Suction brush for vacuum cleaner

1. A suction brush for a vacuum cleaner comprising:

an upper casing;

a lower casing coupled to the upper casing, the lower casing being provided with a suction port through which contaminants are drawn in from a surface to be cleaned;

a lift plate disposed between the upper casing and the lower casing so as to move up and down with respect to the lower casing;

a lift plate driving part to allow the lift plate to move up and down; and

a lift control unit to control the lift plate driving part so that when the surface to be cleaned changes from a hard floor to a carpet, the lift plate is raised, and when the surface to be cleaned changes from the carpet to the hard floor, the lift plate is lowered,

wherein the lower casing contacts the surface to be cleaned when the lift plate is raised, and the lower casing is spaced apart from the surface to be cleaned when the lift plate is lowered.

2. The suction brush of claim 1 , wherein the lift plate driving part comprises:

a driving shaft disposed parallel to the lift plate above the lift plate;

a DC motor configured to rotate the driving shaft;

at least one driving cam formed to project radially from an outer circumferential surface of the driving shaft; and

a battery to supply the DC motor with electrical power,

wherein a receiving portion is recessed on an upper surface of the lift plate to receive either of the driving shaft or the driving cam.

3. The suction brush of claim 2 , wherein when the driving shaft is received in the receiving portion, the lift plate is raised with respect to the lower casing, and when the driving cam is received in the receiving portion, the lift plate is pressed by the driving cam to lower with respect to the lower casing.

4. The suction brush of claim 3 , wherein the lift control unit comprises:

a surface detecting part to detect whether the surface to be cleaned is the hard floor or the carpet;

a first DC motor driving part to operate the DC motor so that when the surface to be cleaned changes from the hard floor to the carpet, the driving shaft is received in the receiving portion; and

a second DC motor driving part to operate the DC motor so that when the surface to be cleaned changes from the carpet to the hard floor, the driving cam is received in the receiving portion.

5. The suction brush of claim 4 , wherein the first DC motor driving part comprises:

a first micro switch disposed near a side of the driving shaft; and

a first control cam formed on the driving shaft so that when the driving shaft is received in the receiving portion, the first control cam allows the first micro switch to maintain an open state.

6. The suction brush of claim 5 , wherein the second DC motor driving part comprises:

a second micro switch disposed side by side with the first micro switch near the side of the driving shaft; and

a second control cam formed on the driving shaft so that when the driving cam is received in the receiving portion, the second control cam allows the second micro switch to maintain an open state.

7. The suction brush of claim 6 , wherein the DC motor is electrically connected with the first and second micro switches,

wherein when the surface to be cleaned is detected as the carpet, the DC motor rotates in one direction until the first micro switch is in the open state, and

wherein when the surface to be cleaned is detected as the hard floor, the DC motor rotates in the same direction until the second micro switch is in the open state.

8. The suction brush of claim 4 , wherein the surface detecting part comprises:

a fixing plate horizontally spaced apart from the surface to be cleaned;

a third micro switch disposed above the fixing plate and electrically connected with the first micro switch and the second micro switch; and

a rotation member rotatably disposed at the fixing plate to have a surface contacting portion formed on one end thereof to contact the surface to be cleaned, and a switch contacting portion formed on the other end thereof to contact a contacting terminal of the third micro switch.

9. The suction brush of claim 2 , further comprising:

a power switch part configured to cut off electrical power supplied from the battery to the DC motor when the suction brush is spaced apart from the surface to be cleaned.