AU773918B2 - Balance weight in drum type washing machine and manufacturing method thereof - Google Patents

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): LG Electronics Inc.

ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Balance weight in drum type washing machine and manufacturing method thereof The following statement is a full description of this invention, including the best method of performing it known to me/us:- (I k' [0001] This application claims the benefit of Korean Application Nos. P2001- 35513 and P2002-20526, respectively filed on June 21, 2001 and April 16, 2002, and which are hereby incorporated by reference.

[0002] The present invention relates to drum type washing machines. More particularly, the present invention relates to balance weights for drum type washing machines that reduce vibration caused by laundry imbalance.

[0003] Generally, a washing machine removes laundry dirt and stains using chemical decomposition and mechanical impact. Modem washing machines are usually one of two basic types, a drum type and a pulsator type. The drum type washing machine is usually more compact than the pulsator type washing machine, has a greater washing capacity, and has reduced laundry entanglements. Thus, demand for drum type washing machines is increasing.

[0004] The construction of a typical drum type washing machine is explained briefly by referring to FIG. 1. As shown, a drum type washing machine includes a tub 2 that is supported by a damper 7 and by a spring 6, which are both attached to a body 1. A rotating cylindrical drum 3 is installed in the tub 2. A driving part 5 is coupled to the drum 3 by a shaft 4. The driving part 5, which is installed at the rear of the tub 3, 2 DC: 102326.1 includes a rotor 5b and a stator 5a. The shaft 4 rotates with the drum 3 and is beneficially directly coupled to the rotor 5b to transfer driving force directly to the drum 3 without that aid of a pulley or belt.

[0005] Still referring to Figure 1, a door 8 is installed at the front of the body 1.

A gasket 9 is installed between the door and drum to maintain the drum 3 airtight. A controller part 10 is installed over the door 8 to enable an operator to control the operation of the washing machine. Additionally, balance weights 14 and 15 are installed on the tub 2 to prevent vibration of the driving part 5 when laundry in the drum 3 is imbalanced.

[0006] The washing machine operates when the turning force of the rotor 5b is transferred to the drum 3 through the washing shaft 4 to rotate the drum 3. Laundry in the drum 3 is lifted up by a baffle 3a so as to fall free due to gavity.

[0007] Referring now to FIG. 2, the balance weights 14 and 15, generically represented by a cement 11 element, are fixed to the tub by a locking boss 12 and by a locking bolt 13. Generally, the balance weights 14 and 15 are made of either cement or cast-iron. A process of making a cement balance weight follows.

[0008] First, a mold having a predetermined shape is disassembled. Cement is then injected into the disassembled mold. Then, the mold is reassembled and the cement is cured by thermal treatment. The mold is then disassembled and the cured and molded cement is removed. The surface of the molded cement is then trimmed and treated with a spray coating. The completed balance weights 14 and 15 are then located on the locking boss 12 and the locking bolt 13 is mated with the locking boss 12 to complete the assembly.

DC: 102326.1 P:\OPERrI8886-02 spedoc-2203/04 -4- [0009] While generally successful, the above process of preparing the balance weights 14 and 15 and fixing them to the tub 2 has problems. For example, the overall process is rather complicated, has low productivity, and is relatively costly. Moreover, cement balance weights 14 and 15 formed and mounted as described suffer from problems related to the locking boss 12 and locking bolt 13 being directly coupled with the cement 11 (which generically represents the balance weights 14 and 15). Relative motion between the cement balance weights 14 and 15 and the locking structure generates dust. Thus, the working environment is degraded and the cement dust can negatively impacts worker's health.

[0010] In contrast to cement weights, cast-iron balance weights require painting to prevent rust, a boring process for forming a locking hole, and a subsequent step of removing metal burrs. Thus, cast-iron balance weights have their own set of fabrication problems. Moreover, cast-iron balance weights 14 and 15 are vulnerable to vibration that unscrews the locking bolt 13.

15 [0011] Therefore, a new cement balance weight would be beneficial. Even more beneficial would be a new cement balance weight that is easier and less costly to fabricate.

