Title:
WASHING MACHINE
Kind Code:
A1


Abstract:
Disclosed is a washing machine. In order to reduce excessive vibration, the washing machine is provided with suspensions between a casing and an outer tub, in which a suspension positioned at one side of the casing and a suspension facing the suspension positioned at one side of the casing are installed so that their damping forces can be asymmetric to each other. Accordingly, even if excessive vibration occurs at the time of an initial dehydration process, the outer tub inclined to a driving unit is prevented from colliding with the casing.



Inventors:
Kim, Young-jong (Gyeongsangnam-Do, KR)
Noh, Dynn-neo (Gyeongsangnam-Do, KR)
Application Number:
12/181078
Publication Date:
02/05/2009
Filing Date:
07/28/2008
Primary Class:
International Classes:
D06F37/24
View Patent Images:



Foreign References:
KR1999024961A
JPH08206388A1996-08-13
KR19990024961A1999-04-06
Other References:
Machine translation of KR 1999024961 to Jeong et al.
Machine translation of KR1999024961 to Jeong et al.
Primary Examiner:
LEE, DOUGLAS
Attorney, Agent or Firm:
BIRCH, STEWART, KOLASCH & BIRCH, LLP (Falls Church, VA, US)
Claims:
1. A washing machine having a plurality of suspensions installed between a casing and an outer tub, wherein the suspensions have different damping forces.

2. The washing machine of claim 1, wherein the suspension installed at one side of the casing has a damping force different from that of the suspension installed at another side facing the one side.

3. The washing machine of claim 2, wherein the suspension installed at one side of the casing where an interval between the casing and the outer tub is relatively narrower due to inclination of the outer tub has a damping force larger than that of the suspension installed at another side facing the one side.

4. The washing machine of claim 3, wherein a driving unit for driving an inner tub installed in the outer tub is eccentrically mounted to a lower surface of the outer tub, and the outer tub is inclined due to the driving unit.

5. The washing machine of claim 1, wherein each of the suspensions having a relatively large damping force among the suspensions comprises: a damper cap mounted to the outer tub; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and a base cap mounted to a lower side of the damper cap.

6. The washing machine of claim 5, wherein each of the suspensions having a relatively small damping force among the suspensions comprises: a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and a base cap mounted to a lower side of the damper cap, wherein an air hole is formed at the damper cap or the base cap.

7. The washing machine of claim 5, wherein each of the suspensions having a relatively small damping force among the suspensions comprises: a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and an extension spring installed below the damper base, and configured to outwardly extend an edge of the damper base, wherein the interval between the damper cap and the damper base is constantly maintained in a circumferential direction by the extension spring.

8. The washing machine of claim 1, wherein each of the suspensions having a relatively large damping force among the suspensions comprises: a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and a base cap mounted to a lower side of the damper cap, wherein an air hole is formed at the damper cap or the base cap.

9. The washing machine of claim 8, wherein each of the suspensions having a relatively small damping force among the suspensions comprises: a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and an extension spring installed below the damper base, and configured to outwardly extend an edge of the damper base, wherein an interval between the damper cap and the damper base is constantly maintained in a circumferential direction by the extension spring.

10. A washing machine having a plurality of suspensions installed between a casing and an outer tub, wherein the suspensions comprise first suspensions installed at one side of the casing and second suspensions installed at another side of the casing facing the first suspensions, and the first suspensions and the second suspensions have damping forces asymmetrical to each other.

11. The washing machine of claim 10, wherein the first suspensions have a damping force larger than that of the second suspensions, and are installed at one side of the casing where a large load occurs due to a load of a driving unit provided to drive an inner tub, thereby preventing collision between the casing and the outer tub at the time of an initial operation of the washing machine.

12. The washing machine of claim 11, wherein each of the first suspensions comprises: a damper cap mounted to the outer tub; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and a base cap mounted to a lower side of the damper cap.

13. The washing machine of claim 12, wherein each of the second suspensions comprises: a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and a base cap mounted to a lower side of the damper cap, wherein an air hole is formed at the damper cap or the base cap.

14. The washing machine of claim 12, wherein each of the second suspensions comprises: a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support the connection rod or the damper spring; and an extension spring installed below the damper base, and configured to outwardly extend an edge of the damper base, wherein an interval between the damper cap and the damper base is constantly maintained in a circumferential direction by the extension spring.

