chair

Abstract

To provide a chair which, while having a function of weight sensing type, possesses design flexibility and which can maintain a proper state as far as possible for the seating posture of a sitting person when the backrest is leaned backward.SOLUTION: A chair is equipped with a seat part elevation mechanism in which a seat part 2 vertically moves in accordance with the tilting of a backrest 4. The seat part elevation mechanism is composed of: a movable arm 8 which extends the seat part forward from the lower end of a backrest support part 5 to make it situated inside a pedestal 3; a fixed shaft 80 which is installed near the rear end of the pedestal and which makes the movable arm journaled in a tiltable manner for a support base 6 in synchronization with the tiltable movement of a backrest support part; a movable shaft 81 which is situated forward from the fixed shaft in the pedestal and which makes a seat support vertically movably journaled for the support base with the tilting of the movable arm; a vertical elevation-long hole 40 which is formed in the support base and which vertically moves the movable shaft; a horizontally long first slidable long hole 53 which is formed in the seat support and which makes the fixed shaft laterally slide; and a horizontally long second slidable long hole 54 which is formed in the seat support so as to intersect the elevation long hole and which makes the movable shaft laterally slide.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention is a chair provided with a seat lifting mechanism configured such that the seat moves up and down in response to the reclining of the backrest.

Background Art

[0002] In a chair having a so-called rocking function in which the backrest reclines when the seated person leans against it, there is a further developed type called a weight sensing type. That is, it is a type of chair in which when the seated person leans against the backrest, the weight applied to the backrest is used to raise and lower the seat. In such a weight sensing type chair, since the seat moves up and down following the reclining of the backrest, an effect can be obtained in that the feeling of the inclination of the backrest is felt in the same way regardless of the difference in the body of the seated person (the weight).

[0003] And as a general type of weight sensing rocking chair, for example, there is one as shown in Patent Document 1. In this chair, the lower end of the reinforcing member 12 of the backrest support rod 9 is pivotally attached to the support base 6 by the first pivot 8, and the upper end of the reinforcing member 12 of the backrest support rod 9 is pivotally attached to the rear part of the seat support member 31 by the fourth pivot 33. When the backrest is reclined, the seat support member 31 rotates rearward and upward about the first pivot 8, and thus the seat 7 supported by the seat support member 31 also moves rearward and upward.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the weight-sensing chair described in Patent Document 1, it is necessary to rotate the reinforcing member 12 of the backrest support 9 in order to raise or lower the seat support 31. However, this requires securing space within the base 6 to move the reinforcing member 12 in an arc shape with at least the first pivot 8 and the fourth pivot 33 as radii, which inevitably imposes various design constraints, including on the base 6. Furthermore, if the seat support 31 is raised or lowered solely by the rotation of the reinforcing member 2, the position of the seat 7 can only be adjusted within the rotational range of the reinforcing member 2, which limits the ability to maintain a more appropriate seating posture for the sitter when the backrest is tilted backward. [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, in order to solve the above problems, the present invention aims to provide a chair that has a weight-sensing function, offers design flexibility, and can maintain the seated posture of the sitter in the most appropriate state possible when the backrest is tilted backward. [Means for solving the problem]

[0007] To solve the aforementioned problems, the present invention provides a chair comprising: legs; a seat positioned above the legs; a support base positioned between the legs and the seat for supporting the seat on the legs; a backrest support connected to the support base for supporting the backrest; and a seat lifting mechanism that causes the seat to move up and down in accordance with the tilting of the backrest, wherein the support base comprises a support base fixed to the upper part of the legs and a seat support fixed to the lower part of the seat, and the seat lifting mechanism comprises a movable arm extending forward from the lower end of the backrest support and positioned within the support base, and a movable arm provided near the rear end of the support base that moves in conjunction with the tilting of the backrest support relative to the support base. The device is characterized by comprising: a fixed shaft that pivotally supports a movable arm so that it can tilt; a movable shaft located in front of the fixed shaft in the support base portion and pivotally supporting the seat so that it can move vertically relative to the support base as the movable arm tilts; a vertically elongated lifting slot formed in the support base for moving the movable shaft up and down; a horizontally elongated first sliding slot formed in the seat for sliding the fixed shaft laterally; a horizontally elongated second sliding slot formed in the seat so as to intersect with the lifting slot for sliding the movable shaft laterally; and a lifting means provided in front of the movable shaft in the support base portion for moving the front end of the seat above the top portion on which the movable shaft moves.

[0008] Furthermore, in the chair according to the present invention, the lifting mechanism can be a link member pivotally supported by the support base and the seat support.

