Robotic vacuum cleaner

[0001] This application claims priorities of Taiwanese Application No. 093111106, filed on Apr. 21, 2004, and Taiwanese Application No. 093117349, filed on Jun. 16, 2004.

[0002] 1. Field of the Invention

[0003] This invention relates to a robotic vacuum cleaner, more particularly to a robotic vacuum cleaner which can proceed with an edge-cleaning mode for improving the cleaning effect.

[0004] 2. Description of the Related Art

[0005] Referring to FIG. 1, a conventional robotic vacuum cleaner 100 is shown to include a casing 11, a plurality of motor-driven wheels 111, a plurality of drive motors (not shown) disposed to drive the wheels 111 so as to move the casing 11 along a floor surface to be cleaned, an electrical control unit 13, and a sensing unit 15. A variety of path programs are stored in the electrical control unit 13 to control the drive motors so as to selectively steer the wheels 111 to cause backward or forward displacement, or rotation of the casing 11. The sensing unit 15 has left and right sensors 151 mounted on lateral front portions of the casing 11, and is electrically connected to the electrical control unit 13 such that once the casing 11 hits an obstacle 91, such as a wall, an article of furniture, and the like, the sensing unit 15 is activated to generate a switching signal to the electrical control unit 13 to enable the electrical control unit 13 to control the wheels 111 to move the casing 11 away from the obstacle 91 for an appropriate distance, and to rotated the casing 11 a random angle before proceeding along the original programmed path.

[0006] Although the robotic vacuum cleaner 100 is moved substantially over the entire floor surface to be cleaned, it cannot easily reach edges of the obstacle 91 like corners of the wall or edges of furniture. Therefore, a distance sensor 17 is mounted to a side of the casing 11 such that when the casing 11 is moved away from the obstacle 91 and is rotated, the distance sensor 17 detects a distance between the casing 11 and the obstacle 91. According to the distance detected by the distance sensor 17, the electrical control unit 13 controls the wheels 111 to move the casing 11 along the programmed path, which is spaced from the obstacle 91 by a fixed distance.

[0007] However, in operation, it may be necessary to adjust the sensitivity of the distance sensor 17 according to the condition of the environment to be cleaned. While higher sensitivity can achieve a better cleaning effect, it may increase chances of bumping of the casing 11 against the obstacle 91 to result in damage to the robotic vacuum cleaner 100. On the other hand, lower sensitivity results in a larger distance between the casing 11 and the obstacle 91 to thereby reduce the cleaning effect of the robotic vacuum cleaner 100.

[0008] The object of the present invention is to provide a robotic vacuum cleaner which can operate in an edge-cleaning mode to achieve a better cleaning effect.

[0009] According to this invention, the robotic vacuum cleaner includes a casing having a lower major wall confronting a floor surface. The lower major wall includes a central area defining a central axis normal thereto, and a surrounding peripheral area surrounding the central area. The surrounding peripheral area includes a leading region which is positioned ahead of the central area when the casing is driven to move along the floor surface, and left and right front regions which flank the leading region. A suction unit is disposed in the lower major wall to draw dust from the floor surface. A motor-driven wheel unit is disposed on the lower major wall and behind the leading region, and is steerable between a normal angle at which the leading region is movable forward straight ahead, and an activating angle at which one of the left and right front regions is movable towards an obstacle. A drive motor unit is disposed to drive the motor-driven wheel unit to move the casing along the floor surface. A tactile sensor unit is disposed outwardly of one of the left and right front regions, and is yieldable radially relative to the corresponding one of the left and right front regions so as to generate a switching signal in response to contact of the tactile sensor unit with the obstacle.

[0010] An electrical control unit is coupled to the tactile sensor unit and the drive motor unit. The control unit is operable to control the motor-driven wheel unit to operate in a starting mode in which the casing is moved along a spiral path, with the leading region heading forwards. Upon receipt of the switching signal from the tactile sensor unit, the control unit controls the motor-driven wheel unit to operate in an edge-cleaning mode in which the motor-driven wheel unit is initially turned to the normal angle, is then driven to move forward a predetermined distance along the floor surface, is subsequently returned to the activating angle, and is thereafter moved toward the obstacle to permit contact of the tactile sensor unit with the obstacle, thereby enabling the motor-driven wheel unit to continue to operate in the edge-cleaning mode.

