GB1598399A - Drum type automatic electric washing machine - Google Patents

Description

(54) DRUM TYPE AUTOMATIC ELECTRIC WASHING MACHINE (71) We, HITACHI LTD., a Japanese Body Corporate of 5-1, 1-chome, Marunouchi, Chiyoda-ku, Tokyo, Japan do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a drum type automatic electric washing machine, in which a drum affording the dual functions of washing and hydroextraction is rotatably supported with its axis of rotation horizontal and more particularly to such an electric washing machine which includes means for reducing vibration of the machine in use thereof by balancing the drum.

An automatic drum type electric washing machine is known, in which a drum affording the dual functions of washing and hydroextraction is rotatably supported, with its axis of rotation horizontal, and with a plurality of perforations being provided in the peripheral walls thereof, whereby in a washing mode of the washing machine, the drum is rotated at a low rotational speed or r.p.m. in a tub containing washing water therein, for repeatedly dropping, from above downwards, articles to be washed within the drum for cleaning, and in a hydroextracting mode of the washing machine, the drum is rotated at a high rotational speed (r.p.m.) for hydroextracting the materials by a centrifugal force which is created during the rotation of the drum. According to the electric washing machines of the type described, prior to a hydroextracting operation, the materials being washed tend to be biased downwards in the drum by the gravity thereof, and hence in case a hydroextracting operation is brought on its way in the aforenoted condition, then a biasing condition of materials forms the cause of an unbalance in the drum thereby producing vibrations in a washing machine. To cope with the aforenoted vibrations, it has been a general practice to attach two or more counterweights having a considerable weight to a stationary, outer casing which houses the drum therein, thereby increasing the weight of the outer casing and hence a moment of inertia thereof, with the outer casing being supported by shockabsorbing members.

However, prior art electric washing machines of the type described suffer from disadvantages such as an increased weight of a washing machine itself, an increased volume, hence a high manufacturing cost, and difficulties in transportion and set-up operation thereof.

Meanwhile, there has been proposed another attempt, in which automatic liquid balancers having hollow annular bodies, each of which contains a liquid of a volume half that of the annular body are attached to a drum, thereby reducing vibrations experienced during a hydroextracting rotation of the drum. However, for achieving a desired vibration-preventive function, the hollow annular bodies need to be so large as to fail to meet the purpose of reducing the size of a washing machine. Still furthermore, the hollow annular body should be provided with seals which prevent the leakage of a liquid contained therein. It follows from this that in case hot washing water is used, it is not recommendable to directly attach automatic liquid balancers to a drum which is to be dipped in washing water in a tub. This dictates to position balancers externally of the tub, into which the drum is to be dipped, thus failing to meet the requirement to reduce the size of the washing machine.

It is accordingly an object of the present invention to provide a drum type automatic electric washing machine which reduces or avoids the aforenoted shortcomings experienced with the prior art machines, and affords improvements in weight-saving and vibrationpreventive characteristic by providing a vibration-preventive device or a balancing device which aids in reducing the size of a washing machine.

According to the present invention there is provided a drum type washing machine wherein a horizontal axis rotary drum is provided internally of a container which is adapted to contain washing water therein in use of the machine, said rotary drum having a plurality of perforations in its peripheral wall and being rotatable at a relatively low rotational speed during the washing and rinsing operations and at a relatively high rotational speed during the hydroextracting operation, said drum being provided with a balancing device therein comprising two hollow annular bodies each having a hollow annular space therein and having a centre of rotation in coincidence with the axis of rotation of said drum, said bodies being attached one to each end wall inner surface at a position adjacent said peripheral wall; and two or more balls placed in each said hollow annular space and freely movable therealong.

The ball type balancer is smaller in size than the liquid type balancer, thereby allowing the attaching thereof inside the drum. With the hollow annular bodies housing balls therein being secured to the axially inner surfaces of flat end plates of the drum near their periphery, the diameter of the hollow annular bodies may be such that the size of ball used may be sufficiently small for there to be no reduction in an effective volume of the drum, in which washing or articles to be washed are placed.