[0009] Furthermore, in the chair according to the present invention, the lifting mechanism can be formed by a lifting slot formed in either the support base or the seat support, and a movable shaft pivotally supported in the lifting slot and moving through the lifting slot. [Effects of the Invention]

[0010] In this invention, a vertically elongated vertical slot is provided in the support base that constitutes the support stand, and by moving a movable shaft pivotally supported by a movable arm up and down through this vertical slot, the seat support can be raised and lowered. This allows for space saving in that part and improves the design flexibility of the support stand.

[0011] Furthermore, the present invention provides the seat support with a horizontally elongated first sliding slot for sliding a fixed shaft laterally and a second sliding slot for sliding a movable shaft laterally. Since the second sliding slot intersects with the vertical slot of the support base, the seat support moves laterally as it moves up and down. Therefore, the seating posture of the sitter can be maintained in the most appropriate state possible when the backrest is tilted backward. In other words, if the seat support only moves the seat upward, it may not be possible to take the proper posture in which the sitter's back is in close contact with the tilted backrest. However, according to the present invention, since the seat support also moves laterally, it is possible to adjust it so that the sitter's back is in close contact with the tilted backrest. In particular, the shape and mounting angle of the seat and backrest vary depending on the chair, but the present invention makes it easy to make fine design adjustments, such as changing the dimensions, position, and inclination of the lifting slot, first sliding slot, and second sliding slot, according to these various circumstances. [Brief explanation of the drawing]

[0012] [Figure 1] Side view of a chair with the seated person not tilting the backrest backward. [Figure 2] A side view showing a chair with the seated person tilted backward. [Figure 3] Exploded perspective view of the support base. [Figure 4] Plan view of the support base. [Figure 5] Side view and longitudinal section of the support base. [Figure 6] A side view and a side vertical cross-sectional view showing the operation of the seat lifting mechanism of the support base. [Figure 7] A side view of the support base showing another embodiment of the lifting mechanism for moving the front end of the seat support upward. [Figure 8] A side view and a side vertical cross-sectional view of the support base illustrating the mechanism for locking the tilt angle of the backrest. [Modes for carrying out the invention]

[0013] Hereinafter, embodiments of the chair according to the present invention will be described with reference to the drawings. Figure 1 is a side view of the chair with the seated person not tilting the backrest backward, Figure 2 is a side view of the chair with the seated person tilting the backrest backward, Figure 3 is an exploded perspective view of the support base, Figure 4 is a plan view of the support base, Figure 5 is a longitudinal cross-sectional side view of the support base, and Figure 6 is a side view and a longitudinal cross-sectional side view showing the operation of the seat lifting mechanism of the support base. The chair of this embodiment is generally composed of a leg portion 1, a seat portion 2 positioned above the leg portion 1, a support base portion 3 located between the leg portion 1 and the seat portion 2 for supporting the seat portion 2 on the leg portion 1, a backrest support portion 5 connected to the support base portion 3 and supporting the backrest 4, and a seat lifting mechanism that causes the seat portion 2 to move up and down in accordance with the tilting of the backrest 5. Furthermore, the aforementioned support base 3 further comprises a support base 6 fixed to the upper part of the leg portion 1 and a seat support 7 fixed to the lower part of the seat portion 2, and a movable arm 8 is formed at the lower end of the backrest support portion 5, extending forward and positioned within the support base 3. By combining these components, the support base 6 and seat support 7 of the support base portion 3 and the movable arm 8 provided at the lower end of the backrest support portion 5, a seat lifting mechanism is formed that allows the seat portion 2 to move up and down in accordance with the tilt of the backrest 5. Moreover, the seat lifting mechanism of the chair in this embodiment is configured to not only move the seat portion 2 up and down but also to move it laterally. Furthermore, the chair described in this embodiment is equipped with a link member 9 as a means for lifting the front end of the seat support 7 up and down. In the description of this embodiment, "rear" refers to the backrest 4 side of the chair, "front" refers to the opposite side, and "right" and "left" refer to the "right" and "left" when viewing the chair from the "front".