Description:

RELATED APPLICATION

The present invention relates to subject matter contained in priority Korean Application No. 10-2007-0076580, filed on Jul. 30, 2007, which is herein expressly incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine, and more particularly, to a washing machine capable of preventing an outer tub inclined toward a driving unit from colliding with an external casing at the time of an initial vibration occurrence, and capable of effectively reducing excessive vibration by asymmetrically installing suspensions, in which the outer tub is supported by installing suspensions having a relatively large damping force at a side where a large load occurs due to the driving unit, etc.

2. Description of the Background Art

Generally, a washing machine serves to wash laundry by using a softening process by detergent, a frictional process by water stream occurring as washing blades rotate, an impact process by washing blades, etc. By using a motor as a main driving force, the washing machine performs a washing process, a rinsing process, and a dehydrating process so as to wash laundry with using detergent and water. The washing machine comprises a motor serving as a driving unit, a mechanical part for transmitting energy to laundry, a controller for controlling washing processes, a water supply unit for supplying water, and a water drain unit for discharging water.

The washing machine is largely divided into a cylinder type, an agitator type, and a pulsator type according to washing methods.

According to the agitator type, an agitator protruding from the center of an inner tub with a wing shape is rotated in right and left directions thus to wash laundry. According to the pulsator type, laundry is washed by using turbulent stream occurring as a disc-shaped pulsator is rotated. According to the cylinder type, water, detergent, and laundry are put into a drum having a plurality of protrusions, and then are rotated with a low speed in a horizontal axis, thereby washing laundry by an impact occurring as the laundry is lifted and dropped by the protrusions.

FIG. 1 is a schematic sectional view of a washing machine in accordance with the related art, FIG. 2 is a sectional view taken along line ‘II-II’ of FIG. 1, and FIG. 3 is a sectional view of a suspension of the washing machine of FIG. 1

Referring to FIGS. 1 and 2, a washing machine 10 comprises a body or a casing 1 that forms appearance; an outer tub 2 mounted in the casing 1; an inner tub 3 mounted in the outer tub 2; and a suspension apparatus or suspensions 4 each having another end connected to a lower side of the outer tub 2, and configured to support the outer tub 2.

A driving unit 12 for driving the inner tub 3 is installed below the outer tub 2. The driving unit 12 is connected to a speed change portion 14 installed at a lower central part of the outer tub 2 by a belt 16.

Here, the driving unit 12 is installed so as to be eccentric from the center (C) of the outer tub 2 by a predetermined distance (W).

Referring to FIG. 3, the suspension 4 comprises a damper cap 4b installed below the outer tub 2; a connection rod 4a having one end penetrating the damper cap 4b, and another end mounted to the casing 1; a damper spring 4c mounted in the damper cap 4b, and configured to absorb vibration from the outer tub 2; and a damper base 4d installed at a lower opening of the damper cap 4b, and configured to support the connection rod 4a or the damper spring 4c.

A narrow air gap 5 is formed between the damper cap 4b and the damper base 4d, and extension springs 6 are installed below the damper base 4d.

The extension springs 6 serve to extend a lower portion of the damper base 4d.

Each of the extension springs has both ends separated from each other, i.e., a non-consecutive circumference. Since non-consecutive part does not come in contact with the damper base 4d, the extension springs 6 do not consecutively contact a lower portion of the damper base 4d.

The suspensions 4 serve to reduce a very large vibration or amplitude occurring by a resonance at the time of excessive vibration (i.e., at the time of starting a dehydration process).

According to a basic vibration reducing mechanism, vibration occurring from the inner tub 3 is reduced by a viscous damping force occurring as air is discharged through an air hole (not shown) of the damper cap 4b, and by a frictional damping force occurring as the damper cap 4b and the damper base 4d come into friction with each other. Here, excessive vibration or amplitude is reduced by a viscous damping force.

However, the conventional mechanism has the following problems.

An air gap 5 which allows a reciprocation of the washing machine is formed between the damper cap 4b and the damper base 4d. If the washing machine 10 is used by approximately 1000 cycles, a clearance of the air gap 5 increases to allow a large amount of air to leak through the air gap 5. This causes a viscous damping force to be greatly lowered, thereby not reducing excessive vibration.

Furthermore, since the driving unit 12 is eccentrically installed from the center (C) below the outer tub 2, an initial static deflection of the outer tub 2 is toward the driving unit 12.

