WO2020159020A1

WO2020159020A1 - Rotation locking device and two-degree-of-freedom (2dof) rotary arm including same

Info

Publication number: WO2020159020A1
Application number: PCT/KR2019/009250
Authority: WO
Inventors: Dong Soo Kwon; Chang Kyun Kim; Duk Yoo Kong; Byung Sik CHEON
Original assignee: Easyendo Surgical, Inc.; Korea Advanced Institute Of Science And Technology
Priority date: 2019-01-31
Filing date: 2019-07-25
Publication date: 2020-08-06
Also published as: KR102188407B1; KR20200095192A

Abstract

Disclosed is a two-degree-of-freedom (2DOF) rotary arm including a base portion, a first rotary link connected with respect to the base portion to be rotatable based on a first rotation axis, a second rotary link connected with respect to the first rotary link to be rotatable based on a second rotation axis, a first rotation locker configured to lock a rotation between the first rotary link and the base portion by operating to provide a frictional force between the base portion and the first rotary link, and a second rotation locker configured to lock a rotation between the second rotary link and the first rotary link by operating to provide a frictional force between the first rotary link and the second rotary link in response to the first rotation locker operating.

Description

ROTATION LOCKING DEVICE AND TWO-DEGREE-OF-FREEDOM (2DOF) ROTARY ARM INCLUDING SAME

One or more example embodiments relates to a rotation locking device and a two-degree-of-freedom (2DOF) rotary arm including same.

In recent years, robot arms are generally manufactured with multi-freedom manipulators having two or more joint joints. There are various mechanisms for locking the rotation of the multi-freedom robot arm.

Generally, a method of locking the rotation of a joint using a hook, a ratchet, a gear, or the like has the advantage in that the rotation can be locked with a small force, but there is a problem in that fixable positions are discontinuously discrete.

In addition, in the case of a robot arm having multiple degrees of freedom, it is necessary to fix all of the individual joints corresponding to one degree of freedom because all of the joints must be fixed.

Accordingly, there is a growing desire for a rotation locking device capable of locking a rotation operation of a multi-degree-of-freedom robot arm, having a continuous fixable position, and simultaneously locking a rotation operation of a plurality of joints.

The background art described above has been possessed or acquired by the inventor(s) in the course of conceiving the present invention and is not necessarily an art publicly known before filing the present application.

An aspect provides a rotation locking apparatus and a two-degree-of-freedom (2DOF) rotary arm including the rotation locking apparatus.

According to an aspect, there is provided a two-degree-of-freedom (2DOF) rotary arm including a base portion, a first rotary link connected with respect to the base portion to be rotatable based on a first rotation axis, a second rotary link connected with respect to the first rotary link to be rotatable based on a second rotation axis, a first rotation locker configured to lock a rotation between the first rotary link and the base portion by operating to provide a frictional force between the base portion and the first rotary link, and a second rotation locker configured to lock a rotation between the second rotary link and the first rotary link by operating to provide a frictional force between the first rotary link and the second rotary link in response to the first rotation locker operating.

The base portion may include a first joint hole penetratingly formed along the first rotation axis. The first rotary link may include a first connection body connected to the first joint hole, a first link member fixed to the first connection body to rotate, and a second joint hole penetratingly formed at the first link member along the second rotation axis. The second rotary link may include a second connection body connected to the second joint hole, and a second link member fixed to the second connection body to rotate. The first rotation locker may be configured to lock the rotation between the base portion and the first rotary link by pressing the first connection body toward the base portion. The second rotation locker may be configured to lock the rotation between the first rotary link and the second rotary link by pressing the second connection body toward the first rotary link.

The first rotation locker may include a screw shaft configured to pass through the first joint hole and the first connection body along the first rotation axis and have a screw thread on a portion of an outer circumferential surface thereof, a tightener screwed to one side of the screw shaft to move relative to the first connection body along the first rotation axis, and a frictional pad installed on the other side of the screw shaft to be in contact with a surface of an end portion of the first connection body. The second rotation locker may include a frictional link configured to be interfered with in response to a movement of the tightener and move relative to the first link member in a direction vertical to the second rotation axis so as to be in contact with an outer surface of the second connection body.

