SHOES FOR ABSORBING SOCK Technical Field [1] The present invention relates to the structure of a shoe which can efficiently absorb shocks applied to the human foot when a wearer of shoes walks or runs. Background Art [2] Generally, an object of shoes for human feet is to absorb shocks, which are applied to the feet of a wearer of the shoes when the wearer steps on the ground while walking or running, thus protecting the ankles and the knee joints of the wearer from shocks. Another object of the shoes is to protect the soles of the wearers' feet from being injured. [3] Thus, the sole of a conventional shoe has a construction comprising an outsole which is made of rubber capable of increasing the friction between the shoe sole and the ground surface, thus preventing a wearer from slipping on the ground surface and ensuring desired precise manners of walking, and a midsole which is bonded to the upper surface of the outsole and to which the upper of the shoe is fixed, which thus cushions the foot sole of the wearer, and relieves fatigue of the foot and protects the foot from being injured. [4] However, the above-mentioned conventional shoe structure, having the outsole bonded to the lower surface of the midsole, is problematic in that the conventional shoe structure cannot efficiently absorb shocks, which are generated when a wearer steps on the ground while walking or running, thus gradually imposing fatigue on the ankles and the knee joints of the wearer. Another problem of the conventional shoe structure resides in that, when a wearer continuously wears conventional shoes for a lengthy period of time, air in the shoes becomes heated and thermally fatigues the feet of the wearer. [5] In an effort to overcome the above-mentioned problems, a shoe structure having an elastic pad unit, comprising a coil spring which is a cushion member to absorb shocks and which is held by upper and lower plates at a position between the midsole and the outsole of the shoe, has been proposed. [6] The upper and lower plates of the above-mentioned elastic pad unit are shaped using a urethane material and hold the spring. The outsole and midsole, which are bonded to the lower and upper plates of the elastic pad unit, respectively, are made of rubber and plastic urethane material (PU), respectively. Thus, when the above- mentioned midsole and outsole are bonded to the upper plate and lower plate of the elastic pad unit, respectively, the toe of the midsole is not flexible and cannot easily be bent due to the hard characteristics of the elastic pad unit, thus being inconvenient to the wearer while walking. [7] Furthermore, when the outsole is bonded to the midsole after the elastic pad unit has been installed in a designated chamber, the chamber is hermetically sealed. Thus, although the body weight of a wearer is applied to and acts on the coil spring of the elastic pad unit in the above state, the spring cannot be efficiently compressed due to air contained in the hermetically sealed chamber, so that the elastic pad unit may fail to execute its desired elastic cushion effect. Disclosure of Invention Technical Problem [8] 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 shoe for absorbing shocks, in which an elastic pad unit to absorb shocks is smoothly moved along with a midsole and stably executes its shock absorbing function. Another object of the present invention is to provide a shoe for absorbing shocks, which is constructed such that, during compression of the elastic pad unit, air in the pad unit chamber flows to the outside of the midsole, thus stably executing the shock absorbing function. Technical Solution [9] In order to accomplish the above objects, the present invention provides a shoe for absorbing shocks, comprising: chambers respectively provided in the lower surfaces of the toe and heel of a midsole, with the upper of the shoe fastened around the edge of the midsole; an elastic pad unit having coil springs installed in each of the chambers; and an outsole bonded to the lower surface of the midsole, thus fixing the elastic pad units in the chambers, further comprising: pressure parts having a dome shape formed both on an inner midsole placed on the midsole and on the upper portion of the second chamber of the midsole; a gap formed in each of the elastic pad units installed in the chambers of the midsole and allowing the midsole to be flexible and deformable; an in¬ termediate air channel formed between the chambers of the midsole; an air discharge channel formed through the midsole to extend from the second chamber; a one-way valve provided in each of the intermediate air channel and the air discharge channel; and an air hole formed through the first chamber, the elastic pad unit and the inner midsole such that the air hole is connected to an air hole formed through an insole. Advantageous Effects [10] When wearing the shoes having the above-mentioned construction according to the present invention, the pressure parts of both the midsole and the inner midsole are in contact with the heel of a wearer's foot. Furthermore, the pressure parts are heavily pressed by the heel of the wearer's foot while walking or running, thus increasing the cushioning effect of the pressure parts. Two one-way valves are operated such that one draws air into the shoe and the other discharges air from the shoe, thus causing air in the shoe to flow in one direction and efficiently deodorizing and dissipating heat from the shoe. [11] Particularly, the elastic pad units stably move according to movement of the midsole, so that the shoe allows the wearer to be comfortable