Adjustable chair

A piece of sitting furniture comprising:

• a seat:
• a backrest;
• a base;
• wherein the seat and the base are movably coupled for reversible relative adjustment in a seating direction from a first configuration for sitting in an upright posture to a second configuration for sitting in a reclined posture,
• wherein the piece of sitting furniture comprises one or more support surfaces and a lever supporting the seat on the base in at least the first and second configurations,
• wherein the lever is rotary about a horizontal lever axis transverse to the seating direction and comprises a first support portion defining a first lever arm about the lever axis and a second support portion defining a second lever arm about the lever axis movably engaging the one or more support surfaces at the first support portion and the second support portion, and the one or more support surfaces define a curved path that is curved about the lever axis, such that displacement of the one or more support surfaces relative to the lever axis in the seating direction causes rotation of the lever about the horizontal lever axis,
• wherein the base comprises a frame;
• and
• wherein the frame supports the backrest on laterally opposite sides, and/or
• wherein the frame and backrest are rotary coupled on laterally opposite sides, and/or
• wherein at least part of the base and/or the backrest is at least partially resilient, allowing sideways flexion and/or torsion about a vertical axis of rotation of at least part of the seat and/or backrest.

A chair comprising:

• a seat;
• a backrest;
• a base;
• wherein the seat and the base are movably coupled for reversible relative adjustment in a seating direction from a first configuration for sitting in an upright posture to a second configuration for sitting in a reclined posture,
• wherein the piece of sitting furniture comprises one or more support surfaces and a lever supporting the seat on the base in at least the first and second configurations,
• wherein the lever is rotary about a horizontal lever axis transverse to the seating direction and comprises a first support portion defining a first lever arm about the lever axis and a second support portion defining a second lever arm about the lever axis movably engaging the one or more support surfaces at the first support portion and the second support portion, and the one or more support surfaces define a curved path that is curved about the lever axis, such that displacement of the one or more support surfaces relative to the lever axis in the seating direction causes rotation of the lever about the horizontal lever axis, and
• wherein the seat and the backrest are movably coupled for reversible combined motion from the first configuration into the second configuration by reversibly deformable couplings and/or rotary couplings defining non-parallel axes of rotation.