Arm assembly and articulated support apparatus

Abstract

To provide an arm assembly in which a hook of an arm lock mechanism does not become an obstacle during normal use.SOLUTION: The articulated support device does not include the base 10 at the proximal end, the support 20 at the distal end that supports the support target 2, and the first arm 30 and the second arm 40 disposed between the base 10 and the support 20. An arm lock mechanism 6 of an arm assembly 5 comprising a first arm 30 and a second arm 40 is provided with an upper structure 60 provided on the second arm 40 and a lower structure 70 provided on the first arm 30. The upper structure 60 includes a rotatable hook 62 having a claw portion 62a at a tip end thereof, and ball plungers 63 (position holding means) that hold the hook 62 at a projecting position and a falling position. The lower structure 70 includes a hook receiver 74 that is movable between an engagement position and a retraction position, a spring 75 that biases the hook receiver 74 toward the engagement position, and a lock release mechanism 80. The engagement of the hook receiver 74 with the hook 62 locks the second arm 40 to the first arm 30.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an arm assembly having an arm lock mechanism that locks an upper second arm to a lower first arm, and to an articulated support device incorporating this arm assembly. [Background technology]

[0002] The articulated support device disclosed in Patent Document 1 is configured by a base, a support that supports a support object, and a series of multiple arms arranged between the base and the support, all of which are rotatably connected around a vertical or horizontal rotation axis. The multiple arms include a first arm connected to the base so as to be horizontally rotatable around the vertical rotation axis, and a second arm whose base end is connected to the tip of the first arm so as to be horizontally rotatable around the vertical rotation axis. The second arm configures a parallel link mechanism by connecting a base-end block, a tip-end block, and upper and lower arm members so as to be rotatable around four horizontal rotation axes, and by rotating the upper and lower arm members up and down relative to the base-end block, the support can be moved up and down while maintaining its orientation.

[0003] The articulated support device shown in Patent Document 1 can be made compact for storage, etc., by aligning the upper second arm approximately parallel to the lower first arm. When the second arm is rotated downward toward the first arm, the claw of the hook protruding downward from the second arm automatically engages with a hook receiver provided on the first arm and biased by a spring, locking the second arm to the first arm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Publication No. 7362844 Summary of the Invention [Problem to be solved by the invention]

[0005] In the arm lock mechanism shown in Patent Document 1, the hook is fixed to the upper second arm in a state where it protrudes downward, which can be a hindrance. For example, when used in an articulated support device for medical use, the tube may get caught on the hook. [Means for solving the problem]

[0006] In order to solve the above problem, the present invention provides an arm assembly including a lower first arm, an upper second arm whose base end is connected to a tip end of the first arm so as to be horizontally rotatable about a vertical rotation axis and vertically rotatable about the horizontal rotation axis, and an arm locking mechanism configured to lock the second arm to the first arm in a state aligned with the first arm, the arm lock mechanism comprises an upper structure provided on the second arm and a lower structure provided on the first arm, wherein the upper structure includes a hook having a claw portion at its tip and supported rotatably between a protruding position where it protrudes from the second arm and a retracted position along the second arm, and position holding means for holding the hook in the protruding position and the retracted position; the lower structure includes a hook receiver movable between an engaged position and a retracted position, a biasing member that biases the hook receiver toward the engaged position, and an unlocking mechanism, wherein when the claw portion of the hook pushes the hook receiver, the hook receiver retracts against the biasing member to allow the claw portion to pass, and when the claw portion has passed, the hook receiver returns to the engaged position by the force of the biasing member, thereby engaging with the claw portion, thereby locking the second arm to the first arm; and the unlocking mechanism has an operating unit provided on the second arm, and is configured to retract the hook receiver from the engaged position by operating the operating unit.

[0007] According to the above-described configuration, the hook, which is used only when locking the second arm to the first arm, is placed in the lowered position, thereby preventing the hook from becoming an obstacle.

[0008] Preferably, the lower structure has a cover having an insertion hole formed therein positioned above the hook receiver, the claw portion of the hook of the upper structure protruding toward the connection portion of the first and second arms when the hook is in the protruding position, the hook further having an insertion portion inserted into the insertion hole and a relief surface on the opposite side of the claw portion between the tip and the insertion portion, the relief surface inclined so as to approach the central axis of the hook toward the tip. According to this configuration, the insertion portion of the hook can be inserted into the insertion hole of the cover with only a small gap, and it is possible to prevent dust from entering the lower structure.