The frictional pad may be installed to be slidable in a direction parallel to the first rotation axis based on the base portion and to be not rotatable based on the first rotation axis.

The tightener may include a knob screwed to the screw shaft, a pressing member configured to move along the first rotation axis in response to the knob being tightened and interfere with the frictional link such that the frictional link moves in a direction vertical to the first rotation axis, and a first elastic body configured to apply an elastic force in a direction in which a distance between the pressing member and the first connection body increases.

The pressing member may include a first contactor having a portion that is in contact with the frictional link and inclined with respect to the first rotation axis. The frictional link may include a second connection body that is in contact with the first contactor and inclined with respect to the first rotation axis.

The frictional link may include a frictional end portion having a curved surface in surface contact with an outer surface of the second connection body.

The frictional link may further include a second elastic body configured to apply an elastic force in a direction in which a distance between the frictional end portion and the second connection body increases.

The second elastic body may be a plunger.

The 2DOF rotary arm may further include a first support structure configured to prevent the first rotary link from performing a translational movement along the first rotation axis with respect to the base portion irrespective of whether the first rotation locker operates, and a second support structure configured to prevent the second rotary link from performing a translational movement along the second rotation axis with respect to the first rotary link irrespective of whether the second rotation locker operates.

According to example embodiments, it is possible to provide a rotation locking apparatus and a two-degree-of-freedom (2DOF) arm including the rotation locking apparatus to simultaneously lock a rotation according to two rotation axes while having a consecutive fixed rotation range.

In addition, because the rotation is not locked by adjusting clearance between joints, a situation in which the rotation is inaccurately performed due to the clearance occurring in each of the joints may be prevented.

Also, even in the unlocked state, each link may precisely and smoothly rotate without clearance.

FIG. 1 is a perspective view of a two-degree-of-freedom (2DOF) rotary arm according to an example embodiment.

FIG. 2 is a block diagram illustrating a rotation locking apparatus according to an example embodiment.

FIG. 3a is an exploded perspective view illustrating a 2DOF rotary arm according to an example embodiment.

FIG. 3b is an enlarged perspective view illustrating a portion A of FIG. 3a.

FIG. 3c is an enlarged perspective view illustrating a portion B of FIG. 3a.

FIG. 4a is a cross-sectional view illustrating a 2DOF rotary arm with a rotation locking apparatus being in a rotation-unlocked state according to an example embodiment.

FIG. 4b is an enlarged cross-sectional view illustrating a portion A of FIG. 4a.

FIG. 5a is a cross-sectional view illustrating a 2DOF rotary arm with a rotation locking apparatus being in a rotation-locked state according to an example embodiment.

FIG. 5b is an enlarged cross-sectional view illustrating a portion A of FIG. 5a.

Hereinafter, some example embodiments will be described in detail with reference to the accompanying drawings. Regarding the reference numerals assigned to the elements in the drawings, it should be noted that the same elements will be designated by the same reference numerals, wherever possible, even though they are shown in different drawings. Also, in the description of embodiments, detailed description of well-known related structures or functions will be omitted when it is deemed that such description will cause ambiguous interpretation of the present disclosure.

In addition, terms such as first, second, A, B, (a), (b), and the like may be used herein to describe components. Each of these terminologies is not used to define an essence, order or sequence of a corresponding component but used merely to distinguish the corresponding component from other component(s). It should be noted that if it is described in the specification that one component is "connected", "coupled", or "joined" to another component, a third component may be "connected", "coupled", and "joined" between the first and second components, although the first component may be directly connected, coupled or joined to the second component.

Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms, such as those defined in commonly used dictionaries, are to be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art, and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein.

FIG. 1 is a perspective view of a two-degree-of-freedom (2DOF) rotary arm according to an example embodiment, FIG. 2 is a block diagram illustrating a rotation locking apparatus according to an example embodiment, FIG. 3a is an exploded perspective view illustrating a 2DOF rotary arm according to an example embodiment, FIG. 3b is an enlarged perspective view illustrating a portion A of FIG. 3a, FIG. 3c is an enlarged perspective view illustrating a portion B of FIG. 3a, FIG. 4a is a cross-sectional view illustrating a 2DOF rotary arm with a rotation locking apparatus being in a rotation-unlocked state according to an example embodiment, FIG. 4b is an enlarged cross-sectional view illustrating a portion A of FIG. 4a, FIG. 5a is a cross-sectional view illustrating a 2DOF rotary arm with a rotation locking apparatus being in a rotation-locked state according to an example embodiment, and FIG. 5b is an enlarged cross-sectional view illustrating a portion A of FIG. 5a.