[0014] As shown in Figures 1 and 2, the leg portion 1 is formed by providing a leg support column 11 in the center of the leg base 10. Specifically, the leg base 10 has a plurality of leg feet 10b, 10b, ... arranged radially so as to extend outward from the center of a cylindrical portion 10a, and is formed with a through hole in the center of the cylindrical portion 10a. Casters 12, 12... are attached to the tips of the leg feet 10b, 10b... of the leg base 10, respectively. On the other hand, the leg support column 11 is a pipe-shaped member and is inserted into the center of the leg base 10, that is, into the through hole in the cylindrical portion 10a, and is supported so as to protrude above and below the leg base 10. The leg support column 11 is equipped with a gas spring inside, although it is not shown in the figure, and the height of the leg portion 1 relative to the seat portion 2 can be adjusted by pressing the button 11a (see Figure 5) at the upper end of the leg support column 11.

[0015] The aforementioned seat portion 2 is a typical one in which a cushion made of an elastic material such as foamed urethane is attached to a base plate, and upholstery is stretched over the upper surface of the cushion.

[0016] The support base 3 is provided so as to be located between the leg portion 1 and the seat portion 2, and is for supporting the seat portion 2 on the leg portion 1. It is formed by a support base 6 fixed to the leg portion 1 side and a seat support 7 fixed to the seat portion 2 side.

[0017] The backrest support portion 5 is a member that connects the backrest 4 to the receiving base portion 3 and supports the backrest 4 while being attached to the chair, and is formed by a pair of support members 15, 15 that are symmetrically formed on the left and right. Specifically, the support member 15 is formed by a standing rod portion 15a having a predetermined length in the vertical direction, an upper rod portion 15b extending forward by a predetermined length from the upper end of the standing rod portion 15a, and a lower rod portion 15c extending inward by a predetermined length from the lower end of the standing rod portion 15a and further extending the inner end thereof forward by a predetermined length. And the backrest 4 is attached between the upper end portions of the left and right standing rod portions 15a, 15a via an attachment member 16. This backrest 4 is a general one in which a cushion formed of a material such as foamed urethane having elasticity is attached to the front surface of the back plate, and a fabric is stretched so as to cover the upper surface of the cushion. Further, the upper rod portion 15b of the backrest support portion 5 serves as an armrest on which the seated person places their elbows. Incidentally, the chair of this embodiment forms the backrest support portion by combining a plurality of rod-shaped members, but this is an example, and for example, it is also possible to form the backrest support portion in a plate shape integrated with the backrest. Also, like the chair of this embodiment, it is not necessary to always provide a portion corresponding to an armrest in the backrest support portion.

