating member <NUM> may be formed inside the housing <NUM> of the second link member <NUM>, and an outer wall of the first uplift portion <NUM> may guide a movement direction of the first operating member <NUM>.

In addition, a first guide groove <NUM> for guiding a motion direction of the first button <NUM> may be formed in the first uplift portion <NUM>.

By configuring the first uplift portion <NUM> in this way, the first uplift portion <NUM> may guide both the motion operations of the first operating member <NUM> and the first button <NUM> along an accurate trace.

Also, one end of the (<NUM>-<NUM>)-th elastic member <NUM> may be connected to the first uplift portion <NUM>, the other end thereof may be connected to the first button <NUM> to support the first button <NUM>, and the (<NUM>-<NUM>)-th elastic member <NUM> may be deformed according to a motion operation of the first button <NUM>.

When the external force is removed, the (<NUM>-<NUM>)-th elastic member <NUM> is out of a deformed state and serves to return the first button <NUM> to its original position.

When an external force is applied to the first button <NUM>, the first operating member <NUM> may move together with the first button <NUM> and the first ratchet rotating portion <NUM> to separate the first ratchet rotating portion <NUM> from the first ratchet base portion <NUM>.

When this separation occurs, the motion constraint of the second link member <NUM> in one direction is released.

The second link member <NUM> may further include a second release portion <NUM> operating independently of the first release portion <NUM> and transmitting an external force to the second ratchet member <NUM> to release the motion constraint state of the third link member <NUM>.

The second release portion <NUM> may have the same structure as the first release portion <NUM> according to an embodiment of the present disclosure.

The second release portion <NUM> may include a second deformable member whose shape or position is changed as an external force is applied.

The second release portion <NUM> may be configured to transmit the applied external force to the second ratchet member <NUM> only when the amount of change in the shape or position of the second deformable member exceeds a predetermined second reference amount.

The second reference amount may have the same properties as the first reference amount and may be set to have the same value.

The second release portion <NUM> may further include a second operating member <NUM> formed inside the second link member <NUM> and supported by a (<NUM>-<NUM>)-th elastic member <NUM>.

The second operating member <NUM> may be supported by the (<NUM>-<NUM>)-th elastic member <NUM>. The (<NUM>-<NUM>)-th elastic member <NUM> may be formed of a coil spring, a leaf spring, a torsion spring, or the like.

One end of the (<NUM>-<NUM>)-th elastic member <NUM> may be fixed to the second operating member <NUM>, and the other end of the (<NUM>-<NUM>)-th elastic member <NUM> may be fixed to the housing <NUM> forming an outer appearance of the second link member <NUM>.

When the external force applied to the second button <NUM> is removed, the (<NUM>-<NUM>)-th elastic member <NUM> may return the second operating member <NUM> to its original position.

The second deformable member may include a second button <NUM> protruding from one outer side surface of the second link member <NUM> and supported by a (<NUM>-<NUM>)-th second elastic member <NUM>.

The second button <NUM> may be a component to which an external force applied by a user is applied.

The second operating member <NUM> may transmit the applied external force to the second ratchet member <NUM> only when the second button <NUM> moves more than a second reference displacement as an external force is applied t the second button <NUM>.

The second reference displacement may be set to a value equal to the first reference displacement.

In addition, when the second button <NUM> moves by more than the second reference displacement <NUM> as an external force is applied, the second operating member <NUM> may contact and interwork with the second button <NUM>.

As such, when the amount of motion of the second button <NUM> is less than the second reference displacement, no external force is transmitted to the second ratchet member <NUM>, and the motion constraint state of the third link member <NUM> continues.

Accordingly, a malfunction of releasing the motion constraint state as the user's hand such as a doctor's hand erroneously touches the button and a certain amount of external force is applied may be prevented.

In addition, a second uplift portion <NUM> penetrating through a hole formed in the second operating member <NUM> may be formed inside the housing <NUM> of the second link member <NUM>, and an outer wall of the second uplift portion <NUM> may guide a moving direction of the second operating member <NUM>.

In addition, a second guide groove <NUM> for guiding a motion direction of the second button <NUM> may be formed in the second uplift portion <NUM>.

By configuring the second uplift portion <NUM> in this manner, the second uplift portion <NUM> may guide both the motion operations of the second operating member <NUM> and the second button <NUM> along an accurate trace.

Also, one end of the (<NUM>-<NUM>)-th elastic member <NUM> may be connected to the second uplift portion <NUM> and the other end thereof may be connected to the second button <NUM> to support the second button <NUM>, and the (<NUM>-<NUM>)-th elastic member <NUM> may be deformed according to a motion operation of the second button <NUM>.

When the external force is removed, the (<NUM>-<NUM>)-th elastic member <NUM> is out of a deformed state and serves to return the second button <NUM> to its original position.

When an external force is applied to the second button <NUM>, the second operating member <NUM> may move together with the second button <NUM> and the second ratchet rotating portion <NUM> to separate the second ratchet rotating portion <NUM> from the second ratchet base portion <NUM>.

When this separation occurs, the motion constraint of the third link member <NUM> in one direction is released.

The (<NUM>-<NUM>)-th elastic member <NUM> may be formed of a coil spring that surrounds the outer wall of the first uplift portion <NUM> (see <FIG>).

The (<NUM>-<NUM>)-th elastic member <NUM> may be inserted into the first button <NUM>. Also, the (<NUM>-<NUM>)-th elastic member <NUM> may also be formed of a coil spring (see <FIG>).