More concretely, as shown in FIG. 2, an interval (D2) between the casing 1 disposed at a side of the driving unit 12 and the outer tub 2 is narrower than an interval (D1) facing the D2. Accordingly, collision between the casing 1 and the outer tub 2 may occur when the washing machine is initially operated.

SUMMARY OF THE INVENTION

Therefore, it is a first object of the present invention to provide a washing machine capable of preventing an outer tub inclined towards a driving unit from colliding with a casing at the time of an initial vibration occurrence, by supporting the outer tub by installing suspensions having a relatively large damping force at one side where a large load occurs due to the driving unit, etc., and by installing suspensions having a relatively small damping force at another side facing the one side.

It is a second object of the present invention to provide a washing machine capable of preventing an outer tub from colliding with a casing by installing suspensions having a large damping force at a side of a driving unit by mounting a base cap to a lower opening of a damper cap, in which a small amount of air leakage occurs even if an air gap between the damper cap and the damper base is widened.

It is a third object of the present invention to provide a washing machine capable of absorbing excessive vibration occurring at a side having a large initial deflection due to a load of a driving unit, by asymmetrically arranging suspensions to each other.

It is a fourth object of the present invention to provide a washing machine capable of effectively reducing excessive vibration by mounting suspensions having an extension spring to an opposite side to a side of a driving unit, the extension spring consecutively contacting a damper base in a circumferential direction.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a washing machine having a plurality of suspensions installed between a casing and an outer tub, in which the suspensions have different damping forces.

Here, the suspension installed at one side of the casing has a damping force different from that of the suspension installed at another side facing the one side. Preferably, the suspension installed at one side of the casing where an interval between the casing and the outer tub is relatively narrower due to inclination of the outer tub has a damping force larger than that of the suspension installed at another side facing the one side.

Under the above configuration, the outer tub inclined toward the casing is prevented from colliding with the casing at the time of an initial driving, thereby preventing noise occurrence and reducing excessive horizontal vibration from the outer tub.

A driving unit for driving an inner tub installed in the outer tub is mounted to a lower surface of the outer tub, and the driving unit is eccentrically installed at a side toward which the outer tub is inclined.

When the driving unit is eccentrically installed from the center of the outer tub, the outer tub is inclined due to a weight or load of the driving unit, thereby narrowing an interval between the casing and the outer tub. However, since suspensions having a damping force are installed at a side of the driving unit, collision between the casing and the outer tub can be prevented.

Each of the suspensions having a relatively large damping force (hereinafter, will be called as ‘first suspensions) among the suspensions includes a damper cap mounted to the outer tub; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support another end of the connection rod or one end of the damper spring; and a base cap mounted to a lower side of the damper cap. As the base cap is mounted to the lower side of the damper cap, air leakage through an air gap between the damper cap and the damper base is prevented thus to increase a viscous damping force.

Each of the suspensions having a relatively small damping force (hereinafter, will be called as ‘second suspensions) among the suspensions includes a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support another end of the connection rod or one end of the damper spring; and a base cap mounted to a lower side of the damper cap. An air hole through which a viscous damping force occurs is formed at the damper cap or the base cap.

Since air is leaked through the air hole formed at the damper cap or the base cap, the second suspensions have a smaller viscous damping force than the first suspensions.

Instead of the second suspensions, one or more third suspensions may be used as suspensions having a relatively small damping force. The third suspension include a damper cap mounted to the outer tub installed in the casing; a connection rod having one end installed via the damper cap; a damper spring mounted in the damper cap; a damper base mounted to one end of the damper cap, and configured to support another end of the connection rod or one end of the damper spring; and a base cap mounted to a lower side of the damper cap. An air hole through which a viscous damping force occurs is formed at the damper cap or the base cap.

Here, the third suspensions have a smaller viscous damping force than the second suspensions due to no base cap provided thereat.

The second suspensions may be used as suspensions having a relatively large damping force, and one or more third suspensions may be used as suspensions having a relatively small damping force. That is, with consideration of an initial deflection or a load of the washing machine, suspensions having different damping forces may be selected from the first to third suspensions.

According to another aspect of the present invention, there is provided a washing machine having a plurality of suspensions installed between a casing and an outer tub, in which so as to reduce excessive vibration of the washing machine, the suspensions installed at one side of the casing and the suspensions installed at another side facing the one side have damping forces asymmetrical to each other.