[0018] The support base 6 is a member fixed to the upper part of the leg portion 1, and as shown in Figure 3, it is formed by a rectangular base bottom plate 20 in plan view and base side plates 21, 21 that are integrally erected from the left and right side edges of the base bottom plate 20. As shown in Figure 5, a support column insertion hole 22 is drilled in the approximate center of the rear half of the base bottom plate 20, and a leg support column attachment member 23 is fixed to the upper surface of the rear half of the base bottom plate 20 so as to cover the support column insertion hole 22. This leg support column attachment member 23 is a downward-facing U-shaped member in side view, consisting of a front side plate, a rear side plate (stopper fixing part), and a top plate, of which a support column insertion hole 24 is drilled in the center of the top plate. A notch 25 is formed extending from the front end of the top plate to the upper end of the front side plate. The upper end of the aforementioned leg support 11 is inserted through the support insertion hole 22 of the base bottom plate 20 and the support insertion hole 24 of the leg support attachment member 23, and is fixed to the support base 6 via the cylindrical body 26. On the other hand, a lock cam housing member 27 is fixed to the upper surface of the front half of the base bottom plate 20. This lock cam housing member 27 is a U-shaped member facing downwards in side view, consisting of a front plate (link contact part), a rear plate, and a top plate, of which a lock cam insertion slit 28 is drilled in the center of the top plate. An inclined lock base 29 is attached to the upper surface of the lock cam housing member 27. The dimensions of this inclined lock base 29 in the front-to-back direction are approximately the same as those of the lock cam housing member 27, and it is sized to fit between the base side plates 21, 21. In addition, a horizontally elongated lock cam insertion slit 30 that penetrates vertically is formed in the center of the inclined lock base 29 in the front-to-back direction. Furthermore, a protruding upright portion 31 is formed on the front side of the insertion slit 30 of the inclined lock base 29, and a horizontally elongated lock plate movement slit 32 is formed at the lower end of this upright portion 31, penetrating from front to back. The lock plate 33 is slidably attached to the lock plate movement slit 32. On the other hand, an inclined lock cam 34 is provided inside the aforementioned lock cam housing member 27. The inclined lock cam 34 has a cylindrical portion formed at its lower part through which the lock cam connecting member 45 of the lever portion 43, which will be described later, is inserted, and its upper part is attached to the lock plate 33 via a lock retainer 35.Furthermore, a link shaft hole 36 that penetrates in the left-right direction is drilled in the front end of the inclined lock base 29. Also, a reinforcing fitting 37 for reinforcing the lock plate 33 is attached to the upper surface of the inclined lock base 29. In addition, a push pipe 38 is positioned between the rear plate of the lock cam housing member 27 and the front side plate of the leg support attachment member 23. This push pipe 38 has a cylindrical portion formed at its lower end through which the rotating rod 46 of the lever portion 43 (described later) is inserted, and at its upper end is a side-view L-shaped pressing piece 38a that extends from the lower part toward the rear. On the other hand, the left and right base side plates 21, 21 each have first link shaft holes 39, 39 at their front ends for pivoting the link member 9, vertically elongated lifting holes 40, 40 in the middle for moving the movable shaft 81 (described later) up and down, and fixed shaft holes 41, 41 at their rear ends for pivoting the fixed shaft 80 (described later). Furthermore, lever insertion holes 42, 42 are drilled below the elongated lifting holes 40, 40. In addition, although not shown in the figures, a connecting member insertion hole is drilled below the first link shaft hole 39 of the left base side plate 21. The upper part of the front end of each of the left and right base side plates 21, 21 is sloped downward toward the front, and the boundary between the front end and upper end of the base side plates 21, 21 is arc-shaped. Furthermore, a lever portion 43 is provided on the support base 6 so as to be located on the left side of its front end. This lever section 43 is used for adjusting the height of the leg section 1 and for maintaining the tilt angle of the seat section 2 in a predetermined position. It consists of a cylindrical lever body 44 equipped with a tilt angle adjustment knob 44a, a lock cam connecting member 45 attached to the base end of the lever body 44, a rotating rod 46 inserted through the center of the lever body 44, and a leg lifting knob 47 that is fitted onto the rotating rod 46 protruding from the tip side of the lever body 44 and is rotatably loosely fitted to the tip of the lever body 44. The lever section 43 is attached to the support base 6 by inserting its rotating rod 46 through lever insertion holes 42, 42 and inserting the lock cam connecting member 45 through the connecting member insertion hole. The rotating rod 46 of the lever section 43 also passes through the cylindrical part of the push pipe 38, so that the push pipe 38 rotates when the leg lifting knob 47 of the lever section 43 is rotated.When the push pipe 38 rotates, the pressing piece 38a at its upper part presses the button 11a at the upper end of the leg support 11, allowing the height of the leg support 11 relative to the seat 2 to be adjusted. In addition, the lock cam connecting member 45 of the lever part 43 is inserted through the cylindrical part of the inclined lock cam 34, and when the tilt angle adjustment knob 44a is rotated, the inclined lock cam 34 and the lock plate 33 move in conjunction with it.

[0019] The seat support 7 is a member fixed to the lower surface of the seat portion 2, and is formed by rectangular seat mounting plates 48, 48 that are long in the front-to-back direction and positioned at a predetermined distance apart on the left and right, seat support side plates 49, 49 that hang down integrally from the inner ends of each of the seat mounting plates 48, 48, and the front and rear ends of these seat support side plates 49, 49, and round bar-shaped horizontal members 50, 50 that are spanned between the inner sides of the left and right seat support side plates 49, 49. Furthermore, screw insertion holes 51, 51... are drilled in the front and rear ends of the left and right seat mounting plates 48, 48, and screws are inserted into these screw insertion holes 51, 51... to screw the seat support 7 to the lower surface of the bottom plate of the seat portion 2. Furthermore, the front ends of the left and right seat support side plates 49, 49 are drilled with holes 52, 52 for inserting the second link shaft 84, which will be described later. Also, the left and right seat support side plates 49, 49 are drilled approximately in the front-to-back center with elongated second sliding holes 53, 53 for sliding the movable shaft 81, which will be described later, laterally. The rear ends of the left and right seat support side plates 49, 49 are drilled with elongated first sliding holes 54, 54 for sliding the fixed shaft 80, which will be described later. The first sliding holes 54, 54 and the second sliding holes 53, 53 are arranged side by side in the front-to-back direction. The first sliding holes 54, 54 are arc-shaped with a convex upper side and are slightly inclined downward toward the rear. On the other hand, the second sliding holes 53, 53 are arc-shaped with a convex lower side and are slightly inclined downward toward the front. Furthermore, the inner dimensions of the left and right seat support side plates 49, 49 are set to be slightly longer than the inner dimensions of the base side plates 21, 21 of the support base 6 as described above. Therefore, when the seat support 7 is positioned above the support base 6, the left and right seat support side plates 49, 49 will be located outside the base side plates 21, 21 of the support base 6. Also, the length of the seat support 7 in the front-to-back direction is set to be longer than the length of the support base 6 in the front-to-back direction. Therefore, when the seat support 7 is positioned above the support base 6, both the front and rear ends of the seat support 7 will protrude from the front and rear ends of the support base 7. Incidentally, in this embodiment, the seat support 7 is shown as an example in which a member consisting of a pair of seat mounting plates 48 and seat support side plates 49, which exist on the left and right sides, is integrated by horizontal members 50, 50. However, as long as a pair of members consisting of seat mounting plates 48 and seat support side plates 49 exist on the left and right sides, the objective of the present invention can be achieved without necessarily integrating the two.That is, it suffices that there is a pair of members including at least a seat mounting plate and seat receiving side plates on the left and right sides.

