WO2008133377A1

WO2008133377A1 - Floor board with reinforced surfaces

Info

Publication number: WO2008133377A1
Application number: PCT/KR2007/004936
Authority: WO
Inventors: Kyoung-Taek Kang
Original assignee: Easywood Inc
Current assignee: Easywood Inc
Priority date: 2007-04-27
Filing date: 2007-10-10
Publication date: 2008-11-06
Anticipated expiration: 2009-10-27

Abstract

The present invention relates to a surface -reinforced floor board including a base board, a patterned wood sheet and melamine-impregnated overlay paper sequentially layered on the base board, coupling means for vertically coupling adjacent floor boards with each other in a length direction or a width direction, and a foamable hot-melt adhesive, having improved stability, applied beneath the base board. The present invention provides a floor board, which has high surface soiling resistance and high hardness, has improved workability because adjacent floor boards are easily coupled with each other vertically, and has improved sound insulation and sound absorption, thus suitably preventing the transmission of noise.

Description

Description FLOOR BOARD WITH REINFORCED SURFACES

Technical Field

[1] The present invention relates to a surface-reinforced floor board, and, more particularly, to a surface-reinforced floor board comprising a base board, patterned wood sheet and melamine-impregnated overlay paper sequentially layered on the base board, coupling means for vertically coupling adjacent floor boards with each other in the length direction or width direction of the base board, and a foamable hot melt adhesive, having improved stability, applied beneath the base board.

[2] The present invention provides a floor board, which has good surface soiling resistance and high hardness, has improved workability because adjacent floor boards are easily coupled with each other vertically, and has improved sound insulation and sound absorption, thus suitably preventing the transmission of noise. Background Art

[3] Floor boards, in the edge of which a convex (ύ) tongue and a concave ([H]) groove are formed, so that the tongue is engaged with the groove, thereby coupling adjacent floor boards with each other, are generally used.

[4] Various conventional floor boards are commonly characterized in that their surfaces are easily damaged and scratched by small external impacts and in that they cannot be easily restored, and in that, since they include horizontal engaging means and vertical locking means, adjacent floor boards must be coupled with each other rotatably and/or horizontally. Further, the natural surfaces of conventional floor boards are generally finished using a UV-curable paint, which is a urethane acrylate resin. However, conventional floor boards are problematic in that their surfaces are easily contaminated and damaged by external impacts and in that the tactile sense when walking thereon is bad and the sound absorption capability thereof is low. Moreover, conventional floor boards have the following problems at the time of coupling adjacent floor boards with each other.

[5] FIG. 1 is an expanded sectional view showing a conventional floor board, in which the facing sides of the floor board are shown to be expanded. A floor board may have various shapes, such as a rectangle, a square, and the like, and generally has a rectangular shape having a length of 1 m, a width of 10 cm and a thickness of 0.5 cm ~ 1.5 cm. Generally, a floor board is fabricated using an original board formed by adhering a patterned wood sheet, HPM or LPM on a plywood board, a raw wood board, a high-density fiber board or a particle board, which is a base board, and is adhered to a concrete floor using a general epoxy adhesive. FIG. 1 shows two facing sides (edges) configured in a length direction or a width direction. As shown in FIG. 1, a conventional floor board 100 is configured such that a locking means 120, including an engaging means 130, is formed along the sides thereof in a length direction or a width direction. The locking means 120 includes a tongue 121 and a groove 122 engaged with the tongue 121. The tongue 121 and groove 122 are obliquely engaged with each other in order to couple a floor board 100 with a pre-formed floor board 100' (see FIG. 2), or are horizontally engaged with each other in order to couple a floor board 100 with a pre-formed floor board 100' (see FIG. 3). In this case, the tongue 121 is inserted into a groove 122 in an adjacent floor board to be locked therewith such that they do not move vertically, and thus the engaging means 130, including a protrusion 133 and a catch 134, serves to prevent the adjacent floor boards from being horizontally detached from each other because the protrusion 133 and catch 134 snap together. In the case in which the tongue 121 and groove 122 are obliquely engaged with each other in order to couple the floor board 100 with the pre-formed floor board 100', the two floor boards 100 and 100' are inserted into each other by rotational movement. In order to make this rotation movement easy, the end of the tongue 121 may be curved. The tongue 121 must be designed to have approximately the same horizontal length as the engaging means such that it can be securely placed between the upper wall 123 of the groove 122 and the lower wall 124 thereof and can sufficiently endure pressure applied from the upper wall thereof to the lower wall thereof. However, due to the fact that the tongue 121 must be designed to have approximately the same horizontal length as the engaging means, when adjacent floor boards are actually coupled with each other, the following problems ensue. That is, when a floor board is coupled with an adjacent floor board in a length direction and/or a width direction, they must be coupled with each other obliquely (rotationally) and/or horizontally. For example, when the length-directional side of a floor board is coupled with an adjacent floor board and then the width-directional side thereof is coupled with another adjacent floor board, since the length-directional side thereof is fixed, the width-directional side thereof can be coupled with another floor board only horizontally. In this case, since the width-directional side thereof can be horizontally coupled with another floor board by roughly adjusting the position of the tongue and groove and then striking the opposite side thereof, there is a problem in that it is inconvenient to couple a floor board with another floor board, thus decreasing working efficiency. Further, there is a problem in that, although a floor board for a Korean floor heating system repeatedly expands and contracts due to heat, the floor boards are detached from each other by the expansion thereof, and thus play occurs therebetween. The occurrence of play can be caused by the fact that conventional means for coupling floor boards with each other is weak. Disclosure of Invention Technical Problem