[0009] Preferably, the upper structure comprises a base on which the hook and the position holding means are supported to form a unit, and the base is fixed to the second arm, and the lower structure comprises a housing in which the hook receiver, the biasing member and the lock release mechanism are housed to form a unit, and the housing is fitted into and fixed to a storage recess formed on the upper surface of the first arm. This configuration simplifies the process of attaching the upper structure and lower structure to the first and second arms.

[0010] In one embodiment, the position holding means includes a ball plunger fixed to the base, a hook holder rotatably supported on the base is fixed to the base end of the hook, and ball receiving recesses are formed at two locations on the periphery of the hook holder to hold the ball of the ball plunger when the hook is in the protruding position and the retracted position.

[0011] Another aspect of the present invention is an articulated support device incorporating the above-mentioned arm assembly, which comprises a base at the base end, a support at the tip end that supports an object to be supported, and a plurality of arms arranged between the base and the support that are connected so as to be rotatable relative to one another, wherein two arms connected in sequence from the base are provided as the first and second arms, and the second arm is configured as a parallel link mechanism by connecting a base member, a tip member, an upper arm member, and a lower arm member so as to be rotatable vertically around a horizontal axis of rotation, and the base member is connected to the tip of the first arm so as to be rotatable horizontally around the vertical axis of rotation, and the upper structure is provided on the lower arm member. [Effects of the Invention]

[0012] According to the present invention, when the arm lock mechanism is not in use, the hook can be laid down along the second arm, and the hook does not get in the way. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a perspective view showing a monitor support device according to one embodiment of the present invention, with the second arm in a substantially horizontal position. [Figure 1B] FIG. 10 is a side view of the monitor support device with the second arm positioned approximately horizontally. [Figure 2] FIG. 10 is a side view of the monitor support device showing the angular range of vertical rotation of the second arm. [Figure 3A] FIG. 10 is a perspective view of the monitor support device showing the stored state in which the second arm is arranged along the first arm. [Figure 3B] FIG. 2 is a side view of the monitor support device showing the stored state. [Figure 4] 1 is a perspective view of a monitor support device showing the upper structure unit and lower structure unit of the arm lock mechanism of the present invention separated from the first and second arms. FIG. [Figure 5] FIG. 10 is a side view of the monitor support device showing the second arm rotated horizontally and positioned directly above the first arm. [Figure 6]FIG. 6 is a side view of the monitor support device, showing the second arm rotated downward from the state in FIG. 5 so that it is aligned approximately parallel to the first arm and locked to the first arm. [Figure 7] FIG. 10 is a side view of the second arm with the upper structure unit shown in cross section, showing the hook held in a lowered position along the second arm. [Figure 8] 8 is a view equivalent to FIG. 7, illustrating a state in which the hook is held in a position protruding downward at a right angle to the second arm. FIG. [Figure 9] FIG. [Figure 10] FIG. 2 is an enlarged cross-sectional side view of the lower structure unit. [Figure 11] FIG. 4 is a cross-sectional plan view of the lower structure unit, showing the locked state. [Figure 12] FIG. 4 is a cross-sectional plan view of the lower structure unit, showing the unlocked state. [Figure 13] FIG. 10 is an enlarged cross-sectional side view showing the upper structure unit and the lower structure unit immediately before locking. [Figure 14] FIG. 10 is an enlarged cross-sectional side view showing the upper structure unit and the lower structure unit after the locking is completed. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-joint monitor support device (articulated support device) according to one embodiment of the present invention will now be described with reference to the drawings. The monitor support device is used, for example, for medical purposes.

[0015] <General configuration and operation of the monitor support device> As shown in Figures 1A and 1B, the monitor support device comprises a base 10 at the base end, a support 20 at the tip end, and a first arm 30, a second arm 40, and a third arm 50 arranged in that order from the base 10 toward the support 20.

[0016] The base 10 has a flat mounting surface 10a, which is fixed to a cart 1 or the like (an object to be mounted). A monitor 2 (an object to be supported) is attached to the support 20. By rotating the arms 30, 40, 50 and the support 20, the monitor 2 can be adjusted to a desired orientation and position.