Referring to FIGS. 1 through 5b, a 2DOF rotary arm 1 may be a robot arm including a plurality of rotary joints and may include a rotation locking apparatus 2 that locks rotation of two rotary joints simultaneously.

For example, the 2DOF rotary arm 1 may be a selective compliance assembly robot arm (SCARA) robot in which rotational axes of a plurality of rotary joints are spaced apart in parallel to a direction of gravity. However, this is only an example, and the 2DOF rotary arm 1 to which rotary links are connected in a manner of a ball joint or the like should also be considered to be included in the scope of the present disclosure. In this disclosure, "2DOF rotary arm" should be understood to mean an arm capable of rotating at least two degrees of freedom. Also, rotary arms capable of rotating at three or more degrees of freedom should be understood that they are included in the scope of the present disclosure if they adopt the structure of the present disclosure. For example, a rotary arm that includes a first rotary link hinged to a base portion and a second rotary link coupled in a ball joint manner to the first rotary link is included in the "2DOF rotary arm" of the present disclosure. Hereinafter, the 2DOF rotary arm 1 which is a SCARA robot will be described as an example.

The 2DOF rotary arm 1 may include a base portion 11, a first rotary link 12 connected with respect to the base portion 11 to be rotatable based on a first rotation axis, a second rotary link 13 connected with respect to the first rotary link 12 to be rotatable based on a second rotation axis, and the rotation locking apparatus 2.

The base portion 11 may be a member which is a reference for rotation of the 2DOF rotary arm 1. The base portion 11 may include a first joint hole 111 into which a first connection body 122 of the first rotary link 12 is inserted, and a bearing 113 inserted into an outer circumferential surface of the first joint hole 111 to guide rotation of the first connection body 122.

A support structure, for example, a bearing may be disposed between the first rotary link 12 and the base portion 11 to prevent both members from performing translational movement relatively along a direction of the first rotation axis. In the above structure, even in a state in which rotation of the rotation locking apparatus 2 is unlocked, the first rotary link 12 may precisely and smoothly rotate with respect to the base portion 11 without clearance. The first rotary link 12 may include the first connection body 122 connected to the first joint hole 111, a first link member 121 fixed to the first connection body 122 to rotate, and a second joint hole 124 penetratingly formed at the first link member 121 along the second rotation axis.

In response to the first connection body 122 inserted in the first joint hole 111 rotating with respect to the base portion 11 based on the first rotation axis, the first link member 121 may rotate with respect to the base portion 11 based on the first rotation axis.

A support structure, for example, a bearing may be disposed between the second rotary link 13 and the first rotary link 12 to prevent both members from performing translational movement relatively along a direction of the second rotation axis. In the above structure, even in a state in which rotation of the rotation locking apparatus 2 is unlocked, the second rotary link 13 may precisely and smoothly rotate with respect to the first rotary link 12 without clearance. The second rotary link 13 may include a second connection body 132 connected to the second joint hole 124 and a second link member 131 fixed to the second connection body 132 to rotate.

Similar to the first joint hole 111, the second joint hole 124 may include a bearing (not shown) formed at the second joint hole 124 to guide rotation of the second connection body 132.

In response to the second connection body 132 inserted in the second joint hole 124 rotating with respect to the first rotary link 12 based on the second rotation axis, the second link member 131 may rotate with respect to the first link member 121 based on the second rotation axis.

For example, when the 2DOF rotary arm 1 is a SCARA robot as illustrated in the drawing, the first rotation axis and the second rotation axis may be formed parallel to a direction of gravity. Accordingly, the first connection body 122 and the second connection body 132 may have shapes of shaft parallel to each other. However, this is merely an example, and the first rotation axis and the second rotation axis may be arranged not parallel to each other. As an example, the second rotation axis may have a twisted position relative to the first rotation axis. As another example, the second rotary link 13 may be installed to be rotatable with respect to the first rotary link 12 in a ball-joint manner. In this example, the second connection body 132 may have a ball-joint shape and the second rotation axis may have a variable angle relationship with the first rotation axis.

