Drum in dryer and method for fabricating the same

Drum in a laundry dryer, and method for fabricating the same, wherein the drum in a dryer including a steel layer which forms a base, anti-corrosive metal film on the steel layer, and an organic film on the metal film, and the method includes the steps of providing a metal sheet having a steel layer, a metal film thereon, and an organic film thereon, rolling the metal sheet into a cylinder, and welding abut joining parts, to form a cylindrical drum, reducing diameters of opposite ends of the cylindrical drum, forming beads in a middle portion of the cylindrical drum except the reduced diameter portions, and hemming opposite edges of the cylindrical drum of the reduced diameter portions, to fold the opposite edges, respectively, thereby reducing production cost significantly, preventing easy visibility of dents in an inside circumferential surface of the drum with naked eyes different from the related art, preventing occurrence of rust, and improving bonding strength of the felt which is a sealing material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application Nos. P2004-0053033 filed on Jul. 8, 2004, and P2004-0056195 filed on Jul. 20, 2004 which are hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a drum in a dryer, and a method for fabricating the same, and more particularly, to a drum in a laundry dryer, and a method for fabricating the same.

2. Discussion of the Related Art

In general, the dryer is an apparatus for drying a drying object, such as clothes introduced into a drum with hot air heated by an electric heater, a gas burner, or the like, of which demand keeps increasing, recently.

FIG. 1illustrates an exploded perspective view of a related art dryer.

Referring toFIG. 1, the related art dryer is provided with a drum1in a cabinet (not shown) that forms an exterior of the dryer. The drum1is cylindrical with opened front and rear, having a belt groove2along an outside circumferential surface for winding a belt (not shown) thereon to be driven by a separate driving source.

The drum1has a chamber5for holding the drying object therein, with a plurality of lifts6each projected a length from an inside circumferential surface of the chamber5, for lifting/dropping the drying object during rotation of the drum1, to turn the drying object upside down, for fast drying of the drying object.

The drum1forms a drying chamber5therein for drying laundry, and has a plurality of lifts6therein for lifting/dropping the drying object in the drying chamber5to upside down the drying object during rotation of the drum1for enhancing a drying efficiency.

The drum1is provided with a front supporter7and a rear supporter9to a front and a rear thereof opposite to each other, respectively. The front supporter7and the rear supporter9close the front and the rear of the chamber5and as well as support the front and the rear of the drum1, respectively.

There is felt10, a sealing material, between the front supporter7and the drum1, and the rear supporter9and the drum1for preventing water from leaking therefrom. The felt is bonded with an adhesive800for metal for better attachment of the sealing material to a metal, such as stainless steel, or steel.

Or course, the front supporter7and the rear supporter9are provided with a plurality of rollers (not shown) at the front and the rear of the drum1for supporting the drum1, respectively.

The front supporter7has an opening8for making the drying chamber5in communication with an outside of the drying chamber5. The opening8is opened/closed by a door, selectively. The rear supporter9is provided with a hot air supply duct12in communication with the drying chamber5as a passage for supplying hot air to the chamber5.

There is an outlet assembly13at one side of the front supporter7under the opening8in the front supporter7as a passage for escaping of air from the drying chamber5. The outlet assembly13has a lint filter14fitted thereto. The lint filter14removes foreign matters (for an example, thread wastes, or dust) from the air escaping from the drying chamber5.

There is a lint duct15in communication with the outlet assembly13, extended to an inside of the lint filter14. Connected to the lint duct15, there is a blower17, for drawing out air from the drying chamber5through the lint duct15. A blower housing18has one side in communication with the lint duct15, and the other side connected to an exhaust pipe19. Accordingly, the air from the drying chamber5passed through the lint duct15is discharged to an outside of the drying chamber5through the exhaust pipe19by the blower17.

In the meantime, the hot air supply duct12has an inlet connected to a guide funnel16. The guide funnel16guides the hot air produced by burning the gas toward the inlet of the hot air supply duct.

In the meantime, in the related art, the drum applied to the dryer is fabricated by the following process.

Referring toFIG. 2, at first, a sheet of stainless steel is rolled into a cylinder, and abutting joining parts thereof are welded. Next, a diameter of a middle portion of the cylindrical drum is expanded, leaving opposite end portions as they are. In this instance, the middle portion of the drum is expanded as dies positioned on an inside thereof respectively press assigned sections of an inside circumferential surface of the drum, outwardly.