The (<NUM>-<NUM>)-th elastic member <NUM> may be formed of a coil spring surrounding the outer wall of the second uplift portion <NUM> (see <FIG>).

The (<NUM>-<NUM>)-th elastic member <NUM> may be inserted into the first button <NUM>. The (<NUM>-<NUM>)-th elastic member <NUM> may also be formed of a coil spring (see <FIG>).

<FIG> and <FIG> are views illustrating a structure of a release portion according to an embodiment of the present disclosure.

As shown in <FIG>, the (<NUM>-<NUM>)-th, (<NUM>-<NUM>)-th, (<NUM>-<NUM>)-th, and (<NUM>-<NUM>)-th elastic members may be formed at positions different from those of the embodiment shown in <FIG>.

That is, the (<NUM>-<NUM>)-th and (<NUM>-<NUM>)-th elastic members may be formed at positions that do not surround the respective uplift portions <NUM> and <NUM> corresponding thereto.

The (<NUM>-<NUM>)-th elastic member <NUM> may be inserted into the first guide groove <NUM> of the first uplift portion <NUM>. The (<NUM>-<NUM>)-th elastic member <NUM> may also be formed as a coil spring.

The (<NUM>-<NUM>)-th elastic member <NUM> may be inserted into the second guide groove <NUM> formed in the second uplift portion <NUM>. The (<NUM>-<NUM>)-th elastic member <NUM> may also be formed as a coil spring.

In addition, at least one of the first operating member <NUM> and the second operating member <NUM> may be hinged to the housing <NUM>. <FIG> shows an embodiment in which the first operating member <NUM> and the second operating member <NUM> share a third hinge pin <NUM>.

As described above, in the embodiment in which at least one of the first operating member <NUM> and the second operating member <NUM> is hinged with the housing <NUM>, the first uplift portion <NUM> or the second uplift portion <NUM> preferably have a shape corresponding to a motion trace of the first operating member <NUM> and the second operating member <NUM>.

In another embodiment, as shown in <FIG>, one end of each of the first operating member <NUM> and the second operating member <NUM> may be integrally fixed to the housing <NUM>.

In this embodiment, the first operating member <NUM> and the second operating member <NUM> may be integrally formed to form a single operating member.

In addition, the first operating member <NUM> and the second operating member <NUM> may be formed of a material having an elastic force (e.g., carbon steel, plastic, etc.) and may be configured, without the (<NUM>-<NUM>)-th elastic member <NUM> and the (<NUM>-<NUM>)-th elastic member <NUM>, to perform a function. In this embodiment, the structure may be simplified and the cost may be reduced.

Meanwhile, in the specification and the claims, terms such as "first", "second", "third", "fourth", and the like, if any, will be used to distinguish similar components from each other and be used to describe a specific sequence or a generation sequence, but is not necessarily limited thereto.

In addition, in the specification and the claims, terms such as "left", "right", "front", "rear", "top", "bottom", "over", "under", and the like do not necessarily indicate relative positions that are not changed, but are used for explanation. It will be understood that these terms are compatible with each other under an appropriate environment so that embodiments of the present disclosure set forth herein may be operated in a direction different from a direction illustrated or described herein. The term "connected" as used herein is defined as being connected directly or indirectly in an electrical or non-electrical manner. Here, targets described as being "adjacent to" each other may physically contact each other, be close to each other, or be in the same general range or region, in a context in which the above phrase is used. Here, the presence of phrase "in an embodiment" means the same embodiment, but is not necessarily limited thereto.

In addition, in the specification and the claims, terms such as "connected", "connecting", "linked", "linking", "coupled", "coupling", and the like, and various modifications of these terms may be used as the meaning including that one component is directly connected to another component or is indirectly connected to another component through the other component.

In addition, terms "module" and "unit" for components used in the present specification are used only in order to easily make the specification. Therefore, these terms do not have meanings or roles that are distinguished from each other.

Claim 1:
A unit chair (<NUM> comprising a link unit (<NUM>) for adjusting a posture of a headrest (<NUM>),
wherein the link unit (<NUM>) includes:
a) a first link member (<NUM>) fixed to a backrest portion (<NUM>) of the unit chair (<NUM>);
b) a second link member (<NUM>) having one end portion hinged to the first link member (<NUM>) by a first hinge pin (<NUM>); and
c) a first ratchet member (<NUM>) formed on one surface of at least one of the first link member (<NUM>) and the second link member (<NUM>) and constraining motion of the second link member (<NUM>) so that the second link member (<NUM>) is rotatable only in one direction based on a central axis line of the first hinge pin (<NUM>),
wherein the first ratchet member (<NUM>) includes
d) a first ratchet base portion (<NUM>) including a plurality of saw teeth formed on one surface, arranged in a ring shape based on the central axis line of the first hinge pin (<NUM>), uplifted in a direction toward the central axis line, and inclined only in one direction, and having an opposite surface fixed to the first link member (<NUM>); and
e) a first ratchet rotating portion (<NUM>) including a plurality of saw teeth formed on one surface and at least partially engaged with at least some of the saw teeth of the first ratchet base portion (<NUM> and having an opposite surface fixed to the second link member (<NUM>);
f) wherein the first ratchet member (<NUM>) constrains motion of the second link member (<NUM>) so that the second link member (<NUM>) is rotatable only in one direction based on the central axis line of the first hinge pin (<NUM>) as the saw teeth of the first ratchet base portion (<NUM>) are engaged with the saw teeth of the first ratchet rotating portion (<NUM>).