The rotation locking apparatus 2 may lock the rotation of the first rotary link 12 with respect to the base portion 11 and, simultaneously, lock the rotation of the second rotary link 13 with respect to the first rotary link 12. The rotation locking apparatus 2 may include a first rotation locker 21 and a second rotation locker 22.

The first rotation locker 21 may operate to provide a frictional force between the base portion 11 and the first rotary link 12 so as to lock relative rotation between the base portion 11 and the first rotary link 12.

In response to the first rotation locker 21 operating, the second rotation locker 22 may operate to provide a frictional force between the first rotary link 12 and the second rotary link 13 so as to lock relative rotation between the first rotary link 12 and the second rotary link 13.

The first rotation locker 21 may press the first connection body 122 toward the base portion 11, thereby locking the rotation between the base portion 11 and the first rotary link 12.

The first rotation locker 21 may include a screw shaft 212 that passes through the first joint hole 111 and the first connection body 122 along the first rotation axis and have a screw thread on a portion of an outer circumferential surface thereof, a tightener 211 screwed to one side of the screw shaft 212 passing through the first connection body 122 to move relative to the first connection body 122 along the first rotation axis, and a frictional pad 213 installed on the other side of the screw shaft 212 passing through the first connection body 122 to be in contact with a surface of an end portion of the first connection body 122 inserted in the first joint hole 111.

The screw shaft 212 may pass the first joint hole 111 and a center of the first connection body 122 along the first rotation axis. The screw shaft 212 may be installed to be slidable along the first rotation axis. The screw shaft 212 and the frictional pad 213 may be mutually fixed so as not to rotate relatively. In the above structure, during the rotation of the tightener 211, the screw shaft 212 may be prevented from spinning with no traction with respect to the frictional pad 213. For example, one end of the screw shaft 212 passing through the first connection body 122 toward the first link member 121 may pass through the first link member 121. Also, the other end of the screw shaft 212 passing through the first connection body 122 toward the base portion 11 may protrude outside the base portion 11.

The tightener 211 may be installed in a portion of the screw shaft 212 passing through the first connection body 122 toward the first link member 121, and the frictional pad 213 may be installed in a portion of the screw shaft 212 passing through the first connection body 122 toward the base portion 11.

The screw shaft 212 may include a threaded portion 2121 having a thread formed on an outer circumferential surface of an end portion protruding and passing through the first connection body 122 toward the first link member 121.

The tightener 211 may move on the screw shaft 212 and transfer a pressing force to lock the rotation of each of the first connection body 122 and the second connection body 132. The tightener 211 may include a knob 2111, a pressing member 2112, and a first elastic body 2113.

The knob 2111 may be screwed to the threaded portion 2121 to rotate. The knob 2111 may rotate with respect to the screw shaft 212, thereby moving in a longitudinal direction of the screw shaft 212, that is, along the first rotation axis. For example, a portion of the knob 2111 may be exposed outside the first rotary link 12 so as to be gripped and easily manipulated by a user.

The pressing member 2112 may be disposed in a part of the screw shaft 212 between the knob 2111 and the first connection body 122. The pressing member 2112 may move while being interfered with by the knob 2111 moving along the first rotation axis, thereby pressing a frictional link 221 of the second rotation locker 22

As illustrated in FIG. 4a and 4b, the pressing member 2112 may be disposed in the first link member 121 to move in the longitudinal direction of the screw shaft 212 in response to the knob 2111 being tightened. For example, the pressing member 2112 may have a hollow through which the screw shaft 212 passes.

In a process in which the pressing member 2112 downwardly moves relative to the screw shaft 212, the pressing member 2112 may (i) be interfered with by the frictional link 221 of the second rotation locker 22 to receive a force upwardly applied to be away from the first connection body 122 or (ii) receive an elastic force in an upward direction to be away from the first connection body 122 by the first elastic body 2113. The force upwardly applied to the pressing member 2112 may allow the screw shaft 212 and the frictional pad 213 connected thereto to move upwardly, so that the frictional pad 213 presses the first connection body 122. The frictional pad 213 may be in surface contact with a lower surface of the first connection body 122 to provide a frictional force against the base portion 11 to prevent relative rotation of the first connection body 122 and the first link member 121 secured thereto.