Here, the suspensions having a relatively large damping force are installed at a side where a large load occurs due to a driving unit for driving an inner tub inside the outer tub. Accordingly when the washing machine is initially operated, collision between the casing and the outer tub is prevented.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

In the drawings:

FIG. 1 is a schematic sectional view of a washing machine in accordance with the related art;

FIG. 2 is a sectional view taken along line ‘II-II’ of FIG. 1;

FIG. 3 is a sectional view of a suspension of the washing machine of FIG. 1;

FIG. 4 is a schematic sectional view of a washing machine according to the present invention;

FIG. 5 is a sectional view of a suspension of the washing machine of FIG. 4 according to a first embodiment of the present invention;

FIG. 6 is a perspective view of a damper base mounted to the suspension of FIG. 5;

FIG. 7 is a sectional view of a suspension of FIG. 5 according to a second embodiment of the present invention;

FIGS. 8A to 8C are views respectively showing an extension spring mounted to the damper base of FIG. 6;

FIGS. 9A to 9C are modification examples of the extension spring of FIG. 8; and

FIG. 10 is an experimental graph comparing excessive horizontal and vertical vibration of the present invention with that of the related art when suspensions of the present invention and the related art are used, respectively.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Hereinafter, configurations and operations of a washing machine according to a first embodiment of the present invention will be explained in more detail with reference to the attached drawings.

Explanation for well-known configurations or functions will be omitted. And the same reference numerals will be given to the same parts as those of the aforementioned configurations, and their detailed explanation will be omitted.

FIG. 4 is a schematic sectional view of a washing machine according to the present invention.

As shown in FIG. 4, a washing machine 100 comprises a casing 110 that forms appearance; an outer tub 120 mounted in the casing 110, and configured to store washing water therein; an inner tub 130 mounted in the outer tub 120, and configured to receive laundry; and suspensions 140 installed at four corners of the casing 110, and configured to elastically support the outer tub 120.

A driving unit 12 (refer to FIG. 1) for driving the inner tub 130 is installed below an outer surface of the outer tub 120. The driving unit 120 is installed so as to be eccentric from the center of the outer tub 120, and is connected to a speed change portion 14 (refer to FIG. 1) installed at a central part of the outer tub 120 by a belt 16 (refer to FIG. 1).

Here, the driving unit may be implemented as a direct drive motor. The motor may include various motors such as an induction motor.

An interval (D4) between the casing 110 and the outer tub 120 at a side (‘A’ in FIG. 4) where the driving unit is installed is narrower than an interval (D3) between the casing 110 and the outer tub 120 at a side (‘B’) facing the ‘A’. That is, the outer tub 120 is inclined toward the side of ‘A’ due to weight of the driving unit.

Here, suspensions having a damping force larger than that of suspensions installed at the side of ‘B’ are mounted to the side of ‘A’ toward which the outer tub 120 is inclined. Accordingly, suspensions having a relatively small damping force are mounted to the side of ‘B’. That is, a damping force of the suspensions installed at the side of ‘A’ is different from, or asymmetric to a damping force of the suspensions installed at the side of ‘B’.

Under the configuration, collision between the outer tub 120 and the casing 110 due to excessive horizontal vibration when the washing machine 100 is initially operated can be prevented.

Hereinafter, in more detail, will be explained configurations of the suspensions 140 installed at the side of ‘A’ where an interval between the outer tub 120 and the casing 110 is relatively narrower, and the suspensions 140′ installed at the side of ‘B’ facing the side of ‘A’.

FIG. 5 is a sectional view of a suspension of the washing machine of FIG. 4 according to a first embodiment of the present invention, FIG. 6 is a perspective view of a damper base mounted to the suspension of FIG. 5, and FIG. 7 is a sectional view of a suspension of FIG. 5 according to a second embodiment of the present invention.

FIG. 5 shows the suspension 140 installed at the side of ‘A’ where an interval between the outer tub 120 and the casing 110 is relatively narrower. Referring to FIG. 5, the suspension 140 includes a damper cap 142 mounted to the outer tub 120; a connection rod 141 having one end installed via the damper cap 142; a damper spring 143 mounted in the damper cap 142; a damper base 145 mounted to one end of the damper cap 142, and configured to support another end of the connection rod 141 or one end of the damper spring 143; and a base cap 146 mounted to a lower opening of the damper cap 142. For convenience, the suspensions 140 will be referred to as ‘first suspensions’.