[6] Therefore, the present inventors have attempted to variously change the side structure of a floor board in order to improve the sound absorption and tactile sense when walking on the lower surface of the floor board and to provide it with a surface reinforcing means to protect the surface thereof from external impacts, smoothly couple adjacent floor boards with each other, and prevent the coupled floor boards from being detached from each other horizontally. Based on these attempts, the present invention was completed. Further, the present inventors found that, when a hot-melt adhesive having excellent foamability and stability, which can replace an epoxy adhesive commonly used in the fabrication of a floor board, is applied on the lower surface of a floor board, the adhesion between the floor board and a concrete floor is sufficiently strong, thus fabricating a floor board having an improved tactile sense when walking, and improved sound absorption. Technical Solution

[7] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a surface-reinforced floor board, comprising a base board, a patterned wood sheet and melamine-impregnated overlay paper sequentially layered on the base board, coupling means for vertically coupling adjacent floor boards with each other in the length direction or width direction of the base board, and a foamable hot-melt adhesive, having improved stability, applied beneath the base board.

[8] Specifically, the present invention provides a floor board, which is fabricated using an original board formed by layering a patterned wood sheet and melamine-impregnated overlay paper on one side of a plywood board, a raw wood board, a high- density fiber board or a particle board, which is a base board, and selectively adhering a foamable synthetic rubber-based hot-melt adhesive having improved stability on the other side thereof in consideration of thermal properties and tactile sense in walking such that the floor board is suitable for a Korean floor heating system (Ondol), and then adhering a release paper thereon, and in which the engaging means is configured such that the horizontal length of the engaging means is 10 or more times the horizontal length of the tongue or the horizontal length of the groove, the floor boards can be vertically coupled with each other, and the catch of the engaging means is designed such that the height thereof is 1/2 the thickness of the floor board, thus preventing the floor boards from being horizontally detached from each other and improving workability.

[9] Further, the present invention provides a surface -reinforced floor board, including: a tongue formed on one side of the floor board and a groove formed in the other side thereof, wherein the tongue is formed downward, the groove, which is engaged with the tongue, is formed upward, an S-line protrusion is formed on one side of the tongue, and an S-line recess, in which the S-line protrusion is securely placed, and an S-line catch are formed at one side of the groove, so that adjacent floor boards can be vertically coupled with each other by forcibly fitting the tongue and groove into each other, and the adjacent floor boards cannot be detached from each other, thus making the assembly, partial maintenance and reassembly of the floor boards easy.

[10] The composition of the hot- melt adhesive according to the present invention includes

5 - 40 wt% of styrene block copolymer having a molecular weight of 40,000 ~ 200,000, a styrene content of 14 ~ 45% and a melt index of 6 ~ 100; 15 - 65 wt% of a tackifier resin having a molecular weight of 300 ~ 2,000, 4 - 9 carbon atoms and a softening point of 80~130°C, in which double bonds are converted into single bonds by adding 80% or more of hydrogen into petroleum resin; and 10-30 wt% of oil including 0 - 30% of aromatic carbon, 25 - 60% of naphthenic carbon and 50 - 70% of paraffinic carbon, or selectively 5 - 30 wt% of polybutene, having a molecular weight of 600 - 2,500, including 80% or more of butane. The composition for the hot-melt adhesive may farther include 1 - 5 wt% of polyethylene wax having a softening point of 70 - 13O⁰C, and 0 - 1 wt% of a benzene propanoic acid-based primary antioxidant or 0 - 1 wt% of a phenol phosphate-based secondary antioxidant.

Advantageous Effects

[11] According to the floor board of the present invention, the floor board is provided thereon with a surface reinforcing layer having improved surface durability and surface soiling resistance, the horizontal length of a tongue is very short compared to that of the engaging means, such that adjacent floor boards can be vertically coupled with each other in a length direction and/or a width direction, and the height of a catch is very large compared to that of the floor board in order to prevent the adjacent floor boards from becoming detached from each other due to horizontal expansion, thus solving the problems with the inefficiency in the assembly of floor boards having pointed out in conventional horizontal and/or rotational assembly processes. In particular, in connection with the assembly of floor boards coated with a stable foamable hot-melt adhesive, the floor boards, which can be vertically coupled with each other, are adhered to a concrete floor and simultaneously closed with each other, thus enabling very efficient assembly of the floor boards.

