Discussion of the Prior Art Generally, a footwear sole is classified into an outsole and a midsole.

The midsole is made of phylon, or bubbling polyurethane or polyethylene, and the outsole is made of a rubber(including a synthetic rubber).

Meanwhile, in specific cases, the footwear sole is used, without separated into the outsole and the midsole.

A typical footwear sole is constructed by using two representative methods. In a first method, the midsole and the outsole are separately manufactured, and then they are bonded with each other by using an adhesive material. Alternatively, in a second method, after the outsole in a soft or non-soft state which covers the adhesive material on the upper surface thereof is inserted into a molding machine, an appropriate amount of bubbling polyurethane is poured into the molding machine. Then, the heat and pressure is applied to the molding machine, to thereby bond the bubbled polyurethane, that is, the midsole and outsole, as a unitary body.

As a modified method in the second method, after a completed midsole is inserted into the molding machine into which the outsole is put, the heat and pressure is applied, to thereby bond the midsole and the outsole as a unitary body. Since the rubber material of outsole has a good quality of molding feature, there occurs no specific problem in performing a sophisticated processing work, but a phylon material of midsole should require an additional intermediate processing step to complete the formation of the midsole. Accordingly, the midsole is processed to match the shape of the outsole in the intermediate processing step (before the pressing process), which is achieved by the following method.

Firstly, a processed line(the line according to the shape of the outsole) is formed on the phylon sheet by using a gauge, and the whole of the edges along the processed line is grinded manually.

Of course, the midsole which completes the grinding operation becomes under the pressing process, to thereby be produced as a completed sole.

In the grinding method by manual work, however, there are several disadvantages in that the quality of the product is substantially deteriorated and the cutting angle and width for the pressing molding are not relatively precise and consistent. Moreover, there occur problems that the work efficiency is low and the occurrence frequency of bad products is high, to thereby reduce the production yield.

To solve these problems, there is presented an automatic grinding machine which is capable of easily performing the grinding operation.

However, the automatic grinding machine only exhibits many disadvantages as follows. Firstly, since a conventional grinding machine has a fixed cutter which can not adjust an angle, the edge(outer periphery) of the midsole is not grinded in a three-dimensional manner.

For instance, the midsole forms an arch portion with which the concave portion of the sole of a foot is in contact. In this case, it is natural that the left and right side angles of the arch portion should be different from each other. However, since the conventional grinding machine has the fixed cutter, the left and right side angles of the arch portion are not really different. Accordingly, there exists a problem that the arch portion should be completed in the manual work process.

Further, the conventional grinding machine is not suitable to the midsole which requires different grinding angles and widths.

Secondly, the conventional grinding machine has a structural disadvantage in that the whole edge of the midsole can not rotated by about 360 , when the midsole is processed. In other words, the half of the midsole is firstly processed in a rotated state by about 180 and the remaining half is then processed. Therefore, it can be lçnown that the product efficiency is low and the preciseness of the grinding state is deteriorated Further, the conventional grinding machine has a complicated structure and can not produce a precise midsole.

And since the cutter is comprised of stone, the abrasion of the cutter is easily generated and the grinding preciseness is accordingly decreased.

Moreover, since the cutter is replaced with a new cutter, whenever required, there occur problems that. cost consumption is increased and the damage of the cutter is easily generated due to a low impact resistance.

Additionally, in the conventional grinding machine, since the cutter can not adjust the cutting speed according to cutting quantity, there are disadvantages that the grinding preciseness is deteriorated and the production efficiency is low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a grinding machine for processing the side surface of a midsole in various shapes, before the midsole of phylon material is compressed under a pressing process, and for executing a greatly difficult work process in an ease and rapid manner, to thereby produce a great number of midsoles in a low production cost.