An upper portion of the damper cap 142 of the first suspensions 140 is upwardly extending like a neck of a bottle, and the upwardly extending portion encompasses the connection rod 141.

The connection rod 141 is positioned inside the damper cap 142 via a through hole 142a formed at the upper portion of the damper cap 142. One end of the through hole 142a is protruding to inside of the damper cap 142, thereby constituting a connection rod supporting portion 142c that encompasses and supports the connection rod 141.

One end of the connection rod 141 is fixed to a connection rod fixing portion 145c of the damper base 145. Preferably, the connection rod fixing portion 145c is protruding from an upper side of the damper base 145, and has a predetermined height so as to stably support the connection rod 141.

A plurality of protrusions 145d are formed on an outer circumferential surface of the connection rod fixing portion 145c. The plurality of protrusions 145d are forcibly inserted into an inner circumferential surface of the damper spring 143, thereby stably supporting the damper spring 143.

A lower end of the damper spring 143 is supported by the protrusions 145d on the surface of the connection rod fixing portion 145c, and an upper end of the damper spring 143 is supported by a spring supporting portion 142b formed on an inner surface of the damper cap 142.

At an initial state, i.e., at a state that the washing machine is not provided is with washing water or laundry therein, the damper spring 143 preferably maintains a compressed state, and the damper base 145 for supporting the damper spring 143 is positioned at an inner side of a lower end of the damper cap 142. The reason is as follows. Once laundry or washing water is introduced into the inner tub 130, the damper spring 143 is extended due to a weight of the laundry or washing water, and the damper base 145 moves to a lower side of the damper cap 142. Here, if the damper base 145 is positioned at the end of the damper cap 142, laundry, etc. is introduced into the inner tub 130, and the damper base 145 is completely separated from the damper cap 142.

Here, the damper spring 143 is preferably a compression coil spring, but is not limited thereto. As the damper spring 143, any elastic means having an elastic restoration force and configured to absorb or attenuate vibration can be used. For example, a rubber member may be used to connect one end of the connection rod 141 and the connection rod fixing portion 145c of the damper base 146. Also, a rubber pillar (not shown) having a cavity therein may be used as the damper s spring 143.

When the damper spring 143 is used as an elastic means, one end of the connection rod 141 positioned in the damper cap 142 is preferably disposed in the damper spring 143.

Between an inner surface of the damper cap 142 and an outermost circumference of the damper base 145, a minute air gap 150 is formed. A frictional damping process occurs through the air gap 150.

The base cap 146 is mounted to a lower opening of the damper cap 142, and is coupled to the damper cap 142 by a hook (not shown) formed at the damper cap 142 with receiving the damper base 145 therein. In order to ensure a sealed state inside the damper cap 142, the damper cap 142 and the base cap 146 may be coupled to each other by forming a screw thread at a coupling portion therebetween.

Extension springs 148, 149 may be mounted to a lower side of the damper base 145. The damper base 145 will be explained in more detail with reference to FIG. 6. The connection rod fixing portion 145c connected to one end of the connection rod 141 is formed above the damper base 145, and the plurality of protrusions 145d are provided on an outer circumferential surface of the connection rod fixing portion 145c. A spring supporting portion 145e is integrally formed below the connection rod fixing portion 145c. Preferably, the spring supporting portion 145e has a wide area so as to sufficiently support the damper spring 143.

A skirt portion 145f having an area wider than that of the spring supporting portion 145e is integrally formed below the spring supporting portion 145e.

Here, the skirt portion 145f is in a thin cylindrical shape having a predetermined height, and an air gap 150 is formed between an outer surface of the skirt portion 145f and an inner surface of the damper cap 142.

A plurality of slits 145b are formed at the skirt portion 145f in a height direction, and extension springs 148 and 149 are mounted to an inner surface of the skirt portion 145f. Here, in order to prevent the extension springs 148 and 149 from being separated from the skirt portion 145f, a concaved groove (not shown) or a stopping jaw 145a is formed on an inner surface of the skirt portion 145f.