With the aforenoted automatic ball balancer, two or more steel balls are placed in each hollow annular space defined therein in a manner to allow the free movement of the balls therealong.

The present invention will now be described in more detail with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view illustrative of a washing machine equipped with an automatic ball balancing device embodying the invention; Figure 2 is a graphical representation showing the relationship between the r.p.m. of the drum and an amplitude of vibrations; Figure 3 is a graphical representation illustrative of angular differences between the direction of eccentricity and the position of a drum unbalanced, at the varying r.p.m. of the drum; Figures 4 to 6 are transverse cross-sectional views of an automatic ball balancer, illustrating the operations thereof, at the beginning of a hydroextracting operation; Figure 7 is a transverse cross-sectional view of the automatic ball balancer, when the r.p.m. thereof exceeds the r.p.m. caused at a resonance point and remains not more than an operational r.p.m. of the drum, upon hydroextraction; Figure 8 is a transverse cross-sectional view of the automatic ball balancer, illustrating the operation thereof, during the normal rotation of the drum, upon hydroextraction; Figure 9 is a transverse cross-sectional view showing the functions of an automatic liquid balancer during the normal rotation of the drum, upon hydroextraction; and Figure 10 is a cross-sectional view taken along the line A-A' of Figure 9.

Referring now to Figure 1, there is shown a cross-sectional view of an example of a washing machine the drum of which is provided with an automatic balancing device. Shown at 1 is an outer frame of a washing machine, at 2 a panel portion mounting thereon control means adapted to control the operations of a washing machine, and at 3 a lid hinged to the top surface of the outer frame 1. Shown at 4 is an outer tub which contains water for use in washing or rinsing, and the outer tub is provided with an opening 5, through which articles 10 washed or to be washed (these articles will be simply referred to as articles, hereinafter) are to be charged or taken out. An outer-tub lid 6 is attached to the peripheral edge of the opening 5. Shown at 7 is a drum serving for the dual purposes of washing and hydroextraction, with a plurality of perforations being provided in the cylindrical peripheral wall of the drum. An opening for charging articles 10 or removing same therethrough is provided in the form of a cut-away portion formed in the cylindrical peripheral wall of the drum, while a lid 8 is hinged to the peripheral edge of the opening for charging articles 10 or removing same therethrough. Shown at 9 are two more lifters secured to the drum 7. The lifters 9 serve to lift and drop articles 10 within the drum 7, for the purposes of cleaning and rinsing at a low rotational speed of the drum 7. Shown at 11 and 12 are rotary shafts which are integrally secured to the centres of flat end walls of the drum 7, at 13 a large pulley secured to the rotary shaft 11. Shown at 15 are automatic ball balancers, each of which is fixedly secured to the inner surface of a respective end wall plate of the drum. The balancers are each located at the radially outer periphery of the respective end walls of the drum adjacent the peripheral wall of the drum. The balancers 15 are each of such an arrangement that two or more balls 16 made of such as steel are placed in an hollow annular body 15b. The number of balls 16 to be placed therein should be such as to cover a range smaller than half the circumference of the hollow annular body 15b. Shown at 17 is a variable-speed type electric motor, which rotates at a r.p.m. corresponding to the low rotational speed (for instance, 50 to 70 r.p.m.) of the drum 7 in the case of washing, and at a high rotational speed of the drum (for instance, 600 to 800 r.p.m.) in the case of hydroextraction, respectively. The motor 17 is mounted on a bottom portion of the outer tub 4. Shown at 18 is a small pulley secured to a shaft of the electric motor 17, at 19 an endless belt which transmits the rotation of the electric motor from the small pulley 18 to the large pulley 13. Shown at 20 is a water-discharging electromagnetic valve connected to a discharge port in the outer tub 4 by means of a pipe, and at 21 a water-discharging hose connected to an outlet port of the water-discharging electromagnetic valve 20. Shown at 22 is a timer knob, which is used for operating programming timers (not shown) adapted to control respective steps of washing. Shown at 23 is a pressure switch adapted to detect a water level in the outer tub 4 and to control the operations of a water-feeding electromagnet valve 26 to be described hereinafter. Shown at 24 is a trap adapted to detect a water level and provided on a bottom portion of the outer tub 4, and at 25 a flexible pipe having a small diameter and adapted to transmit a pressure. Shown at 26 is a water-feeding electromagnetic valve for feeding water to the outer tub 4, with an inlet of the valve 26 being connected through the medium of a pressure hose to a water cock (not shown), and with an outlet of the valve 26 being connected to a water-inlet port (not shown) provided in a top wall of the outer tub 4, respectively. Shown at 27 are shock absorbers provided between a bottom portion of the outer tub 4 and a bottom portion of the outer frame 1. In general, two or more shock absorbers 27 are provided for absorbing vibrations created from internally thereof. In operation of the drum type automatic electric washing machine equipped with automatic ball balancers 15, the step of "washing" is carried out by: energizing the water feeding electromagnetic valve 26 so as to feed water from a water cock (not shown) into the outer tub 4; then detecting the water level in the outer tub 4 by means of the pressure switch; interrupting the electric power supply, when the water level reaches a given level, while supplying an electric power to the electric motor 17 so as to be driven at a low rotational speed; and rotating the drum 7 at a low r.p.m. On the other hand, the step of "hydroextraction" is carried out by: energizing the water-discharging electromagnetic valve 20 so as to open the valve 20 so as to discharge water from the outer tub 4; supplying an electric power to the electric motor 17 so as to be driven at a high r.p.m.; and rotating the drum 7 at a high rotational speed.

