Adjustable neck brace

1. An adjustable neck brace, including:

a neck collar, including only one sliding engaging groove which is disposed at middle front of the neck collar, the only one sliding engaging groove extending in an extension direction and having a first engaging portion;

only one positioning member, attached to the neck collar and movable along the only one sliding engaging groove, having a second engaging portion, the second engaging portion being releasably positioningly engaged with the first engaging portion;

a chin support, relatively movably connected to the neck collar;

at least one connecting member, connecting the only one positioning member and the chin support wherein one of the first engaging portion and the second engaging portion includes at least one recess, and the other of the first engaging portion and the second engaging portion includes at least one protrusion, wherein the first engaging portion includes a plurality of recesses arranged along the extension direction in intervals, and the second engaging portion is releasably positioningly engaged with one of the recesses; the neck collar further includes a sliding seat corresponding to the only one sliding engaging groove; the only one positioning member includes a mount portion which is slidably arranged on the sliding seat and an operating member which is connected to the mount portion; the mount portion includes a mount body which is saddled on the sliding seat, a position-restricting block which is connected to the at least one connecting member and located by two opposite sides of the only one sliding engaging groove with the mount body and a pin which is disposed through the only one sliding engaging groove and connecting the mount body and the position-restricting block, and the pin has the second engaging portion; the operating member is movably disposed through the mount body and the sliding seat and connected to the pin; an elastic member is disposed between the operating member and the mount body, and the elastic member makes the pin have a tendency to move toward the at least one recess normally.

2. The adjustable neck brace of claim 1 , wherein the first engaging portion includes a plurality of recesses arranged along the extension direction in intervals, and the second engaging portion includes an engaging block which is releasably positioningly engaged with one of the recesses.

3. The adjustable neck brace of claim 1 , wherein the neck collar further has two guiding slots, the two guiding slots are located by two sides of the only one sliding engaging groove and extend tiltedly away from the only one sliding engaging groove, a number of the at least one connecting member is two, and one of two end portions of each said connecting member is slidably disposed within one of the guiding slots.

4. The adjustable neck brace of claim 3 , wherein the two connecting members are flexible.

5. The adjustable neck brace of claim 1 , wherein the only one positioning member includes a mount portion which is slidably arranged on the neck collar and an operating member which is connected to the mount portion, the at least one connecting member is connected to the mount portion, and an operating member has the second engaging portion.

6. The adjustable neck brace of claim 5 , wherein the neck collar further includes two through slots extending in the extension direction and located by two sides of the only one sliding engaging groove, the mount portion includes two wing portions, a distal end of each said wing portion is disposed through one of the through slots, and the distal end of each said wing portion is connected to one of the connecting members.

7. The adjustable neck brace of claim 6 , wherein the mount portion includes a base having the two wing portions and two blocking walls connected to two sides of the base, the operating member is disposed between the two blocking walls, an elastic member is disposed between the operating member and the base, and the elastic member makes the second engaging portion have a tendency to move toward the first engaging portion normally.

8. The adjustable neck brace of claim 7 , wherein the two blocking walls are detachably connected to the base.

9. The adjustable neck brace of claim 8 , wherein the first engaging portion includes a plurality of recesses arranged along the extension direction in intervals, each said recess has two sides each having a spacing wall, and the second engaging portion includes an engaging block which is releasably positioningly engaged with one of the recesses; the neck collar further has two guiding slots, the two guiding slots are located by the two sides of the only one sliding engaging groove and extend tiltedly away from the only one sliding engaging groove, a number of the at least one connecting member is two, one of the two end portions of each said connecting member is slidably disposed within one of the guiding slots, and the other of the two end portions of each said connecting member is pivoted to one of the wing portions; the neck collar has an inner wall which is curved, and the two connecting members are flexible and extend along the inner wall of the neck collar; the two blocking walls are opposite to the two spacing walls of one of the recesses and capable of positioningly restricting the operating member therebetween.