Since the extension springs 148 and 149 are mounted to the skirt portion 145f with a diameter decreased than the original diameter, they have an elastic restoration force to restore the original diameter. Due to the elastic restoration force, the edge of the damper base 145 is extended to an inner surface of the damper cap 142. That is, the skirt portion 145f is pushed to the damper cap 142 thus to be extended. Here, the skirt portion 145f can have a large extension degree by having the plurality of slits 145b. The skirt portion 145f can be outwardly extended even by the extension springs 148 and 149 having a small elastic restoration force.

Either the stopping jaw 145a or the slits 145b, or both the stopping jaw 145a and the slits 145b can be formed with consideration of the size of the damper base 145, or an elastic force of the extension springs 148 and 149, etc.

Since a lower opening of the damper cap 142 of the first suspension 140 is blocked by the base cap 146, a viscous damping force by air inside the damper cap 142 is very large. When the inner tub 130 is in a severely excessive vibration state, air inside the damper cap 142 is not discharged out thus to damage the damper cap 142. In order to prevent the damage of the damper cap 142, an air hole (not shown) is preferably formed at the damper cap 142.

Accordingly, the most preferably, the first suspensions 140 are installed at the side of ‘A’.

Hereinafter, the suspensions 140′ having a smaller damping force than the first suspensions 140 will be explained in more detail with reference to FIG. 7. For convenience, the suspensions 140′ of FIG. 7 will be referred to as ‘second suspensions’. The second suspension 140′ has the same configuration as the first suspension 140, except that an air hole 147 is formed at a base cap 146′ so as to implement a smaller damping force than the first suspension 140. That is, while air inside the damper cap 142 is discharged out through the air hole 147 of the base cap 146′, a viscous damping force occurs. Accordingly, the second suspensions have a smaller damping force than the first suspensions 140.

If an air hole (not shown) is formed at the damper cap 142 of the first suspension 140, an additional air hole (not shown) has to be formed at the damper cap 142 of the second suspension 140′ so as to implement a damping force of the second suspension 140 to be smaller than that of the first suspension 140.

More concretely, the second suspension 140′ has the same configuration as the first suspension 140, except that an air hole 147 is further formed at a base cap 146′. The air hole 147 may be formed at the damper cap 142 or the base cap 146′ of the second suspension 140′. The air hole 147 of the damper cap 142 may be blocked by a lubricant such as grease deposited onto the surface of the damper cap 142, whereas the air hole 147 of the base cap 146′ has a low possibility to be blocked by a lubricant. One or more suspensions having a smaller damping force than the second suspensions 140′ may be mounted to an opposite side to the first suspensions 140, which will be referred to as ‘third suspensions’.

The third suspensions have the same configuration as the first suspensions 140 or the second suspensions 140′ from which the base caps 146 and 146′ are removed, respectively. That is, the third suspension has the damper cap 142 with a lower side thereof opened. However, the damper base 145 is mounted to the third suspension.

The third suspension may occur air leakage through an air gap 150 between the damper cap 142 and the damper base 145. Therefore, it is important to manage abrasion of the air gap 150. To this end, the extension springs 148 and 149 have to make an important role. Hereinafter, the extension springs 148 and 149 of the third suspension will be explained in more detail. The configuration of the extension springs of the first suspensions 140 and the second suspensions 140′ are equal to that of the third suspensions.

FIGS. 8A to 8C are views respectively showing an extension spring mounted to the damper base of FIG. 6, and FIGS. 9A to 9C are modification examples of the extension spring of FIG. 8.

As shown in FIG. 8, the extension spring 148 of the third suspension is in a ring shape having a consecutive circumference. That is, when viewed from the front, the extension spring 148 is in an approximate ring shape (refer to FIG. 8B), whereas when viewed from the side, the extension spring 148 has some parts overlapping each other in a longitudinal direction (refer to FIG. 8C). That is, the extension spring 148 is wound so that both ends thereof can overlap each other by a predetermined length.

Here, curved portions 148a and 148b are formed at both ends of the extension spring 148 toward the center of the extension spring 148. The curved portions 148a and 148b are used to mount the extension spring 148 to the damper base 145. When the curved portions 148a and 148b are pressed at both sides, a diameter of one side of the extension spring 148 is decreased to allow the extension spring 148 to be easily mounted to the damper base 145. Then, when the curved portions 148a and 148b are released, the extension spring 148 is restored to the original state. At the same time, the skirt portion 145f is outwardly extended.