[12] According to the floor board of the present invention, the floor board includes a downward tongue and a groove for forming a complementary space corresponding to the tongue such that such that adjacent floor boards can be vertically coupled with each other in a length direction and/or a width direction, a S-line protrusion is formed at one side of the tongue, and the S-line protrusion is securely placed in a S-line recess of the groove, corresponding to the S-line protrusion, and is not detached therefrom by a S- line catch, thus solving the problem of inefficiency pointed out in conventional horizontal and/or rotational assembly processes. In particular, in connection with the assembly of a floor board coated with a foamable hot-melt adhesive having stability, the floor boards, which can be vertically constructed, are adhered to a concrete floor and simultaneously closed with each other, thus enabling very efficient assembly of the floor boards. Brief Description of the Drawings

[13] FIG. 1 is an expanded sectional view showing a conventional floor board in a length direction or a width direction;

[14] FIGS. 2 and 3 are sectional views showing the modes for coupling conventional floor boards with each other in a length direction or a width direction;

[15] FIG. 4 is an expanded sectional view showing a floor board according to an embodiment of the present invention in a length direction or a width direction;

[16] FIGS. 5 and 6 are sectional views showing the modes for coupling floor boards according to an embodiment of the present invention with each other in a length direction or a width direction;

[17] FIG. 7 is a sectional view showing the state in which the floor boards according to an embodiment of the present invention are completely coupled with each other;

[18] FIG. 8 is an expanded sectional view showing a floor board according to another embodiment of the present invention in a length direction or a width direction;

[19] FIG. 9 is a sectional view showing the mode for coupling floor boards according to another embodiment of the present invention with each other in a length direction or a width direction; and

[20] FIG. 10 is a sectional view showing the state in which the floor boards according to another embodiment of the present invention are completely coupled with each other. Best Mode for Carrying Out the Invention

[21] An aspect of the present invention provides a surface -reinforced floor board, which is fabricated using a unit original board formed by cutting an original board, integrally prepared by layering a patterned wood sheet and melamine-impregnated overlay paper on one side of a base board, such as a plywood board, a raw wood board, a high- density fiber board or a particle board, at predetermined length and width through a cold-pressing or hot-pressing process, comprising: a tongue formed on one side of the floor board; a groove formed in the other side thereof, and an engaging means including a protrusion formed on the upper surface of the tongue and a recess formed on the upper surface of the groove, wherein the engaging means is configured such that the horizontal length L of the engaging means is 10 or more times, preferably 10 ~ 15 times of a horizontal length E of the tongue such that the floor boards can be vertically coupled with each other in a length direction and/or a width direction. In this case, in order to prevent the floor boards from being horizontally detached from each other due to the expansion of the floor board, a catch provided at a rear portion of the recess of the engaging means is designed such that the height of the catch is about 1/2, and preferably 1/3 ~ 1/2 of the thickness of the floor board.

[22] Another aspect of the present invention provides a surface-reinforced floor board, which is fabricated using a unit original board formed by cutting an original board, integrally prepared by layering a patterned wood sheet and melamine-impregnated overlay paper on one side of a base board, such as a plywood board, a raw wood board, a high-density fiber board or a particle board, to a predetermined length and width through a cold-pressing or hot-pressing process, comprising: a tongue formed on one side of the floor board; and a groove formed in the other side thereof, wherein the tongue projects downwards such that the floor boards are vertically coupled with each other in a length direction and/or a width direction, and the groove, forcibly fitted into the tongue, faces up. The floor boards coupled with each other by inserting the tongue into the groove cannot become horizontally detached from each other. In this case, in order to prevent the coupled floor boards from being vertically detached from each other, an S-line protrusion is formed on one side of the tongue, and an S-line recess, in which the S-line protrusion is securely placed, and an S-line catch are formed on one side of the groove. [23] A surface reinforcing layer is formed on the floor board, and a conventional inefficient UV coating process is not required thanks to the method of forming a surface reinforcing layer according to the present invention, so that the productivity of the floor board is increased, and physical properties, such as surface durability, surface soiling resistance, etc., are improved. Meanwhile, a foamable synthetic rubber-based hot-melt adhesive is applied beneath the floor board, and a release paper is adhered to the hot-melt adhesive. The hot-melt adhesive, including synthetic rubber as a main component, is a solvent-free adhesive which is harmless to the human body, and serves to attach a floor board to a concrete floor having a rough surface, prevent a floor board made of timber from changing (expanding, contracting) depending on the heating conditions in residential environment and the change in water content, and impart improved sound absorption and sound insulation for absorbing or insulating impact sounds generated by a floor when walking on the floor board.

[24] When floor boards of the present invention are vertically coupled with each other, a floor board is coupled with a pre-constructed floor board by inserting a tongue of the floor board into the groove in the pre-constructed floor board vertically or rotationally, and, notably, a hot-melt adhesive applied beneath the floor board is adhered to a concrete floor, so that the floor boards are easily closely assembled, and the tongue extending in a width direction can be clicked into and held in the groove when slight pressure is applied to the tongue after adjusting the position of the tongue in a direction perpendicular to the groove in the pre-constructed floor board. The floor board according to the present invention is advantageous in that the assembly thereof is very convenient compared to conventional floor boards, in which a tongue can be engaged with a groove only horizontally, particularly in which it is inconvenient to engage the tongue in the width direction, with the groove with an adhesive adhered on a concrete floor.