Then, beads are formed in the middle portion of the expanded drum after the expansion. Then, front and rear edges of the drum are hemmed.

However, the related art method for fabricating the drum has the following problems.

In the related art method for fabricating a drum in a dryer, the middle portion of the drum is expanded by pressing the inside circumferential surface of the middle portion of the drum with the dies. Therefore, after finishing fabrication of the drum, traces of the dies remain on the drum, resulting in a poor outer appearance. Also, as a circular shape of the drum is impaired, noise and vibration is generated during rotating the drum.

In the meantime, reasons of causing such a problem will be reviewed in detail.

As the dies mounted individually, and separately in the drum push the middle portion of the drum from an inside to an outside of the drum in a state diameters of the drum at various axial positions of the drum are hardly consistent right after the rolling and welding of the metal sheet, to expand more at a portion the diameter is small, and less at a portion the diameter is great, the traces are formed at the boundary.

Moreover, due to a difference of the expansion, an exterior of the drum is not smooth, and the diameters in the middle portion varies along axial positions of the drum, leading to cause substantial differences of roundness between the axial positions of the drum, to increase vibration and noise of the dryer having the drum applied thereto, to impair product reliability.

Along with this, the related art drum in a dryer causes the following problems due to properties of the material.

The stainless steel of the drum in the dryer makes cost of the drum very expensive. The glossy stainless steel drum is liable to form dents in an inside circumferential surface easily visible with naked eyes, formed by metal buttons attached to clothes, or coins, or shoe drying rack during mounting/dismounting.

Along with this, the drum of stainless steel is liable to make consumers misunderstood that the dryer is defective when red rust is formed on the surface of the stainless steel drum.

Moreover, the related art drum in a dryer has difficulty in protecting a surface of the drum during forming the drum because there is no portion that lubricates between the die and the sheet.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a drum in a laundry dryer, and a method for fabricating the same that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a drum in a laundry dryer, and a method for fabricating the same, which can make that dents in an inside circumference of the drum are not liable to be seen by naked eyes, and rust on the inside surface of the drum is not liable to form, can fabricate the drum at a substantially low cost, and can enhance bonding strength of the felt which prevents hot air from leaking.

Another object of the present invention is to provide a drum in a laundry dryer, and a method for fabricating the same, which leaves no traces of die separation, and improves an overall roundness of the drum, for improving reliability of the dryer when the drum is applied to the dryer.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a drum in a dryer includes a steel layer which forms a base, anti-corrosive metal film on the steel layer, and an organic film on the metal film.

Preferably, the anti-corrosive metal film and the organic film on the metal film are applied to both sides of the steel layer.

In another aspect of the present invention, a drum in a dryer includes a cylindrical body portion having a welded portion butt welded at butt parts, opening potions at opposite ends of the body each having a diameter smaller than a diameter of the body portion, bead portions formed in the body portion for reinforcing of strength the body, and hemmed portions at opening portions of the drum respectively having edges thereof folded, wherein each of the body portion, the opening portions, and the bead portions includes a steel layer which forms a base, anti-corrosive metal film on the steel layer, and an organic film on the metal film.

In another aspect of the present invention, a method for fabricating a drum in a dryer includes the steps of providing a metal sheet having a steel layer which forms a base, a metal film thereon, and an organic film thereon, rolling the metal sheet into a cylinder, and welding abut joining parts, to form a cylindrical drum, reducing diameters of opposite ends of the cylindrical drum, forming beads in a middle portion of the cylindrical drum except the reduced diameter portions, and hemming opposite edges of the cylindrical drum of the reduced diameter portions, to fold the opposite edges, respectively.

In another aspect of the present invention, a method for fabricating a drum in a dryer includes the steps of providing a steel sheet, rolling the steel sheet into a cylinder, and welding abut joining parts, to form a cylindrical drum, reducing diameters of opposite ends of the cylindrical drum, forming beads in a middle portion of the cylindrical drum except the reduced diameter portions, and hemming opposite edges of the cylindrical drum of the reduced diameter portions to fold the opposite edges respectively, coating a metal film on circumferential surfaces of the drum so as to include at least an inside circumferential surface thereof for preventing corrosion, and coating an organic film on the metal film.

