ADJUSTING DEVICE FOR SEAT UNIT AND SEAT UNIT

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]The present application is a Continuation Application of PCT Application No. PCT/CN2022/132594 filed on Nov. 17, 2022, which claims priority of Chinese Patent Applications No. 2022109497457 filed on Aug. 9, 2022 before CNIPA. All the above are hereby incorporated by reference in their entirety as part of the present disclosure.

TECHNICAL FIELD

[0002]The present disclosure relates to the field of seat unit and, particularly, to an adjusting device for a seat unit and a seat unit.

BACKGROUND

[0003]Functional seats can be adjusted for sitting, stretching, and lying positions. Among them, the sitting position is the standard folded position, and the seat is in the primitive state, offering people to sit down for normal use in daily life. At this time, the seat part is in a generally horizontal orientation and the backrest is set to be basically upright. The stretching position is usually called the TV position, and the footrest part is extended to the front of the seat part, while the backrest remains upright enough to allow the user of the seat unit to watch TV comfortably. As well as the reclining position (or lying position), the backrest is positioned backward from the stretching position at an obtuse angle to the seat part for resting or sleeping. The existing functional seat adjustment angle is small, and it is difficult to achieve zero gravity (the user's calf level being higher than the heart position) when the functional seat is in the stretching position or lying position, and the comfort is low.

SUMMARY

[0004]In view of the deficiencies of the prior art, a first objective of the present disclosure is to provide an adjusting device for a seat unit, which enables a user to achieve a zero gravity state through the seat unit by cooperatively adjusting the corresponding height and angle of the backrest part, the seat part and the footrest part, thereby improving the comfort of the seat unit.

[0005]Another objective of the present disclosure is to provide a seat unit having a high degree of comfort and enabling a user to be in a zero gravity state when in the lying position.

[0006]Embodiments of the present disclosure are achieved by the following technical solutions:

[0007]An adjusting device for a seat unit, configured to switch the seat unit between a sitting position, a stretching position, and a lying position, in which the adjusting device includes a backrest connecting assembly, an intermediate transmission assembly, and a footrest connecting assembly that are connected in sequence. The backrest connecting assembly at least includes a backrest connecting block. The intermediate transmission assembly at least includes a seat frame and an adjusting mechanism configured to adjust the seat frame. The adjusting mechanism includes a first connecting member, the first connecting member is configured with a first hinge hole, a second hinge hole, and a third hinge hole in sequence, a distance between the first hinge hole and the third hinge hole is A1, a distance between the second hinge hole and the third hinge hole is A2, and a ratio of A2 to A1 is not greater than 0.5; The adjusting mechanism further includes a fixed base plate and a rotary driving plate disposed opposite to each other, two seventh connecting members disposed between the seat frame and the rotary driving plate, and the rotary driving plate is configured with a ninth hinge hole, a tenth hinge hole, and an eleventh hinge hole in sequence. The eleventh hinge hole is disposed close to the footrest connecting assembly, the ninth hinge hole is disposed close to the backrest connecting assembly, and the two seventh connecting members are hinged to the tenth hinge hole and the eleventh hinge hole respectively. A distance between the ninth hinge hole and the tenth hinge hole is C1, a distance between the ninth hinge hole and the eleventh hinge hole is C2, and a ratio of C1 to C2 is not greater than 0.35. A variation of an angle between a side edge of the backrest connecting block and the horizontal plane is not less than 25° when the backrest connecting block is adjusted between the stretching position and the lying position.

[0008]In accordance with an implementation, the adjusting mechanism further includes a second connecting member hinged to the first connecting member, and the second connecting member is configured with a fourth hinge hole, a fifth hinge hole, and a sixth hinge hole in sequence. The fifth hinge hole is coaxial with the third hinge hole. A distance between the fourth hinge hole and the sixth hinge hole is B1, a distance between the fifth hinge hole and the sixth hinge hole is B2, and a ratio of B2 to B1 is not greater than 0.5.

[0009]In accordance with an implementation, the adjusting mechanism further includes a third connecting member hinged to the second connecting member, and the third connecting member is configured with a seventh hinge hole and an eighth hinge hole. The seventh hinge hole is coaxial with the sixth hinge hole. A distance between the seventh hinge hole and the eighth hinge hole is not greater than 230 mm.