0. Still more beneficial would be a new cement balance weight that does not produce cement 0 0.

dust.

P:\OPER\A 48886-02 sp.doc-25/03/04 [0012] Accordingly, the present invention provides a drum type washing machine comprising: a drum connected to a shaft tilted to a horizon direction with the ground; a tube accommodating the drum within and having a balance weight mounted on an outer periphery; and a coupling element attached to the tube through the opening, wherein the balance weight includes: a housing having a roughly rectangular shape and a predetermined inner space, a cement in said inner space, wherein the housing includes: a bottom surface close to the tub, having a step portion that creates a height difference and a leg that has a length that substantially the same as the height difference, an upper surface having a cement injection inlet, i:i: 15 an opening passing through the housing.

[0013] The specification also describes a method of manufacturing a balance weight for the drum type washing machine.

•[0014] Preferably, the housing includes a lower case having a bottom surface for coupling with a tub and a lateral side. The housing then further includes an upper cover for sealing the lower case. Beneficially, such a balance weight further includes a separation prevention mechanism that prevents separation of the upper cover and the lower case and that prevents escape of cement dust.

[0015] Alternatively, the housing is an integral unit having an upper surface with a cement injection inlet, a bottom surface, and a lateral surface between the upper and S. 25 bottom surfaces, wherein the upper, bottom, and lateral surfaces surround a predetermined space inside the housing. The balance weight can include a cover over a cement injection inlet. For example, the cover could be a wire netting solidified by cement.

[0016] Beneficially, the coupling system includes an insertion hole for receiving at least one locking bolt and that extends from the upper surface to the bottom surface.

[0017] The upper surface preferably includes a concave recess that extends from the opening to an edge of the housing.

P:\OPERA l\48886-02 spedoc-25/03/04 -6- [00181 The housing may include at least one air vent. The air vent is preferably formed through the bottom surface. The bottom surface may also include a landing recess that is preferably semicircular.

[0019] Molding can be performed by plastic injection molding to form a lower case and an upper cover, wherein the lower case comprises bottom and lateral surfaces that surround a predetermined space, wherein the lower case includes at least a first insertion hole, and wherein the upper cover seals an opening of the lower case and has a second insertion hole.

[0020] Curing can be performed at room temperature or by the application of steam at a temperature higher than room temperature.

[0021] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

[0022] Accordingly, preferred embodiments of the present invention are directed 15 to a balance weight for a drum type washing machine that substantially obviates one or more problems due to limitations and disadvantages of the related art.

[0023] The specification also describes in relation to the drum type washing machine of the preferred embodiment a low cost balance weight for the drum type washing :i machine and a manufacturing method thereof.

P:OPER\U'48886-02 spc.doc-I2/I2/03 -7- [0024] Another object of the preferred embodiment of the present invention is to provide a balance weight in a drum type washing machine that does less harm while reducing production costs.

[0025] Another object of the preferred embodiment of the present invention is to provide a simple method of manufacturing a balance weight for a drum type washing machine.

[0026] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention by way of example only. In the drawings: [0027] FIG. 1 illustrates a cross-sectional view of a general drum type washing machine according to the related art; [0028] FIG. 2 illustrates a cross-sectional view of a balance weight used in a drum type washing machine according to a related art; [00291 FIG. 3 illustrates a cross-sectional view of a balance weight according to a first embodiment of the present invention; [0030] FIG. 4 illustrates a cross-sectional view of another balance weight according to a first embodiment of the present invention; [0031] FIG. 5 illustrates a top down view of a balance weight according to a 20 second embodiment of the present invention; [0032] FIG. 6 illustrates a bottom view of the balance weight according to the S• second embodiment of the present invention; o0 [0033] FIG. 7 illustrates a cross-sectional view taken along cutting line I-I in FIG. [0034] FIG. 8 illustrates a top downview of a balance weight according to the principles of the present embodiment that is installed on the side of a tub; [0035] FIG. 9 illustrates a top down view of a balance weight according to the principles of the present embodiment that is installed on a front face of a tub; and [00361 FIG. 10 illustrates a process of forming a housing used in the second embodiment of the present invention.