and stable without stimulating the foot sole of the wearer while walking. Brief Description of the Drawings [12] FlG. 1 is a sectional view illustrating the inner construction of a shoe adapting the present invention; [13] FlG. 2 is an enlarged perspective view of an elastic pad unit provided in the present invention; [14] FlG. 3 is a perspective view of another embodiment of the elastic pad unit according to the present invention; [15] FlG. 4 is an enlarged perspective view of part of an inner midsole included in the shoe of the present invention; [16] FlG. 5 is a cross-sectional view illustrating the construction of the elastic pad unit according to the present invention; [17] FlG. 6 is a sectional view illustrating deformation of a midsole and variation in the state of a sole of the shoe according to the present invention when the heel of the shoe sole is pressed on the ground surface; [18] FlG. 7 is a sectional view illustrating deformation of the midsole and variation in the state of the shoe sole according to the present invention when the toe of the shoe sole is pressed on the ground surface; [19] FlG. 8 is an enlarged view of the portion A of FlG. 7; and [20] FlG. 9 is an enlarged sectional view of a subsidiary sheet provided on the elastic pad unit of the present invention, and illustrates states of the subsidiary sheet before and after the subsidiary sheet is deformed. [21 ] *Description of reference characters of important parts* [22] 100: shoe 101: upper [23] 103: insole 104: air hole [24] 105: inner midsole 106: air hole [25] 107: pressure part 109: slit [26] 110: midsole 113: first chamber [27] 115: second chamber 117: intermediate air channel [28] 119: air discharge channel 120: outsole [29] 200: elastic pad unit 203: lower plate [30] 204: gap 205: holding rim [31] 213: upper plate 217: connection rib [32] 220: subsidiary sheet 300: one-way valve Best Mode for Carrying Out the Invention [33] Herein below, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. [34] FlG. 1 is a sectional view illustrating the inner construction of a shoe adapting the present invention. FlG. 2 is an enlarged perspective view of an elastic pad unit provided in the present invention. FlG. 3 is a perspective view of another embodiment of the elastic pad unit according to the present invention. FlG. 4 is an enlarged perspective view of part of an inner midsole included in the shoe of the present invention. FlG. 5 is a cross-sectional view illustrating the construction of the elastic pad unit according to the present invention. [35] As shown in FlG. 1, the shoe 100 for absorbing shocks of the present invention comprises a first chamber 113 and a second chamber 115 which are respectively provided in the lower surfaces of the toe and heel of a midsole 110, with the upper 101 of the shoe fastened around the edge of the midsole 110. An elastic pad unit 200 having coil springs 210 is installed in each of the chambers 113 and 115. An outsole 120 is bonded to the lower surface of the midsole 110, thus fixing the elastic pad units 200 in the chambers 113 and 115. [36] Part of the upper surface of the midsole 110, which corresponds to the second chamber 115, protrudes upwards to form a dome shape, so that a pressure part 112 to efficiently press the coil springs 210 downwards is provided. [37] Furthermore, an inner midsole 105, which is bonded to the upper surface of the midsole 110, is provided with a pressure part 107 having a dome shape. The surface of the inner midsole 105 is cut in radial directions at a position corresponding to the second chamber, thus forming slits 109 to define pieces 108. [38] The inner midsole 105, which is bonded both to the upper surface of the first chamber 113 formed in the midsole 110 and the upper surface of the midsole 110, is perforated to form a plurality of air holes 106, through which air in the interior of the shoe is discharged to the atmosphere. An intermediate air channel 117 is formed through the midsole 110 between the first and second chambers 113 and 115. [39] A positioning rib 111 projects from the upper end of an air hole 114, which is formed in the midsole 110, so that the positioning rib 111 is inserted into the air hole 106 of the inner midsole 105, thus positioning the inner midsole 105 relative to the midsole 110. [40] To discharge air, which flows through the intermediate air channel 117, to the atmosphere, an air discharge channel 119 is formed through the midsole 110 such that the channel 119 extends from the second chamber 115 to the outside of the shoe. A one-way valve 300 is provided in each of the intermediate air channel 117 and the air discharge channel 119 which extend from opposite ends of the second chamber 115 of the midsole 110 in opposite directions. Thus, air is drawn into the first chamber 113 and is discharged from the second chamber 115 to the atmosphere. [41] The elastic pad units 200, installed in the respective first and second chambers 113 and 115 of the midsole 110, each comprise an upper plate 203 and a lower plate 213, with the coil springs 210 interposed between the upper and lower plates 203 and 213. To hold the coil springs 210, a plurality of holding rims 205, each having a locking ring 207, is provided on each of the upper and lower plates 203 and 213. [42] The mouth of each of the holding rims 205 is provided with a curved guide surface 206 to allow a coil spring 210 to be easily inserted into the holding rim 205. [43] The upper plate 203 of each of the elastic pad unit 200 having the coil springs 210 is cut along the intermediate portion thereof into two parts, with a gap 204 