[0010]In accordance with an implementation, the first connecting member, the second connecting member, the third connecting member, a fourth connecting member, a fifth connecting member, and a sixth connecting member are provided between the fixed base plate and the rotary driving plate. The first connecting member is hinged to the rotary driving plate through the first hinge hole. The second connecting member is hinged to the fixed base plate through the fourth hinge hole. An end of the sixth connecting member is hinged to the second hinge hole, an opposite end of the sixth connecting member is hinged to an end of the fourth connecting member. An opposite end of the fourth connecting member is hinged to the fixed base plate. An end of the fifth connecting member is hinged between two ends of the fourth connecting member, and an opposite end of the fifth connecting member is hinged to the rotary driving plate. The third connecting member is hinged between two ends of the sixth connecting member through the eighth hinge hole.

[0011]In accordance with an implementation, the footrest connecting assembly includes a footrest connecting block. The fixed base plate is provided with a rear mounting hole, a horizontal plane at which a center of the rear mounting hole is located is defined as a reference plane. A height between a lowest point of the footrest connecting block and the reference plane is H1 when the backrest connecting block is in the sitting position, with H1 not greater than 100 mm. A height between a highest point of the footrest connecting block and the reference plane is H2 when the backrest connecting block is in the lying position, with H2 not greater than 600 mm.

[0012]In accordance with an implementation, an ascending distance of the footrest connecting block is not greater than 300 mm during adjustment from the stretching position to the lying position.

[0013]In accordance with an implementation, a distance between a highest point of the backrest connecting block and the reference plane is not greater than 400 mm in the sitting position, and a distance between the highest point of the backrest connecting block and the reference plane is not greater than 320 mm in the lying position.

[0014]In accordance with an implementation, the backrest connecting assembly further includes a backrest limit block, a backrest limit rod, and a ninth connecting member, the backrest connecting block is hinged to the backrest limit block, an end of the ninth connecting member is hinged between two ends of the backrest connecting block, an opposite end of the ninth connecting member is hinged to the backrest limit rod, the backrest limit rod is provided with a limit protrusion, the backrest limit block is provided with a limit surface matching the limit protrusion, and a descending distance of a center of the ninth connecting member is in a range of 30 to 100 mm during adjustment from the stretching position to the lying position.

[0015]In accordance with an implementation, an elastic cushioning device is provided between the backrest limit block and the backrest limit rod.

[0016]In accordance with an implementation, the elastic cushioning device is a sponge mad and/or a spring.

[0017]In accordance with an implementation, a variation of an angle between a side edge of the seat frame and the horizontal plane not less than 5° when the seat frame is adjusted between the stretching position and the lying position.

[0018]In accordance with an implementation, a first adjustment stage refers to the seat unit being adjusted from the sitting position to the stretching position, a second adjustment stage refers to the seat unit being adjusted from the stretching position to the lying position, and both the first adjustment stage and the second adjustment stage are driven by a same drive source.

[0019]In accordance with an implementation, the drive source is connected to the backrest connecting assembly or the intermediate transmission assembly, and an output end of the drive source is connected to the footrest connecting assembly.

[0020]In accordance with an implementation, the drive source is a linear motor, the linear motor is provided with an output shaft, and the output shaft is connected to the footrest connecting assembly.

[0021]In accordance with an implementation, the drive source is a cylinder, the cylinder is provided with a piston rod, and the piston rod is connected to the footrest connecting assembly.

[0022]In accordance with an implementation, the first connecting member includes an extension segment a, an extension segment b, and a first transition segment c that are connected in sequence, and the extension segment a is parallel to the extension segment b. Both the second hinge hole and the third hinge hole are provided on the extension segment a, and the first hinge hole is provided on the extension segment b.

[0023]In accordance with an implementation, the second connecting member includes an extension segment d, an extension segment e, and a second transition segment f that are connected in sequence, and the extension segment d is parallel to the extension segment e. Both the fifth hinge hole and the sixth hinge hole are provided on the extension segment d, and the fourth hinge hole is provided on the extension segment e.