[0037] Reference will now be made in detail to illustrated embodiments of the present invention, examples of which are shown in the accompanying drawings.

Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or to like parts.

[0038] A balance weight according to a first embodiment of the present invention is explained with reference to both FIG. 3 and to FIG. 4. FIG. 3 illustrates a cross-sectional view of a first balance weight according to a first embodiment of the S.present invention, while FIG. 4 illustrates a cross-sectional view of another balance weight according to the first embodiment of the present invention.

[0039] FIG. 3 shows a locking boss 12 that is formed on a tub. In practice, the o• tub might have numerous locking bosses. In FIG. 3 a balance weight is attached to an •upper part of the locking boss 12. The balance weight itself includes a lower case 21 ooo* having both a bottom surface and a lateral surface that surround a predetermined space. Cement 11 is received in the space and held there by the lower case 21. An 8 DC: 102326.1 upper cover 22 seals a top opening of the lower case 21. Thus, the lower case 21 and uipper cover 22 construct a housing that holds cement 1 1.

[0040] The housing (and thus the lower case 21 and upper cover 22) can have any number of shapes, such as a hexahedron, a sphere, or the like. However, the bottom surface of the lower case 2 1 preferably corresponds to the surface of the tub.

[0041] To couple the lower case 2 1 to the upper cover 22, and to couple the housing to the tub, the lower case 21 includes a first insertion hole 21a defined by the lateral surface. A second insertion hole 22a is defined by the upper cover 22. A locking bolt 13 passes through the second insertion hole 22a and couples the locking boss 12 to the balance weight.

[0042] Beneficially, the first insertion hole 21a extends from the bottom surface of the lower case 21 to a location that is equal to or lower than the top of the lateral surface of the lower case 21. Furthermore, the second insertion hole 22a extends from the top of the upper cover 22 downward so as to pass all the way through the first insertion hole 21a. Thus, the outer diameter of the second insertion hole 22a is less than the inner diameter of the first insertion hole 21a. Additionally, an end part 22b of the second insertion hole 22a beneficially fits into a recessed upper end 12a of the locking boss 12. This assists positive coupling of the housing to the tub.

[0043] Since the locking bolt 13 couples to the locking boss 12 through the second insertion hole 22a, and since the second insertion hole 22a penetrates the first insertion hole 21a, the lower case 21 and the upper cover 22 are strongly coupled together. A cross-sectional view of the housing shows a rectangular space having predetermined dimensions that are defined by the lower case 21 and by the upper cover 22. That rectangular space is filed by cement 11.

9 DC: 102326.1 100441] To prevent separation of the ends of the lower case 21 and the uipper cover 22 when cement 11 is placed in the space, the housing beneficially includes a separation prevention mechanism that prevents separation of the ends of the upper cover 22 and the lower case 21. One separation prevention mechanism is shown in the expanded bubble of FIG 3. An undercut 21 b is formed at the end of the lateral surface of the lower case 21. As shown, the undercut 21 b extends inward and covers an edge of the upper surface of the upper cover 22 [0045] Another separation prevention mechanism is shown in the expanded bubble of FIG. 4. As shown, the separation prevention mechanism includes a protrusion 3 lb that extends outward from the lateral surface of a lower case 31. A hook 32c extends from an edge of an upper cover 32 and hooks over the protrusion 3 lb. The length of the protrusion 31 b should be within the elastic range of the hook 32c.

[0046] The undercut 21b, or the protrusion 31b and the hook 32c, depend on the elasticity of the material that forms the lower case 21 or 31 and the upper cover 22 or 32. Beneficially, that material is a synthesized resin material (plastic) having a predetermined elasticity.