To achieve this and other objects according to the present invention, there is provided a grinding machine for processing a side surface of a footwear sole comprising: an acting unit which secures and rotates a phylon sheet and transfers a side surface of the phylon sheet to be correspond with a sample; a cutting angle adjusting unit which is engaged with the acting unit and adjusts a cutting angle of a cutting surface; a plate elevation adjusting unit which is engaged with the acting unit and the cutting angle adjusting unit and adjusts upper and lower cutting widths of the cutting surface; a cutting unit which is engaged with the cutting angle adjusting unit and the plate elevation adjusting unit and is ascended at the time when a cutter is in an angle movement forwardly and backwardly to directly perform a cutting operation; and a vibroisolating unit for preventing powder dust generated when grinding a midsole from being splashed.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and aspects of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which: FIG. 1 is a schematic top view illustrating a grinding machine for processing a side surface of a footwear sole according to the present invent ion; FIG. 2 is a schematic plan view illustrating a grinding machine for processing a side surface of a footwear sole according to the present invent ion; FIG. 3 is a schematic bottom view illustrating a grinding machine for processing a side surface of a footwear sole according to the present invent ion; FIG. 4 is a sectional view illustrating an acting unit embodied according to the present invention; FIG. 5 is a sectional view illustrating a holder within. an acting unit of FIG. 4; FIG. 6 is a side view illustrating a cutting angle adjusting unit embodied according to the present invention; FIG. 7 is a sectional view illustrating a cam within the cutting angle adjusting unit of FIG. 6; FIG. 8 is a sectional view illustrating a roller and parts related therewith within the cutting angle adjusting unit of FIG. 6; FIG. 9 is a sectional view illustrating a plate elevation adjusting unit embodied according to the present invention; FIG. 10 is a side view illustrating a cutting unit embodied according to the present invention; FIGS. 11 and 12 are views illustrating a cutter and its using state embodied according to the present invention; FIG. 13 is an exploded perspective view illustrating a midsole working jig embodied according to the present invention; FIG. 14 is a perspective view illustrating a midsole which is produced by a grinding machine embodied according to the present invention; FIG. 15 is a view illustrating a using state of a vibroisolating unit embodied according to the present invention; FIGS. 16 and 17 are sectional and part perspective views illustrating a cam manufacturing method embodied according to the present invention; and FIG. 18 is a sectional view illustrating an embodiment of an acting unit embodied according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an explanation on the construction and operation of the grinding machine for processing a side surface of a footwear sole embodied according to the present invention will be in detail discussed with reference to accompanying drawings. Referring to FIGS. 1 to 3, there is provided a grinding machine for processing a side surface of a footwear sole comprising: an acting unit 1 which secures and rotates a phylon sheet S and transfers the side surface of the phylon sheet S to be correspond with a sample; a cutting angle adjusting unit 2 which is engaged with the acting unit 1 and adjusts a cutting angle of a cutting surface 9a; a plate elevation adjusting unit 3 which is engaged with the acting unit 1 and the cutting angle adjusting unit 2 and adjusts upper and lower cutting widths of the cutting surface 9a; a cutting unit 4 which is engaged with the cutting angle adjusting unit 2 and the plate elevation adjusting unit 3 and is ascended at the time when a cutter 45 is in an angle movement forwardly and backwardly to directly perform a cutting operation; and a vibroisolating unit 5 for preventing powder dust generated when grinding a midsole 9 from being splashed..

The acting unit 1, as shown in FIG. 4, is assembled to a housing 15 which is movable on a sliding shaft 11, and a bracket 12 is installed on the housing 15. A shaft 13 is installed on the bracket 12 and a working jig 14 is coupled on the shaft 13. A spiral gear 8 formed on the bottom surface of the shaft 13 is engaged with a spiral gear 8' of the housing 15 which is coupled with the sliding shaft 11. A timing pulley 6 is coupled on the opposite side of the housing 15 and is connected to a driving shaft of a motor M by means of a timing belt 61. The driving force of the motor M is obtained by rotating the shaft 13 which is connected to the sliding shaft 11 to thus rotate the working jig 14 on the shaft 13.

The working jig 14 is comprised of a gripping table 14a and a guide table 14b, which have the same shapes. Also, the gripping table 14a and the guide table 14b have the same shape and standard as the outer periphery of a midsole 9. The phylon sheet S to be processed is attached on the gripping table 14a, and the outer peripheral surface of the guide table 14b is in contact with a guide roller 17. A plurality of needles 14c are installed in all directions on the upper surface of the gripping table 14a of the working jig 14, to thereby secure in a stabilized state the phylon sheet S to be molded. A stress bed 72 is positioned on the upper portion of the gripping table 14a and presses the phylon sheet S disposed on the gripping table 1ZLa.

The stress bed 72 is installed on an air cylinder 71, and the bracket 12 in which the air cylinder 71 is formed is movable forwardly and backwardly along a slide rail 12a on the upper surface of a horizontal frame B.