In another aspect of the present invention, a drum in a dryer includes a steel layer which forms a base, an anti-corrosive metal film on the steel layer, an organic film on the metal film, felt bonded on a predetermined portion of the organic film, and plastic adhesive between the organic film and the felt for bonding the felt thereto.

In another aspect of the present invention, a drum in a dryer includes a cylindrical body portion having a welded portion butt welded at butt parts, opening potions at opposite ends of the body each having a diameter smaller than a diameter of the body portion, bead portions formed in the body portion for reinforcing of strength the body, and hemmed portions at opening portions of the drum respectively having edges thereof folded, wherein each of the body portion, the opening portions, and the bead portions includes a steel layer which forms a base, anti-corrosive metal film on the steel layer, and an organic polymer film on the metal film, and plastic adhesive is applied to edges of the opening portions, and felt is bonded to the edges of the opening with the plastic adhesive inbetween to wrap the edge.

In another aspect of the present invention, a method for fabricating a drum in a dryer includes the steps of providing a metal sheet having a steel layer which forms a base, a metal film thereon, and an organic film thereon, rolling the metal sheet into a cylinder, and welding abut joining parts, to form a cylindrical drum, reducing diameters of opposite ends of the cylindrical drum, forming beads in a middle portion of the cylindrical drum except the reduced diameter portions, and hemming opposite edges of the cylindrical drum of the reduced diameter portions, to fold the opposite edges respectively, coating plastic adhesive on the hemmed portions of the cylindrical drum, and bonding felt on the hemmed portions where the plastic adhesive is coated.

In another aspect of the present invention, a method for fabricating a drum in a dryer includes the steps of providing a steel sheet, rolling the steel sheet into a cylinder, and welding abut joining parts, to form a cylindrical drum, reducing diameters of opposite ends of the cylindrical drum, forming beads in a middle portion of the cylindrical drum except the reduced diameter portions, and hemming opposite edges of the cylindrical drum of the reduced diameter portions to fold the opposite edges respectively, coating a metal film on circumferential surfaces of the drum so as to include at least an inside circumferential surface thereof for preventing corrosion, coating an organic film on the metal film, coating plastic adhesive on inside and outside of the hemmed portions of the cylindrical drum, and bonding felt on the hemmed portions where the plastic adhesive is coated.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3illustrates a section of a drum showing a material configuration of the drum in accordance with a preferred embodiment of the present invention, including a steel layer100which forms a base, anti-corrosion metal films110on the steel layer100, organic film120on the metal films110, felt10which are sealing members bonded on predetermined portion of the organic films120, and plastic adhesive800aplaced between the organic films and the felt10for bonding the felt.

It is preferable that the anti-corrosive metal film110on the steel layer100, and the organic film120on the metal film110are applied to opposite surfaces, i.e., upper, and lower sides of the steel layer.

It is also preferable that the felt10is bonded to wrap around opposite edges of the drum with the plastic adhesive800a. The plastic adhesive800amay be one selected from epoxy, polyester, epoxy-polyester, polychloroprene, nitrile rubber, and so on.

Meanwhile, thoughFIG. 3illustrates that the anti-corrosive film110on the steel layer100and the organic film120on the metal film110are applied to the upper side, and the lower side of the steel layer100, if the metal film and the organic film are applied only to one side of the steel layer, the drum is fabricated that the organic film120is on an inside of the drum, and the steel layer100is on an outside of the drum.

A method for fabricating a drum of above materials in accordance with a preferred embodiment of the present invention will be outlined with reference toFIGS. 4A and 4B.

FIG. 4Aillustrates a block diagram showing the steps of a method of fabricating a drum in accordance with a preferred embodiment of the present invention, andFIG. 4Billustrates a reference diagram showing states of a drum in the steps of the method for fabricating a drum ofFIG. 4A.

Referring toFIGS. 4A and 4B, the method for fabricating a drum in a dryer includes the steps of forming a cylindrical drum1, reducing diameters of opposite ends1aof the cylindrical drum1, forming beads1bin a middle portion except the opposite ends1aof the cylindrical drum1, hemming opposite edges of the opposite ends of the cylindrical drum1by folding the opposite edges, applying plastic adhesive800ato inside and outside surfaces of the opposite edges of the opposite ends of the cylindrical drum, and bonding felt10to the plastic adhesive800aapplied to the opposite edges.