[0047] A process of manufacturing the first embodiment balance weight is explained as follows. First, a plastic is injected into a metal mold having a predetermined shape so as to form the lower case and upper cover by injection molding. Thus, the lower case 21 or 31 includes a bottom surface and a lateral surface that surround a predetermined space and that forms a first insertion hole 21a or 3 Ia.

Additionally, an upper cover 22 and 32 having a second insertion hole 22a or 32a is formed by injection molding. Subsequently, cement 11 is injected into the DC: 102326. I predetermined space. Then, the lower case 2 1 or 3 1 and the upper cover 22 or 32 are mated such that the second insertion hole 22a or 32a penetrates the first insertion hole 21a or 3 la, and such that the separation prevention mechanism prevents the housing from separating. The cement 11 is then cured, beneficially by natural curing at room temperature or using steam at a higher temperature. Then, the balance weight is mounted on the locking boss 12 and the locking bolt 13 is screwed into the locking boss 12.

[0048] A balance weight in a drum type washing machine according to a second embodiment of the present invention is explained with reference to Figs. 5-7 and [0049] FIG. 5 illustrates a top down view of a balance weight according to the second embodiment of the present invention, FIG. 6 illustrates a bottom view of the second embodiment, and FIG. 7 illustrates a cross-sectional view taken along line I-I of FIG. [0050] Referring now to FIG. 5 through FIG. 7, a balance weight according to the second embodiment includes a housing 50 having a bottom surface 52, a lateral surface, and an upper surface 51 that surround a predetermined inner space. Cement 11 fills the inner space of the housing [0051] To assist couple the housing 50 to a tub, the housing 50 includes a step 52c on the bottom surface 52. For example, the bottom surface 52 includes a first bottom surface 52a and a lower second bottom surface 52b.

[0052] A cement injection inlet 54 is formed at the center of the upper surface 51. Additionally, at least one air vent 56 is formed through the bottom surface 52. Air in the housing 50 comes out through the vent 56 when cement 11 is injected into the

II

DC: 102326.1 housing 50. While the air vent 56 could be formed through any surface of the housing since the cement 11 is injected through the cement injection inlet 54, the air vent 56 is preferably formed through the bottom surface 52.

[0053] Additionally, a plurality of locking bolt insertion holes 53 are formed near the cement injection inlet 54 of the housing 50 so as to penetrate the upper and bottom surface 51 and 52. Locking bolts can then couple the balance weight to a tub having a locking boss via the locking bolt insertion hole 53. A concave recess 59 is beneficially formed on the upper surface 51. The concave recess 59 is formed outside a locking bolt insertion hole 53 so as to make a smooth flow of resin when the housing 50 is molded. Additionally, a flange 55 is formed at the edge of the cement injection inlet 54. This assists cement 11 injection and prevents cement from overflowing the cement injection inlet 54.

[0054] Additionally, a leg 58 beneficially protrudes from the bottom surface of the housing. The leg 58 compensates for the step when the cement 11 injected by making the housing level. Thus, the leg 58 should protrude the height h between the first and second bottom surface 52a and 52b.

[0055] If strong vibrations are repeatedly transferred to the balance weight by the tub, the cement 11 could break. In that event cement pieces could come out the cement injection inlet 54. To prevent this, a cover 60 (see FIG. 7) is located over the cement injection inlet 54. The cover 60 is preferably a wire netting that is solidified by the cement 11. When the wire netting 60 is solidified by the cement 11, the strength of the cement around the wire netting is greatly improved. Hence, even if strong vibrations are repeatedly applied to the tub, the cement 11 near the cement injection inlet 54 is unlikely to be broken.

12 DC: 102326.1 [00561 In some applications it will be beneficial to stack a number of housings together. However, the flange 55 that protrudes from the upper surface 51 hinders stacking. To overcome this problem, a landing recess 57 (see FIG. 6) is beneficially formed at the bottom surface 52. That landing recess 57 mates with the flange [0057] If the bottom surface 52 of the housing 50 has a step difference, it is sufficient to form the landing recess 57 at the higher bottom surface 52a only. For instance, the landing recess 57 shown in FIG. 6 is formed in the first bottom surface 52a. Beneficially, the landing recess 57 is semicircular.

