A height-adjustable backrest assembly includes a connecting member an upper end mounted between a positioning board having vertically spaced positioning grooves and a backrest movable relative to the positioning board in a vertical direction. A lower end of the connecting member is coupled to a seat or a base. A positioning button is pivotably mounted to the connecting member and has a positioning section biased by a spring to releasably engage one of the positioning grooves. A transfer groove below the bottommost positioning groove receives the positioning button when the positioning section of the positioning button disengages from the positioning grooves. The positioning button abuts against an abutment member on the connecting member to limit the positioning section in a position not aligned with the positioning grooves. The abutment section disengages from the abutment member when an abutment protrusion of the positioning board presses against the positioning section.

BACKGROUND OF THE INVENTION

The present invention relates to a height-adjustable backrest assembly and, more particularly, to a height-adjustable backrest assembly with improved adjusting convenience and enhanced operational stability.

A backrest separate from a seat is generally connected by a connecting member to the seat. The connecting member is substantially L-shaped and includes a first end fixed to the backrest and a second end fixed to the seat or a base, mounting the backrest behind the seat. However, users having different heights lay against the backrest at different locations. Specifically, the backrest can not provide lying comfort for various users.

To mitigate the above disadvantage, height adjusting mechanisms have been proposed to allow the backrest to move upward/downward relative to the connecting member, and the backrest is then fixed by bolts after the height adjustment. However, such height adjusting mechanism are inconvenient to operate and can not reliably fix the backrest in place.

BRIEF SUMMARY OF THE INVENTION

An objective of the present invention is to provide a height-adjustable backrest assembly with improved adjusting convenience and enhanced operational stability.

A height-adjustable backrest assembly according to the present invention includes a backrest including a rear side having a coupling groove. The coupling groove includes an opening in a lower end thereof. A connecting member includes an upper end coupled to the backrest. The connecting member further includes a lower end adapted to be coupled to a seat or a base. The upper end of the connecting member is received in the coupling groove of the backrest. An abutment member is provided on a rear surface of the connecting member. The abutment member includes an end having an outer side. The abutment member includes a first inclined guiding face protruding from the outer side towards a center of the end of the abutment member. The end of the abutment member further includes a first stop face at a side thereof. The first inclined guiding face and the first stop face extend beyond the rear surface of the connecting member.

A positioning button is pivotably mounted to the rear surface of the connecting member. The positioning button includes an axle portion having an axle hole. A pivot extends through the axle hole and pivotably connected to the connecting member. A positioning section protrudes from the axle portion and includes a second inclined guiding face and a second stop face. The axle portion further includes a mounting section through which the axle hole extends. A spring includes first and second tangs and a coil portion between the first and second tangs. The coil portion is mounted to the mounting section of the positioning button. The pivot extends through the coil portion of the spring and is connected to the connecting member. The first tang abuts against the connecting member, and the second tang abuts against the positioning button.

A positioning board is mounted in a location outside of the coupling groove of the backrest. The connecting member is securely received in the coupling groove of the backrest and is securely sandwiched between the backrest and the positioning board. The positioning board includes a movement groove extending in a vertical direction. The movement groove includes a rectilinear side corresponding to the axle portion of the positioning button. The positioning board further includes a plurality of positioning grooves spaced from each other in the vertical direction. The positioning section of the positioning button is releasably engaged in one of the plurality of positioning grooves. Each of the plurality of positioning grooves includes an upper edge, a lower edge located below the upper edge in the vertical direction, and an inner edge between the upper edge and the lower edge. The spring biases the positioning button to pivot relative to the plurality of positioning grooves of the positioning board. The positioning section of the positioning button abuts the inner edge of one of the plurality of positioning grooves. An opening between the upper edge and the lower edge of each of the plurality of positioning grooves has a width larger than a width of the positioning section of the positioning button to provide room allowing movement of the positioning button. The positioning section of the positioning button abuts the lower edge of one of the plurality of positioning grooves when the backrest is moved to adjust a height of the backrest relative to the connecting member.

