KR20230155391A - Washing machine - Google Patents

Abstract

The present invention relates to a washing machine in which a cylindrical drum made by processing a metal plate is configured to rotate about a horizontal axis, wherein the drum holds the metal plate at a plurality of points spaced apart along the circumferential direction when viewed from the front. Each is provided with a lifter formed by processing, and the lifter includes first and second protrusions formed by pressing the metal plate to protrude 10 mm or more inside the drum and extending along the longitudinal direction of the drum, The first protrusion and the second protrusion are aligned on a moving line along the longitudinal direction of the drum, and the front end of the second protrusion is spaced apart from the rear end of the first protrusion.

Description

washing machine{WASHING MACHINE}

The present invention relates to a washing machine having a drum that rotates about a horizontal axis, and particularly to a washing machine having a lifter formed by processing the drum.

Washing machines configured so that a drum into which laundry is loaded rotates around a horizontal axis are widely known. For example, in the washing machine disclosed in Korean Patent Publication No. 10-2011-0022359 (Prior Art 1), a lifter disposed on the inner peripheral surface of a drum lifts laundry when the drum rotates.

In a washing machine with a lifter installed on the drum, the laundry is lifted to a certain height and then dropped due to the physical force applied by the lifter to the laundry, or a friction effect is induced between the lifter and the laundry. Therefore, a certain level of washing power can be secured, and this washing power is less affected by the amount of water filled in the drum, the amount of laundry (weight), and the rotation speed (RPM) of the drum compared to a structure without a lifter. am.

US registered patent US 8,893,532 (Prior Art 2) discloses a drum for a washing machine having a linear elevation formed on the inner circumferential surface. The drum of prior art 2 is made by plastic processing a metal sheet to form the protruding structure, then rolling the metal sheet into a round shape and joining both ends together. However, since the protruding structure is convex on the inner circumferential surface of the drum but concave on the outer circumferential surface (i.e., a form processed by locally bending a metal plate), a drum with a large number of such protruding structures formed in the circumferential direction is vulnerable to distortion. there is. In particular, when the drum is rotated with the cloth placed in the drum tilted to one side, excessive vibration that occurs may cause deformation (distortion) of the drum, and in severe cases, the part where both ends of the metal plates are joined. There is a risk of a safety accident resulting in destruction.

The problem to be solved by the present invention is, first, in a washing machine provided with a drum formed by rolling a metal plate into a cylindrical shape and joining both ends, and having a lifter protruding into the drum by plastic processing the metal plate, the structure of the lifter The aim is to provide a washing machine that strengthens the rigidity of the drum by improving the.

Second, even if the drum rotates eccentrically and causes vibration, the present invention provides a washing machine that prevents deformation (particularly, distortion) of the drum and destruction of the joint at both ends of the metal plate.

Third, to provide a washing machine that minimizes deformation due to bending moment in the longitudinal direction (X direction, see FIG. 9) of the drum.

The present invention relates to a washing machine in which a cylindrical drum made by processing a metal plate is configured to rotate around a horizontal axis. The drum is provided with lifters formed by processing the metal plate at a plurality of points spaced apart along the circumferential direction when viewed from the front.

The lifter includes first and second protrusions formed by pressing the metal plate to protrude 10 mm or more inside the drum and extending along the longitudinal direction of the drum.

The first protrusion and the second protrusion are aligned on a moving line along the longitudinal direction of the drum, and the front end of the second protrusion is spaced apart from the rear end of the first protrusion.

The gap between the rear end of the first protrusion and the front end of the second protrusion may be 15 mm or more.

The drum may have a reinforcement groove extending in the circumferential direction formed in an area corresponding to the gap between the rear end of the first protrusion and the front end of the second protrusion. The reinforcement groove may have a length longer than the width of the lifter. When the drum is viewed from the front, the reinforcement groove may cross the lifter in a circumferential direction. The reinforcement groove may be 70 mm or more.

A plurality of reinforcement grooves may be spaced apart along the longitudinal direction of the drum. The number of reinforcement grooves may be three or more.

The depth of the reinforcement groove may be 3 mm or more and less than 10 mm.

The drum may be flat between the plurality of reinforcement grooves.

The reinforcement groove may be formed on the inner peripheral surface of the drum to make the outer peripheral surface of the drum convex.

The lifters may be formed at three points arranged at equal intervals with respect to the center of the drum.

At least one of the first protrusion and the second protrusion may protrude 10 to 30 mm inside the drum.