[0024]A seat unit, including a backrest part, a seat part, a footrest part, and the aforementioned adjusting device for the seat unit. The backrest connecting block is configured to be connected with the backrest part; the seat frame is configured to be connected with the seat part; and a height difference between a highest point of the footrest part and the backrest part is not greater than 400 mm when in the lying position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]In order to illustrate the technical solutions of the embodiments of the present disclosure more clearly, the following drawings are briefly described as required in the context of the embodiments. It should be understood that the following drawings only illustrate only some of the embodiments of the present disclosure and should therefore not be considered as limiting the scope. Other relevant drawings may be obtained on the basis of these drawings without any creative effort by those skilled in the art.

[0028]FIG. 1 is a schematic structural diagram of the seat unit of the present disclosure when in the sitting position;

[0029]FIG. 2 is a schematic structural diagram of the seat unit of the present disclosure when in the stretching position;

[0030]FIG. 3 is a schematic structural diagram of the seat unit of the present disclosure when in the lying position;

[0031]FIG. 4 is a schematic structural diagram of the seat unit adjusting mechanism of the present disclosure when in the sitting position;

[0032]FIG. 5 is a schematic structural diagram of the seat unit adjusting mechanism of the present disclosure when in the stretching position;

[0033]FIG. 6 is a schematic structural diagram of the seat unit adjusting mechanism of the present disclosure when in the lying position;

[0034]FIG. 7 is a schematic structural diagram of the seat unit adjusting mechanism of FIG. 6 in a corresponding rear view;

[0035]FIG. 8 is a schematic structural diagram of the rotary driving plate of the present disclosure in a front view;

[0036]FIG. 9 is a schematic structural diagram of the first connecting member of the present disclosure in a front view;

[0037]FIG. 10 is a schematic structural diagram of the second connecting member of the present disclosure in a front view;

[0038]FIG. 11 is a schematic structural diagram of the third connecting member of the present disclosure in a front view;

[0039]FIG. 12 is a schematic structural diagram of the fixed base plate of the present disclosure mounted on the frame.

[0040]Labels: 1 backrest part, 10 backrest connecting assembly, 11 backrest connecting block, 12 backrest limit block, 121 limit surface, 13 backrest limit rod, 131 limit protrusion, 14 eighth connecting member, 15 ninth connecting member, 2 seat part, 20 intermediate transmission assembly, 201 fixed base plate, 2011 limit post, 2012 rear mounting hole, 202 rotary driving plate, 2021 ninth hinge hole, 2022 tenth hinge hole, 2023 eleventh hinge hole, 21 seat frame, 22 seventh connecting member, 23 first connecting member, 231 first hinge hole, 232 second hinge hole, 233 third hinge hole, 234 extension segment a, 235 first transition segment c, 236 extension segment b, 24 second connecting member, 241 fourth hinge hole, 242 fifth hinge hole, 243 sixth hinge hole, 244 extension segment d, 245 second transition segment f, 246 extension segment e, 25 third connecting member, 251 seventh hinge hole, 252 eighth hinge hole, 26 fourth connecting member, 27 fifth connecting member, 28 sixth connecting member, 3 footrest part, 30 footrest connecting assembly, 31 footrest connecting block, 4 frame.

DETAILED DESCRIPTION

[0041]For a better understanding and implementation, the technical solutions in the embodiments of the present disclosure are clearly and completely described below in conjunction with the attached drawings of the present disclosure.

[0042]In the description of the present disclosure, it is to be noted that the terms “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside” and other orientation or position relationships are based on the orientation or position relationships shown in the attached drawings. It is only intended to facilitate description of the present disclosure and simplify description, but not to indicate or imply that the referred device or element has a specific orientation, or is constructed and operated in a specific orientation. Therefore, they should not be construed as a limitation of the present disclosure.

[0043]Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. The terms used herein in the specification of the present disclosure are used only to describe specific embodiments and are not intended as a limitation of the disclosure.