[0020] The movable arm 8 is a member connected to the front end of the lower shaft portion 15c of the backrest support portion 5, and is formed by a rectangular base plate 55 in plan view and side plates 56, 56 that are integrally erected from the left and right edges of the base plate 55. The front half of the movable arm 8 is located inside the support base portion 3, specifically between the support base 6 and the seat support 7, and the rear half is positioned to protrude behind the support base portion 3, specifically behind the support base 6 and the seat support 7. A rectangular opening 57 is provided in the front half of the base plate 55 of the movable arm 8, so that when the movable arm 8 is placed inside the support base 3, the upper end of the leg support column 11 fixed to the support base 6 and the pressing piece 38a on the upper part of the push pipe 38 can protrude from the opening 57. Furthermore, the rear half of the base plate 20 serves as a mounting section for attaching the lower shaft portion 15c of the backrest support portion 5. Bolts are inserted through multiple mounting holes drilled in this mounting section to connect it to the backrest support portion 5. Additionally, a tilt locking member 60 is attached to the upper surface of the front end of the base plate 20. This tilt locking member 60 is formed in a rectangular concave shape in plan view, and both ends are bearings 61, 61 that support the movable shaft 81, which will be described later. Multiple recesses 62, 62 are formed on the front surface of the tilt locking member 60, and these recesses 62, 62 are the parts that receive the lock plate 33 of the support base 6. Furthermore, a reinforcing fitting 63 for reinforcing the movable arm 8 is attached to the upper surface of the tilt locking member 60. Moreover, a tilt stopper 65, which is triangular in side view, is attached to the lower surface of the front end of the mounting portion of the base plate 55, approximately in the center of the base plate 55 in the front-rear direction. On the other hand, the left and right side plates 56, 56 of the movable arm 8 have movable shaft holes 67, 67 drilled below their front ends for inserting a movable shaft 81 (described later), and fixed shaft holes 68, 68 drilled approximately above the center in the front-to-back direction for inserting a fixed shaft 80 (described later). The positional relationship between these movable shaft holes 67 and fixed shaft holes 68 is such that the fixed shaft holes 68 are positioned higher than the movable shaft holes 67. Furthermore, a round bar-shaped spring fastening portion 69 is provided slightly behind the fixed shaft holes 68, 68 on the left and right side plates 56, 56, spanning across the inside of the left and right side plates 56, 56.Furthermore, two torsion coil springs 70, 70 are mounted between the fixing shaft holes 68, 68 of the left, right side plates 56, 56. Specifically, the two torsion coil springs 70, 70 are placed side by side, two cylindrical spring supports 71, 71 are inserted into the coil portions from the outside, and the two cylindrical spring supports 71, 71 are joined in the center to mount the torsion coil springs 70, 70. These cylindrical spring supports 71, 71 have through holes formed in their centers through which the fixing shaft 80 is inserted. In addition, the free ends of the torsion coil springs 70, 70 that extend linearly rearward from the coil portion are hooked onto the spring hook portion 69, and the free ends that extend linearly forward from the coil portion are fixed by the spring retainer member 72. The spring retaining member 72 is fixed to the support base 6 with its lower end facing the opening 57 of the bottom plate 55. These torsion coil springs 70, 70 allow the backrest 4 to maintain its normal, non-tilted position as long as no external force is applied to it. Incidentally, in this embodiment, an example of the movable arm 8 being separately attached to the lower rod portion 15c of the backrest support portion 5 is shown, but this is not always necessary. For example, the movable arm may be formed integrally with the backrest support portion by being continuous with the lower part of the backrest support portion. In other words, the objective of the present invention can be achieved even if the movable arm is formed integrally with the backrest support portion.

