1. A chair armrest device comprising:a main frame including an upper end having a first coupling portion and a lower end having a second coupling portion;
an outer sleeve including a third coupling portion and an insertion portion, wherein the third coupling portion is coupled to the first coupling portion, wherein the insertion portion includes an insertion groove extending in a vertical direction, wherein a positioning portion is disposed in the insertion groove and extends in the vertical direction, wherein the positioning portion includes a plurality of positioning grooves spaced from each other in the vertical direction, and wherein the insertion portion further includes a passage located at a side of the positioning portion and extending in the vertical direction;
a cover mounted above the outer sleeve, wherein the cover includes a top wall and a peripheral wall extending downward along a periphery of the top wall, wherein the top wall includes a through-hole aligned with the insertion groove of the outer sleeve, wherein the outer cover further includes a stopper for blocking the opening of the passage of the outer sleeve;
an inner sleeve including a shank at a lower end thereof, wherein the shank is received in the insertion portion of the outer sleeve, wherein a fourth coupling portion is disposed on top of the shank, wherein the shank includes an annular wall and a bottom wall, wherein the shank further includes a first compartment in a central portion thereof, wherein the annular wall of the shank includes a slot, wherein the fourth coupling portion includes a second compartment;
a control device including a coupling board, an actuating rod, a button, and an elastic element, wherein the coupling board is fixed in the second compartment, wherein the actuating rod extends in the vertical direction and is pivotably received in the first compartment of the inner sleeve, wherein the actuating rod includes a rectilinear rod portion having a lower portion and an upper portion, wherein a positioning peg is formed on the lower portion of the rectilinear rod portion and extends through the slot of the shank of the inner sleeve for releasably engaging with one of the plurality of positioning grooves, wherein a guiding peg is formed on the upper portion of the rectilinear rod portion, wherein the button includes a pivotal hole pivotably connected to the coupling board, wherein the button includes a guiding portion and a pressing portion, wherein the guiding portion includes an inclined guiding groove through which the guiding peg extends, and wherein the elastic element provides the button with operational elasticity; and
a pad mounted above the fourth coupling portion of the inner sleeve,
wherein when the pressing portion is not pressed, the positioning member is received in one of the plurality of positioning grooves,
wherein when the pressing portion is pressed, the guiding portion actuates the actuating rod to pivot, and the positioning peg is moved into the passage of the outer sleeve, permitting adjustment of a height of the pad.