Washing machine comprising a ball balancer

Abstract: A washing machine is disclosed and includes a rotatably mounted drum (4) for receiving a load of laundry and a plurality of balls (31,74,78,85,89) arranged to move in an annular channel (13,43,53,63,73,77,83,87) fixed relative to the drum (4) towards a counterbalancing position in response to an imbalance in a load during rotation of the drum (4). The balls move from a retaining station (21,45,55,65,75,84,88) to the guide means when a predetermined rotational speed of the drum is reached. In the preferred embodiment, the retaining station has an inclined radial outer wall (23) configured so that the balls travel up the wall out of the retaining station to the guide means when the drum (4) reaches the predeterminded speed.

Description: The present invention relates to a washing machine comprising an external cabinet, an outer tub suspended inside said external cabinet, a rotary tub rotatably installed inside said outer tub for containing the laundry therein, and a ball balancer installed at a circumference of said rotary tub for balancing a rotation of said rotary tub, wherein said ball balancer comprises a casing installed at the circumference of said rotary tub and having at least one annular chamber formed therein, a multiplicity of balancing balls contained in said annular chamber of said casing, and a viscous fluid contained in said annular chamber of said casing, and wherein said annular chamber of said casing is formed at the bottom of said annular chamber with at least one groove for receiving said balancing balls over a predetermined circumferential length, and said groove has an inclined radial outer wall for guiding an upward movement of said balancing balls, as a rotational speed of said rotary tub increases. A conventional washing machine 101, is illustrated in Figure 7 and includes an external cabinet 2, tub 3 elastically suspended therein and a drum 4 for containing laundry mounted for rotation within the tub 3. A pulsator 5 is mounted on the bottom of the drum 4 to create a flow of washing water. The drum 4 or the pulsator 5 is selectively rotated in a forward or reverse direction, by a power transmission unit 9 installed below the tub 3, having a driving motor 7 and a shaft assembly 8. When the washing machine 101 is in operation, and the drum 4 rotates, vibration is generated due to uneven distribution of laundry within the drum 4. The vibration is severe, especially when the laundry is unbalanced. Therefore a balancer 111 is mounted on the drum 4 to counteract the imbalance of the tub 4 and decrease the vibration. The balancing device generally includes an annular casing having an annular chamber formed therein. The balancer is classified into a solid, liquid or ball balancer, depending upon the material contained in the chamber of the casing. Such a balancer is disclosed in US-A-4433592. The conventional washing machine 101 illustrated in Figure 7 includes the ball balancer 111 which uses a multiplicity of balancing balls 115 and a viscous fluid 117 movable within an annular chamber 113. The movement of the balancing balls 115 is limited by the viscosity of the viscous fluid 117, so that collision between the balancing balls 115 during rotation of the drum 4 is prevented and noise is reduced. The balancing balls 115 move inside the annular chamber 113 by the centrifugal force generated during the rotation of the drum 4, towards a position in which the unbalanced load of laundry within the drum is counterbalanced. Accordingly, the drum 4 can be balanced, and the vibration and noise prevented. However, in the conventional ball balancer 111, the balancing balls 115 are irregularly arranged on the flat bottom of the chamber 113, regardless of the rotational speed of the drum 4. The irregularly arranged balancing balls move toward the unbalanced load of laundry until the rotational speed of the drum 4 reaches a predetermined value. Accordingly, when the drum 4 rotates at a low speed, especially at an initial stage of spin cycle, the movement of the balancing balls 115 towards the unbalanced load side increases the rotational imbalance of the drum 4 thereby increasing the vibration and noise. It is an aim of the present invention to overcome or substantially alleviate the aforementioned problem. A washing machine according to the present invention is characterised in that the or each groove has circumferential inclined surfaces at the opposite ends thereof for facilitating a returning movement of said balancing balls to said groove. Preferably, the grooves extend to the bottom of said chamber through circumferenital surfaces. In the preferred embodiment, a plurality of said annular chambers are arranged vertically to form an upper chamber and a lower chamber. Preferably, the inclination angle of said inclined surface formed at said grooves of said upper chamber is greater than that of said inclined surface formed at said grooves of said lower chamber. In another embodiment, a plurality of annular chambers are arranged horizontally to form an outer chamber and an inner chamber. Preferably, the width of each groove is proportional to the diameter of the balls contained therein. The expression "washing machine" should be taken to include within its meaning spin dryers, tumble dryers and the like. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a section of a washing machine having a ball balancer according to a first embodiment of the present invention; Figure 2 shows a section of the ball balancer of Figure 1; Figure 3 shows an enlarged section of the ball balancer taking along line I-I of Figure 2; Figure 4 shows an enlarged section of the ball balancer taken along line II-II of Figure 2; Figure 5 shows a section of a ball balancer for use in a washing machine according to a second embodiment of the present invention; Figure 6 shows a partially cut-out perspective view of a ball balancer for use in a washing machine according to a third embodiment of the present invention; and Figure 7 shows a section of the conventional washing machine. Referring to Figure 1, a washing machine 1 having a ball balancer 11, according to a first embodiment of the present invention includes an external cabinet 2, a tub 3 suspended inside the external cabinet 2 by a suspension unit 6, and a drum 4 mounted for rotation within the tub 3. The external cabinet 2 is generally rectangular in shape, and the tub 3 and drum 4 are cylindrical. The wall of the drum 4 is provided with a plurality of holes through which washing water communicates between the tub 3 and the inside of the drum 4. A pulsator 5 is mounted in the bottom of the drum 4 to generate a spiral flow of washing water. The suspension unit 6 elastically suspends the tub 3 with respect to the external cabinet 2, to decrease vibration of the tub 3. The suspension unit 6 includes a suspension bar 6a and a damper 6b mounted at the lower end of the suspension bar 6a fixed to the tub 3. The damper 6b has a bell-shaped friction cover (not shown), a frictional member installed in the friction cover (not shown) and a spring (not shown). The frictional member is fixed to the end of the suspension bar 6a and frictionally slides inside the friction cover according to vibration of the tub 3. The vibration is suppressed by frictional contact between the friction cover and the frictional member. A power transmission unit 9 having a driving motor 7 and a shaft assembly 8 is installed beneath the tub 3 and is surrounded by a saddle (not shown). The power transmission unit 9 selectively rotates the drum 4 or the pulsator 5 in a forward or reverse direction according to a program stored in a controller (not shown), so that washing, rinsing and spin drying operations are sequentially performed. A flange 10 is formed outwardly on the upper circumferential edge of the drum 4 and contacts a supporting rib 33 (refer to Figure 3) formed on the annular casing 12 to support the ball balancer 11. Referring to Figures 2, 3 and 4, the ball balancer 11 includes an annular casing 12 mounted concentrically within the drum 4 and has an annular chamber 13 formed therein. The casing 12 has an outer wall member 15, an inner wall member 17 and a bottom member 19 which are integrally formed, and a cover member 20 for covering a receiving space formed by the outer and inner wall members 15 and 17 and the bottom member 19 to form the chamber 13. The supporting rib 33 is formed on a circumferential portion connecting the outer wall member 15 and the bottom member 19. The supporting rib 33 is seated on the flange 10 of the drum 4 to support the ball balancer 11. The bottom member 19 of the ball balancer 11 and the upper portion of the drum 4 are held together by fastening means such as a screw 37 (see Figure 1). A multiplicity of balancing balls 31 and a viscous fluid 35 are contained inside the chamber 13 and the balancing balls 31, which are preferably made of metal such as aluminium or steel, are free to move inside the chamber 13 and are immersed in the viscous fluid 35. The balancing balls 31 and the viscous fluid 35 are placed in the chamber 13 before the cover member 20 is fitted. The viscous fluid 35 has a predetermined viscosity so as to limit the movement of the balancing balls 31, and prevent collision between them. Referring to Figure 2, a plurality of preferably three grooves 21 are formed on the upper surface 18 of the bottom member 19 at spaced locations and the balancing balls 31 are disposed in the grooves 21. Inclined surfaces 25 are formed at the opposite ends of each