[0021] The link member 9 is pivotally supported by the support base 6 and the seat 7, respectively, and is a member that moves the front end of the seat 7 up and down relative to the support base 6. The link member 9 has a predetermined thickness and has a beak-shaped anti-rotation portion 9a formed on its lower front side. First link bearings 9b are formed on both the left and right sides of the lower end for inserting the first link shaft 83, which will be described later, and second link bearings 9c are formed on both the left and right sides of the upper end for inserting the second link shaft 84, which will be described later. The length of the link member 9 in the left-right direction is approximately the same as the outer dimensions of the support base 6 in the left-right direction, but a narrow, thin section 9d is formed from the lower end of the anti-rotation portion 9a to the rear end of the link member 9. This thin section 9d allows the link member 9 to slide smoothly along the front upper end of the base side plate 21 of the support base 6 when it rotates.

[0022] As described above, the support base 3 is formed by a support base 6 and a seat support 7, and a movable arm 8 is housed inside the support base 6 and seat support 7. The seat lifting mechanism is constructed by pivotally supporting a fixed shaft 80 and a movable shaft 81 on these components. Specifically, the fixed shaft 80 is pivotally supported by being inserted through the first sliding elongated hole 54 of the seat support side plate 49 of the seat support 7 located on the outside, the fixed shaft hole 41 of the base side plate 21 of the support base 6 located in the middle, and the fixed shaft hole 68 of the side plate 56 of the movable arm 8 located on the inside. The movable shaft 81 is pivotally supported by being inserted through the second sliding elongated hole 53 of the seat support side plate 49 of the seat support 7 located on the outside, the vertically elongated lifting elongated hole 40 of the base side plate 21 of the support base 6 located in the middle, and the movable shaft hole 67 of the side plate 56 of the movable arm 8 located on the inside. Furthermore, the first sliding elongated hole 54 of the seat support side plate 49 is located at a position where it intersects with the fixed shaft hole 41 of the base side plate 21 and the fixed shaft hole 68 of the side plate 56 of the movable arm 8, and the second sliding elongated hole 53 of the seat support side plate 49 is located at a position where it intersects with the lifting elongated hole 40 of the base side plate 21 and the movable shaft hole 67 of the side plate 56 of the movable arm 8. As a result, as the movable arm 8 tilts, the seat portion 2 to which the seat support 7 is fixed moves in the vertical direction as well as in the horizontal direction. Details of this will be described later. In addition, the chair in this embodiment is provided with a lifting mechanism for raising and lowering the front end of the seat support 7 relative to the support base 6 as part of the seat lifting mechanism. Specifically, the first link shaft 83 is pivotally supported by being inserted through the first link shaft hole 39 of the support base 6 located on the outside, the first link bearing 9b of the link member 9 located on the inside, and the link shaft hole 36 of the inclined lock base 29 located further inside. Furthermore, the second link shaft 84 is pivotally supported by being inserted through the second link shaft hole 52 in the seat support side plate 49 of the seat support 7 located on the outside, and through the second link bearing 9c of the link member 9 located on the inside.