Embodiment 1

[0044]Referring to FIGS. 1 to 3, a seat unit includes a backrest part 1, a seat part 2, and a footrest part 3. FIGS. 1 to 3 correspond in sequence to a seating position, a stretching position, and a lying position respectively that can be adjusted by an adjusting device. A first adjustment stage refers to the seat unit being adjusted from the seating position in FIG. 1 to the stretching position in FIG. 2. In the first adjustment stage, an angle of the backrest part 1 remains basically unchanged, and the footrest part 3 extends upward from the lowest point thereof. A second adjustment stage refers to the seat unit being adjusted from the stretching position in FIG. 2 to the lying position in FIG. 3. In the second adjustment stage, the angle of the backrest part 1 becomes larger, and the footrest part 3 continues to lift until it is adjusted to the final lying position. In the present embodiment, as shown in FIG. 3, the highest point of the backrest part 1 and the highest point of the footrest part 3 are equal in height. In other embodiments, the height difference between the highest point of the backrest part 1 and the highest point of the footrest part 3 is not greater than 400 mm. In some embodiments, it may be 100 mm, 200 mm, or 300 mm.

[0045]As shown in FIG. 12, the frame 4 is fixedly mounted on the ground, the fixed base plate 201 is mounted on the frame 4, and the fixed base plate 201 is stationary relative to the ground. The fixed base plate 201 is provided with a rear mounting hole 2012, a horizontal plane at which a center of the rear mounting hole 2012 is located is defined as a reference plane.

[0046]In the present embodiment, the aforementioned seat unit is adjusted in attitude by the adjusting device for the seat unit. Please refer to FIGS. 4 to 6, which respectively correspond to the three states of the seat unit in FIGS. 1 to 3. In conjunction with FIGS. 1 to 6, specifically, an adjusting device for a seat unit, configured to switch the seat unit between a sitting position, a stretching position, and a lying position. The adjusting device includes a backrest connecting assembly 10, an intermediate transmission assembly 20, and a footrest connecting assembly 30 that are connected in sequence. The backrest connecting assembly 10 at least includes a backrest connecting block 11. The backrest connecting block 11 is configured to connect and adjust the backrest part 1. The intermediate transmission assembly 20 at least includes a seat frame 21 and an adjusting mechanism configured to adjust the seat frame 21. The seat frame 21 is configured to connect and adjust the seat part 2. The footrest connecting assembly 30 includes a footrest connecting block 31 configured to connect and adjust the footrest part 3.

[0047]The adjusting mechanism includes a first connecting member 23, a second connecting member 24, a third connecting member 25, a fourth connecting member 26, a fifth connecting member 27, a sixth connecting member 28, a seventh connecting member 22, a fixed base plate 201, and a rotary driving plate 202. The fixed base plate 201 and the rotary driving plate 202 are oppositely disposed. The first connecting member 23, the second connecting member 24, the third connecting member 25, the fourth connecting member 26, the fifth connecting member 27, and the sixth connecting member 28 are disposed between the fixed base plate 201 and the rotary driving plate 202. A first end of each of two seventh connecting members 22 is hinged to the rotary driving plate 202, and a second end of each of the two seventh connecting members 22 are hinged to the seat frame 21.

[0048]Specifically, referring to FIGS. 4 to 7, and 9, the first connecting member 23 is configured with a first hinge hole 231, a second hinge hole 232, and a third hinge hole 233 in sequence, a distance between the first hinge hole 231 and the third hinge hole 233 is A1, a distance between the second hinge hole 232 and the third hinge hole 233 is A2, and a ratio of A2 to A1 is not greater than 0.5. In the present embodiment, the ratio of A2 to A1 is 0.291, more specifically, A2=25 mm, and A1=86 mm. In other embodiments, the ratio of A2 to A1 may be 0.3, 0.4, or 0.45. In the present embodiment, the first connecting member 23 is hinged to the rotary driving plate 202 through the first hinge hole 231, the second hinge hole 232 is hinged to the sixth connecting member 28, the third hinge hole 233 is hinged to the second connecting member 24, the variation of the angle between the first connecting member 23 and the reference plane is in a range of 65.4° to 136.6°, and an ascending height of the first hinge hole 231 is 38 mm. The seat frame 21 is driven forward and upward, and then drives the footrest connecting assembly 30 forward and upward, so that the legs are higher than the head to achieve a zero-gravity effect.