The housing 15 is connected to a piston rod of an air cylinder 1.5a on the bottom surface thereof, and if the air cylinder 15a operates, the housing 15 and the bracket 12 are pulled, to thereby contact the outer peripheral surface of the guide table 14b of the working jig 14 to the guide roller 17.

The guide roller 17 is installed on a holder 18 and is screw-coupled to a reed gear 19 on the rear end thereof. The reed gear 19 is engaged with a transmission gear 19a, and the transmission gear 19a is engaged with an adjusting gear 19b which is coupled on a shaft 16. The shaft 16 is installed on the horizontal frame B and is coupled with an adjusting handle 16a on the end thereof. On the other hand, the cutting angle adjusting unit 2 serves to adjust and determine the inclining angle of the cutting surface 9a of the midsole 9. In construction, a cam flange 23 on which a cam 2t,a for guiding an inclined degree of the cutting surface 9a is assembled is coupled on a shaft 22. The shaft 22 is installed on the horizontal frame B. and a spiral gear Sa Which is coupled on the lower end of the shaft 22 is connected to a spiral gear 8b on a horizontal shaft 21. A timing pulley 6a is assembled with an opposite side of the spiral gear 8b and is connected to a motor 42 by means of a timing belt. The timing pulleys 6 and 6a on the sliding shaft 11 and the horizontal shaft 21 are designed to have the same rotational ratio, to thereby make the rotational ratio of the working jig 14 and the cam 23a substantially same. Thus, the inclined degree of the cutter 45 is adjusted in accordance with the rotation of the cam 23a, such that the cutter 45 is placed at a desired position and angle on the phylon sheet S.

Meanwhile, the cam 23a is in contact with a cam roller 24 which is assembled on a holder 25, and a rack gear 26 of the holder 25 is engaged with a spur gear 26a. The spur gear 26a is engaged with another spur gear 27a on the same shaft, and the spur gear 27a is engaged with a rack gear 27 which is assembled with a link bracket 29 on the end portion thereof.

Each of the rational ratios of the rack gear 26 to the spur gear 26a and of the rack gear 27 to the spur gear 27a is 1 : 3, and for the purpose of compacting the size of the system, it is preferable that the forward and backward moving distance of the holder 25 moving along the orbit of the peripheral surface of the cam 23a is transmitted to the link bracltct 31 in the ratio of 1 : 3. The rack gear 26 and the spur gear 26a and the rack gear 27 and the spur gear 27a are installed in an additional housing, and the link 29 and the link bracket 31 are connected to the rear end of the rac gear 27 in an angle-moveable state. The rear end of the holder 25 is formed as an inclined surface 25a, and an adjusting handle 25b which has an inclined surface 25c on the lower end thereof is formed on the perpendicular direction to the inclined surface 25a. At the time, the inclined surfaces 25a and 25c are in surface-contact with each other.

If the adjusting handle 25b operates, the holder 25 moves forwardly and backwardly, such that the contacted distance of the cam roller 24 with the cam 23a is adjusted to thereby adjust the movement angle of the link bracket 29. Accordingly, the midsole 9 can be processed with the single cam 23a irrespective of a variety of sizes thereof. The cutting unit 4 is installed on the link bracket 31 and is comprised of a plate 41 on which the link bracket 31 is coupled. A motor 42 is installed on the plate 41 and is connected with pulleys 43 and 46 of the cutter 45 by means of a belt 44.

The cutter 45 takes a form of a circular cone having a large portion and a small lower portion. At the time, it is desirable that the rotational speed of the cutter 45 should be freely adjusted by using a direct current motor as the motor 42. The cutter 45 is manufactured by a tool steel. and a plurality of cutting edges 45a are formed by a constant interval in all directions on the whole outer peripheral surface of the cutter 45. As a result, powder dust(minute scrap) generated when grinding the phylon sheet S is not accumulated on the outer peripheral surface of the cutter 45.