Description will now be turned to the functions of the automatic ball balancers. In the vibration system including automatic ball balancers shown in Figure 1, when the drum 7 is rotated for hydroextraction in an unbalanced condition, then the automatic ball balancers 15 cause vibrations at an amplitude having a relationship as shown in Figure 2. In other words, as shown, the amplitude thereof is increased with an increase in r.p.m. of the drum, peaking at an r.p.m. of the drum at a resonance point N. From the r.p.m. at the resonance point N on, the amplitude is decreased in a manner to be converged to a given value.

Meanwhile, shown at a point S is a normal r.p.m. of the drum at the time of hydroextraction. Figure 3 shows angular differences between the direction of articles causing an unbalance and the direction of eccentricity of the center of the drum, at varying r.p.m. of the drum. In other words, as shown, the angular difference between the direction of articles causing an unbalance and the direction of eccentricity of the center of the drum is progressively increased, with an increase in r.p.m. of the drum, reaching 90" at the resonance point N, and is then further increased with a further increase in r.p.m. of the drum, thus eventually reaching close to 180 at the normal r.p.m. of the drum, upon hydroextraction.

Figures 4 to 8 show the relationship among a degree of an unbalance relative to the r.p.m.

of the drum (the unbalance is caused by articles 10 to be washed.), an amplitude of vibrations, and balls 16 housed in automatic ball balancers 15, with reference to Figure 2 and 3. Meanwhile, a point X shown therein represents a line connecting the axes of the rotary shafts 11 and 12 together, a point 0 represents a center, about which the point X is moved, at the time of hydroextraction (This point will be referred to as a moving-around center), and an arrow mark P represents the direction of rotation of the drum 7, upon hydroextraction. Accordingly. a distance OX between the point 0 and the point X represents an amplitude.

Figures 4, 5, 6 show conditions where, upon starting a hydroextracting operation, the r.p.m. of the drum is lower than that resulting at the resonance point N as shown in Figures 2 and 3, a centrifugal force acting on the balls 16 placed in the automatic ball balancer 15 is smaller than the gravity of the balls, and the total weight of the balls 16 housed in the balancer is lighter than the weight of the articles 10, which causes an unbalanced condition.