The bottommost positioning groove includes an extension extending from the lower edge thereof. The positioning board further includes a transfer groove formed below the bottommost positioning groove. The transfer groove receives the positioning button when the positioning section of the positioning button disengages from the plurality of positioning grooves. The transfer groove includes a first side connected to the rectilinear side of the movement groove. The transfer groove further includes a second side having a rectilinear guiding section connected to the extension of the bottommost positioning groove. The positioning section of the positioning button is guided by the rectilinear guiding section of the transfer groove while the positioning button is moving into the transfer groove. The second inclined guiding face of the positioning button slides along the first inclined guiding face of the abutment member. The second stop face of the positioning button abuts against the first stop face of the abutment member to limit the positioning section of the positioning button in a position not aligned with the plurality of positioning grooves. The movement groove further includes a top end having an abutment protrusion. The abutment section of the positioning button disengages from the abutment member when the abutment protrusion of the movement groove presses against a top end of the positioning section of the positioning button.

Preferably, the axle portion of the positioning button includes a ridge. The ridge presses against the rectilinear edge of the movement groove when the positioning section of the positioning button is received in one of the plurality of positioning grooves.

Preferably, the rear side of the backrest includes a recessed portion having two lateral walls, a bottom wall extending perpendicularly to and extending between the two lateral walls, and an upper wall extending perpendicularly to the bottom wall and the two lateral walls and extending between the two lateral walls. The coupling groove is defined in the bottom wall of the recessed portion, forming two ledges on opposite sides of the coupling groove. Each ledge has a plurality of fixing holes. The positioning board is received in the recessed portion of the backrest and has a plurality of fixing holes aligned with the plurality of fixing holes of the backrest. A plurality of fasteners extends through the plurality of fixing holes of the positioning board and the plurality of fixing holes of the backrest to securely fix the connecting member in the coupling groove of the backrest.

Preferably, each lateral wall of the recessed portion of the backrest includes a rib. The positioning board includes a notch in each of two lateral sides thereof. The ribs of the backrest are engaged in the notches of the positioning board.

Preferably, the pivot includes an enlarged head abutting the coil portion of the spring. An attachment peg is provided the rear surface of the connecting member and includes an enlarged section. The first tang of the spring abuts against the attachment peg of the connecting member. The enlarged section of the attachment peg prevents the first tang of the spring from disengaging from the attachment peg. The positioning section has an attachment block. The second tang of the spring abuts against the attachment block of the positioning button. The positioning board further includes a slot extending in the vertical direction. The slot receives the attachment peg.

Preferably, a lid is mounted to an outer side of the positioning board. The lid includes a plurality of mounting pegs received in a plurality of mounting holes in the positioning board.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1-6, a height-adjustable backrest assembly according to the present invention includes a backrest1, a connecting member2, a positioning button3, a spring4, and a positioning board5. The backrest1includes a rear side including a recessed portion11having two lateral walls12, a bottom wall extending perpendicularly to and extending between the lateral walls12, and an upper wall13extending perpendicularly to the bottom wall and the lateral walls12and extending between the lateral walls12. A coupling groove14is defined in the bottom wall of the recessed portion11and has a width smaller than that of the recessed portion11, forming two ledges15on opposite sides of the coupling groove14. The coupling groove14includes an opening141in a lower end thereof. Each ledge15has a plurality of fixing holes151. Each lateral wall12of the recessed portion11includes a rib121.

The connecting member2is a plate and includes an upper end coupled to the backrest1. The connecting member2further includes a lower end adapted to be coupled to a seat (not shown) or a base (not shown). The upper end of the connecting member2is received in the coupling groove14of the backrest1. The connecting member2further includes a rear surface21. An attachment peg22is provided on the rear surface21of the connecting member2and includes an enlarged section221. Furthermore, an abutment member24is mounted in a fixing hole23in the connecting member2. The abutment member24is in the form of a column and includes an end having an outer side. The abutment member24includes a first inclined guiding face241protruding from the outer side towards a center of the end of the abutment member24. The end of the abutment member24further includes a first stop face242at a side thereof. The attachment member24extends through the fixing hole23of the connecting member2, with the first inclined guiding face241and the first stop face242extending beyond the rear surface21of the connecting member2. The connecting member2further includes a mounting hole25below the fixing hole23.