The plate elevation adjusting unit 3 is installed on the both sides of the plate 41. The plate elevation adjusting unit 3 is comprised of a cutting means installing bracket 34 on which the plate 41 is assembled. The cutting means installing bracket 34 is coupled by means of a pin 33 on the upper end of an elevating shaft 32 and is angle-movable. The elevating shaft 32 is mounted ascendably on an elevating hole 37 of the bracket 31 on the horizontal frame B and is coupled to a guide roller 32a on the lower end thereof. The guide roller 32a is in contact with a "Z" cam 36 which is assembled on a cam shaft 35, and the "Z" cam 36 is protruded on the outer peripheral surface thereof and serves to regularly elevate the elevating shaft 32. On the rear end of the cam shaft 35 on which the "Z" cam 36 is assembled, is coupled a timing pulley and is connected to a motor M by means of a timing belt. An elevation nut 38 is formed on the elevating shaft 32 and adjusts an elevating length of the elevating shaft 32 in accordance with the size of the midsole 9. On the other hand. FIGS. 16 and 17 show a processing work state of the cam 23a. A circular type of cam material C is coupled on the cam flange 23, and then the cam flange 23 is rotated. A working material holder 28 on which a working material 28a for displaving the orbit of the cam on the cam material C is installed is associated on the holder 25. Next, the completed midsole 9 is coupled to the gripping table 14a and the cutter 45 is guided along the cutting surface 9a of the midsole 9. As a result, the cutting angle of the plate 41, on which the cutter 45 is installed, is varied and the variable degree of the plate 41 is transmitted through the link bracket 29 and the rack gear 27, the spur gear 27a, the rack gear 26, the spur gear 26a which are connected to the bracket 31 to the holders 25 and 18, to thereby guide the working material holder 28.

The working material 28a of the working material holder 28 displays the orbit of the cam 23a on the cam material C of the cam flange 23, which is in contact with the roller 24, along the cutting surface 9a of the completed midsole 9. Thus, the manufacturing of the cam 23a is achieved.

To prevent the powder dust generated when grinding the midsole 9 from being splashed, there is provided a vibroisolating unit 5, which is comprised of an absorption duct 52 which is installed on the rear portion of the cutter 45 of the cutting unit 4 and an air injection nozzle 53 which is formed on the upper portion thereof and blows the power dust to the absorption duct 52.

Further, an air injection nozzle 54 is installed on the front side of the horizontal frame B and blows the powder dust to the absorption duct 52, to thereby prevent the powder dust from being splashed to the exterior.

Additionally, a vibroisolating panel 51 is installed on the top surface and left and right sides of the horizontal frame B, respectively and blows the powder dust to the absorption duct 52, to thereby prevent the powder dust from being splashed to the exterior. Under the construction as the above, after the working jig 14 is selected in accordance with the size and shape of the midsole 9 to be processed, the phylon sheet S is secured on the.gripping table 14a. In this working state, an operator can produce a precise product in an ease manner. The working jig 14 is assembled on the shaft 13 of the acting unit 1, and the cam 23a, which guides a cutting angle corresponding to the shape of the outer peripheral surface of the midsole 9 and the angle of the cutting surface 9a, is coupled to the cam flange 23 of the cutting angle adjusting unit 2. Under the above state. the outer peripheral surface of the phylon sheet S is mounted to correspond with the outer peripheral surface of the gripping table 1tea. on the gripping table 14a.

At the time, the phylon sheet S is stably secured by the plurality of needles 14c on the upper surface of the gripping table 14a, and the stress bed 72, which is descended by the operation of the air cylinder 71, is in contact with tlle upper surface of the phylon sheet S, to thereby prevent the phylon sheet S from being moved. Of course, during the above process. the operator turns the adjusting handle 16a and rotates the reed gear 19 which is engaged with the adjusting gear 19b and the transmission gear 19a, to thereby rotate the holder 18 which is screw-coupled to the reed gear 19 in the forward/baclçward directions.. As a result, since the interval of the guide table 14b which is in contact with the guide roller 17 is adjusted, a working. starting point of the phylon sheet S is adjustable in accordance with the size of the midsole 9. The guide table 14b is in contact with the guide roller 17 on the rear side thereof, and the phylon sheet S which is coupled to the gripping table 14a is in contact with the cutter 45. Then, if the motor M is driven, the sliding shaft 11 of the acting unit which is connected to the motor M and the timing pulley 6 via the timing belt 61, the horizontal shaft 21 of the cutting angle adjusting unit 2, and the cam shaft 35 are rotated in the same rotational ratio.