In this case, as shown, the balls 16 in the automatic ball balancer 15 are positioned below the center of the automatic ball balancer 15 all the time, regardless of the position of the articles 10, so that the balls 16 act in a manner slightly to increase an amplitude of vibrations in the case of Figure 4, and decrease an amplitude of vibrations in the case of Figure 6, as compared with the case where the automatic ball balancers 15 are not provided. As a result, due to the aforenoted increase and decrease in amplitude, a vertical amplitude (the total amplitude) remains almost the same as that of the case where the automatic ball balancer 15 is not provided. Even when the articles 10 are positioned sidewise of the drum 7, the balls 16 exert no influence on an amplitude of vibrations in the horizontal direction. In short, the automatic ball balancer 15 exerts little or no influence on an increase and a decrease in amplitude of vibrations, when the r.p.m. of the drum is not higher than that experienced at the resonance point N.

Figure 7 denotes the case where the r.p.m. of a drum exceeds the r.p.m. produced at the resonance point N but not more than the normal r.p.m. S, upon the hydroextraction, and a centrifugal force creased by the rotation of the drum 7 is such as to be able to neglect the influence of gravity. In this case, a centrifugal force of the balls 16 is the highest, so that the balls 16 are collected in the OX direction, which is stable, (in the direction of the amplitude), so that balls are positioned on a side of the drum opposite to the articles 10.

Figure 8 represents the case where r.p.m. of the drum 7 is a normal r.p.m. S of the drum, upon hydroextraction, and hence the case where an angular difference between the articles 10 and the balls 16 is almost 1800C. Accordingly, at the normal r.p.m. of the drum 7 during hydroextraction, the automatic ball balancer 15 acts in a manner to reduce an unbalancing action of the articles 10.

Description will be given of the reasons why the automatic ball balancer according to the present invention presents a thin contour and a lighter weight, as compared with an automatic liquid balancer acting in the similar manner to the former. Figure 9 shows the articles 10, an amplitude OX and the distribution of a liquid in the automatic liquid balancer 28. Figure 10 is a cross-sectional view taken along the line A-A' of Figure 9. The automatic liquid balancer 28 is of such an arrangement that water or liquid 29 of an amount corresponding to half the volume of a hollow annular body is filled therein sealingly. The distribution of liquid 29 within the automatic liquid balancer 28 is such that the outer contour of liquid describes a circle having its center at the point X, while the inner contour of liquid describes a circle having its center at the point 0. Accordingly, the liquid 29 filled therein is biased to a side opposite to the articles 10, thereby reducing an unbalance.

Balancing actions of the automatic ball balancer and liquid balancer will be described with reference to Figures 8, 9 and 10. In Figure 8, assume a radius R of the inner peripheral surface of the outer wall of the automatic ball balancer 15, a radius rs of a ball 16, weight w of a ball, and the number n of the balls housed, an amplitude OX being as e. Then, an extent of an unbalance, which is to be reduced, is given as follows: [nwe + nw (R - rs)j o)2/g (1) wherein w represents normal r.p.m. of a drum during a hydroextracting operation, and g represents the acceleration of gravity. Likewise, in Figures 9 and 10, assume a radius R of the inner peripheral surface of an outer wall of the automatic liquid balancer 28, height h, radius r of the inner peripheral surface of the liquid 29 filled therein and, density p, amplitude OX being as e. Then, an extent of an unbalance which is to be reduced is given in the following equation: [:: (R2 - r2) h pe + zr2hp-e]-oz2/g . . . (2) Assume that the total weight nw of the balls 16 contained in the automatic ball balancer 15 is equal to the weight a(R r2) hp of the liquid 29 filled in the automatic liquid balancer 28, then h = nw/sc(R' - 4)p. On the other hand, a ratio of the second term in parentheses in the equation (1) to the second term in parentheses in the second equation (2) is nw (R rs)/::r2hp.e. When h is substituted by the value of the aforenoted h, then the ratio will be given as follows: nw (R - rs)/sr2hp-e = (R - rs)(R2 - r1)/e . (3) In general, the automatic liquid balancer 28 is of such an arrangement that a value of (R - r) be equal to the amplitude OX = e. Accordingly, when the relationship (R - r) = e is introduced into the equation (3), then (R - rs)(R2 ~ r2)/r2e = (R - rs)(R + r)/r2 (4) In case the balls 16 are so selected as to provide the relationship (R - rs) = r, the value of the equation (4) will be greater than 2.