[0017] The first arm 30 is inclined, and its base end is connected to the upper end of the base 10 so as to be horizontally rotatable about a vertical rotation axis L1. The base end of the second arm 40 is connected to the tip of the first arm 30 so as to be horizontally rotatable about a vertical rotation axis L2. The base end of the third arm 50 is connected to the tip of the second arm 40 so as to be horizontally rotatable about a vertical rotation axis L3. A connecting portion 21 protrudes from the back surface of the support 20, and this connecting portion 21 is connected to the tip of the third arm 50 so as to be vertically rotatable about a horizontal rotation axis L4.

[0018] As will be described later, the second arm 40 constitutes a parallel link mechanism having four horizontal rotation axes. As shown in Figure 2, the second arm 40 rotates vertically around its base end, and the positions of the third arm 50 and the support 20 are adjusted in the up and down direction while maintaining their orientation and posture.

[0019] 3A and 3B, the monitor support device can be placed in a suitable storage position when not in use. That is, the second arm 40 is placed next to the first arm 30, and these arms 30, 40 are oriented so as not to interfere with the cart 1, and the support 20 and monitor 2 are oriented so as not to interfere with the arms 30, 40.

[0020] <Schematic configuration of the second arm> 8, the second arm 40 includes a base end block 41 (base end member), a tip end block 42 (tip end member), and upper and lower arm members 43, 44 hung between these blocks 41, 42. The base end block 41 is connected to the tip end of the first arm 30 so as to be horizontally rotatable about a vertical rotation axis L2. The base end of the third arm 50 is connected to the tip end of the tip end block 42 so as to be horizontally rotatable about a vertical rotation axis L3.

[0021] The base ends of the arm members 43, 44 are connected to the upper end of the base-end block 41 so as to be rotatable about horizontal rotation axes Xa, Xb, respectively. The tip ends of the arm members 43, 44 are connected to the base end of the tip-end block 42 so as to be rotatable about horizontal rotation axes Xc, Xd, respectively. The distance between the rotation axes Xa and Xb is equal to the distance between the rotation axes Xc and Xd, and the distance between the rotation axes Xa and Xc is equal to the distance between the rotation axes Xb and Xd. As a result, the blocks 41 and 42 and the arm members 43 and 44 form a parallel link mechanism.

[0022] <General configuration and operation of the arm assembly and locking mechanism> As shown in FIG. 4, the arm assembly 5 consisting of the first arm 30 and the second arm 40 is provided with an arm lock mechanism 6 that locks the second arm 40 in a state where it is attached to the first arm 30.

[0023] The arm lock mechanism 6 includes an upper structure unit 60 (upper structure) attached to the lower arm member 44 of the second arm 40, and a lower structure unit 70 (lower structure) attached to the first arm 30. A cover 35 that hides the fixing screws for the lower structure unit 70 is attached to the underside of the first arm 30. A cover 45 that covers part of the upper structure unit 60 is attached to the underside of the lower arm member 44 of the second arm 40, and a cover 46 that covers the entire upper arm member 43 is attached to the upper arm member 43.

[0024] To place the monitor support device in the aforementioned stored state, as shown in Fig. 5, the second arm 40 is rotated horizontally about the rotation axis L2 to position it directly above the first arm 30. Next, as shown in Fig. 6, the upper arm 43 and the lower arm 44 are rotated downward about the rotation axes Xa and Xb of the second arm 40 to align them substantially parallel to the first arm 30. At this time, the upper structure unit 60 approaches and engages with the lower structure unit 70, locking the second arm 40 to the first arm 30.

[0025] <Configuration of the superstructure unit> 7 and 8, the upper structure unit 60 includes a base 61, a hook 62, and a ball plunger 63 (position-retaining means). The base 61 has an inverted U-shaped cross section and includes an upper plate portion 61a and a pair of side plate portions 61b.

[0026] The base end of the hook 62 is fixed to a hook holder 64. The hook holder 64 is disposed between the pair of side plate portions 61b and is aligned with the rotation axis X F The rotation axis X is supported by the pair of side plate portions 61b. F are parallel to the rotation axes Xa to Xd of the parallel link mechanism of the second arm 40.

[0027] The ball plunger 63 is accommodated in a cylindrical plunger holder 65, and the plunger holder 65 is fixed to the upper plate portion 61a of the base 61. The ball plunger 63 is aligned with the rotation axis X of the hook 62. F The hook holder 64 has a central axis that intersects the rotation axis X at a right angle, and has a ball 63a that can protrude and retract along the central axis. The ball 63a is biased in the protruding direction by a built-in spring. The outer circumferential surface of the hook holder 64 is F The outer circumferential surface of the semi-cylindrical member 64 is formed with ball receiving recesses 64a and 64b at positions spaced 90° apart in the circumferential direction.