[0049]In the present embodiment, referring to FIG. 10, the first connecting member 23 includes an extension segment a 234, an extension segment b 236, and a first transition segment c 235 that are connected in sequence, and the extension segment a 234 is parallel to the extension segment b 236. The second hinge hole 232 and the third hinge hole 233 are provided on the extension segment a 234, and the first hinge hole 231 is provided on the extension segment b 236. The second connecting member 24 is hinged to the first connecting member 23, and the second connecting member 24 is configured with a fourth hinge hole 241, a fifth hinge hole 242, and a sixth hinge hole 243 in sequence. The fifth hinge hole 242 is coaxial with the third hinge hole 233. A distance between the fourth hinge hole 241 and the sixth hinge hole 243 is B1, a distance between the fifth hinge hole 242 and the sixth hinge hole 243 is B2, and a ratio of B2 to B1 is not greater than 0.5. In the present embodiment, the ratio of B2 to B1 is 0.316, more specifically, B2=30 mm, and B1=95 mm. In other embodiments, the ratio of B2 to B1 may be 0.35, 0.40, or 0.45.

[0050]In the present embodiment, the second connecting member 24 includes an extension segment d 244, an extension segment e 246, and a second transition segment f 245 that are connected in sequence, and the extension segment d 244 is parallel to the extension segment e 246. Both the fifth hinge hole 242 and the sixth hinge hole 243 are provided on the extension segment d 244, and the fourth hinge hole 241 is provided on the extension segment e 246.

[0051]The fourth hinge hole 241 is hinged to the fixed base plate 201, the fifth hinge hole 242 is hinged to the first connecting member 23, the sixth hinge hole 6 243 is hinged to the third connecting member 25, The variation of the angle between the second connecting member 24 and the reference plane is in a range of 43.4° to 102.1°, and an ascending height of the sixth hinge hole 243 is 27.5 mm. The backrest connecting assembly 10 is driven forward and backward, so that the angle of the backrest achieves a zero-gravity effect.

[0052]Referring to FIG. 11, the third connecting member 25 is hinged to the second connecting member 24, and the third connecting member 25 is configured with a seventh hinge hole 251 and an eighth hinge hole 252. The seventh hinge hole 251 is coaxial with the sixth hinge hole 243. A distance between the seventh hinge hole 251 and the eighth hinge hole 252 is not greater than 230 mm. In the present embodiment, a distance between the seventh hinge hole 251 and the eighth hinge hole 252 is 183.44 mm. In other embodiments, the distance between the seventh hinge hole 251 and the eighth hinge hole 252 may be 180 mm, 190 mm, or 200 mm.

[0053]The number of the seventh connecting members 22 is two. Referring to FIG. 8, the rotary driving plate 202 is configured with a ninth hinge hole 2021, a tenth hinge hole 2022 and an eleventh hinge hole 2023 in sequence. The eleventh hinge hole 2023 is disposed close to the footrest connecting assembly 30, the ninth hinge hole 2021 is disposed close to the backrest connecting assembly 10, and the two seventh connecting members 22 are hinged to the tenth hinge hole 2022 and the eleventh hinge hole 2023 respectively. The first hinge hole 231 is coaxial with the ninth hinge hole 2021. A distance between the ninth hinge hole 2021 and the tenth hinge hole 2022 is C1, a distance between the ninth hinge hole 2021 and the eleventh hinge hole 2023 is C2, and a ratio of C1 to C2 is not greater than 0.35. In the present embodiment, the ratio of C1 to C2 is 0.154, more specifically, C1=50.37 mm, and C2=326.01 mm. In other embodiments, the ratio of C1 to C2 may be 0.15, 0.25, or 0.3.

[0054]In the present embodiment, a limit post 2011 is provided on the fixed base plate 201, and the second connecting member 24 is abutted against the limit post 2011 when the backrest connecting block 11 is in the sitting position. The limit post 2011 herein is configured to limit the second connecting member 24 when in the sitting position to maintain the sitting position. By setting the hinge holes on the rotary driving plate 202, in accordance with the above ratio, the rotation angle of the seat frame 21 can meet corresponding requirements, that is, when in the sitting position, the angle of the seat frame 21 relative to the horizontal plane is 8.9°, and the distance from the highest point of the seat frame 21 to the reference plane is H3, H3=204 mm. When in the lying position, the distance from the highest point of the seat frame 21 to the reference plane is H4, H4=340 mm, which can achieve zero gravity effect. The seat frame 21 can smoothly drive the backrest part 1 to descend and the footrest part 3 to ascend.