In the step of forming the drum1, a metal sheet having the steel layer100which forms the base, the metal film100on the steel layer100, and an organic film120on the metal film110is provided, and rolled into a cylinder, and abutting joining parts are welded. That is, the joining parts are butt-welded with a plasma-TIG welder.

The steps of a method for fabricating a drum in accordance with a preferred embodiment of the present invention will be described in more detail in association with a drum forming apparatus.

FIG. 5illustrates a block diagram showing the steps of a method of fabricating a drum in accordance with a preferred embodiment of the present invention, in more detail, andFIGS. 6A to 6Hillustrate reference state diagrams each showing a drum and a forming apparatus as the steps of a method for fabricating a drum progresses.

The drum forming apparatus used for forming the drum1includes an upper die assembly40having a motor30, an upper cam41coupled to a shaft of the motor30, an upper core die42mounted to be expandable and contractable in a radial direction along the upper cam41, and an upper outer die43mounted spaced outwardly from the upper core die42so as to be movable in up/down directions independent from the upper core die42; a middle die assembly50having a middle cam51on a shaft in line with the shaft of the motor30, and a middle core die52mounted expandable and contractable in the radial direction along the middle cam51having escape grooves520in an outside surface; a lower die assembly60having the same configuration with the upper die assembly40but positioned opposite to the upper die assembly40; and a press (not shown) for applying a pressure to the upper die assembly40.

That is, the lower die assembly60has a lower cam61mounted on a shaft passed through the middle core die52, a lower core die62mounted to be expandable or contractable in the radial direction along the lower cam61, and a lower outer die63spaced outwardly from the lower core die62so as to be movable in up and down directions, independently.

The drum is formed by above drum forming apparatus according to the following method.

Referring toFIG. 6A, a cylindrical drum1is loaded on the drum forming apparatus by inserting the drum1on an outside of the middle core die52of the drum forming apparatus.

In this instance, the cylindrical drum1inserted on the outside of the middle core die52is held by the middle core die52and the lower core die62. The cylindrical drum1may be formed by rolling a metal sheet and welding abutting joining parts, or other known methods.

After loading the cylindrical drum1on the outside of the core dies in the apparatus for forming the drum, the upper die assembly40is pressed down by the press (not shown), such that an upper edge of the drum1is inserted between the upper core die42and the upper outer die43of the upper die assembly40, to perform the step of reducing a diameter of an upper end portion of the drum1(seeFIG. 6B).

In this instance, the upper end portion of the drum1is deformed by a pressure in a fashion a diameter of the drum is reduced following an inside surface profile of the upper outer die43having a shape in complementary to an outside surface of the upper core die42.

If the upper die assembly40keeps moving down in a state the diameter reduction of the upper end portion of the drum1is finished, the lower end portion of the drum1is inserted between the lower core die62and the lower outer die63of the lower die assembly60, to perform the step of reducing a diameter of the lower end portion of the drum (seeFIG. 6C).

Subsequently, after completion of reduction of diameters of the lower and upper end portions of the drum1, the retracting step of the upper outer die43, and the lower outer die63is performed (seeFIG. 6D).

Then, beads1bare formed in predetermined positions of the drum1excluding the opposite ends1athereof (seeFIG. 6E).

In formation of the beads1bin the body of the cylindrical drum1, the motor30of the drum forming apparatus is put into operation to rotate the core dies, and, under this state, the rollers70on an outside of the drum1are moved to respective escape grooves520, and press an outside circumferential surface of the drum1to deform portions pressed by the roller70according to forms of the grooves520, to form the beads.

Then, after formation of the beads1bis finished, opposite edges of the drum1are folded, i.e., hemmed (seeFIG. 6F).

After all the steps of forming the drum is finished as the hemming of the opposite edges of the finished, the core dies42,52and62are contracted in an arrow direction on the drawing, to cast off the drum1(seeFIG. 6G). Accordingly, as interference between the drum1and the core dies are prevented, the drum1can be moved out of the core dies.

In this instance, before the core dies are contracted, the lower outer die63retracted outwardly is moved to a position at which the lower outer die63can support a bottom end of the drum1.

If interference even in moving upward is prevented as the upper die assembly40is moved up after the interference between the core dies and the drum1are prevented, the drum can be taken out of the apparatus (seeFIG. 6H).