The protrusion height of at least one of the first protrusion and the second protrusion may be gradually increased.

A plurality of embossings may be formed between the plurality of points, protruding 5 mm or less to the inside of the drum.

The drum may have flat front and rear bands formed at the front and rear ends, respectively. The lifter may be disposed between the front band portion and the rear band portion.

The metal plate is made of stainless steel and may have a thickness of 0.4 to 0.6 mm.

The washing machine of the present invention, first, forms a lifter integrally with the drum, and the lifter includes two protrusions spaced apart from each other in the longitudinal direction of the drum, so that it is equipped with a lifter consisting of a single long protrusion conventionally. Compared to drums, the rigidity of the drum is improved.

Second, by reinforcing the rigidity of the drum, it is possible to prevent the drum from being deformed (particularly, distorted) even by vibration generated when the drum rotates, and thus, the joint at both ends of the metal plate constituting the drum is destroyed. It has the effect of preventing safety accidents in advance.

Third, by minimizing deformation due to bending moment in the longitudinal direction (X direction, see FIG. 9) of the drum, stability can be secured even when the drum rotates at higher speeds than before.

1 is a side cross-sectional view of a washing machine according to an embodiment of the present invention.
Figure 2 schematically shows a cross section of the washing tank shown in Figure 1.
Figure 3 schematically shows a longitudinal cross-section of the washing tank shown in Figure 1.
Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3.
Figure 5 is a graph showing the wrapping speed according to the height of the protrusion.
Figure 6 is a diagram used to explain the correlation between the height of the protrusion and the side angle.
Figure 7 shows the flow of foam according to the rotation speed of the drum.
Figure 8 shows the stress distribution in the drum of Comparative Example 1 (a) and the stress distribution in the drum of Comparative Example 2 (b).
Figure 9 shows a portion of an expanded drum according to an embodiment of the present invention.
Figure 10 shows the bending moment and the resulting deformation form when the lifter is made up of one long protrusion (a), and the bending moment and the resulting deformation form when the lifter consists of two protrusions (b). (c) shows the bending moment and the resulting deformation in the case where a reinforcing groove is formed between the protrusions (c).
Figure 11 is a graph showing the improvement rate of drum rigidity according to the depth, number, and length of reinforcement grooves.
Figure 12 shows the stress distribution of the drum in the case where the lifter includes two protrusions, with (a) and without (b) the reinforcement groove.
Figure 13 shows a portion of an expanded drum according to another embodiment of the present invention.
FIG. 14 is a cross-sectional view taken along line XIV-XIV of FIG. 13.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The present embodiments are merely provided to ensure that the disclosure of the present invention is complete and to be understood by those skilled in the art. It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Referring to Figure 1, a washing machine according to an embodiment of the present invention includes a casing (1) forming the exterior, a water storage tank (3) disposed in the casing (1) and storing washing water, and a water storage tank (3) that can be rotated. It includes a washing tub 4 into which laundry is placed, and a motor 9 that rotates the washing tub 4.

The washing tub 4 includes a front cover 41 with an opening for loading and unloading laundry, a cylindrical drum 42 arranged approximately horizontally and the front end coupled to the front cover 41, and a rear end of the drum 42. Includes a rear cover 43 that is coupled. The rotation axis of the motor 9 may pass through the rear wall of the water tank 3 and be connected to the rear cover 43. A through hole 42h (see FIG. 13) may be formed in the drum 42 so that water can exchange between the washing tank 4 and the water storage tank 3.

The washing tub 4 is rotated around a horizontal axis. Here, “horizontal” does not mean geometrical horizontal in the strict sense, and as shown in FIG. 1, even when tilted at a predetermined angle to the horizontal, it is closer to horizontal than vertical, so the washing tub 4 is Let us say that it rotates around a horizontal axis.

The drum 42 is provided with lifters 20 formed by processing the metal sheet at a plurality of points spaced apart along the circumferential direction when viewed from the front. The plurality of lifters 20 extend long in the front-back direction on the inner peripheral surface of the drum 42, and are preferably arranged at a constant angle (equal angle) with respect to the center O of the drum 42.

Each lifter 20 has a first protrusion 21 and a second protrusion 22 formed by protruding a metal plate 10 mm or more inside the drum 42 and pressing it to extend along the longitudinal direction of the drum 42. Includes.