[0017] Referring to FIG. 2, the preferred embodiment of a robotic vacuum cleaner 200 according to the present invention is shown to comprise a casing 21, a suction unit 26, a motor-driven wheel unit, a drive motor unit, a tactile sensor unit 25, and an electrical control unit 22.

[0018] The casing 21 has a lower major wall 212 which is adapted to confront a floor surface to be cleaned, and which includes a central area that defines a central axis normal to the central major wall, and a surrounding peripheral area that surrounds the central area about the central axis. The surrounding peripheral area includes a leading region 211 which is positioned ahead of the central area when the casing 21 is driven to move along the floor surface, left and right front regions 213, 214 which flank the leading region 211, and left and right rear regions 215, 216 which are disposed rearwardly of the left and right front regions 213, 214, respectively.

[0019] The suction unit 26 is disposed in the lower major wall 212, and is driven by means of a power supply unit 24 to draw dust from the floor surface to be cleaned in a known manner. Briefly, the suction unit 26 includes a duct 262 which is disposed in the casing 21 and which has a vacuum inlet extending downwardly of the lower major wall 212, and an impeller 261 which is disposed in the casing 21 and downstream of the vacuum inlet so as to draw dust from the floor surface.

[0020] In this embodiment, the motor-driven wheel unit includes left and right wheels 233 which are mounted on the left and right rear regions 215, 216, respectively. The drive motor unit includes left and right drive motors 231 which are disposed to drive the left and right wheels 233, respectively, so as to steer the left and right wheels 233 to move the casing 21 along the floor surface in a certain motion to be described in greater detail hereinafter.

[0021] The tactile sensor unit 25 includes a shielding plate 251. The shielding plate 251, which when receives an applied force it is able to shift toward the casing 21 in the side where the shielding plate 251 receives the applied force and shifts back to its original position when not receives the applied force, is mounted to the casing 21 and outwardly covers the leading region 211 and left and right front regions 213, 214. Once the shielding plate 251 is brought to hit against an obstacle 92, such as a wall shown in FIG. 3, the shielding plate 251 shifts toward the left front region 213 or the right front region 214 of the casing 21 to depress the left or right sensor 252 according to which front region of the casing 21 is a depressed side. After the left or right sensor 252 is thus depressed by the shielding plate 251, the tactile sensor unit 25 generates a switching signal until releasing the shielding plate 251 from depressing the sensor 252 by allowing the shielding plate 251 to shift outward from the depressed side.

[0022] The electrical control unit 22 includes a memory for storing a variety of path programs, is coupled to the left and right sensors 252 for receiving the switching signals, and is electrically connected to and controls the motor-driven wheel unit and the drive motor unit for controlling the motor-driven wheel unit to move along the floor surface. In operation, the electrical control unit 22 controls the motor-driven wheel unit to operate in a starting mode in which the casing 21 is moved over the floor surface, with the leading region heading forwards, along a spiral path, such as a circular spiral path constituted by a plurality of consecutive winding segments (as shown in FIG. 3), and a rectangular spiral path constituted by a plurality of consecutive straight segments with each two adjacent straight segments being perpendicular to each other (as shown in FIG. 4).

[0023] Referring to FIG. 5, once the shielding plate 251 is brought to contact the obstacle 92, one of the sensors 252 is activated to generate a switching signal, which is sent to the electrical control unit 22. Upon receipt of the switching signal, the electrical control unit 22 controls the motor-driven wheel unit to operate in an edge-cleaning mode. That is, the motor-driven wheel unit initially turns the casing 21 away from the obstacle 92 until there is not received the switching signal from the tactile sensor unit, as shown in FIG. 6, and moves forward a predetermined distance along the floor surface, as shown in FIG. 7. Thereafter, the motor-driven wheel unit turns to an activating angle such that the casing 21 moves forward to contact with the obstacle 92 until receipt of another switching signal from the tactile sensor unit 25, thereby enabling the motor-driven wheel unit to continue to operate in the edge-cleaning mode. Thus, the casing 21 can be controlled to move along the floor surface substantially along the edge of the obstacle 92 to achieve a better cleaning effect, as shown in FIG. 9.

[0024] When the motor-driven wheel unit is steered to one of the normal angle and the activating angle in the edge-cleaning mode, the left and right wheels 233 are moved in opposite directions so as to turn the casing 21 away from or toward the obstacle 92. Alternatively, the left and right wheels 233 are moved in the same direction and at different speeds to permit turning of the casing 21 away from or toward the obstacle 92.

[0025] While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.