As shown in FIG. 8A, the extension spring 148 consecutively contacts lower side surfaces of the damper base 145, i.e., the skirt portion 145f due to its consecutive circumference, and contacts all parts of the skirt portion 145f. Accordingly, the air gap 150 between the damper cap 142 and the damper base 145 is uniformly maintained in a circumferential direction of the extension spring 148, thereby preventing non-uniform clearance of the air gap 150.

As the extension spring 148 having a consecutive circumference is used, the skirt portion 145f of the damper base 145 is prevented from being flatly abraded even when coming into friction with an inner surface of the damper cap 142.

FIGS. 9A to 9C are modification examples of the extension spring of FIG. 8.

Referring to FIG. 9, the extension spring 149 has the same shape as the extension spring 148 of FIG. 8, except that there are no curved portions at both ends thereof.

When viewed from the front, the extension spring 149 is in a ring shape having a consecutive circumference (refer to FIG. 9B), whereas when viewed from the side, the extension spring 149 has some parts overlapping each other in a longitudinal direction (refer to FIG. 9C). The extension spring 149 can maintain its elastic restoration force for a long time due to its overlapping parts, and can be easily mounted to the skirt portion 145f. That is, once the extension spring 149 is held by a user with its central part being pressed, a diameter of one side of the extension spring 149 is decreased to allow the extension spring 149 to be easily mounted to the skirt portion 145f.

The extension spring 148 of FIG. 8 has the same shape as the extension spring 149 of FIG. 9, except that the curved portions 148a and 148b are formed at both ends thereof. Accordingly, the extension springs 148 and 149 can be fabricated by using the same molding pattern. More concretely, the extension spring 148 of FIG. 8 can be fabricated by a molding pattern of the extension spring 149 of FIG. 9, and then by forming two curved portions at both ends thereof in a pressing manner, etc. Accordingly, one molding pattern can be used to fabricate two types of extension springs, which enhances the productivity.

The third suspension can constantly maintain the air gap 150 between the damper cap 142 and the damper base 145 by using the extension springs 148 and 149, thereby increasing a viscous damping force by air leaked through the air gap 150.

The third suspension is implemented so that the damper cap 142 has a lower opening to which the base caps 145 and 145′ have not been mounted, thereby occurring air leakage more than the first suspensions 140 or the second suspensions 140′. Accordingly, the third suspensions have a damping force smaller than that of the first suspensions 140 or the second suspensions 140′.

When suspensions having different damping forces are to be installed, suitable suspensions are selected from the first to third suspensions thus to be arranged so that damping forces can be asymmetric to each other centering around the center of the outer tub 120.

That is, when the first suspensions are used to have a large damping force, either the second suspensions 140′ or the third suspensions are selected as suspensions having a small damping force. On the contrary, when the second suspensions 140′ are used to have a large damping force, the third suspensions are selected as suspensions having a small damping force. For these selections, a load of a driving unit or a mechanical part, or an initial deflection of the outer tub have to be considered.

FIG. 10 is an experimental graph comparing excessive horizontal and vertical vibration or amplitude of the present invention where the first suspensions 140 are mounted to the side of ‘A’ and the second suspensions 140′ are mounted to the side of ‘B’, with that of the related art where suspensions symmetrical to each other are used. Referring to FIG. 10, the horizontal axis shows horizontal and vertical vibration of the outer tub 120, whereas the vertical axis shows an amplitude (mm) according to the vibration. Referring to FIG. 10, according to the present invention where the first suspensions 140 are mounted to the side of ‘A’ toward which the outer tub 120 is inclined and the second suspensions 140′ are mounted to the side of ‘B’ facing the ‘A’, a horizontal amplitude was increased by 1.01 mm than the conventional one, but a vertical amplitude was decreased by 5.27 mm from 19.84 mm to 14.57 mm. That is, when the suspensions 140 and 140′ of the present invention are used, excessive vibration is decreased by approximately 27% to the maximum than the conventional one.

So far, the present applicant explained about the washing machine, but the present invention may be applied not only to the washing machine, but also to various fields such as a washing machine compatible with a drier, a dryer, or a combined washing system.

Also, in the present invention, it was explained that the outer tub is inclined to one side due to eccentric installation of a motor such as the driving unit. However, when a direct drive motor is used, or when a load of the driving unit or the mechanical part is not completely symmetrical to each other in a circumferential direction centering around the center of the outer tub, the outer tub may be inclined to one side. The latter case may be applied to claims of the present invention.

The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments.

As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.