The first protrusion 21 and the second protrusion 22 are aligned on a line along the longitudinal direction of the drum 42, and the front end of the second protrusion 22 is the rear end of the first protrusion 21. It is separated from The rigidity of the drum 42 is improved by forming the lifter 20 as a combination of two protrusions 21 and 22 spaced apart from each other, rather than forming the lifter 20 as one long piece. In this regard, let's look at Figure 8.

Figure 8 shows the stress distribution in the drum of Comparative Example 1 (a) and the stress distribution in the drum of Comparative Example 2 (b). In the drum 42 of Comparative Example 1 shown in (a) of FIG. 8, two lifters 421 and 422 consisting of one protrusion are spaced apart in the circumferential direction. As shown in (a) of FIG. 8, it can be seen that when an external force is applied to the drum 42, stress is concentrated on the lifters 421 and 422. (The redder the stress, the greater the stress.)

On the other hand, the drum 42 of Comparative Example 2 shown in (b) of FIG. 8 has a lifter by a combination of the first protrusion 423 and the second protrusion 424 arranged along the longitudinal direction of the drum 42. is configured, and in this case, it can be seen that the stress acting on the protrusions 423 and 424 is small compared to Comparative Example 1. That is, according to this experiment, compared to the case where the lifter 20 consists of one long protrusion, the lifter 20 is composed of two protrusions extending in the front and rear directions of the drum 42 and spaced apart from each other at a predetermined distance. In some cases, it can be seen that there is an effect of dispersing stress. The gap is preferably 15 mm or more.

Figure 9 shows a portion of an expanded drum according to an embodiment of the present invention. Figure 10 shows the bending moment and the resulting deformation form when the lifter is made up of one long protrusion (a), and the bending moment and the resulting deformation form when the lifter consists of two protrusions (b). (c) shows the bending moment and the resulting deformation in the case where a reinforcing groove is formed between the protrusions (c).

9 to 10 , in the case where the lifter 20 includes a first protrusion 21 and a second protrusion 22 as in the embodiment, when an external force is applied to the drum 42, the first protrusion Bending moments acting in the X, Y, and Z directions in the area between (21) and the second protrusion 22 are indicated. And, τ1, τ2, and τ3 shown in FIG. 10 indicate the stress acting on the drum, and “+” and “-” indicate the direction in which the bending moment or stress acts.

As shown in FIG. 10, when the lifter 20 is made of one long protrusion (a), the bending moment (M1-x) acting in the X direction is the largest compared to the other cases (M1-x > M2-x > M3-x), it can be seen that although the deformation in case (b) is smaller than that in case (a), the deformation in case (c) is smaller than in case (b). That is, extending in the circumferential direction between the first protrusion 21 and the second protrusion 22 (i.e., an area corresponding to the gap between the rear end of the first protrusion 21 and the front end of the second protrusion 22). Forming the reinforcement groove 25 is advantageous in securing the rigidity of the drum 42. This can be seen by comparing the stress distribution in the case with (a) and without (b) the reinforcement groove shown in FIG. 12.

The reinforcement groove 25 is formed on the inner peripheral surface of the drum 42. Specifically, the reinforcement groove 25 is formed by bending or pressing the metal plate forming the drum 42. Accordingly, a concave surface is formed on the inner peripheral surface of the drum 42 by the reinforcement groove 25, and a convex surface is formed at a corresponding point on the outer peripheral surface of the drum 42.

However, the reinforcement groove 25 may be formed on the outer peripheral surface of the drum 42, and in this case, a concave surface is formed on the outer peripheral surface of the drum 42, and a convex surface is formed on the inner peripheral surface of the drum 42. A face will be formed.

The influence of the reinforcement grooves 25 on the rigidity of the drum 42 varies depending on the depth, number, and length of the reinforcement grooves 25. Referring to FIG. 11, the rigidity of the drum 42 is higher when the depth of the reinforcement groove 25 is 3 mm rather than 2 mm, and when the number of reinforcement grooves 25 is 3 rather than 2, the reinforcement groove 25 ) can be seen to be more improved when the length is 70mm than when it is 50mm.

In particular, it can be seen that the effect on the rigidity of the drum 42 is greater in the order of length, number, and height of the reinforcement grooves 25. Considering this, it is desirable that the length of the reinforcing grooves 25 be 70 mm or more, the number of reinforcement grooves 25 should be multiple (preferably 3 or more), and the depth should be 3 mm or more and less than 10 mm (since it should be lower than the protrusions 21 and 22).

The plurality of reinforcement grooves 25 are spaced apart along the longitudinal direction of the drum 42, and the space between adjacent reinforcement grooves 25 may be flat.