The positioning button3is pivotably mounted to the rear surface21of the connecting member2. The positioning button3includes an axle portion31having an axle hole311. A pivot312extends through the axle hole311and is pivotably received in the mounting hole25of the connecting member2. The pivot312includes an enlarged head3121. The axle portion31further includes a ridge313. The axle portion31further includes a mounting section314through which the axle hole311extends. A positioning section32protrudes from the axle portion31and includes a rounded end. The positioning section32includes a second inclined guiding face321and a second stop face322. The positioning section32further has an attachment block323.

The spring4is in the form of a torsion spring and includes first and second tangs42and43and a coil portion41between the first and second tangs42and43. The coil portion41is mounted to the mounting section314of the positioning button3. The pivot312extends through the coil portion41of the spring4and is received in the mounting hole25of the connecting member2, with the enlarged head3121of the pivot312abutting against the coil portion41, with the first tang42abutting against the attachment peg22of the connecting member2, and with the second tang43abutting against the attachment block323of the positioning button3. The enlarged section221of the attachment peg2prevents the first tang42from disengaging from the attachment peg22. The positioning button3is moved towards the connecting member2under the elasticity of the spring4and can pivot under the torsion of the spring4. A spacing c between two adjacent turns of the coil portion41of the spring4allows movement of the positioning button3.

The positioning board5is mounted in a location outside of the coupling groove14of the backrest1. The positioning board5includes a notch51in each of two lateral sides thereof. The ribs121of the backrest1are engaged in the notches51of the positioning board5to increase assembling stability. The positioning board5has a plurality of fixing holes52aligned with the fixing holes151of the backrest1. The positioning board5is received in the recessed portion11of the backrest1, and fasteners6extend through the fixing holes52of the positioning board5and the fixing holes151of the backrest1to securely fix the connecting member2in the coupling groove14of the backrest1. The positioning board5further includes a slot53extending in the vertical direction. The slot53receives the attachment peg22.

The positioning board5further includes a movement groove54extending in a vertical direction. The movement groove54includes a rectilinear side541corresponding to the axle portion31of the positioning button3. The ridge313can press against the rectilinear edge541of the movement groove54. The positioning board5further includes a plurality of positioning grooves55spaced from each other in the vertical direction. The positioning section32of the positioning button3is releasably engaged in one of the positioning grooves55. Each positioning groove55includes an upper edge552, a lower edge553located below the upper edge552in the vertical direction, and an inner edge551between the upper edge552and the lower edge553. The inner edge551of each positioning groove55is arcuate. The positioning section32of the positioning button3abuts the inner edge551of one of the positioning grooves55. The spring4biases the positioning button3to pivot relative to the positioning grooves55of the positioning board5. With reference toFIG. 5, an opening554between the upper edge552and the lower edge553of each positioning groove55has a width a larger than a width b of the positioning section32of the positioning button3to provide room allowing movement of the positioning button3. The lower edge553of an upper positioning groove55is connected to the upper edge552of a lower positioning groove55. The positioning section32of the positioning button3abuts the lower edge553of one of the positioning grooves55when the backrest1is being moved to adjust a height of the backrest1relative to the connecting member2.