[25] Further, the hot-melt adhesive, including synthetic rubber as a main component, is a solvent- free adhesive harmless to the human body, and serves to attach a floor board to a concrete floor having a rough surface, prevent a floor board made of timber from changing (expanding, contracting) depending on the heating conditions in a residential environment and changes in water content, and impart improved sound absorption and sound insulation for absorbing or insulating impact sounds generated by a floor when walking on the floor board.

[26] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In the specification, in a rectangular floor board, "a length direction" is defined as a long axis direction, and "a width direction" is defined as a short axis direction. In a square floor board, it can be understood that "a length direction" and "a width direction" indicate either side direction, the two sides being perpendicular to each other. Further, "a horizontal direction" means a direction horizontal to the lower surface of a floor, and "a vertical direction" means a direction perpendicular to the lower surface thereof. However, a horizontal direction or a vertical direction means a horizontal direction or a vertical direction as understood by those skilled in the art, and does not necessarily mean a completely parallel direction or a completely perpendicular direction. Mode for the Invention

[27] < Example 1 >

[28] FIG. 4 is an expanded sectional view showing a floor board in a length direction or a width direction, FIGS. 5 and 6 are sectional views showing the modes for coupling floor boards shown in FIG. 1 with each other in a length direction or a width direction, and FIG. 7 is a sectional view showing the state in which the floor boards shown in FIG. 4 are coupled with each other.

[29] - Formation of surface reinforcing layer

[30] A surface-reinforced floor board 200 was manufactured by sequentially layering a patterned wood sheet 270 and melamine-impregnated overlay paper 271 on the upper surface of a base board. First, a water-resistant adhesive, formed of a mixture of melamine resin, a curing agent and wheat flour, was applied on a base board at an application rate of 80 ~ 150 g/nf using a spreader, and then the patterned wood sheet 270 was adhered on the base board using the water-resistant adhesive, cold-pressed at a pressure of 2 ~ 5 kg/cm² for about 10 minutes, and then hot-pressed at a temperature of 100 ~ 13O⁰C for 45 ~ 90 seconds to prepare a patterned wood sheet-adhered original board. Subsequently, the original board was sufficiently cooled, coated with melamine resin at an application rate of 20 ~ 60 g/nf using a reverse coater, and then cured while passing through a hot air blower at a temperature of 8O⁰C for 5 - 10 seconds to obtain overlay paper 271 impregnated with 50-100% of melamine resin at an average application rate of 20 - 48 g/m². Subsequently, the overlay paper 271 was hot-pressed at a temperature of 160 - 200⁰C and a pressure of 10 - 20 kg/cm² for 15 - 50 seconds to fabricate a surface-reinforced original board. The surface-reinforced original board w as cut at a predetermined size to form a surface-reinforced floor board 200. The following engaging structure was formed on the sides of the surface-reinforced floor board 200. [31] - Vertical engaging structure

[32] An engaging means including a protrusion 230 and a recess 251 and a locking means including a tongue 221 and a groove 222 are formed along the sides of the floor board 200 in a length direction or a width direction. The locking means serves to prevent adjacent floor boards from becoming vertically detached from each other, and the engaging means serves to prevent adjacent floor boards from becoming horizontally detached from each other.

[33] The tongue 221 and the groove 222 are shaped to be complementary to each other, and the tongue 221 is designed such that the horizontal length of the tongue 221, that is, the horizontal length E of the upper surface 225 of the tongue 221, is half the horizontal length S of the inclined surface 241 of the tongue 221. The inclined surface 241 of the tongue 221 has an angle of about 50°based on the horizontal direction, and thus it can receive pressure applied from the upper portion of the floor board 200 and effectively transfer the pressure to the chamfer 240 and the upper surface 225 of the tongue 221 in an adjacent floor board. The tongue 221 and groove 222 are designed such that a space is formed therebetween, and are configured such that the front surface 226 of the tongue 221 is not tightly engaged with the front surface of the groove 222, and thus a space for containing dust and residue may be formed between the floor boards coupled with each other. The upper surface 225 of the tongue 221 is securely placed on the upper wall 223 of the groove 222, and the inclined surface 241 of the tongue 221 is engaged with the chamfer 240 of the groove 222, thus preventing the tongue 221 from being detached from the groove 22 in an upward direction. In particular, the tongue 221 is designed such that the horizontal length E thereof is very short in order to enable the tongue 221 to be clicked vertically. In order to accomplish the two objects, that is, prevent the tongue from being vertically detached from the groove and engage the tongue with the groove such that the tongue can click when vertically engaged, the tongue is designed such that the horizontal length thereof is within a predetermined range. For this, the engaging means is configured such that the horizontal length L of the engaging means is 10 times, preferably 10 - 15 times the horizontal length E of the tongue. The range of the horizontal length is not limited as long as it is within a range suitable for accomplishing the object of engaging the tongue with the groove such that the tongue can be vertically clicked. In Example 1, a floor board having an E of 0.5 mm, an S of 1.05 mm and an L of 7.99 mm was manufactured.