In other words, because e (R - rs) in the equation (1), and (R2 - r2) < < r2 in the equation (2), in case the size of articles to be washed, and weights thereof are the same, an automatic ball balancer 15 provides a function to reduce an unbalance to a degree twice the degree of an unbalance in the case of the automtic liquid balancer 28.

In this respect, it is not recommendable for the automatic liquid balancer 28 that, for achieving the an unbalance-reducing effect equivalent to that achieved by the automatic ball balancer 15, the height h is to be increased, or the density p of the liquid is to be increased, because an increase in height h leads to an increase in size as well as in weight of a washing machine, and in addition, the liquid having an increased density p is not available with ease. In conclusion, the automatic liquid balancer provides less advantage, as compared with the automatic ball balancer.

Accordingly, the use of the automatic ball balancer leads to a slight increase in weight, and may dispense with the counterweights, so that the size and weight of the washing machine may be reduced as a whole.

The size of the automatic ball balancer 15 will now be compared with that of the automatic liquid balancer of Figure 9.

Referring to Figure 1, assume the condition of a washing machine as follows: the weight of a body proper of the outer frame 1 which is supported for preventing vibrations by shock absorbers 27, is 20 kg; a radius of each of the hollow annular bodies 9 of the automatic ball balancers 15, which are attached to the opposed inner surfaces of the end walls of the drum 7, is 21.4 cm; eight steel balls 15 having a diameter 1.9 cm are housed in each of the balancers 15'; a mass of materials causing unbalance is 0.9 kg; and the position of materials causing an unbalance is spaced 20 cm from the center of the drum, as measured in the radial direction thereof. Then, an amplitude of an eccentric motion of the center of the drum, during the normal rotation of the drum during hydroextraction (The amplitude corresponds to OX shown in Figure 8.) was found to be 0.41 cm. In this case, the thickness of the hollow annular body 15b of the automatic ball balancer 15 is equal to the diameter (1.9 cm) of the ball 16, and the weight of eight steel balls is 0.230 kg. In contrast thereto, automatic liquid balancers equipped with hollow bodies containing water therein are picked up for comparison purpose. Assume that a radius of a hollow annular body and the condition of materials causing an unbalance are equal to those of the automatic ball balancers 15. Then, the thickness of the automatic liquid balancer for providing an amplitude (0.41 cm) of an eccentric motion of the drum, during the normal rotation during hydroextraction, was determined as being 8 cm, which was about four times as large as that of the ball balancer, and the amount of water to be filled in the balancer was found to be 0.430 kg which was about twice as large as that of the eight steel balls.

With the automatic ball balancers 15 provided integrally within the drum 7, the automatic ball balancers 15 are positioned internally of the outer tub 4, with the result that a noise produced, when the balls 16 are moved, may be shielded by means of the outer tub 4, thus providing a noise shielding advantage. For achieving smooth movement of balls 16 in the hollow annular bodies, a quantity of liquid occupying a minor portion of the annular space may be provided therein with the balls 16. In this case, a stable movement and uniform distribution of balls 16 may result.

WHAT WE CLAIM IS: 1. A drum type washing machine wherein a horizontal axis rotary drum is provided internally of a container which is adapted to contain washing water therein in use of the machine, said rotary drum having a plurality of perforations in its peripheral wall and being rotatable at a relatively low rotational speed during the washing and rinsing operations and at a relatively high rotational speed during the hydroextracting operation, said drum being provided with a balancing device therein comprising two hollow annular bodies each having a hollow annular space therein and having a centre of rotation in coincidence with the axis of rotation of said drum, said bodies being attached one to each end wall inner surface at a position adjacent said peripheral wall: and two or more balls placed in each said hollow annular space and freely movable therealong.