[0023] Next, the operation of the chair of this embodiment, configured as described above, will be explained. Figures 1 and 6(a) show the normal state in which the seated person has not tilted the backrest 4 backward. In this state, the movable arm 8 connected to the backrest support 6 is held in a substantially horizontal position inside the support base 6. The movable shaft 81, which is pivotally supported at the front end of the movable arm 8 and is located approximately in the front-rear center of the support base 3, is located at the lower end of the lifting slot 40 of the base side plate 21 of the support base 6 and at the rear end of the second sliding slot 53 of the seat support side plate 49 of the seat support 7. The fixed shaft 80, which is pivotally supported at the front-rear center of the movable arm 8 and is located at the rear end of the support base 3, is located at the rear end of the first sliding slot 54 of the seat support side plate 49 of the seat support 7. Furthermore, the link member 9, which is pivotally supported between the support base 6 and the seat support 7 at the front end of the support base 3, has its inner (rear) side of the anti-rotation portion 9a in contact with the front end of the support base 6. Then, when a seated person puts their weight on the backrest 4 and pushes it with their back, the backrest 4 tilts backward, and consequently, the movable arm 8 rotates upward on its front side, with the fixed shaft 80 as the pivot point. That is, the movable shaft 81, which is pivotally supported in the movable shaft hole 67 at the front end of the movable arm 8, moves upward along the elongated lifting hole 40 of the support base 6, causing the front side of the movable arm 8 to lift up. At this time, since the horizontally elongated second sliding hole 53 of the seat support 7 intersects with the elongated lifting hole 40 of the support base 6, the front-to-back center of the seat support 7 is also lifted as the movable shaft 81 moves upward. Simultaneously, as shown in Figures 6(b) and 6(c), the movable shaft 81 slides forward along the second sliding hole 53 of the seat support 7, and the fixed shaft 80 slides forward along the first sliding hole 54, causing the seat support 7 to gradually move backward. Furthermore, the front end of the seat support 7 is lifted upward by the link member 9. When the link member 9 lifts the front end of the seat support 7, the part of the link member 9 inside the thin portion 9d slides along the arc-shaped front upper end and the inclination behind it of the base side plate 21, so that the link member 9 rises smoothly. Incidentally, in Figure 6(b), the movable arm 8 is tilted 10 degrees downward from the normal state in Figure 6(a), and in Figure 6(c), the movable arm 8 is tilted 20 degrees downward from the normal state in Figure 6(a).When the chair reaches the state shown in Figure 6(c), the inclined stopper 65 provided on the lower surface of the movable arm 8 contacts the rear plate (stopper stopper portion) of the leg support attachment member 23 of the support base 6, preventing the movable arm 8 from rotating any further. On the other hand, when the sitter releases the weight they were leaning on the backrest 4, the chair returns to the normal state shown in Figure 6(a) through the reverse of the aforementioned operation. Thus, the chair shown in this embodiment is designed so that when the sitter leans their weight on the backrest 4 as if pushing it with their back, the seat 2 rises accordingly. In other words, it has a so-called weight-sensing function that changes the force that tilts the backrest 4 backward in accordance with the increase or decrease in the sitter's weight. However, the chair in this embodiment is not only designed to do this, but the seat 2 also moves backward as it rises. In other words, because the seat 2 rises and moves backward simultaneously in accordance with the backward tilt of the backrest 4, even if the sitter leans against the backrest 4 and the backrest 4 tilts backward, the seat 2 moves and approaches the backrest 4, bringing the sitter's body closer to the backward-tilting backrest 4. Therefore, the sitter's back can be reliably kept in contact with the backrest 4 regardless of its position.

[0024] Figure 7 shows another embodiment of the lifting mechanism for moving the front end of the seat support 7 upward. This embodiment shares many components with the previous embodiment, and therefore, the same reference numerals are used to describe the common parts. This lifting mechanism is constructed by pivoting a pivot 91 in vertically elongated guide holes 90, 90 formed in the front ends of the seat support side plates 49, 49 of the seat support 7 and in shaft holes drilled in the front ends of the base side plates 21, 21 of the support base 6. The guide holes 90 are inclined, with their lower ends facing forward and their upper ends facing backward, and are also curved in a convex shape towards the rear. When a person sits on the backrest 4, the front end of the movable arm 8 rotates upward around the fixed shaft 80 as a pivot point, lifting the front-to-back center of the seat support 7. In conjunction with this, the pivot 91 slides downward through the guide holes 90, 90, and the front end of the seat support 7 is also lifted. In other words, in the state shown in Figure 7(a) where the backrest 4 is not tilted backward, the fixed shaft 91 located at the upper end of the guide slots 90, 90 changes position downward as the front end of the movable arm 8 rises, and when the backrest 4 is tilted backward to its deepest extent, it will be located at the lower end of the guide slots 90, 90, as shown in Figure 7(c). At this time, the front end of the seat support 7 is lifted to its highest position.