[0028] As shown in Figure 7, when the ball 63a of the ball plunger 63 is fitted into one of the ball receiving recesses 64a, the hook 62 is held in a lying position along the second arm 40. Also, as shown in Figure 8, when the ball 63a of the ball plunger 63 is fitted into the other of the ball receiving recesses 64b, the hook 62 is held in a protruding position perpendicular to the second arm 40. The hook 62 is rotatable between the lying position and the protruding position.

[0029] A claw portion 62a is formed at the tip of the hook 62, and an insertion portion 62b with a circular cross section that is coaxial with the central axis Ox is formed in the axial middle portion away from the claw portion 62a, and a relief surface 62c is formed between the tip and the insertion portion 62b. 8, when the hook 62 is in the protruding position, the claw portion 62a is biased to one side with respect to the central axis Ox and protrudes toward the base end of the second arm 40 (i.e., toward the rotational connection portion between the first arm 30 and the second arm 40). The relief surface 62c is formed on the side opposite to the protruding direction of the claw portion 62a and is inclined so as to approach the central axis Ox toward the tip. In this embodiment, the tip of the relief surface 62c reaches the central axis Ox.

[0030] The upper structure unit 60 configured as described above can be attached to the lower arm 44 with a simple operation by fixing its base 61 to the plate portion 44a of the lower arm 44.

[0031] <Configuration of the lower structure unit> 9 and 10, the lower structure unit 70 includes a housing 71 that is open at the bottom, a bottom plate 72 that closes the bottom opening of the housing 71, and various components housed in the space formed by the housing 71 and the bottom plate 72. The housed components include an insertion tube 73, a hook receiver 74, a spring 75, and a lock release mechanism 80. The housing 71 also serves as a cover that covers these housed components.

[0032] The insertion tube 73 (see Figure 10) is attached to the housing 71 by inserting it into a through-hole formed in the upper wall of the housing 71 and fixing the lower end flange 73a to the underside of the upper wall of the housing 71. The insertion tube 73 forms part of the cover. The insertion hole 73b defined by the insertion tube 73 is the only opening in the lower structure unit 70 that is open to the top. This insertion hole 73b has a cross-sectional shape and dimensions that correspond to the insertion portion 62b of the hook 62.

[0033] The hook receiver 74 has an upper plate portion 74a and a hanging plate portion 74b that hangs down at a right angle from one side edge of the upper plate portion 74a. The upper plate portion 74a has a hole 74c formed therein that receives the claw portion 62a of the hook 62, as will be described later. The peripheral portion of the hole 74c on the tip side of the first arm 30 (the side of the rotational connection portion between the first arm 30 and the second arm 40) serves as an engagement edge portion 74x.

[0034] An upper plate portion 74a of the hook receiver 74 is disposed below the insertion tube 73. The hook receiver 74 is movable in the longitudinal direction of the first arm 30. During this movement, the upper plate portion 74a is guided by a pair of upright plate portions 72a that stand up from the bottom plate 72 and the lower end of the insertion tube 73. A spring support member 76 is attached to the depending plate portion 74b of the hook receiver 74. The spring 75 is held by this spring support member 76 and is disposed in a compressed state between the depending plate portion 74b and an end wall of the housing 71 (the wall facing the tip of the first arm 30). The hook receiver 74 is urged by this spring 75 toward the engaged position. When the hook receiver 74 is in the engaged position, an engaging edge portion 74x protrudes from the inner periphery of the insertion tube 73 and occupies a part of the insertion hole 73b. The edge portion of the bottom plate 72 (the edge portion on the tip side of the first arm 30) serves as a stopper 72b that engages the lower end of the depending plate portion 74b of the hook receiver 74, thereby maintaining the hook receiver 74 in the engaged position.