Simultaneously, the pressing member 2112 may be interfered with by the frictional link 221 of the second rotation locker 22 accepted in the first link member 121 and move the frictional link 221 toward the second connection body 132 such that the frictional link 221 presses the second connection body 132. The frictional link 221 may be in surface contact with a side surface of the second connection body 132 to provide a frictional force against the first rotary link 12 to prevent relative rotation of the second connection body 132 and the second link member 131 secured thereto.

The pressing member 2112 may include a first contactor 21121 as a portion that is in contact with the frictional link 221 and inclined with respect to the first rotation axis. An angle at which the first contactor 21121 is inclined based on the first rotation axis may be, for example, 45 degrees (°).

The first elastic body 2113 may be interposed between the pressing member 2112 and the first connection body 122 to apply an elastic force in a direction in which a distance between the pressing member 2112 and the first connection body 122 increases. The first elastic body 2113 may prevent an occurrence of clearance of the pressing member 2112 in the first rotary link 12 when the rotation of the rotation locking apparatus 2 is unlocked, thereby improving a stability of the entire apparatus.

The frictional pad 213 may be disposed on the screw shaft 212 passing through the first connection body 122 toward the base portion 11 to be in contact with a surface of an end portion of the first connection body 122 inserted in the first joint hole 111. For example, the frictional pad 213 may include a pad member in a shape of a plane vertical to the first rotation axis and may be formed of a material having a high coefficient of friction.

The frictional pad 213 may be slidable along the first rotation axis based on the base portion 11 and not be rotatable based on the first rotation axis. The frictional pad 213 may include a guide shaft 2131 that protrudes in a direction parallel to the first rotation axis and be slidably inserted into the base portion 11 and a guide bush 2132 that is installed in the base portion 11 to slidably accept the guide shaft 2131.

The guide shaft 2131 and the guide bush 2132 may support an attitude of the frictional pad 213 such that the frictional pad 213 is in surface contact with an accurate position of the surface of the end portion of the first connection body 122 inserted into the first joint hole 111 in response to the frictional pad 213 moving along the first rotation axis. Simultaneously, when the frictional pad 213 contacts the first connection body 122, the guide shaft 2131 and the guide bush 2132 may support the frictional pad 213 such that the frictional pad 213 is not rotated by the first connection body 122.

The second rotation locker 22 may lock the rotation between the first rotary link 12 and the second rotary link 13. The second rotation locker 22 may include the frictional link 221 and a sliding guide 222.

The frictional link 221 may be installed to be slidable with respect to the first link member 121 and interfered with in response to a movement of the tightener 211, thereby providing a frictional force to the second connection body 132. For example, the frictional link 221 may be a columnar member having a shape extending in a direction vertical to the first rotation axis in the first link member 121. For example, a longitudinal direction and/or a moving direction of the frictional link 221 may be vertical to the first rotation axis and the second rotation axis. For example, the frictional link 221 may be disposed parallel to a direction in which the first link member 121 extends in the first link member 121. A translation movement axis of the frictional link 221 may be formed orthogonal to the first rotation axis and the second rotation axis. Likewise, the translation movement axis of the frictional link 221 may be orthogonal to a central axis of the first connection body 122 and the second connection body 132.

The frictional link 221 may include a second contactor 2211 formed in one end portion contacting the pressing member 2112, a frictional end portion 2212 formed in the other end portion contacting the second connection body 132, and a second elastic body 2213 that applies an elastic force in a direction in which a distance between the frictional end portion 2212 and the second connection body 132 increases.

The second contactor 2211 may be interfered with by the first contactor 21121 to receive a force for moving the frictional link 221 in a direction vertical to the first rotation axis. For example, the second contactor 2211 may be inclined so as to be in surface contact with the first contactor 21121. For example, based on a moving direction of the pressing member 2112, an angle at which the second contactor 2211 is inclined may be 45°.

The frictional end portion 2212 may contact the second connection body 132, thereby providing a frictional force for locking the rotation of the second rotary link 13 with respect to the first rotary link 12. For example, the frictional end portion 2212 may be in surface contact with an outer surface of the second connection body 132.