groove 21 in a circumferential direction. Also, an inner inclined surface 39 (Figure 3) and an outer inclined surface 23 are respectively formed at the radial inner wall and outer wall of the grooves 21 in a lengthwise direction. An equal number of balancing balls 31 are contained in each groove 21 to uniformly distribute the load of the balancing balls 31. The balancing balls 31 ascend along the outer inclined surface 23 by centrifugal force generated during the rotation of the drum 4. In the washing machine having the above structured ball balancer 11, when the drum 4 rotates at a low speed, for example, at an initial stage of a spin drying cycle, the balancing balls 31 remain in the grooves 21 and do not move toward the unbalanced load side of the laundry inside the drum 4, thereby preventing an increase in vibration unlike in the conventional washing machine. When the rotational speed of the drum 4 increases, the balancing balls 31 ascend along the inclined surfaces 23 and 25 from the bottom of the grooves onto the upper surface 18 of the bottom member 19 by the centrifugal force. The balancing balls 31 located on the upper surface 18 of the bottom member 19 move along the chamber to oppose the imbalance of the drum 4. As described above, when the drum 4 rotates at a low speed, vibration and noise is decreased, compared with the conventional washing machine because the balancing balls are disposed in the grooves formed in the annular chamber 13. As the rotational speed of the drum 4 decreases, the rotational speed of the balancing balls 31 and the drum 4 differ from each other, so that they return to the grooves 21. The inclined surfaces 23 and 25 facilitate the returning of the balancing balls 31 to the grooves 21. Referring to Figure 5, a ball balancer 41 for use in a washing machine according to a second embodiment of the present invention includes a casing 12a formed with a plurality of, preferably, three annular chambers 43, 53 and 63 which are concentrically and horizontally arranged. The chambers 43, 53 and 63 are provided with grooves 45, 55 and 65 arranged at regular intervals, that is, 120° without overlapping. The shape of the grooves 45, 55 and 65 is the same as the grooves 21 described with reference to Figures 1 to 3, and therefore a detailed description thereof will be omitted. The width of the outer groove 45 is larger than that of the central groove 55, and the width of the central groove 55 is larger than that of the inner groove 65. The diameters of the balancing balls 31 arranged in the respective grooves 45, 55 and 65 are also proportional to the widths of the grooves 45, 55 and 65. In the washing machine having the above structured ball balancer 41, when the drum 4 rotates at a low speed, the balancing balls 31 remain in the grooves 45, 55 and 65 thereby preventing an increase in vibration of the drum 4. As the rotational speed of the drum 4 increases, the balancing balls 31 move out of the grooves 45, 55 and 65 to counteract the imbalance of the drum 4. Although the grooves 45, 55 and 65 preferably neither overlap nor are separated in their lengthwise direction in the present embodiment, their lengths may be shorter or longer as necessary. Also each of the grooves 45, 55 and 65 may be formed in a paired structure in which case, it is preferable that each pair of grooves are arranged opposite to each other. The outer inclined surfaces 23 of the respective grooves 45, 55 and 65 may have different angles of inclination and it is preferable that the angle of inclination is greatest for the inclined surface of the groove 65 and least for the groove 45. Accordingly, as the rotational speed of the drum 4 increases, the balancing balls 31 sequentially move out of the grooves 45, 55 and 65, that is, first out of the inner groove 65, then out of the central groove 55 and last out of the outer groove 45. According to this modified embodiment, a variety of vibration damping effects can be achieved according to the rotational speed of the drum 4. Furthermore, the diameter of the balancing balls 31 may gradually increase from the inner groove 65 to the outer groove 45 so as to perform the same function. Since the moments of inertia of the balancing balls 31, which resist the centrifugal forces applied thereto, are proportional to the fifth power of their diameters when the centrifugal forces are applied to the balancing balls 31 by the rotation of the drum 4, the balancing balls 31 in the inner groove 65 ascend first, and the balancing balls 31 in the outer groove 45 ascend last. Accordingly, various vibration damping effects can be achieved according to the rotational speed of the drum 4. Referring to Figure 6, a ball balancer 71 for use in a washing machine according to a third embodiment of the present invention