[34] - Application of foamable hot-melt adhesive [35] A foamable hot-melt adhesive 280 was applied on the lower surface of a floor board

200, and then a release paper was adhered thereto, thus completing a surface- reinforced floor board. The composition for the hot-melt adhesive includes 5 - 40 wt% of styrene block copolymer having a molecular weight of 40,000 ~ 200,000, a styrene content of 14 ~ 45% and a melt index of 6 - 100; 15 - 65 wt% of a tackifier resin having a molecular weight of 300 - 2,000, 4 - 9 carbon atoms and a softening point of 80~130°C, in which double bonds are converted into single bonds by adding 80% or more of hydrogen into petroleum resin; and 10-30 wt% of oil including 0 - 30% of aromatic carbon, 25 - 60% of naphthenic carbon and 50 - 70% of paraffinic carbon, or selectively 5 - 30 wt% of polybutene, having a molecular weight of 600 - 2,500, including 80% or more of butane. The composition for the hot-melt adhesive may farther include 1 - 5 wt% of polyethylene wax having a softening point of 70 - 13O⁰C, and 0 - 1 wt% of a benzene propanoic acid-based primary antioxidant or 0 - 1 wt% of a phenol phosphate-based secondary antioxidant.

[36] In this case, the styrene block copolymer is selected from the group consisting of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butadiene-styrene block copolymer, styrene- ethylene-propylene-styrene block copolymer, and mixtures thereof. When the amount of the styrene block copolymer is below 5 wt%, heat resistance and foamability are decreased, thus deteriorating the noise transmission prevention effect. In contrast, when the amount thereof is above 40 wt%, workability is problematic due to high viscosity. When the amount of the tackifier resin is below 15 wt%, the adhesivity of the hot-melt adhesive is decreased. In contrast, when the amount thereof is above 65 wt%, the hot-melt adhesive is hardened, thus decreasing the stability of the hot- melt adhesive. When the amount of oil is below 10 wt%, the adhesivity of the hot-melt adhesive is decreased, and the hot-melt adhesive is hardened, thus increasing the stability of the hot-melt adhesive. In contrast, when the amount thereof is above 30 wt%, the hot-melt adhesive is excessively softened, thus decreasing the adhesivity of the hot-melt adhesive. When the amount of the polybutene is 5 wt% or more, the initial adhesivity of the hot-melt adhesive is increased. In contrast, when the amount thereof is above 30 wt%, the hot-melt adhesive sticks to the human body, thus causing displeasure in sanitation. When the amount of the polyethylene wax is 1 wt% or more, the foamability of the hot-melt adhesive is improved. In contrast, when the amount thereof is above 5 wt%, the adhesivity of the hot-melt adhesive is decreased. A small amount of the antioxidant is advantageous in antioxidation, but when the amount of the antioxidant is above 1 wt%, the effect of antioxidation is not improved, but the viscosity of the hot-melt adhesive is increased due to side reactions, thus deteriorating workability.

[37] The hot-melt adhesive may be prepared through the following processes. That is, the method of preparing the hot-melt adhesive may include: mixing 15 wt% of oil, including 32% of naphthenic carbon and 68% of paraffinic carbon, 2 wt% of polyethylene wax, having a softening point of 116⁰C, 23 wt% of tackifier resin having a molecular weight of 450, a softening point of 85⁰C and five carbon atoms, 23 wt% of tackifier resin, having a molecular weight of 470, a softening point of 103⁰C and five carbon atoms, including 80% or more of hydrogen, 10 wt% of tackifier resin, having a molecular weight of 1,800, a softening point of 125⁰C and nine carbon atoms, including 80% or more of hydrogen, and a very small amount of antioxidant under a nitrogen atmosphere to form a first mixture; completely melting the first mixture at a temperature of 15O⁰C; adding 20 wt% of styrene-isoprene-styrene block copolymer having a molecular weight of 120,000, a styrene content of 15% and a melt index of 8, and 10 wt% of styrene-butadiene-styrene block copolymer having a molecular weight of 120,000, a styrene content of 18% and a melt index of 9 to the melted first mixture to form a second mixture; and melting the second mixture and then removing foam therefrom. The hot-melt adhesive prepared in this way has a viscosity of 950 ~ 3,000, a softening point of 8O⁰C or more, an adhesivity of 2.0 or more, a foaming magnitude of 150 or more and a stability of 50, and has sufficient adhesivity, absorption and tactile sense when walking.

[38] The floor boards in Example 1 can also be coupled with each other vertically (see

FIG. 5) or rotationally (see FIG. 6). When the floor boards in Example 1 are coupled with each other rotationally, the lower end of the front surface 226 of the tongue 221 of the floor board 200 comes into contact with the lower inclined surface 236 of the groove 222 of a pre-constructed floor board, and the tongue 221 is engaged with the groove 22 by rotating the tongue 221 downward. For this, the lower end of the front surface 226 of the tongue 221 of the floor board 200 is curved. Due to the curved shape, the collision between the lower inclined surface 236 of the groove 222 and the lower end of the front surface 226 of the tongue 221 can be alleviated, and effective rotation movement can be realized.