[0055]In the present embodiment, the hinge point between the seventh connecting member 22 and the seat frame 21 is 138 mm distant from the hinge point between the seventh connecting member 22 and the rotary driving plate 202. In other embodiments, such a distance may be other values between 130 mm and 150 mm, which can be set according to specific needs.

[0056]The first connecting member 23 is hinged to the rotary driving plate 202 through the first hinge hole 231, the second connecting member 24 is hinged to the fixed base plate 201 through the fourth hinge hole 241, an end of the sixth connecting member 28 is hinged to the second hinge hole 232, an opposite end of the sixth connecting member 28 is hinged to an end of the fourth connecting member 26, an opposite end of the fourth connecting member 26 is hinged to the fixed base plate 201, an end of the fifth connecting member 27 is hinged between two ends of the fourth connecting member 26, an opposite end of the fifth connecting member 27 is hinged to the rotary driving plate 202, and the third connecting member 25 is hinged between two ends of the sixth connecting member 28 through the eighth hinge hole 252.

[0057]In summary, when the adjusting device for the seat unit of the present embodiment is in use, the fixed base plate 201 is fixedly connected to the frame 4 of the seat unit, and the frame 4 is placed on the ground, that is, the fixed base plate 201 is stationary relative to the ground during the adjustment of the seat unit. The two seventh connecting members 22, the seat frame 21, and the rotary driving plate 202 form a planar four-bar mechanism, and the attitude of the planar four-bar mechanism is adjusted by driving the rotary driving plate 202 to achieve the attitude adjustment of the seat frame 21. Further, the first connecting member 23 is hinged to the fixed base plate 201 through the second connecting member 24, and the first connecting member 23 is hinged to the rotary driving plate 202 through the sixth connecting member 28, the fourth connecting member 26, and the fifth connecting member 27. As shown in FIG. 7, the seat unit is adjusted from the stretching position to the lying position. During the process, the second connecting member 24 rotates counterclockwise around the fourth hinge hole 241. The first connecting member 23, an end of the seat frame 21 proximal to the backrest part 1, and an end of the rotary driving plate 202 proximal to the backrest part 1 are all lowered in height relative to the fixed base plate 201. At the same time, as shown in FIG. 6, the second connecting member 24 adjusts the seat unit from the stretching position to the lying position. During the process, the second connecting member 24 rotates clockwise around the fourth hinge hole 241. The second connecting member 24 serves as a driving part herein, the second connecting member 24 drives the third connecting member 25 to move towards the footrest part 3, and the third connecting member 25 drives the fifth connecting member 27 to rotate counterclockwise around the hinge point between the fifth connecting member 27 and the fourth connecting member 26 through the fourth connecting member 26, so that an end of the rotary driving plate 202 proximal to the footrest part 3 is lifted in height relative to the fixed base plate 201. Generally speaking, the angle between the upper surface of the seat frame 21 and the ground is increased, so that the user's calf level can be higher than the heart position to achieve a zero gravity state.

[0058]In the present embodiment, by setting the hinge points on the structural parts such as the first connecting member 23, the second connecting member 24, the third connecting member 25, and the rotary driving plate 202 described above, the structure of the adjusting mechanism is more reasonable, the stable support and large angle adjustment provided by the adjusting mechanism to the seat frame 21 is achieved by applying as few structural parts as possible, reducing the cost while reducing the complexity of the adjusting mechanism, facilitating post-maintenance, and reducing the volume of the adjusting mechanism and reducing its space occupation.

[0059]Further, the maximum angle variation of the backrest connecting block 11 is not less than 25° when adjusted between the stretching position and the lying position, and the maximum angle variation of the seat frame 21 is not less than 5° when adjusted between the stretching position and the lying position. In the present embodiment, an angle between the right surface of the backrest connecting block 11 and the horizontal plane is basically unchanged from FIG. 4 to FIG. 5. In the present embodiment, the angle between the right surface of the backrest connecting block 11 and the horizontal plane is 117° in FIG. 5, the angle between the right surface of the backrest connecting block 11 and the horizontal plane is 166° in FIG. 6, which varies by 49°. In other embodiments, the angle variation range is not less than 25°, and further, not less than a range of 25° to 90°. In some embodiments, the angle variation range may be 50°, 55°, or 60°. The adjustment angle of an upper surface of the seat frame 21 to the ground in the second adjustment stage varies by an amount of 10°, which varies from 13° to 23°. In other embodiments, the angle variation range may be selected to be not less than 5°, and in some embodiments, may be 8°, 10°, or 15°. Such an angle change further provides a descending distance to the backrest part 1 and at the same time raises the footrest part 3, so that the backrest part 1 and the footrest part 3 are finally close to horizontal, allowing the user can lie as horizontally as much as possible in the lying position, and the user's calf level can reach or even higher than the heart position to achieve a zero-gravity state, improving the comfort of the seat unit.