The bottommost positioning groove55includes an extension555extending from the lower edge553thereof. The positioning board5further includes a transfer groove56formed below the bottommost positioning groove55. The transfer groove56receives the positioning button3when the positioning section32of the positioning button3disengages from the positioning grooves55. The transfer groove56includes a first side connected to the rectilinear side541of the movement groove54. The transfer groove56further includes a second side having a rectilinear guiding section561connected to the extension555of the bottommost positioning groove55. The positioning section32of the positioning button3is guided by the rectilinear guiding section561of the transfer groove55while the positioning button3is moving into the transfer groove56, with the second inclined guiding face321of the positioning button3sliding along the first inclined guiding face241of the abutment member24, and with the second stop face322of the positioning button3abutting against the first stop face242of the abutment member24to limit the positioning section32of the positioning button3in a position not aligned with the positioning grooves55. The movement groove54further includes a top end having an abutment protrusion57. The abutment protrusion57of the movement groove54can press against a top end of the positioning section32of the positioning button3to disengage the abutment section32of the positioning button3from the abutment member24. The positioning board5further includes a plurality of mounting holes58.

In assemblage, the attachment peg22and the attachment member24are mounted to the connecting member2. The upper end of the connecting member2is received in the coupling groove14of the backrest1. The positioning board5is fixed by the fasteners6to the ledges15of the backrest1. Thus, the upper end of the connecting member2is enveloped by the backrest1and the positioning board5to provide an aesthetic appearance and assembling stability. The positioning button3and the spring4are mounted to the connecting member2by the pivot312, with first and second tangs42and43to the spring4respectively abutting against the attachment peg22of the connecting member2and the attachment block323of the positioning button3. The positioning button3is biased by the spring4to pivot in the clockwise direction such that the positioning section32is engaged in one of the positioning grooves55. Under the action of the gravitational force on the backrest1, the inner edge551and the upper edge552of the positioning groove55abut against the positioning section32of the positioning button3to prevent the positioning button3from further pivoting in the clockwise direction, fixing the backrest1in a desired height. In this case, the ridge313of the axle portion31presses against the rectilinear side541of the movement groove54to increase the positioning effect.

A lid7is mounted to an outer side of the positioning board5and includes mounting pegs71engaged in the mounting holes58.

With reference toFIG. 7, when it is desired to adjust the height of the backrest1, the backrest1is moved upward, the lower edge553of the positioning groove55receiving the positioning section32of the positioning button3presses against the positioning section32to pivot the positioning button3in the counterclockwise direction, allowing smooth upward movement of the backrest1. With reference toFIG. 8, when the backrest1reaches the desired height, the positioning section32of the positioning button3pivots clockwise under the torsion of the spring4until the positioning section32aligns with the corresponding positioning groove55. Under the action of the gravitational force of the backrest1, the inner edge551and the upper edge552of the positioning groove55abut against the positioning section32of the positioning button3, and the ridge313on the axle portion31presses against the rectilinear side541of the movement groove54to retain the backrest1in the desired height while providing an excellent positioning effect.

With reference toFIGS. 9-11, when it is desired to move the backrest1to a lower position, the backrest1is firstly moved to the highest position, with the extension555of the bottommost positioning groove55pressing against the positioning section32of the positioning button3to pivot the positioning button3in the counterclockwise direction, and the positioning button3is received in the transfer groove56below the movement groove54. The positioning section32is guided by the rectilinear guiding section561such that the second stop face322of the positioning section32engages with the second stop face242of the attachment member24to limit the positioning section32in the vertical direction not aligned with the direction of the positioning grooves55. In this case, the backrest1can be moved downward, as shown inFIG. 11. Under the action of the gravitational force on the backrest1, the abutment protrusion57of the movement groove54presses against the top end of the positioning section32of the positioning button3to disengage the second stop face322of the abutment section32of the positioning button3from the first stop face242of the abutment member24. Thus, the positioning section32pivots clockwise under the torsion of the spring4and engages with the topmost positioning groove55, as shown inFIG. 5. Thus, the height-adjustable backrest assembly according to the present invention can be operated conveniently and possesses operational stability.

In view of the foregoing, the height-adjustable backrest assembly according to the present invention provides operational convenience and possesses operational stability. Note that the first tang42of the spring4can directly be fixed to the connecting member2without using the attachment peg22. Furthermore, the attachment member24can directly be formed on the connecting member2.