[39] The floor boards in Example 1 are coupled with each other by an engaging means including a protrusion 250 and a recess 251 together with a locking means including the tongue 221 and the groove 222, thus preventing the floor boards from becoming horizontally detached from each other. As shown in FIG. 4, a protrusion 250 formed between the lower inclined surface 235 of the tongue and the upper inclined surface 230 thereof is securely placed in a recess 251 formed between the lower inclined surface 236 of the groove and the upper inclined surface 231 thereof, and the protrusion 250 cannot be horizontally detached from the recess 251 because of a catch 234 having a large vertical length H formed along the upper inclined surface 231 of the groove. The catch 234 is designed such that the vertical length H thereof is half the thickness D of the floor board, but the vertical length H thereof is not limited thereto as long as adjacent floor boards can be coupled with each other vertically or rotationally while not being coupled with each other horizontally. Meanwhile, the angle of the upper inclined surface 231 of the groove was set after many trials and errors. The angle thereof may be 50° based on a horizontal direction, but is not limited thereto. The present inventors fabricated the catch having the above angle of the upper inclined surface 231 and vertical length of catch 234 and then tested the catch. As a result, it was found that the horizontal movement between the coupled floor boards can be completely prevented and adjacent floor boards can be easily coupled with each other vertically. The protrusion 250 in the engaging means may be formed to have a curved shape. Due to this curved shape, when adjacent floor boards are coupled with each other rotationally (see FIG. 6), collisions between the protrusion 250 and the upper inclined surface 231 of the groove can be reduced, thus advantageously preventing the catch 234 from being damaged. Further, the catch 234 of the present invention includes an upper inclined surface 231, a top surface 260 and a vertical rear surface 261, and the top surface 260 and rear surface 261 may not be formed in a curved shape. It can be seen from this fact that, compared to conventional floor boards, which are coupled with each other horizontally, adjacent floor boards can be coupled with each other only vertically or rotationally.

[40] In the coupling of adjacent floor boards in a length direction or a width direction in

Example 1, as shown in FIG. 5, the adjacent floor boards can be coupled with each other vertically. When a protrusion 250 of a floor board is brought near a recess 251 of a pre-constructed adjacent floor board, the upper end of the front surface of a tongue 221 comes into contact with a chamfer 240 of a groove 222, and the tongue 221 is engaged with the front surface 227 of the groove 222 along the chamfer 240 with a click. In this case, since the protrusion 250 is formed in a curved shape, the friction between the protrusion 250 and the upper inclined surface 231 of the groove 222 can be weakened, the protrusion 250 can be more easily inserted into the groove 222, and the impact occurring when a catch 234 is instantaneously and elastically pushed backward can be alleviated. The coupling of the adjacent floor boards vertically can be conducted because the horizontal length E of the tongue is much shorter than the horizontal length L of the engaging means, and thus cannot be conducted when the horizontal length E of the tongue is almost equal to or greater than the horizontal length L of the engaging means. Further, in the coupling of adjacent floor boards in the length direction or the width direction in Example 1, as shown in FIG. 6, the adjacent floor boards can be coupled with each other rotationally. That is, the lower end of the front surface of a tongue of a floor board faces the lower inclined surface 236 of a pre- constructed adjacent floor board and rotates around the tangent line therebetween as an axis, and thus the tongue 221 is inserted into the groove 222 in the pre-constructed adjacent floor board, and simultaneously the curved protrusion 250 can be securely placed into a recess 251 along the upper inclined surface of the groove 222, having a steep angle of about 50°. In this case, the catch 234 is elastically bent slightly backward, but can return to its original shape due to the secure placing of the protrusion.

[41] FIG. 7 is a schematic sectional view showing the state in which the floor boards in

Example 1 are completely coupled with each other. As described above, the front surface 226 of the tongue 221 may not be completely engaged with the front surface 227 of the groove 222, and a space 260 may be formed therebetween. Further, the rear surface 261 of the groove 222 may also not be engaged with the corresponding portion of the adjacent floor board, thus forming play due to horizontal expansion. Meanwhile, in the case of the floor board coated therebeneath with a hot-melt adhesive, its tongue 221 is engaged with the groove 222 provided in a pre-constructed adjacent floor board, and is simultaneously adhered to the bottom thereof, thus completing the assembly of the floor boards.

[42] < Example 2 >

[43] FIG. 8 is an expanded sectional view showing a floor board in a length direction or a width direction, FIG. 9 is a sectional view showing the mode for coupling floor boards shown in FIG. 8 with each other vertically, and FIG. 10 is a sectional view showing the state in which the floor boards shown in FIG. 9 are coupled with each other according to the mode for coupling the floor boards with each other. Compared to Example 1, the constitutions of a surface reinforcing layer and a hot- melt adhesive, except for the vertical engaging structure, in Example 2 may be the same as those in Example 1, but the surface reinforcing layer may be formed through the following processes. Hereinafter, the process of forming the surface reinforcing layer and the vert ical engaging structure will be described.