defined between the two parts of the upper plate 203 to allow the upper plate 203 to be deformed. Thus, when the shoe is bent, the pad of the upper plate 203 may be deformed along with the deformation of the midsole 110. [44] The upper plate 203 is cut along its intermediate portion into two parts with the gap 204 defined between the two parts as described above, so that the upper plate 203 may be easily deformed. In the present invention, the gap 204 may be formed as a gap having a predetermined width by completely cutting the upper plate 203 into two parts as shown in FlG. 2, or may be formed as a latticed gap having connection ribs 217 by partially cutting or punching the upper plate 203 as shown in FlG. 3. [45] A subsidiary sheet 220, made of a highly flexible and deformable material, is attached to each of the upper surface of the upper plate 203 and the lower surface of the lower plate 213 of each elastic pad unit 200, so that the two elastic pad units 200 may be easily attached to the respective chambers 113 and 115 and the outsole 120 may be easily bonded to the lower plates 213. The subsidiary sheet 220 comprises upper and lower sheets 221 and 222 which are horizontally placed one on top of the other, with a flexible gap defined between the two sheets 221 and 222. Furthermore, a plurality of strands 225 of the upper sheet 221 is vertically connected to the lower sheet 222, while a plurality of strands 225 of the lower sheet 222 is vertically connected to the upper sheet 221, so that the upper and lower sheets 221 and 222 may move horizontally within a range allowed by the flexibility of the strands. [46] In the shoe according to the present invention having the above-mentioned con¬ struction, a one-way valve 300 is provided in the intermediate air channel 117 formed between the first and second chamber 113 and 115 of the midsole 110. Furthermore, another one-way valve 300 is provided in the air discharge channel 119 which is formed in the midsole 110 to extend from the second chamber 115. (see FIG. 1) [47] As shown in FIG. 5, when the coil springs 210 are seated and held between the upper and lower plates 203 and 213 of the elastic pad unit 200, the coil springs 210 are easily and smoothly inserted into the holding rims 205 by the curved guide surfaces 206 formed around the mouths of the locking rims 205. Once the coil springs 210 are inserted into the holding rims 205, the locking rings 207 of the rims 205 hold the outer perimeter of the coil springs 210. [48] The subsidiary sheet 220, having the horizontal flexible gap, is attached to the surface of each of the upper and lower plates 203 and 213 using a bonding agent. Furthermore, after the bonding agent is applied on the upper and lower surfaces of the subsidiary sheets 220, the elastic pad units 200 are inserted into the respective chambers 113 and 115 of the midsole 110. Thereafter, the outsole 120 is bonded to the lower surface of the midsole 110. [49] When an upper 101 is fastened to the upper surface of the midsole 110, a shoe 100 having the two elastic pad units 200 capable of absorbing shocks is produced. [50] Furthermore, in the shoe 100, an inner midsole 105 having a predetermined surface strength to maintain a desired surface hardness is bonded to the upper surface of the midsole 110. An insole 103, which is made of a material capable of absorbing sweat and of being easily washed, is placed on the upper surface of the inner midsole 105. In the above state, the air hole 106 of the inner midsole 105 must be aligned with the air hole 114 of the first chamber 113. [51] When the air hole 106 of the inner midsole 105 is aligned with the positioning rib 111 projecting from the toe of the midsole 110 during a process of assembling the parts of the shoe into a single structure, the air hole 114 of the midsole 110 is naturally aligned with the air hole 106 of the inner midsole 105. Furthermore, when the dome- shaped pressure part 107 formed on the heel of the inner midsole 105 is placed on the heel of the midsole 110, the pieces 108 which are separated from each other by the slits 109 are brought into contact with the pressure part 112 of the midsole 110. [52] Due to the above-mentioned construction of both the pressure part 112 and the po¬ sitioning rib 111 of the midsole 110, a skilled or unskilled person may easily and simply align the air holes 106 and 114 of both the inner midsole 105 and the midsole 110 to each other without failure. When aligning the air holes 106 and 114 with each other as described above, the air holes 106 and 114 are also aligned with both the in¬ termediate air channel 117 and the air discharge channel 119 of the midsole 110. [53] When a person wearing the shoes 100 steps on the ground while walking as shown in FIG. 6, the midsole 110 is compressed at the heel by the weight of the wearer. Thus, the elastic pad unit 200 installed in the second chamber 115 is compressed. [54] In the above state, the coil springs 210 of the elastic pad unit 200 installed in the second chamber are compressed by shocks and naturally absorb the shocks due to their elastic restoring force. [55] Furthermore, when the midsole 110 is pressed by the wearer's foot, the dome- shaped pressure part 107 is compressed toward the elastic pad unit 200, thus further compressing the coil springs 210 of the elastic pad unit 200. Therefore, the pieces 108, provided on the dome shape of the inner midsole 105 placed on the midsole 110, actively press the pressure part 107. [56] When the coil springs 210 of the elastic pad unit 200 are further compressed by the pressure part 107, shocks are more