The frictional end portion 2212 may have a curved surface to be in surface contact with an outer surface of the second connection body 132 having a cylindrical shape. Thus, when the frictional end portion 2212 is in contact with the second connection body 132, the frictional end portion 2212 may be in surface contact with the outer surface of the second connection body 132 so as to be precisely shaped to with the outer surface, thereby locking the rotation of the second connection body 132 with the high frictional force.

The second elastic body 2213 may be installed such that at least a portion protrudes from the frictional end portion 2212 towards the center of the second connection body 132. Through this, the second elastic body 2213 may apply the elastic force in a direction in which a distance between the frictional link 221 and the second connection body 132 increases.

For example, the second elastic body 2213 may include a compressible structure in which a portion is embedded from a surface of the frictional end portion 2212 in a direction vertical to the first rotation axis and the second rotation axis and a remaining portion protrudes toward the second connection body 132. The second elastic body 2213 may be, for example, a plunger. The plunger may include, for example, a stroke plunger, a roller plunger, a ball plunger, and the like. According to the above structure, in an unlocked state, the frictional force between the second elastic body 2213 and the second connection body 132 may be significantly reduced so that the second rotary link 13 smoothly rotates with respect to the first rotary link 12.

For example, the frictional end portion 2212 may be in contact with the second connection body 132 and lock the rotation of the second connection body 132. In this example, the portion of the second elastic body 2213 outwardly protruding from the surface of the frictional end portion 2212 may be pressed by the second connection body 132 to be compressed toward an inside of the frictional end portion 2212.

According to the second elastic body 2213, similar to the first elastic body 2113, when the knob 2111 is released to unlock the rotation of the first connection body 122 and the second connection body 132, the frictional link 221 may be separated to be away from the second connection body 132, so that the rotation of the second connection body 132 is unlocked and, simultaneously, the second contactor 2211 is moved to a vicinity of the first connection body 122. Also, when the rotation locking apparatus 2 unlocks, an occurrence of clearance of the frictional link 221 in the first rotary link 12 may be prevented, thereby improving a stability of an overall apparatus.

The sliding guide 222 may be fixed to the first link member 121 to guide the frictional link 221 sliding in the direction vertical to the first rotation axis and the second rotation axis. For example, the sliding guide 222 may be formed to cover a portion of a circumference of the frictional link 221 to guide a moving direction of the frictional link 221 such that the frictional link 221 moves only in the direction vertical to the first rotation axis and the second rotation axis.

Referring to FIGS. 4a through 5b, an operation structure of the rotation locking apparatus 2 may be confirmed. Specifically, FIG. 4a and 4b illustrates a configuration of the rotation locking apparatus 2 in an unlocked state and FIG. 5a and 5b illustrates a configuration of the rotation locking apparatus 2 in a locked state.

In the unlocked state of FIGS. 4a and 4b, the frictional pad 213 may remain spaced from an end portion of the first connection body 122. Also, since, the first rotary link 12 remains supported by the bearing 113 with respect to the base portion 11 without clearance irrespective of whether to be locked or unlocked, the first rotary link 12 may rotate precisely and smoothly with respect to the base portion 11.

Also, in the unlocked state, the frictional link 221 may remain spaced apart from the outer surface of the second connection body 132. Also, since the second rotary link 13 remains supported by a bearing (not shown) with respect to the first rotary link 12 without clearance irrespective of whether to be locked or unlocked, the second rotary link 13 may rotate precisely and smoothly with respect to the first rotary link 12.

When the knob 2111 is rotated in a tightened direction as illustrated in FIGS. 5a and 5b, the frictional pad 213 may be elevated to be in contact with the first connection body 122 and the frictional link 221 may move in a rightward direction to be in contact with the second connection body 132, whereby the rotation of each of the first connection body 122 and the second connection body 132 is locked.

Specifically, in a process of tightening the knob 2111, (i) a force acting between the frictional pad 213 and the end portion of the first connection body 122, (ii) a force acting between the pressing member 2112 connected to the first connection body 122 and the frictional link 2211, (iii) a force acting between the frictional link 2211 and the outer surface of the second connection body 132 may increase together. The three forces may be forces acting between successively contacting members under the principal of action and reaction. The three forces may reach a maximum value simultaneously without saturating some of the forces. In other words, the rotation between the base portion 11 and the first rotary link 12 and the rotation between the first rotary link 12 and the second rotary link 13 may be locked by maximally rotating a single knob 2111.