[0058] As shown in FIG. 8 and FIG. 9, the first and second embodiment balance weights can be installed on the circumference of, or at the front of, the tub 2.

Even though the shapes of the balance weight housings 50 and 70 are different, the structures and functions of the respective components are identical to each other.

[0059] A method of manufacturing the above-constructed balance weight according to the second embodiment of the present invention is explained as follows.

[0060] First a housing is molded using a metal mold having a predetermined shape. The process is as follows.

[0061] FIG. 10 illustrates a process of forming the housing of the second embodiment of the present invention. As shown, a metal mold 100 having a predetermined and desired interior shape is opened. Then, a tube 110 made of a blow molding resin is inserted into the metal mold 100. For example, the blow molding resin could be polypropylene, polyethylene, or the like.

[00621 The metal mold 100 is then closed, and air is blown into the tube 110 through an air nozzle 120. This blows the tube into the mold. The temperature should be maintained at a sufficient temperature so as not to harden the tube 110. As the tube 13DC: 102326.1 DC: 102326.1 110 expands it takes the form of the metal mold 100. Thus, the tube 110 becomes the shape of the housing.

10063] Then, the metal mold 100 is cooled to harden the tube 110. Thus, the housing 50 having the same shape of the inner shape of the metal mold 100 is formed.

Thereafter, the metal mold is opened and the housing is removed.

[00641 Subsequently, cement 11 is injected into the housing 50. As a plurality of air vents 56 are formed at the bottom surface of the housing 50, the cement 11 is injected uniformly without a void caused by an air pocket. The cement 11 inside the housing 50 is then cured, beneficially either at room temperature or by steam having a temperature higher than the room temperature. Thereafter, the balance weight is complete.

[0065] A balance weight for the drum type washing machine according to the preferred embodiments of the present invention and a manufacturing method thereof provides advantages.

[0066] First, the balance weight is formed such that cement is solidified in the housing. Fabrication is simplified and product costs are reduced. Exterior trimming, spray processes, boring, and burr removal are not required (as in the related art).

[0067] Second, the locking bolt does not directly penetrate the cement, thus cement dust is prevented and fabrication workers are provided with a healthy work environment.

[0068] It will be apparent to those skilled in the art than various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

.ooo 14 DC: 102326.1 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims (5)

1. A drum type washing machine comprising: a drum connected to a shaft tilted to a horizon direction with the ground; a tube accommodating the drum within and having a balance weight mounted on an outer periphery; and a coupling element attached to the tube through the opening, wherein the balance weight includes: a housing having a roughly rectangular shape and a predetermined inner space, a cement in said inner space, wherein the housing includes: a bottom surface close to the tub, having a step portion that creates a height difference and a leg that has a length that substantially the same as the height difference, :i:i 15 an upper surface having a cement injection inlet, an opening passing through the housing.

2. The drum type washing machine of claim 1, wherein the upper surface includes a concave recess that extends from the opening to an edge of the housing.

3. The drum type washing machine of claim 1 or 2, wherein the housing includes at least one air vent. S 4. The drum type washing machine of claim 3, wherein the air vent is formed through :25 the bottom surface. The drum type washing machine of any one of claims 1-4, further comprising a flange formed around a cement injection inlet.

6. The drum type washing machine of claim 5, wherein the bottom surface includes a landing recess. P:\OPER\Ar48886-02 spc.doc-25/03/04

17- 7. The drum type washing machine of claim 6, wherein the landing recess is semicircular. 8. The drum type washing machine of any one of claims 1-7, further comprising a cover on a cement injection inlet. 9. The drum type washing machine of claim 8, wherein the cover is a wire netting solidified by cement. A drum type washing machine substantially as hereinbefore described with reference to Figures 3-10 and/or Examples. Dated this 25th day of March, 2004 LG Electronics Inc. S* By DAVIES COLLISON CAVE Patent Attorneys for the Applicant *0*