On the inner peripheral surface of the drum 42, between a pair of adjacent lifters 20 randomly (or randomly) selected from among the plurality of lifters 20, a protruding structure is higher than any one of the plurality of lifters 20. does not exist. In other words, no matter how a pair of adjacent protrusions 20 are taken, there is no structure protruding higher than the protrusions 20 between them.

A plurality of embossings 425 may be provided on the inner peripheral surface of the drum 42. The embossing 425 is a protruding structure formed on the inner peripheral surface of the machine, and the height of the embossing 425 protruding inside the drum 42 is lower than that of any of the plurality of lifters 20. On the inner peripheral surface of the drum 42, there is no protruding structure other than at least one of the plurality of embossings 425 between a pair of adjacent protrusions arbitrarily selected from among the plurality of protrusions 20.

The embossing 425 may be formed integrally with the drum 42, and the plurality of embossings 425 do not need to be constant in size and/or height, and as shown in FIG. 3, the plurality of embossings 425 may be formed integrally with the drum 42. A plurality of embossings 425 may be formed whose size gradually increases or decreases in the longitudinal direction. The height of the embossing 425 is 5 mm or less.

Meanwhile, the drum 42 is made by processing a metal plate of stainless steel, and may have a thickness of 0.4 to 0.6 mm. The cylindrical drum 42 can be formed by rolling up a rectangular metal plate and joining (for example, welding) both ends to each other. The metal plate is preferably STS430 series, but is not necessarily limited thereto.

A laundry inlet is formed in the front of the casing (1), and a door (2) for opening and closing the laundry inlet is rotatably provided on the casing (1). A water supply valve (5), a water supply pipe (5), and a water supply hose (8) may be installed inside the casing (1). When the water supply valve (5) is opened and water is supplied, the washing water that has passed through the water supply pipe (5) is mixed with detergent in the dispenser (14) and then can be supplied to the water storage tank (3) through the water hose (8).

The input port of the pump 11 is connected to the water storage tank 3 by the discharge hose 10, and the discharge port of the pump 11 is connected to the drain pipe 12. The water discharged from the water storage tank 3 through the discharge hose 10 is pumped by the pump 11, flows along the drain pipe 12, and is then discharged outside the washing machine.

Figure 7 shows the flow of foam according to the rotation speed of the drum. Hereinafter, refer to FIG. 7. In the process of rotating the drum 42, the forces acting on the cloth inserted into the drum 42 are centrifugal force (Fc) caused by the rotation of the drum 42, gravity (Fg), and force applied from the lifter 20. Lifting force (Fn) can be mentioned.

As shown in (a) of FIG. 7, when the drum 42 is rotated at low speed, the centrifugal force (Fc) is relatively small, so the fabric is lifted to a certain height by the lifter 20, and the centrifugal force (Fc) ) and the support force (Fn) cannot handle the gravity (Fg), the gun is separated from the lifter 20 and falls (separated from the drum 42 and falls down, or falls while rolling along the drum 42). This movement of the fabric is defined as rolling motion.

In Figure 7(b), the rotational speed of the drum 42 is greater than in Figure 7(a), and the gun rises to a higher position and then falls. In particular, the position where the cloth falls is at a rotation angle of 90 degrees or more from the lowest point of the drum, and this movement of the cloth is hereinafter defined as tumbling motion.

When the rotational speed of the drum 42 further increases, the gun does not fall even at the highest point of the drum 42 and rotates while sticking to the drum 42, as shown in (c) of FIG. 7. The lowest value of the rotation speed of the drum 42 that can cause wrapping of the type shown in (c) of FIG. 7 is hereinafter defined as the wrapping speed (Vf).

When there is no lifter 20 in the drum 42, the support force (Fn) is eliminated, so only centrifugal force (Fc) and gravity (Fg) remain as the forces acting on the cloth. In this case, the packing speed (vf) can be obtained from the balance equation that equates centrifugal force and gravity. Since the mass of the cloth is canceled on both sides of the above balance equation, the cloth loading speed (Vf) is independent of the mass of the cloth and becomes a value dependent on the diameter of the drum, and is a fixed value that can be obtained by knowing the diameter of the drum.

However, when the lifter 20 is formed on the drum 42, the support force Fn acts more, so the wrapping speed Vf is generally lower than when the lifter 20 is not applied. The laundry speed (Vf) at this time will vary depending on the structure of the lifter 20, but can be used in a typical washing machine in which the drum 42 has a diameter of 24 to 27 inches and the height of the lifter (protrusion) is 40 mm or more. The speed (Vf) is approximately 5560rpm or less.