[0060]Further, the footrest connecting assembly 30 includes a footrest connecting block 31. In the present embodiment, the distance from the highest point of the footrest connecting block 31 in the lying position to the reference plane is H2, H2=550 mm, and the distance from the lowest point of the footrest connecting block 31 in the sitting position to the reference plane is H1, H1=70 mm, H2: H1≈7.86. In other embodiments, the ratio range may be other values not less than 7.8, and in some embodiments, the ratio may be 8, 8.2, or 8.4. In the present embodiment, the distance from the lowest point of the footrest connecting block 31 in the sitting position to the reference plane is H1, and H1 is not greater than 100 mm. The distance from the highest point of the footrest connecting block 31 in the lying position to the reference plane is H2, and H2 is not greater than 600 mm.

[0061]This setting ensures that, the footrest part 3 is raised to a suitable level when in the stretching position, so that the user's legs are comfortable while maintaining a good sitting position, and the footrest part 3 is significantly raised when switched to the lying position, lifting the user's legs further, so that the user can enter a comfortable lying position as soon as possible. In the present embodiment, an ascending distance of the footrest connecting block 31 is not greater than 300 mm during adjustment from the stretching position to the lying position.

[0062]In the present embodiment, a distance between a highest point of the backrest connecting block 11 and the reference plane is H5 when in the sitting position, and H5 is not greater than 400 mm. A distance between the highest point of the backrest connecting block 11 and the reference plane is H6 when in the lying position, and H6 is not greater than 320 mm. In such a setup, a significant height difference is caused on the backrest part 1 when switched from the sitting position to the lying position, so that the user's upper body sinks in a significant amplitude, with the obvious elevation of the footrest part 3, allowing the user to enter the comfortable state of the lying position as soon as possible.

[0063]As shown in FIGS. 6 and 7, the backrest connecting assembly 10 also includes a backrest limit block 12 and a backrest limit rod 13, the backrest connecting block 11 is hinged to the backrest limit block 12, and a limit surface 121 matched with the backrest limit rod 13 is provided on the backrest limit block 12. Specifically, the backrest limit block 12 is bifurcated and has two ends, with an upper end and a lower end. An end of the backrest connecting block 11 is hinged to the upper end of the backrest limit block 12, and the lower end of the backrest limit block 12 is hinged between the two ends of the backrest limit rod 13.

[0064]The backrest connecting assembly 10 also includes an eighth connecting member 14 and a ninth connecting member 15, an end of the ninth connecting member 15 is hinged between two ends of the backrest connecting block 11, an opposite end of the ninth connecting member 15 is hinged to an end of the backrest limit rod 13 close to the backrest connecting block 11, a limit protrusion 131 is provided on the backrest limit rod 13, and the limit surface 121 is provided near the lower end of the backrest limit block 12 and is adapted to the limit protrusion 131. Further, an end of the eighth connecting member 14 is hinged to the fixed base plate 201, and an opposite end thereof is hinged to an end of the backrest limit rod distal to the backrest connecting block 11. During the adjustment from the stretching position to the lying position, the center point of the ninth connecting member 15 is moved downward by a distance of 30 mm to 100 mm. In the present embodiment, the center point of the ninth connecting member 15 is moved downward at a distance of 70 mm. In other embodiments, the center point of the ninth connecting member 15 is moved downward at a distance of 30 mm, 60 mm, or 80 mm. The lowest point at which the backrest 1 changes between positions depends on the locations of the backrest limit rod 13 and the backrest limit block 12. The backrest limit rod13 is provided as a descendable limit rod, and synchronously descend with the backrest part 1 when adjusting, so that the descending space of the backrest part 1 is larger, and it is easier to form substantially the same level as the footrest part 3.