efficiently absorbed, so that the wearer feels reduced shocks while stepping on the ground. [57] Thereafter, the heel of the shoe 100 is naturally separated from the ground, and the toe of the shoe 100 is pressed on the ground prior to being separated from the ground to execute a subsequent step. In the above state, the toe of the midsole 110 is bent as shown in FIG. 7 while the elastic pad unit 200 installed in the first chamber 113 of the midsole 110 is compressed. [58] When the elastic pad unit 200 is bent as described above, the points of application of the coil springs 210 change. In the above state, since the gap 204, formed on the upper plate 203 of the elastic pad unit 200, allows the elastic pad unit 200 to be deformed, the midsole 110 may be easily and efficiently bent along with deformation of the elastic pad unit 200. Thus, the shoe 100 does not impose fatigue on the toe of the wearer's foot, protects the coil springs 210 which must be repeatedly compressed and deformed, and efficiently executes the shock absorbing function. [59] Particularly, when the midsole 110, the elastic pad units 200 and the outsole 120 are elastically deformed, each of the subsidiary sheets 220, made of the highly flexible material and attached to the upper and lower surfaces of the elastic pad unit 200, overcomes the problems caused by the partial heterogeneity of the different materials of the above-mentioned parts. [60] Described in detail, the midsole 110 is elastically flexible due to the intrinsic properties of its material, so that the midsole 110 may be easily deformed cor¬ responding to the bending and spreading motions of the wearer's foot. However, the elastic pad units 200, installed in the first and second chambers 113 and 115 of the midsole 110, are made of rigid materials, but the upper and lower plates 203 and 213 are coupled to each other by the coil springs 210. Thus, even if the midsole 110 is deformed, the elastic pad units 200 may not be deformed. [61] However, in the present invention, the subsidiary sheets 220, attached to the midsole 110 at a position above each elastic pad unit 200 and to the outsole 120 below the elastic pad unit 200, are constructed such that the upper and lower sheets of each subsidiary sheet 220 may move horizontally in opposite directions within a range allowed by the flexibility of the strands provided in the flexible gap of the subsidiary sheet 220. Thus, the subsidiary sheets 220 change the forcible hard deformation of both the midsole 110 and the elastic pad units 200, which owes to their intrinsic properties to soft deformation. Particularly, the gap 204, formed on the upper plate 203 of each elastic pad unit 200, allows deformation of the midsole 110 due to the space defined by the gap 204 as shown in FIGS. 6 and 7, thus allowing and maintaining desirable soft deformation of the shoe 100. [62] Furthermore, when a person wearing the shoes 100 repeats the step motion of pressing the heel of the shoe sole, pressing the toe of the shoe sole and, thereafter, pressing the heel of the shoe again while walking or running, the one-way valves 300, installed in the intermediate air channel 117 and the air discharge channel 119 of the midsole 110, repeat the function of discharging air from the shoe 100 through the in¬ termediate air channel 117 and the air discharge channel 119. [63] Described in detail, when pressing the heel of the shoe sole, the one-way valve 300, installed in the second chamber 115, closes, so that air that was stored in the second chamber 115 is discharged to the atmosphere through the one-way valve 300 installed in the air discharge channel 119. In the above state, the first chamber 113 is not compressed, so that air which was drawn from the shoe 100 into the first chamber 113 through the air holes 104 and 106 of the insole 103 and the inner midsole 105 remains stored in the chamber 113. [64] Thereafter, when pressing the toe of the shoe sole, the first chamber 113 is compressed, thereby the air stored in the first chamber 113 flows through the one-way valve 300 of the intermediate air channel 117, thus reaching the second chamber 115. In the above state, the one-way valve 300, installed in the air discharge channel 119 of the second chamber 115, is closed, so that the air cannot pass through the valve 300, but remains in the second chamber 115. [65] Due to the above-mentioned repeated motion of alternately pressing the heel and toe of the shoe sole, shocks applied to the wearer's foot are efficiently absorbed and air in the shoe is efficiently discharged to the atmosphere. [66] When air in the shoes is discharged to the atmosphere as described above, the shoes efficiently reduce their inner temperatures and accomplish the desired deodorization function. Industrial Applicability [67] When wearing the shoes having the above-mentioned construction according to the present invention, the pressure parts of both the midsole and the inner midsole are in contact with the heel of a wearer's foot. Furthermore, the pressure parts are heavily pressed by the heel of the wearer's foot while walking or running, thus increasing the cushioning effect of the pressure parts. Two one-way valves are operated such that one draws air into the shoe and the other discharges air from the shoe, thus causing air in the shoe to flow in one direction and efficiently deodorizing and dissipating heat from the shoe. [68] Particularly, the elastic pad units stably move according to movement of the midsole, so that the shoe allows the wearer to be comfortable and stable without stimulating the foot sole of the wearer while walking.