[44] - Formation of surface reinforcing layer

[45] First, a predetermined sized veneer board having a thickness of 0.5- lmm was provided. Then, a water-resistant adhesive formed of a mixture of melamine resin, a curing agent and wheat flour was applied on the veneer board at an application rate of 80 ~ 150 g/m² using a spreader, and then patterned wood sheet was adhered on the veneer board using the water-resistant adhesive, and then the veneer board, on which the patterned wood sheet was adhered, was cold-pressed at a pressure of 2 ~ 5 kg/cm² for about 10 minutes. Subsequently, an overlay paper impregnated with 50-100% of melamine resin at an average application rate of 20 - 48 g/m² was placed on the patterned wood sheet, and was then hot-pressed at a temperature of 160 - 200⁰C at a pressure of 10 - 20 kg/cm² for 15 - 50 seconds to form a surface reinforcing layer. Subsequently, a woodworking adhesive for cold pressing (MPU500, manufactured by Okong Corp.) was applied on a base board, such as plywood, HDF, PB or the like, and then the formed surface reinforcing layer was placed on the base board, and then the base board, on which the surface reinforcing layer was placed, was cool-pressed at a pressure of 5 - 15 kg/cm² for about 90 minutes to fabricate an original board having a surface reinforcing layer. The original board having the surface reinforcing layer was cut to a predetermined size to form a surface-reinforced floor board 300. The following engaging structure was formed at the sides of the surface-reinforced floor board 300.

[46] - Vertical engaging structure

[47] An engaging means including a protrusion 350 and a recess 351 and a locking means including a downward tongue 321 and a groove 322 shaped to be complementary thereto are formed along the sides of the floor board 300 in a length direction or a width direction. The locking means serves to prevent adjacent floor boards from being horizontally detached from each other, and the engaging means serves to prevent adjacent floor boards from being vertically detached from each other.

[48] The downward tongue 321 and groove 322 are configured such that they are engaged with each other. The outer surface 326 of the tongue 321 is inwardly inclined and joins one end of the lower surface 361 of the tongue 321, and the other end of the lower surface of the tongue 321 is curved, vertically inwardly inclined and joins the inner surface 328 of the tongue 321, thus forming a curved protrusion 350 surrounded by the lower surface 361 and inner surface of the tongue 321. Hereinafter, this curved protrusion 350 is referred to as an S-line protrusion. The inner surface 328 of the tongue 321 is also curved, like the protrusion 350, and horizontally extends. The downward tongue 321 and groove 322 are designed such that they are forcibly fitted into each other and are thus vertically engaged with each other, thus forming a space 330 therebetween. That is, the outer surface 326 of the tongue 321 is not tightly engaged with the vertical inner surface 327 of the groove 322, and thus a space for containing dust and residue can be formed between the floor boards coupled with each other. Meanwhile, the groove 322 is a space in which the downward tongue 321 can be shaped to be complementary to the groove 322 by forcibly fitting them into each other. The vertical inner surface 327 of the groove 322, which forms the space 330 together with the outer surface 326 of the tongue 321, vertically joins one end of the horizontal lower surface of the groove 322, and the other end of the lower surface of the groove 322 is curved, vertically inwardly inclined, and joins with the outer surface 329 of the groove 322, thus forming a curved recess 351 surrounded by the lower surface 362 and outer surface 329 of the groove 322. Hereinafter, this curved recess 351 is referred to as an S-line recess. The S-line protrusion 350 of the downward tongue 321 is securely placed in the S-line recess such that they are shaped to be complementary to each other. The inner surface 329 of the groove 322 is also curved as the recess 351 and horizontally extends, thus forming a curved catch 334. This curved catch is referred to as an S-line catch. After the tongue 321 and groove 322 are engaged with each other, the S-line catch can function as a blocking factor for preventing the S-line protrusion 350, securely placed in the S-line recess 351, from being detached upwardly, that is, vertically.

[49] Although the adjacent floor boards in Example 2 are primarily coupled with each other by the downward tongue and the groove shaped to be complementary thereto, it must be understood that the S-line protrusion 350 and S-line catch 334 can prevent the downward tongue and groove from being vertically detached from each other. In particular, due to the S-line shape, when the tongue 321 is engaged with the groove 322, damage caused by the collision between the protrusion 350 and catch 334 can be prevented, and the tongue 321 and groove 322 are smoothly clicked and engaged with each other. That is, the S-line protrusion and S-line catch are designed to accomplish the two objects, that is, vertical detachment prevention and vertical click engagement.

[50] The floor boards in Example 2 cannot be coupled with each other rotationally, and can be coupled with each other only vertically (see FIG. 9). In the assembly of the floor board in a length direction and/or a width direction, as shown in FIG. 9, since the floor boards can be coupled with each other only vertically, the problems with horizontal assembly or rotational assembly noted for conventional floor boards can be overcome. First, when a protrusion 350 of a floor board is brought near a recess 351 of a pre-constructed adjacent floor board, the S-line of the protrusion 350 comes into contact with the S-line of a catch 334, and, when slight pressure is applied thereto, the downward tongue 321 can be clicked and engaged with the groove 322 along the S- line by forcibly fitting the tongue 321 and groove 322 into each other. In this case, due to the S-line of the protrusion, the friction between the protrusion and catch can be decreased, and thus the tongue and groove can be easily fitted into each other, and the impact occurring when the catch is instantaneously and elastically pushed backward can also be decreased. In this case, the catch 334 is elastically bent backward slightly, but can return to its original shape when the protrusion 350 is securely placed in the recess 351. This vertical assembly of floor boards can be conducted by a downward tongue, a groove corresponding to the downward tongue, an S-line protrusion and a recess corresponding to the S-line protrusion. Further, the vertical detachment of adjacent floor boards can be prevented by the S-line catch.