Then, not metal adhesive, but plastic adhesive800a, is applied to an inside and outside of the opposite edges (i.e., the hemmed portions) of the drum, and felt10is bonded to wrap around opposite edges of the drum (seeFIG. 7).

Thus, in a case the felt10is bonded to the drum, instead of metal adhesive of the related art, the plastic adhesive800ais used, because the metal adhesive of the related art impairs adhering capability of the felt to the drum due to the organic film on the surface of the drum.

In this instance, since the felt10has a form of a “⊂” or “⊃” section substantially (see the enlarged part inFIG. 7), the felt10is inserted on the edge, and bonded to the edge of the drum with the plastic adhesive800a, to as a sealing member when the drum is applied to the dryer.

The reduction of diameter of opposite ends of the drum1instead of expansion of the middle portion of the drum1resolves, not only the problem of the poor outer appearance of the drum caused by traces of separate core molds remained at the middle portion of the drum1, but also the problems of dropping roundness of the middle portion of the drum since the middle portion of the drum1is left intact.

Accordingly, if the drum of the present invention is applied to the dryer, the outer appearance of the drum can be maintained smooth, and minimized vibration and noise.

In the meantime,FIG. 7illustrates a front view of a drum having a method for fabricating a drum of the present invention applied thereto.

Referring toFIG. 7, the drum1in a dryer includes a cylindrical body portion having a welded portion butt welded at butt parts of a metal sheet, opening potions at opposite ends of the body each having a diameter smaller than a diameter of the body portion, bead portions formed in the body portion for reinforcing of strength the body, and hemmed portions at opening portions of the drum respectively each having a felt10bonded thereon with plastic adhesive800a.

The metal sheet has a thickness of 0.5˜0.8 mm, and, more preferably, 0.55˜0.7 mm.

An inside diameter (or an outside diameter) ratio of the body portion to the opening portion of the drum1is made to be greater than 0.9, and more preferably 0.93˜0.94.

A depth “C” from the outside diameter of the body portion to the outside diameter of the opening portion is made to be below 25 mm. That is, a depth of diameter reduction “C” is made to be below 25 mm.

The anti-corrosion metal film110coated on the steel layer100of the metal sheet may be formed of aluminum or a zinc merely, or an alloy of the aluminum and zinc. Of course, composition of the aluminum and the zinc may be equal or variable. The film of aluminum or zinc may be applied by melting, and enhances resistance to corrosion and wear. The film of molten zinc coating prevents corrosion of the steel layer as the zinc itself is corroded instead of the steel layer even if the steel layer100is exposed, locally. The film of molten aluminum coating has high chemical resistance, high endurance, high sulfurization resistance, and high wear resistance.

The organic film120, on the anti-corrosive metal film110of the metal sheet, is formed of a polymer, such as synthetic polymer of urethane, polyester, and so on, or epoxy-polyester. The organic film120performs lubrication at a part the dies and the metal sheet are in contact during pressing, to improve workability.

In summary, the present invention permits not only save cost by applying the anti-corrosion metal coating on general steel, but also improves formability in the pressing by means of the organic film, and the double surface treatment of the metal film and the organic film permits to improve corrosion resistance performance of the surface of the drum, to maintain an initial surface state for a long time.

In the meantime, an anti-vibration band (not shown) of rubber or metal may be attached to an outside wall of the body portion or the bead portions. Different from the drum inFIG. 4or7, a width, or a number of the bead portions may be varied with type of capacity of the dryer.

Though the opening portions can be formed by reducing a diameter of the drum, different from this, the opening may be formed by expanding a diameter of the body portion. For easy hemming of the opposite edges of the drum, predetermined lengths of non-welding portions may be provided at the opposite edges of the welding portions.

The requirement that the thickness of the metal sheet of the drum1is to be within a range of 0.5˜0.8 mm has the following implications.

If the thickness of the metal sheet is below 0.5 mm, the base metal is liable to tear during the reduction or expansion of the diameter of the drum. Moreover, if the thickness of the metal sheet is below 0.5 mm, noise is loud when a metal button or the like on clothes under drying hits the drum1.