[0065]In the present embodiment, the hinge point between the backrest limit rod 13 and the backrest limit block 12 is 143.7 mm distant from the hinge point between the backrest limit rod 13 and the eighth connecting member 14. The hinge point between the eighth connecting member 14 and the backrest limit rod 13 is not less than 90 mm distant from the hinge point between the eighth connecting member 14 and the fixed base plate 201, which is 94.14 mm in the present embodiment. In other embodiments, it may be 92 mm, 95 mm, or 98 mm.

[0066]In the present embodiment, the first adjustment stage and the second adjustment stage are driven by the same drive source. The drive source is connected to the backrest connecting assembly 10, and an output end of the drive source is connected to the footrest connecting assembly 30. The drive source is a linear motor, the linear motor is provided with an output shaft, and the output shaft is connected to the footrest connecting assembly 30. During the movement, the output shaft of the linear motor pushes the footrest connecting assembly 30. Since the footrest connecting assembly 30 is hinged to the intermediate transmission assembly 20, the footrest connecting assembly 30 rotates relative to the intermediate transmission assembly 20. After rotating to a certain position, the footrest connecting assembly 30 transmits an opposite force to the linear motor. Driven by the opposite force, the footrest connecting assembly 30 synchronously moves with the backrest connecting assembly 10, and finally the lying position is adjusted in place.

Embodiment 2

[0067]The present embodiment is an improvement on embodiment 1, and the repetition is not repeated herein.

[0068]The first adjustment stage and the second adjustment stage are driven by the same drive source. The drive source is connected to the backrest connecting assembly 10, and an output end of the drive source is connected to the footrest connecting assembly 30. The drive source is a cylinder, the cylinder includes a piston rod, and the piston rod is connected to the footrest connecting assembly 30. During the movement, the piston rod of the cylinder pushes the footrest connecting assembly 30. Since the footrest connecting assembly 30 is hinged to the intermediate transmission assembly 20, the footrest connecting assembly 30 rotates relative to the intermediate transmission assembly 20. After rotating to a certain position, the footrest connecting assembly 30 transmits an opposite force to the cylinder. Driven by the opposite force, the footrest connecting assembly 30 synchronously moves with the backrest connecting assembly 10, and finally the lying position is adjusted in place. Compared with the linear motor, the cylinder can be adjusted more quickly and directly, and can achieve rapid change of seat positions, while the linear motor is more stable, both of which have their own advantages.

Embodiment 3

[0069]The present embodiment is an improvement on embodiment 1, and the repetition is not repeated herein.

[0070]An elastic cushioning device is provided between the backrest limit block 12 and the backrest limit rod 13. Specifically, the elastic cushioning device is a spring. In other embodiments, the elastic cushioning device may be a sponge, or other analogs that are elastic and can play a cushioning and vibration-absorbing role. By providing an elastic cushioning device, it helps the sofa to reduce the impact to the head during descending, and it will not be too loud when the backrest limit block 12 collides the backrest limit rod 13 in the final state.

Embodiment 4

[0071]There is also an elastic cushioning device in the present embodiment, but there is a difference from embodiment 3. The present embodiment is set on the basis of embodiment 1. The backrest connecting assembly 10 also includes a backrest limit block 12 and a backrest limit rod 13. The backrest connecting block 11 is hinged to the backrest limit block 12. A moment spring is provided at the hinge connection between the backrest connecting block 11 and the backrest limit block 12. In some embodiments, the moment spring is a leaf spring. By providing the elastic cushioning device at the hinge connection of the two parts, it is also conducive to reducing the impact of the seat on the human body during adjustment and the sound generated by the collision when the seat is limited. In other possible embodiments, an elastic cushioning device may be provided between other key rotating components.

[0072]The seat unit provided in all the aforementioned embodiments is a home sofa, lounge chair, a theater seat, a hospital seat, or a vehicle seat.

[0073]The technical means disclosed in the solution of the present disclosure are not limited to those disclosed in the embodiments mentioned above but also include technical solutions consisting of any combination of the above technical features. It should be noted that for those skilled in the art, multiple improvements and modifications may be made without departing from the principles of the present disclosure. These improvements and modifications are also considered to be within the scope of protection of the present disclosure.