[51] FIG. 10 is a schematic sectional view showing the state in which the floor boards in

Example 2 are completely coupled with each other. As described above, the outer surface 326 of the tongue 321 may not be completely engaged with the inner surface 327 of the groove 322, and a space 330 may be formed therebetween. Further, the rear surface 368 of the groove 322 may not be engaged with the corresponding portion of the adjacent floor board, thus forming play due to horizontal expansion. Meanwhile, in the case of the floor board coated therebeneath with a hot-melt adhesive, its tongue 321 is engaged with the groove 322 provided in a pre-constructed adjacent floor board, and is simultaneously adhered to the bottom thereof, thus completing the assembly of the floor boards.

[52] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] A surface-reinforced floor board, comprising: a tongue formed on one side of the floor board; a groove formed in the other side thereof; an engaging means including a protrusion formed on a lower surface of the tongue and a recess formed in a lower surface of the groove, in which the engaging means is configured such that a horizontal length L of the engaging means is 10 ~ 15 times a horizontal length E of the tongue such that the floor boards can be vertically coupled with each other in a length direction and/or a width direction; a patterned wood sheet and a melamine-impregnated overlay paper, which are sequentially layered on the floor board; and a foamable hot-melt adhesive applied beneath the floor board.

[2] The surface-reinforced floor board according to claim 1, wherein the floor board comprises a catch provided at a rear portion of the recess of the engaging means, which is designed such that a height H thereof is 1/3 ~ 1/2 of a thickness of the floor board in order to prevent the floor boards from becoming horizontally detached from each other.

[3] The surface-reinforced floor board according to claim 1 or 2, wherein the tongue and the groove are shaped to be complementary to each other, and the protrusion and the recess are shaped to be complementary to each other.

[4] The surface-reinforced floor board according to claim 1 or 2, wherein a horizontal length E of the tongue is about 1/2 of a horizontal length S of an inclined surface of the tongue.

[5] The surface-reinforced floor board according to claim 2, wherein the catch includes a front upper inclined surface, a top surface and a rear vertical surface, and an angle of the front upper inclined surface is 50° with respect to a horizontal direction.

[6] The surface-reinforced floor board according to claim 1, wherein the hot- melt adhesive comprises 5 - 40 wt% of styrene block copolymer having a molecular weight of 40,000 ~ 200,000, a styrene content of 14 ~ 45% and a melt index of 6 ~ 100; 15 ~ 65 wt% of a tackifier resin having a molecular weight of 300 ~ 2,000, 4 - 9 carbon atoms and a softening point of 80- 13O⁰C, in which double bonds are converted into single bonds by adding 80% or more of hydrogen into petroleum resin; and 10-30 wt% of oil including 0 ~ 30% of aromatic carbon, 25 ~ 60% of naphthenic carbon and 50 ~ 70% of paraffinic carbon, or selectively 5 ~ 30 wt% of polybutene, having a molecular weight of 600 ~ 2,500, including 80% or more of butane.

[7] A surface-reinforced floor board, comprising: a tongue formed on one side of the floor board and projecting downwards such that the floor boards are vertically coupled with each other in a width direction; a groove formed in another side thereof and having a space for receiving the protrusion; an S-line protrusion formed at one side of the tongue; an S-line recess, in which the S-line protrusion is securely placed, and an S- line catch, formed at one side of the groove; a patterned wood sheet and a melamine-impregnated overlay paper, which are sequentially layered on the floor board; and a foamable hot-melt adhesive applied beneath the floor board.

[8] The surface-reinforced floor board according to claim 7, wherein the tongue and the groove are shaped to be complementary to each other, and the protrusion and the recess are shaped to be complementary to each other.

[9] The surface-reinforced floor board according to claim 7, wherein an outer surface of the tongue is slightly inwardly inclined.

[10] The surface-reinforced floor board according to claim 7, wherein an upper end of an inner surface of the tongue is horizontally extended.

[11] The surface-reinforced floor board according to claim 7, wherein the hot- melt adhesive comprises 5 - 40 wt% of styrene block copolymer having a molecular weight of 40,000 - 200,000, a styrene content of 14 - 45% and a melt index of 6

- 100; 15 - 65 wt% of a tackifier resin having a molecular weight of 300 - 2,000, 4 - 9 carbon atoms and a softening point of 80~130°C, in which double bonds are converted into single bonds by adding 80% or more ofhydrogen into petroleum resin; and 10-30 wt% of oil including 0 - 30% of aromatic carbon, 25

- 60% of naphthenic carbon and 50 - 70% of paraffinic carbon, or selectively 5

- 30 wt% of polybutene, having a molecular weight of 600 - 2,500, including 80% or more of butane.