Washing power is determined by several factors such as flexion, friction, and drop of the cloth. These factors are closely related to the rotational speed of the drum 42, and in particular, the drop of the cloth or relative to the drum, such as rolling or tumbling motion. Movement (or flow within the drum) is induced, and the higher the rotation speed of the drum 42 at this time, the more advantageous it is to enhance washing power.

In this respect, it is necessary to find a way to increase the wrapping speed (Vf) while rotating the drum 42 at a higher speed than before. In this respect, the present invention provides The height (h1, that is, the height protruding inside the drum 42) was lowered compared to the prior art to reduce the bearing force (Fn). At this time, the height (h) of at least one of the first protrusion 21 and the second protrusion 22 is 2.0 to 6.0% of the diameter (D) compared to the diameter (D) of the drum 42, and in absolute value, It is approximately 10 to 30 mm. At this time, the height (h) of the protrusions 21 and 22 from the base to the top does not necessarily have to increase at a constant rate. That is, at least one of the first protrusion 21 and the second protrusion 22 can be raised stepwise from the base to the top.

Figure 2 schematically shows a cross section of the washing tank shown in Figure 1. Figure 3 schematically shows a longitudinal cross-section of the washing tank shown in Figure 1. Figure 4 is a cross-sectional view taken along line IV-IV of Figure 3. Hereinafter, refer to FIGS. 2 to 4.

When viewed from the front of the drum 42, the lifter 20 has a length in the longitudinal direction (or front-to-back direction) of the drum 42 that is longer than the width of the drum 42 in the circumferential direction. These lifters 20 are arranged symmetrically with respect to the center of the drum 42. In the embodiment, three lifters 20 are arranged at an isometric angle of 120 degrees with respect to the center of the drum 42, but this is not necessarily limited. .

The lifter 20 is formed integrally with the drum 42. For example, the lifter 20 can be formed by plastic processing a metal plate.

In order to smoothly lift the fabric by expanding the contact area between the lifter 20 and the fabric (or the area where the lifter 20 applies support force (Fn) to the fabric), the length of the lifter 20 must be appropriate. In this respect, the present invention suggests that the length L1 from the front end to the rear end of the lifter 20 is 50 to 100% of the length L0 of the drum 42. In particular, even when the length (L1) of the lifter (20) is close to 50% of the length (L0) of the drum (42), the lifter (20) can be arranged encompassing the front and rear of the drum (42). It is better to install the lifter 20 so that the front end of the drum 42 is spaced rearward from the front end of the drum 42.

Specifically, the drum 42 is formed with a flat front band portion 42a and a rear band portion 42b at the front and rear ends, respectively, and the lifter 20 may be disposed between the front band portion 42a and the rear band portion 42b. there is.

Meanwhile, referring to FIG. 4, the lifter 20 has a first side portion forming a positive first angle (+θ) with the inner circumferential surface at a first point P1 on the inner circumferential surface of the drum 42 when viewed from the front. (210) and a second side portion 220 forming a negative second angle (-θ) with the inner circumferential surface at a second point (P2) spaced in the circumferential direction from the first point (P1) on the inner circumferential surface. You can. Here, at least one of the first angle and the second angle is 17.5 degrees or less. Hereinafter, angle θ is defined as a side angle.

In the embodiment, the first side portion 210 and the second side portion 220 are symmetrical, and the first angle and the second angle have the same size, but are not necessarily limited thereto.

Figure 5 is a graph showing the wrapping speed (Vf) according to the height of the protrusion. Figure 6 is a diagram used to explain the correlation between the height of the protrusion and the side angle. First, Figure 5 shows that, as described above, the higher the height (h) of the lifter 20, the lower the wrapping speed (Vf). However, when the height (h) of the lifter 20 is 5 mm or less, the laundry attachment speed (Vf) is high, so it seems that washing performance is good, but in reality, this is not the case.

When the height (h) of the lifter (20) is 5 mm or less, the support force (Fn) of the lifter (20) is so small that the gun rolls almost in place when it does not reach the drum (42) gun loading speed (Vf). It shows the behavior of moving only up and down within a very small rotation angle section, but suddenly begins to stick to the drum 42 when it reaches the above-described packing speed (Vf). The flow of this type of fabric becomes worse as the amount of fabric becomes smaller, and the washing power is poor because the fabric is not smoothly induced to drop or bend. For this reason, the height h of the lifter 20 should be at least 5 mm greater, and preferably greater than 10 mm.