includes a multi-layer casing 12b having upper and lower chambers 73 and 77 which are vertically arranged and include grooves 75, respectively. A multiplicity of upper and lower balancing balls 74 and 78 are contained in the upper and lower chambers 73 and 77, respectively. As in the first and second embodiments, when the rotary tub 4 rotates at a low speed, the balancing balls 74 and 78 remain in the grooves 75, thereby preventing the increase in vibration of the drum 4. In this structure, when the drum 4 rotates, the radius of gyration of the upper chamber 73 is larger than that of the lower chamber 77. Accordingly, as the rotational speed of the drum 4 increases, the upper balancing balls 74 move out of the upper groove 75 first, followed by the balancing balls 78 in the lower groove 75, so that rotation of the drum 4 can be effectively balanced according to the rotational speed thereof. In the third embodiment, the diameters of the upper and lower balancing balls 74 and 78 may be different from each other as necessary. Also, the inclination angles of the inclined surfaces of the upper and lower grooves 75 may be different from each other. As described above, according to the present invention, a groove is formed at the bottom of a chamber of a casing in which balancing balls are contained, so that the balancing balls remain in the groove when a rotary tub rotates at a low speed, for example, at an initial stage of a spin cycle thereby preventing increase in vibration of the drum. Further, when the casing is formed with a plurality of chambers which are arranged vertically or horizontally, a variety of vibration damping effects can be obtained according to rotational speed of the drum.

Claims: A washing machine comprising: an external cabinet (2); an outer tub (3) suspended inside said external cabinet (2); a rotary tub (4) rotatably installed inside said outer tub for containing the laundry therein; and a ball balancer (11) installed at a circumference of said rotary tub (4) for balancing a rotation of said rotary tub (4); wherein said ball balancer (11) comprises a casing (12) installed at the circumference of said rotary tub (4) and having at least one annular chamber (13) formed therein; a multiplicity of balancing balls (31) contained in said annular chamber (13) of said casing (12), and a viscous fluid contained in said annular chamber (13) of said casing (12); and wherein said annular chamber (13) of said casing (12) is formed at the bottom of said annular chamber (13) with at least one groove (21) for receiving said balancing balls (31) over a predetermined circumferential length, and said groove (21) has an inclined radial outer wall surface (23) for guiding an upward movement of said balancing balls (31), as a rotational speed of said rotary tub (4) increases, characterised in that the or each groove (21) has circumferential inclined surfaces (25) at the opposite ends thereof for facilitating a returning movement of said balancing balls (31) to said groove (21). A washing machine as claimed in claim 1 wherein said grooves (21) are spaced at regular circumferential intervals. A washing machine as claimed in claim 1 or claim 2, wherein said grooves (21) extend to said bottom of said chamber (13) through circumferential surfaces. A washing machine as claimed in claim 1, 2 or 3, wherein a plurality of said annular chambers (73, 77) are arranged vertically to form an upper chamber (73) and a lower chamber (77). A washing machine as claimed in claim 4, wherein the inclination angle of said inclined surface (23) formed at said grooves (75) of said upper chamber (73) is greater than that of said inclined surface (23) formed at said grooves of said lower chamber (77). A washing machine as claimed in claim 4 or 5, wherein the diameter of said balancing balls (74) contained in said upper chamber (73) is larger than that of said balancing balls (78) contained in said lower chamber (77). A washing machine as claimed in claim 1, 2 or 3, wherein a plurality of said annular chambers (43, 53, 63) are arranged horizontally to form an outer chamber (43) and an inner chamber (63). A washing machine as claimed in claim 7, wherein the inclination angle of said inclined surface (23) formed at said grooves (45) of said outer chamber (43) is greater than that of said inclined surface (23) formed at said grooves (65) of said inner chamber (63). A washing machine as claimed in claim 7 or claim 8, wherein the diameter of said balancing balls (31) contained in said outer chamber (43) is larger than that of said balancing balls (31) contained in said inner chamber (63).

Inventors: KIM DO WEON, SHIN SUNG JAE, KIM, DO WEON, SHIN, SUNG JAE
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1997
Main classification: D06F37
IPC codes: D06F37