Swivel supporting device

1. A swivel supporting device, comprising:

a stand;

a baseplate; and

a switchable structure, disposed on the stand and capable of rotating synchronously with the stand above the baseplate and including a first engagement washer, a second engagement washer, an elastic washer and a pivot member, wherein

the pivot member includes a screw and a nut, the screw penetrates through and clamps the baseplate, the first engagement washer, the second engagement washer and the elastic washer in sequence;

the screw has a head portion, a body portion and a terminal portion opposite to the head portion and screwed to the nut;

the head portion is pressed against the baseplate, whereas the body portion has a non-circular cross-sectional shape and penetrates through the baseplate, the first engagement washer, the second engagement washer and the elastic washer in sequence so as to clamp the baseplate, the first engagement washer, the second engagement washer and the elastic washer between the head portion and the nut;

the first engagement washer is fastened to the stand and has a first through hole in a circular shape and plural recesses of different depths;

the second engagement washer has a second through hole in a complementary shape to a cross-sectional shape of the body portion and at least one protrusion capable of being positioned in selective one of the recesses of the first engagement washer; and

the elastic washer is capable of being forced upward into deformation by the second engagement washer;

when an external force is applied on the head portion for rotation of the screw, the second engagement washer is brought into rotation with respect to the first engagement washer by the screw so that the protrusion of the second engagement washer is switched among the recesses of the first engagement washer; and

by virtue of difference in interference extent caused by the protrusion of the second engagement washer being positioned in the different recesses of the first engagement washer, friction generated during rotation of the stand and the switchable structure with respect to the baseplate is capable of being adjusted.

2. The swivel supporting device of claim 1 , wherein a larger interference extent between the first engagement washer and the second engagement washer is induced when the protrusion is engaged with shallower one of the recesses, and a smaller interference extent between the first engagement washer and the second engagement washer is induced when the protrusion is engaged with deeper one of the recesses.

3. The swivel supporting device of claim 2 , wherein the stand includes a base, an upright extending from the base and a fixing plate associated with the upright for holding a display device.

4. The swivel supporting device of claim 3 , wherein the switchable structure further includes a friction washer that is fastened to the stand and slidably contacts the baseplate.

5. The swivel supporting device of claim 4 , wherein the friction washer and the first engagement washer are fastened to the base.

6. The swivel supporting device of claim 3 , wherein (i) the base has a guide trough, (ii) the second engagement washer has an extension portion disposed in the guide trough, and (iii) when a force is applied on the head portion for rotation of the screw, the extension portion of the second engagement washer moves within the guide trough so as to restrict pivot angle of the screw.

7. The swivel supporting device of claim 3 , wherein the baseplate includes a foundation plate and an abutment member fastened to the foundation plate, and the foundation plate has an opening to expose a selected portion of the abutment member from the opening and to permit the head portion of the screw to abut against the abutment member.

8. The swivel supporting device of claim 7 , wherein the baseplate further includes a foot pad attached to the foundation plate.

9. The swivel supporting device of claim 7 , wherein the elastic washer is a bowl-shaped washer.

10. The swivel supporting device of claim 1 , wherein the first engagement washer has three recess sets around circumference, each of which has three recesses of different depths, whereas the second engagement washer has three protrusions that correspond to the three recess sets, respectively, and are capable of being simultaneously positioned in the corresponding recesses thereof with the same depth.