The rotation locking apparatus 2 and the 2DOF rotary arm 1 including the rotation locking apparatus 2 may simultaneously lock the rotation according to two rotation axes while having a consecutive fixed rotation range. In addition, because the rotation is not locked by adjusting clearance between joints, a situation in which the rotation is inaccurately performed due to the clearance occurring in each of the joints may be prevented. Also, even in the unlocked state, each link may precisely and smoothly rotate without clearance.

Although a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

A two-degree-of-freedom (2DOF) rotary arm comprising:

a base portion;

a first rotary link connected with respect to the base portion to be rotatable based on a first rotation axis;

a second rotary link connected with respect to the first rotary link to be rotatable based on a second rotation axis;

a first rotation locker configured to lock a rotation between the first rotary link and the base portion by operating to provide a frictional force between the base portion and the first rotary link; and

a second rotation locker configured to lock a rotation between the second rotary link and the first rotary link by operating to provide a frictional force between the first rotary link and the second rotary link in response to the first rotation locker operating.
The 2DOF rotary arm of claim 1, wherein the base portion comprises a first joint hole penetratingly formed along the first rotation axis,

the first rotary link comprises a first connection body connected to the first joint hole, a first link member fixed to the first connection body to rotate, and a second joint hole penetratingly formed at the first link member along the second rotation axis,

the second rotary link comprises a second connection body connected to the second joint hole, and a second link member fixed to the second connection body to rotate,

the first rotation locker is configured to lock the rotation between the base portion and the first rotary link by pressing the first connection body toward the base portion, and

the second rotation locker is configured to lock the rotation between the first rotary link and the second rotary link by pressing the second connection body toward the first rotary link.
The 2DOF rotary arm of claim 2, wherein the first rotation locker comprises:

a screw shaft configured to pass through the first joint hole and the first connection body along the first rotation axis and have a screw thread on a portion of an outer circumferential surface thereof;

a tightener screwed to one side of the screw shaft to move relative to the first connection body along the first rotation axis; and

a frictional pad installed on the other side of the screw shaft to be in contact with a surface of an end portion of the first connection body, and

the second rotation locker comprises a frictional link configured to be interfered with in response to a movement of the tightener and move relative to the first link member in a direction vertical to the second rotation axis so as to be in contact with an outer surface of the second connection body.
The 2DOF rotary arm of claim 3, wherein the frictional pad is installed to be slidable in a direction parallel to the first rotation axis based on the base portion and to be not rotatable based on the first rotation axis.
The 2DOF rotary arm of claim 3, wherein the tightener comprises:

a knob screwed to the screw shaft;

a pressing member configured to move along the first rotation axis in response to the knob being tightened and interfere with the frictional link such that the frictional link moves in a direction vertical to the first rotation axis; and

a first elastic body configured to apply an elastic force in a direction in which a distance between the pressing member and the first connection body increases.
The 2DOF rotary arm of claim 5, wherein the pressing member comprises a first contactor having a portion that is in contact with the frictional link and inclined with respect to the first rotation axis, and

the frictional link comprises a second connection body that is in contact with the first contactor and inclined with respect to the first rotation axis.
The 2DOF rotary arm of claim 2, wherein the frictional link comprises a frictional end portion having a curved surface in surface contact with an outer surface of the second connection body.
The 2DOF rotary arm of claim 7, wherein the frictional link further comprises a second elastic body configured to apply an elastic force in a direction in which a distance between the frictional end portion and the second connection body increases.
The 2DOF rotary arm of claim 8, wherein the second elastic body is a plunger.
The 2DOF rotary arm of claim 1, further comprising:

a first support structure configured to prevent the first rotary link from performing a translational movement along the first rotation axis with respect to the base portion irrespective of whether the first rotation locker operates; and

a second support structure configured to prevent the second rotary link from performing a translational movement along the second rotation axis with respect to the first rotary link irrespective of whether the second rotation locker operates.