Accordingly, the guide table 14b of the working jig 14 which is assembled on the shaft 13 rotates by about 360 and is simultaneously moved in the forward and backward directions along the slide rail 12a, while being contacted with the guide roller 17. At the time, the gripping table 14a is slid forwardly and backwardly, while rotating by about 360 , and the phylon sheet S secured on the gripping table 14a is grinded on the outer peripheral surface thereof by means of the cutter 45.

The above working process is possible because the shaft 13 rotating the working jig 14 and the housing 15 on the lower end of the bracket 12 which is connected to the shaft 13 are always pulled in the backward direction by the air- cylinder 15a, to thereby contact the guide table 14b with the guide roller 17 under the rotation of the shaft 13 and to allow the bracket 12 to be slid along the slide rail 12a forwardly and backwardly.

Accordingly, the phylon sheet S secured on the gripping table 14a is guided by the guide table 14b which is contacted with the guide roller 17 and is grinded by the cutter 45. The cutting angle of the midsole 9 which is processed in the state of being secured on the gripping table 14a is adjusted and determined by the cutting angle adjusting unit 2. The operation of the cutting angle adjusting unit 2 will be discussed hereinafter.

The phylon sheet S secured on the gripping table 14a is grindetl by the cutter 45 and simultaneously the cam 23a. which is assembled on tlle cam flange 23 on the shaft 22 connected to the horizontal shaft 21 of the cutting angle adjusting unit 2, is rotated. The roller 24 which is in contact with the cam 23a moves the rad: gear 26 forwardly and backwardly, while the holder 25 is slid forwardly and backwardly along the outer peripheral surface of the cam 23a. As a result, the spur gear 26a is rotated forwardly and reversely, and the forward and reverse rotation force of the spur gear 2Ga is transmitted to the spur gear 27a, to thereby move the rack gear 27 forwardly and backwardly. Of course, each rotation ratio of the rac gear 26 to the spur gear 26a and the rack gear 27 to the spur gear 27a is 1 : 3.

At the time, assuming that the moving width of the holder 25 to which the roller 24 is coupled is "1", the width of the link bracket 31 which is connected to the rack gear 27 is "3", to thereby angle-move the plate 41 which is connected to the link bracket 29. As a result, the cutter 45 on the plate 41 is in the angle movement, to thereby grind the outer peripheral surface of the phylon sheet S which is secured on the gripping table 14a at an accurate cutting angle. The processing width of the cutting surface 9a of the cutting angle adjusting unit 2 is adjusted by the following process.

As the elevating shaft 32 to which the guide roller 32a contacted with the "Z" cam 36 is coupled is elevated. the cutting means installing braclcet 34 which is associated to be angle-movable is ascended on the basis of the pin 33. Next, the plate 41 which is associated on the cutting means installing braclçet 34 is elevated, and the upper and lower grinding interval between the cutter 45 an the phylon sheet S is adjustable, to thereby adjust the upper and lower grinding width of the cutting surface 9a.

Accordingly, the cutter 45 is ascended by the elevating operation of the elevating shaft 32, and simultaneously the angle adjustment of the cutting surface 9a is achieved by the cam 23a, to thereby perform the grinding operation of the cutting surface 9a. In other words, one midsole of the left and right midsoles is completed. On the other hand, if the processing of another midsole 9 is executed, the working jig 14 is simply turned over and the same working process as mentioned in the above is applied. In more details, after the working jig 14 is separated from the shaft 13, the gripping table 14a is disposed at the lower portion and the guide table 14b is disposed at the upper portion. Then, if the overturned working jig 14 is coupled on the shaft 13, the shapes of the guide table 14b and the gripping table 14a of the working jig 14 are in a reverse direction <BR> <BR> <BR> <BR> <BR> <BR> to that upon the first process. At the t time. the cam 23a is assembled in a reverse order to adjust the angle of the cutting surface 9a. but since the shape of the cutting surface 9a is formed in the left and right synmctrical directions and the angle of the cutting surface 9a is the same, the reverse order of assembly of the cam 23a does not matter.

In other words, if the starting point of the gripping table bia which is guided by the guide roller 17 corresponds to the starting point of the cam 23a, the reverse order of assembly of the cam 23a is not required.

Meanwhile, the. holder 25, which adjusts the angle of the cutting surface 9a, while being contact with the cam 23a, rotates the adjusting handle 25b, to thereby move the holder 18 forwardly and backwardly.