[0025] Next, the mechanism for locking the tilt angle of the backrest 4 will be explained with reference to Figure 8. Figure 8(a) shows the state where the tilt angle is not locked, that is, when a seated person leans against the backrest 4, the backrest 4 can freely tilt backward. In this state, the lock plate 33 on the tilt lock base 29 of the support base 6 is located within the lock plate movement slit 32, and its rear end is flush with the rear end of the tilt lock base 29, that is, it does not protrude from the tilt lock base 29. Now, if you want to lock the backrest 4 so that the seated person cannot tilt it backward, first, you lift the tilt angle adjustment knob 44a of the lever part 43 located in the front-to-back center on the left side of the support base 6 upward by hand. This causes the lever body 44, which is integrated with the tilt angle adjustment knob 44a, to rotate clockwise. Then, as shown in Figure 8(b), the lock cam connecting member 45 connected to the lever body 44 moves backward. Furthermore, the lower end of the inclined lock cam 34, which is connected to the lock cam connecting member 45 within the lock cam housing member 27 of the support base 6, moves backward. At this time, since the central part of the inclined lock cam 34 is pivotally supported, the upper end of the inclined lock cam 34 moves in the opposite direction to the lower end, i.e., forward. As a result, the lock plate 33, which is attached to the upper end of the inclined lock cam 34 by the lock retainer 35, also moves forward, and its rear end protrudes from the rear end of the inclined lock base 29 and contacts the upper surface of the inclined lock member 60 located at the front end of the movable arm 8. As a result, the upper surface of the inclined lock member 60 is pressed down by the lock plate 33, restricting the upward movement of the movable arm 8, and consequently locking the inclination angle of the backrest 4. On the other hand, if the seated person wants to return the backrest 4 to a state where it can be tilted backward again, they can return it to the free state shown in Figure 8(a) by performing the reverse of the above operation. Figure 8(b) shows the locking of the tilt angle in the normal state where the backrest 4 is not tilted backward, but it is also possible to lock the backrest 4 in a position tilted backward by a predetermined angle. That is, with the seated person tilting the backrest 4 backward, if they lift the tilt angle adjustment knob 44a of the lever part 43 upward by hand, the lock plate 33 will fit into the recess 62 of the tilt locking member 60 of the movable arm 8, and the backward tilt of the backrest 4 can be locked in that position.

[0026] In this invention, the length of the vertically elongated slot can be freely set, as long as it is formed in a vertical shape. Furthermore, as shown in the above embodiment, it does not necessarily have to be an arc-shaped slot, but may also be a straight slot, and the vertically elongated slot may be formed at an angle. Similarly, the length of the first sliding slot and the second sliding slot can also be freely set, as long as they are formed in a horizontal shape. In this way, in this invention, the vertically elongated slot, the first sliding slot, and the second sliding slot can be freely set, so for example, it becomes possible to make subtle adjustments so that the seated person's back is in close contact with the reclined backrest, resulting in a proper posture. Also, for example, by shortening the length of the vertically elongated slot, it is possible to reduce the thickness of the support base and design the support base to a compact size. In any case, by adopting the seat height adjustment mechanism of this invention, it is possible to increase the degree of design freedom while providing a weight-sensing function, and to maintain the seated person's posture in the most appropriate state possible when the backrest is reclined. Furthermore, in the above embodiment, the lifting slot, the first sliding slot, and the second sliding slot are set so that when the backrest is tilted backward, the front end of the seat support is higher and the rear end of the seat support is lower. However, it is not necessary to set them in this way, and it is also possible to set them so that the front end of the seat support is lower and the rear end is higher, or so that the front end and rear end of the seat support are at the same height. In addition, the length and inclination of the guide slot in the above embodiment can be freely set as long as it is formed in a vertical shape. [Explanation of symbols]

[0027] 1 leg 2 Seat part 3 cradle part 4 Backrest 5 Backrest support part 6. Support base 7 Seating New Year Movable Arm 9 Link members 40 Elevating slot 53 Second sliding elongated hole 54 First sliding elongated hole 80 Fixed axis 81 Movable axis 90 Guide slots 91 Axis

Claims

[Claim 1] A chair comprising legs, a seat positioned above the legs, a support base located between the legs and the seat for supporting the seat on the legs, a backrest support connected to the support base for supporting the backrest, and a seat lifting mechanism that causes the seat to move up and down in accordance with the tilt of the backrest, The support base comprises a support base fixed above the leg portion and a seat support fixed below the seat portion. The seat lifting mechanism comprises: a movable arm extending forward from the lower end of the backrest support and positioned within the support base; a fixed shaft provided near the rear end of the support base that pivotally supports the movable arm so as to be able to tilt in sync with the tilting of the backrest support; a movable shaft located in front of the fixed shaft in the support base that pivotally supports the seat so as to be able to move up and down in accordance with the tilting of the movable arm; a vertically elongated lifting slot formed in the support base for moving the movable shaft up and down; a horizontally elongated first sliding slot formed in the seat for sliding the fixed shaft in the front-rear direction; a horizontally elongated second sliding slot formed in the seat so as to intersect with the lifting slot for sliding the movable shaft in the front-rear direction; and a lifting means provided in front of the movable shaft in the support base that moves the front end of the seat above the top where the movable shaft moves. The chair is characterized in that the lifting mechanism is a link member pivotally supported by the support base and the seat support, and the inside of the link member is formed to be slidable on the arc-shaped front upper end of the support base.

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