[0035] As shown in FIGS. 9 and 11, the lock release mechanism 80 includes a push button 81 (operating member) disposed in an operating hole 71a formed in a pair of side walls of the housing 71, and a cam mechanism that converts the pressing force of the push button 81 into movement of the lock receiver 74 in the backward direction. The cam mechanism includes a pair of cam members 82 fixed to the pair of push buttons 81, respectively, and a follower member 83 fixed to the depending plate portion 74b of the hook receiver 74. The pair of cam members 82 have inclined surfaces 82a formed on their inner ends. The follower member 83 has a wedge portion, and the wedge portion has a pair of inclined surfaces 83a formed on the wedge portion. The inclined surfaces 83a contact the inclined surfaces 82a of the pair of cam members 82, respectively. When the hook receiver 74 is in the above-described engaged position, the inner ends of the pair of cam members 82 are spaced apart from each other, as shown in FIG. 11.

[0036] The pair of cam members 82 are guided by a first guide 85 fixed to the bottom plate 72 and a pair of second guides 86 inserted into the elongated holes 82b of the cam members 82 and fixed to the bottom plate 72.

[0037] The lower structure unit 70 configured as described above can be easily attached to the first arm 30 by fitting and fixing the housing 71 into the storage recess 31 formed on the upper surface of the first arm 30 as shown in FIG.

[0038] <Arm lock mechanism action> 4 and 5, by rotating the second arm 40 downward, the second arm 40 can be locked to the first arm 30 by the arm lock mechanism 6. This process will be described in detail below.

[0039] As shown in FIG. 13 , the hook 62 of the upper structure unit 60 is in the protruding position, and the upper and lower arm members 43, 44 of the second arm 40 rotate about the horizontal rotation axes Xa, Xb, causing the second arm 40 to descend toward the first arm 30. At this time, the hook 62 traces an arc centered on the rotation axis Xb of the lower arm 44, so that the claw portion 62a at the tip enters the insertion hole 73b and then moves diagonally as shown by the arrow in FIG. 13 , approaching the engagement edge 74x of the hook receiver 74. Therefore, when the claw portion 62a enters the insertion hole 73b, it is necessary to move the claw portion 62a away from the engagement edge 73a in the radial direction of the insertion hole 73b. Moving the claw portion 62a away from the engagement edge 73a in this way could cause interference between the tip of the hook 62 and a portion of the peripheral wall of the insertion tube 73 far from the engagement edge 73a. To avoid this interference, the diameter of the insertion hole 73b must be increased. However, in this embodiment, a relief surface 62c is formed on the opposite side of the claw portion 62a, so that the insertion hole 73b has a cross-sectional shape and dimensions corresponding to the insertion portion 62b of the hook 62, and even if it has a small diameter, interference between the tip of the hook 62 and the insertion tube 73 can be avoided.

[0040] When the second arm 40 is further lowered, the inclined lower surface of the claw portion 62a of the hook 62 presses against the engagement edge portion 74x of the hook receiver 74, causing the hook receiver 74 to retract against the spring 75. This allows the engagement edge portion 74x to allow the claw portion 62a to pass. When the claw portion 62a passes the engagement edge portion 74x, the hook receiver 74 is returned to its original engagement position by the spring 75. As a result, as shown in FIG. 14 , the claw portion 62a of the hook 62 and the engagement edge portion 74x of the hook receiver 74 engage with each other, and the second arm 40 can be locked to the first arm 30.

[0041] As shown in Figure 13, when the tip of the hook 62 is inserted into the upper end of the insertion hole 73b, the escape surface 62c is approximately parallel to the movement trajectory of the claw portion 62a, so that the hook 62 does not interfere with the insertion tube 73 even when moving toward the engagement edge portion 74x of the hook receiver 74.

[0042] 14, when the claw portion 62a of the hook 62 engages with the engagement edge portion 74x of the hook receiver 74, the insertion portion 62b of the hook 62 enters into the insertion hole 73b. Because the diameter of the insertion hole 73b is small corresponding to the insertion portion 62b, the insertion portion 62b can enter the insertion hole 73b with only a small gap. Therefore, when the monitor support device is stored, it is possible to prevent dust from entering.

[0043] <Unlock> 12, when the monitor support device is returned from the stored state to the used state, the pair of push buttons 81 are pressed to move the pair of cam members 82 toward each other, and the cam action of the inclined surfaces 82a of the cam members 82 and the inclined surfaces 83a of the follower members 83 causes the hook receivers 74 to retract, releasing the engagement between the engagement edges 74x and the claws 62a of the hooks 62 and releasing the lock state of the second arm 40 relative to the first arm 30. After the lock is released, the second arm 40 is rotated upward to remove the hooks 62 from the lower structure unit 70.