Since the operating distance of the roller 24 which is in contact with the cam 23a is adjusted, the moving distance of the link bracket 31 is adjusted and the angle of the cutting surface 9a is appropriately adjustable in accordance with the size of the midsole 9. Hence, the operator does not have various cams 23a according to the size of the midsole 9, and with the simple operation as mentioned above, the midsole 9 can be grinded.

The vibroisolating unit 5 serves to all absorb the powder dust generated during the grinding operation to the absorption duct 52. to thereby maintain a clean working environment and prevent the pollution of surroundings due to the powder dust. FIG. 18 shows the acting unit which secures the midsole 9 on the gripping table 14a by the vacuum state. without installing the needles on the gripping table 14a.

Referring to FIG. 1S, a hole 81 is formed on the center portion of the gripping table 14a, and an inclined surface 80 which is inwardly inclined is formed towards the hole 81. Then, a hole 90, which is opened on the upper portion thereof, is formed on the center portion of the shaft 13, and a plurality of holes 91 which are crossed perpendicularly to the hole 90 are formed on the lower portion of the hole 90. Next, the upper end of the shaft 13 is inserted into the hole 80 of the working jig 14 and secured by means of a key or set bolt, and then a hole 301 is formed on a bearing casing 300 of the bracket 12. A flexible hose 130 is connected to the hole 301 and is also connected to a connection hose 120 which is connected to a solenoid valve 100. A connection hose 111 which is connected to a blower 110 is connected to the solenoid valve 100. It is of course natural that a sealing technique is adapted to the interior of the bearing casing 300, to keep the closing of the bearing casing 300, and a silencer 101 is preferably attached on the solenoid valve 100. Under the construction as the above, the nli(lsole 9 can be accurately secured on the gripping table 14a. without installing the needles on the gripping table 14a. Accordingly. since the marks mace by the needles are not formed on the midsole 9, the quality of product can be improved, and further since the midsole is preserved without any flaw or scar, the durability of the product can be ensured.

If the blower 110 operates, the solenoid valve 100 is simultaneously operated to connect the upper and lower connection hoses 120 and 111.

Thereby, the air remaining within the holes 81 and 91 on the shaft 13 of the working jig 14 and flexible hose 130 is discharged to the exterior.

Accordingly, the whole hose lines are in the vacuum state, and the midsole 9 on the upper surface of the gripping table 14a is absorbed toward the hole 81 and is solidly contacted with the inclined surface 80 of the gripping table 14a. Since the following working process is the same as the above, an explanation thereon will be avoided for the brevity of description of the present invention. The structure as mentioned above removes the needles on the gripping table 14a, to thereby improve the quality of midsole and the durability thereof. In addition, there is an advantage that the stress bed 72 for stressing the midsole 9 from the upper portion to the lower portion is not required, when the midsole 9 is grinded by the cutter 45. In other words, the position of the midsole 9 can be stably secured to grind the side surface of the midsole 9, without adapting the stress bed 72 and the air cylinder 71. Therefore, since the intereference of the grinding operation caused due to the stress bed and the peripheral devices is not generated, various functions, such as the angle adjusting function of the cutter, the rotation function of about 3604 of the working jig, the width adjusting function of the cutting surface, the cutting angle adjusting function and so on, can be executed, such that more precise products as well as a great variety of products can be presented.

Further, the problem that the cutter is contacted with the peripheral devices can be solved, such that the durability of the cutter may be improved. As apparent from the foregoing, there is provided a grinding machine for processing a side surface of a footwear sole, in which since the angle adjustment of a cutter is freely made, the different left and right angles of midsole can be processed, and since the edges of the midsole are rotated by about 3600 , the midsole can be precisely grinded. Further, in the grinding machine according to the present invention, the grinding width adjustment of a cutting surface can be easily made and the durability of the cutter can be considerably improved. Therefore, if the material to be processed is inserted and a simple manipulation is then executed, the midsole can be precisely produced in a rapid manner. As compared with the conventional grinding machine, the grinding machine according to the present invention ensures improved cost saving and productivity and decreases the occurrence ratio of bad products, to thereby produce a precise degree of midsole on a large scale. Although a preferred form of the invention has been described, it will be understood by those skilled in the field that variations therefrom, and analogous uses, are within the knowledge of those skilled in the art. Accordingly, it is intended that the scope of the invention be defined, not by the scope of the foregoing description, but rather by the scope of, the claims as interpreted in view of the pertinent prior art.