2. A drum type washing machine as claimed in Claim 1, wherein a quantity of liquid

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. In general, the automatic liquid balancer 28 is of such an arrangement that a value of (R - r) be equal to the amplitude OX = e. Accordingly, when the relationship (R - r) = e is introduced into the equation (3), then (R - rs)(R2 ~ r2)/r2e = (R - rs)(R + r)/r2 (4) In case the balls 16 are so selected as to provide the relationship (R - rs) = r, the value of the equation (4) will be greater than 2. In other words, because e (R - rs) in the equation (1), and (R2 - r2) < < r2 in the equation (2), in case the size of articles to be washed, and weights thereof are the same, an automatic ball balancer 15 provides a function to reduce an unbalance to a degree twice the degree of an unbalance in the case of the automtic liquid balancer 28. In this respect, it is not recommendable for the automatic liquid balancer 28 that, for achieving the an unbalance-reducing effect equivalent to that achieved by the automatic ball balancer 15, the height h is to be increased, or the density p of the liquid is to be increased, because an increase in height h leads to an increase in size as well as in weight of a washing machine, and in addition, the liquid having an increased density p is not available with ease. In conclusion, the automatic liquid balancer provides less advantage, as compared with the automatic ball balancer. Accordingly, the use of the automatic ball balancer leads to a slight increase in weight, and may dispense with the counterweights, so that the size and weight of the washing machine may be reduced as a whole. The size of the automatic ball balancer 15 will now be compared with that of the automatic liquid balancer of Figure 9. Referring to Figure 1, assume the condition of a washing machine as follows: the weight of a body proper of the outer frame 1 which is supported for preventing vibrations by shock absorbers 27, is 20 kg; a radius of each of the hollow annular bodies 9 of the automatic ball balancers 15, which are attached to the opposed inner surfaces of the end walls of the drum 7, is 21.4 cm; eight steel balls 15 having a diameter 1.9 cm are housed in each of the balancers 15'; a mass of materials causing unbalance is 0.9 kg; and the position of materials causing an unbalance is spaced 20 cm from the center of the drum, as measured in the radial direction thereof. Then, an amplitude of an eccentric motion of the center of the drum, during the normal rotation of the drum during hydroextraction (The amplitude corresponds to OX shown in Figure 8.) was found to be 0.41 cm. In this case, the thickness of the hollow annular body 15b of the automatic ball balancer 15 is equal to the diameter (1.9 cm) of the ball 16, and the weight of eight steel balls is 0.230 kg. In contrast thereto, automatic liquid balancers equipped with hollow bodies containing water therein are picked up for comparison purpose. Assume that a radius of a hollow annular body and the condition of materials causing an unbalance are equal to those of the automatic ball balancers 15. Then, the thickness of the automatic liquid balancer for providing an amplitude (0.41 cm) of an eccentric motion of the drum, during the normal rotation during hydroextraction, was determined as being 8 cm, which was about four times as large as that of the ball balancer, and the amount of water to be filled in the balancer was found to be 0.430 kg which was about twice as large as that of the eight steel balls. With the automatic ball balancers 15 provided integrally within the drum 7, the automatic ball balancers 15 are positioned internally of the outer tub 4, with the result that a noise produced, when the balls 16 are moved, may be shielded by means of the outer tub 4, thus providing a noise shielding advantage. For achieving smooth movement of balls 16 in the hollow annular bodies, a quantity of liquid occupying a minor portion of the annular space may be provided therein with the balls 16. In this case, a stable movement and uniform distribution of balls 16 may result. WHAT WE CLAIM IS:

1. A drum type washing machine wherein a horizontal axis rotary drum is provided internally of a container which is adapted to contain washing water therein in use of the machine, said rotary drum having a plurality of perforations in its peripheral wall and being rotatable at a relatively low rotational speed during the washing and rinsing operations and at a relatively high rotational speed during the hydroextracting operation, said drum being provided with a balancing device therein comprising two hollow annular bodies each having a hollow annular space therein and having a centre of rotation in coincidence with the axis of rotation of said drum, said bodies being attached one to each end wall inner surface at a position adjacent said peripheral wall: and two or more balls placed in each said hollow annular space and freely movable therealong.

2. A drum type washing machine as claimed in Claim 1, wherein a quantity of liquid

occupying a minor portion of the interior space of the annular body is sealed, together with said balls within each annular space.

3. A drum type washing machine constructed and arranged to operate substantially as hereinbefore described with reference to and as shown in Figure 1 of the accompanying drawings.