In addition, the height (h) of the lifter 20 is preferably 30 mm or less. In this case, the wrapping speed (Vf) is approximately 65 rpm or more, and the wrapping speed is approximately 18% compared to 55 rpm at the conventional height of 40 mm. An increase in speed can be expected.

The preferred values of the lower limit (LSL) and upper limit (USL) of the height (h) of the lifter 20 for each diameter (D) of the drum 42 are as follows. Here, the diameter of the drum 42 may be any of the inner diameter of the drum 42, the outer diameter, or an intermediate value between the inner diameter and the outer diameter.

Drum diameter (D(mm)) LSL(mm) USL(mm) 484 10.0 30.0 515 10.6 30.9 575 11.8 34.5 590 12.1 35.4

Meanwhile, referring to FIG. 6, it can be seen that in the area (A) where the height (h) of the lifter 20 is less than 5 mm and the side angle (θ) is less than 17.5 degrees, rolling or tumbling of the gun cannot be caused. Therefore, even if the height h of the lifter 20 is 5 mm, the side angle θ is preferably at least 17.5 mm to prevent rolling or tumbling. The area B shown in Figure 6 is the lifter ( 20) indicates an area where the height (h) is 5 mm or more and the side angle (θ) is 17.5 or more, and it is possible to cause rolling or tumbling motion of the fabric in this area. However, washing by such motion The height of the lifter 20, where performance can be further enhanced, is preferably 10 mm or more.

Meanwhile, the curve shown as a dotted line in FIG. 6 connects the threshold values of the side angle (θ) that can cause rolling or tumbling.

In the above, preferred embodiments of the present invention have been shown and described, but the present invention is not limited to the specific embodiments described above, and can be used in the technical field to which the invention pertains without departing from the gist of the present invention as claimed in the patent claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be understood individually from the technical idea or perspective of the present invention.

Claims (15)

casing;
a water storage tank disposed within the casing;
a washing tank rotatably disposed within the water storage tank, the rotation center line of which passes through the rear of the casing; and
Including a motor that rotates the washing tub,
The washing machine is:
Cylindrical drum;
A rear cover coupled to the rear end of the drum and connected to the motor; and
It is provided on the drum and includes a plurality of lifters protruding inside the drum,
At least one lifter among the plurality of lifters:
first protrusion; and
It includes a second protrusion spaced rearward from the first protrusion,
The plurality of lifters
A washing machine formed integrally with the drum and protruding 10 to 30 mm inside the drum.
According to claim 1,
The rear end of the first protrusion is located ahead of the front end of the second protrusion.
According to claim 1,
The first protrusion and the second protrusion are aligned in the front-back direction.
According to claim 1,
Further comprising a reinforcement groove disposed between the first protrusion and the second protrusion,
The reinforcement groove is disposed between the rear end of the first protrusion and the front end of the second protrusion in the front-back direction.
According to clause 4,
The reinforcement groove extends along the circumferential direction of the drum and has a length longer than the width of the lifter.
According to clause 5,
The reinforcement groove is,
A washing machine in which the lifter moves circumferentially across the drum when viewed from the front.
According to clause 5,
A washing machine in which the length of the reinforcement groove is 70 mm or more.
According to clause 4,
The reinforcement groove is,
A washing machine in which a plurality of drums are spaced apart along the longitudinal direction of the drum.
According to clause 4,
A washing machine in which the depth of the reinforcement groove is 3 mm or more and less than 10 mm.
According to clause 8,
The drum is a washing machine where the space between the plurality of reinforcement grooves is flat.
According to clause 8,
The reinforcement groove includes a first reinforcement groove,
The first reinforcement groove is,
A washing machine formed on the inner peripheral surface of the drum to make the outer peripheral surface of the drum convex.
According to claim 1,
A washing machine wherein the plurality of lifters are arranged at equal intervals along the circumferential direction of the drum.
According to claim 1,
The lifter is a washing machine in which the protrusion height increases step by step.
According to claim 1,
The drum includes an embossing area in which a plurality of embossings protruding by 5 mm or less are formed between the plurality of lifter areas,
A washing machine in which no protruding structure higher than any one of the plurality of lifters exists in the embossing area.
According to claim 1,
A washing machine wherein the gap between the rear end of the first protrusion and the front end of the second protrusion is 15 mm or more.

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