Opposite to this, if the thickness of the metal sheet is over 0.8 mm, without question, the drum not only requires high material cost, but also, in view of formation, requires a high pressing force in reduction or expansion of the drum, and causes difficulty in assembly of the drum1with the cabinet due to weight. Moreover, as the drum1is heavy, the drum1imposes much load on the roller that supports the drum1. Accordingly, in order to solve above problems, the drum1in the dryer of the present invention is required to have a thickness of the metal sheet to be within a range of 0.5˜0.8 mm.

Next, the inside (or outside) diameter ratio of the body portion to the opening portion (i.e., a ratio of drum diameter reduction) has the following implications.

When the drum1is fabricated by reduction (or expansion) of the drum diameter, the thickness of the metal sheet influences to an extent of diameter reduction of the drum1. That is, the diameter reduction of the drum1uses ductility of metal, if the thickness of the metal sheet is too thin, the diameter reduction of the drum is not possible.

In the meantime, in order to increase a capacity of the drum1within a limited inside size of the cabinet, and in order to take a relation between the opening portion of the drum1and the front support7(seeFIG. 1) at the front of the drum into account, it is required to reduce diameters of the opening portions more than certain extent from the body portion.

To do this, the present invention has been optimized through numerous experiments, such that the present invention can provide a structure of a drum in a dryer of which diameter can be reduced to a minimum thickness as required.

As a range that can satisfies above requirement, when the inside diameter ratio of the body to the opening (B/A) is over 0.9, tearing of the metal sheet can be prevented. An optimum range of the ratio is in a range of 0.93˜0.94 when security and so on are taken into account.

That is, in a preferred embodiment of the present invention, the thickness of the metal sheet is 0.5 mm, the outside diameter of the body is 663 mm, a difference between the outside diameter of the body and the outside diameter of the opening portion is 40˜47 mm, with a distance from the outside diameter of the body portion to the outside diameter of the opening portion (C; a depth of reduction of drum diameter) being 20˜23.5 mm.

When it is assumed that the metal sheet has a thickness of 0.5 mm, the outside diameter of the body portion is 663 mm, and the inside diameter ratio of the body to the opening portion is 0.9, a difference of outside diameters of the body portion and the opening portion is 67 mm, and a distance between the outside diameter to the outside diameter of the opening portion (C; the depth of the reduction of drum diameter) is 33.5 mm.

If the depth is greater than 33.5 mm, the metal sheet is liable to tear during formation of the drum, it is preferable that the depth is below 33.5 mm.

In the meantime, in another preferred embodiment of the present invention, the depth is in a range of 44 mm when the thickness of the metal sheet is 0.6 mm.

In order to reinforce of strength of the drum, at least one bead portion is formed in the body.

Moreover, in order to absorb, or attenuate noise and vibration caused by laundry in the drum1, anti-vibration bands are wound on the outside diameter of the body portion or the bead portions where no belt is wound. The anti-vibration band may be formed of rubber or metal, and the anti-vibration band is attached to an outside wall of the body portion or an outside wall of the bead portions, securely.

The joining parts of the drum1are butt welded (edges of the metal sheet is welded in a state the edges are not overlapped, but abut) with a plasma-TIG welder. This is because if the metal sheet overlaps, deformation of the overlapped portion the same with other portion can not be secured in the diameter reduction or expansion).

For hemming of the edges of the opening portions, it is required that certain lengths of opposite edges of the joining part are not welded.

In the meantime, according to another preferred embodiment of the present invention, after the steps of6A and6H are passed to form a drum by using the metal sheet of steel, the anti-corrosion film is applied to an inside, and outside circumferential surfaces of the drum, and subsequent to this, an organic film is applied to the metal film, to fabricate the drum of the present invention.

As has been described, the drum in a dryer has the following advantages.

Different from the related art, the improved structure of the drum in a dryer of the present invention permits to make consumers to have reliance on the product in view of outer appearance as no dint is visible even if dint occurs in an inside circumferential surface of the drum.

The double surface treatment with the metal film and the organic film enhance corrosion resistance of the inside surface of the drum.

The present invention permits production of the drum at a cost significantly lower than the related art.

Different for the related art metal adhesive (stainless steel bond), the use of plastic adhesive for bonding felt to opposite edges of the drum permits to increase bonding strength of the felt bonded to the edges of the drum, significantly.

Since no traces of individual dies are left on the drum and the roundness of the drum is improved, reliability of the dryer having the drum applied thereto can be improved.