[0044] During normal use, hook 62 is rotated from the protruding position shown in Fig. 8 against the pressing force of ball plunger 63 to switch to the retracted position shown in Fig. 7. This prevents protruding hook 62 from getting in the way.

[0045] In this embodiment, the monitor support device can also be used as a device without an arm lock function by not attaching the upper structure unit 60 and the lower structure unit 70 to the second arm 40 and the first arm 70. In this case, it is preferable to store and fix a dummy member having the same shape as the housing 71 in the storage recess 31 of the first arm 30.

[0046] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the arm assembly of the present invention may be incorporated into devices other than articulating support devices. The lock release mechanism can have various known structures. [Industrial Applicability]

[0047] The present invention is applicable to an arm assembly incorporated into an articulated support device or the like. [Explanation of symbols]

[0048] 5 Arm assembly 6 Arm lock mechanism 10 base 20 Support 30 First Arm 31 Storage recess 40 Second Arm 41 Base end block (base end member) 42 Tip block (tip member) 43 Upper arm member 44 Lower arm member 60 Superstructure Unit 61 base 62 Hook 63 Ball plunger (position retention means) 63a Ball 64 Hook holder 64a Ball receiving recess 70 Undercarriage Unit 71 Housing (cover) 73b Insertion hole 74 Hook holder 75 Spring 80 Unlocking mechanism 81 Push button (operating member)

Claims

1. An arm assembly comprising: a lower first arm; an upper second arm whose base end is connected to a tip end of the first arm so as to be horizontally rotatable about a vertical rotation axis and vertically rotatable about the horizontal rotation axis; and an arm lock mechanism configured to lock the second arm to the first arm in a state aligned with the first arm, the arm lock mechanism includes an upper structure provided on the second arm and a lower structure provided on the first arm, the upper structure includes a hook having a claw portion at a tip end and supported rotatably between a protruding position protruding from the second arm and a reclined position along the second arm, and a position holding means for holding the hook at the protruding position and the reclined position, the lower structure includes a hook receiver movable between an engaged position and a retracted position, a biasing member that biases the hook receiver toward the engaged position, and a lock release mechanism; When the claw portion of the hook pushes the hook receiver, the hook receiver retreats against the biasing member to allow the claw portion to pass, and when the claw portion has passed, the hook receiver returns to an engagement position by the force of the biasing member to engage with the claw portion, thereby locking the second arm to the first arm, The arm assembly is characterized in that the lock release mechanism has an operating portion provided on the second arm, and is configured to retract the hook receiver from the engagement position by operating the operating portion.

2. The lower structure has a cover, and the cover has an insertion hole formed therein and positioned above the hook receiver; the claw portion of the hook of the upper structure projects toward the connection portion of the first and second arms when the hook is in the projected position; 2. The arm assembly according to claim 1, wherein the hook further has an insertion portion that is inserted into the insertion hole, and has a relief surface on the opposite side of the claw portion between the tip and the insertion portion, the relief surface being inclined so as to approach the central axis of the hook toward the tip.

3. the upper structure includes a base, the hook and the position holding means are supported on the base to form a unit, and the base is fixed to the second arm; 2. The arm assembly according to claim 1, wherein the lower structure is a unit formed by housing the hook receiver, the biasing member, and the lock release mechanism housed within the housing, and the housing is fitted and fixed in a housing recess formed in an upper surface of the first arm.

4. the position-retaining means includes a ball plunger fixed to the base; 4. The arm assembly according to claim 3, wherein a hook holder rotatably supported on the base is fixed to the base end of the hook, and ball receiving recesses are formed at two locations on the circumferential surface of the hook holder to hold the ball of the ball plunger when the hook is in the protruding position and the retracted position.

5. An articulated support device incorporating the arm assembly according to any one of claims 1 to 4, comprising a base at a base end, a support at a tip end that supports a supported object, and a plurality of arms arranged between the base and the support, which are connected to each other so as to be capable of rotating relative to each other, Two arms connected in sequence from the base are provided as the first and second arms, the second arm is configured as a parallel link mechanism by connecting a base end member, a tip end member, an upper arm member, and a lower arm member so as to be vertically rotatable about a horizontal rotation axis, and the base end member is connected to the tip end of the first arm so as to be horizontally rotatable about a vertical rotation axis, an articulated support device, characterized in that the upper structure is mounted on the lower arm member;

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