Patent Publication Number: US-2019176284-A1

Title: Nozzle, nozzle module, and machine tools provided with them

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority under 35 USC 119 of Japanese Patent Application No. 2017-237801 filed on Dec. 12, 2017, the entire disclosure of which is incorporated herein by reference in its entirety for all purposes. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a nozzle and a nozzle module for supplying a fluid, and machine tools provided with them. More specifically, the present invention relates to a nozzle which discharges coolant such as water or oil. The nozzle of the present invention is applicable to various machine tools such as a grinding machine, a drilling machine, a cutting machine, or a machining center. 
     2. Description of the Related Art 
     Conventionally, when a workpiece made of a metal or the like is machined into a desired shape by a machine tool such as the grinding machine or the drilling machine, coolant is supplied to a predetermined area including a contact portion between the workpiece and a tool such as a blade to cool heat generated during machining or remove debris of the workpiece (also referred to as chips) from a machining spot. Cutting heat caused by high pressure and frictional resistance at the contact portion between the workpiece and the blade abrades the edge of the blade and lowers the strength of the blade, thereby reducing tool life of the blade. In addition, if the chips of the workpiece are not sufficiently removed, they can stick to the edge of the blade during machining, which may degrade machining accuracy. 
     The coolant decreases the frictional resistance between the tool and the workpiece, removes the cutting heat, and performs cleaning to remove the chips cut off from a surface of the workpiece. Therefore, for the machine tool, it is important to discharge the coolant to the contact portion between the tool and the workpiece and the periphery thereof accurately and efficiently. 
     For example, Japanese Utility Model Application Laid-Open Publication No. 1985-175981 published on Nov. 21, 1985, discloses a conduit for supplying coolant or the like and a nozzle connected to the end of the conduit. It is possible to obtain a desired length of the conduit by connecting a plurality of pairs of female and male units in spherical contraposition to each other. The nozzle may have a female part forming spherical contraposition with a male part of the conduit on the inlet side and be formed in the shape of a truncated cone on the outlet side. Otherwise, the nozzle may have a thickness dimension gradually decreasing and a width dimension gradually increasing toward the outlet. 
     In the case of using the conduit and the nozzle as a coolant supply means for the machine tool, a cooling efficiency is not good because a discharge direction of the coolant from the nozzle tip is not determined with a high accuracy and sometimes the coolant is not concentrated on the machining spot. 
     According to the conventional technology as described above, the coolant cannot be discharged or sprayed in a sufficiently appropriate position or direction. In addition, in the case that the type of the machine tool, the shape or size of the tool such as a grinding blade, or the shape or size of the workpiece changes, there exists a problem that it is difficult to discharge the coolant to a predetermined area including the contact portion between the tool and the workpiece accurately and efficiently. 
     SUMMARY OF THE INVENTION 
     The present invention was made in light of the problems mentioned above. An object of the present invention is to provide a nozzle capable of improving the straightness of a fluid, for example, the coolant, discharged or sprayed from its outlet and concentrating the fluid on a target position or in a target direction. 
     In order to achieve the above object, an aspect of the present invention provides a nozzle including an inlet through which a fluid is supplied, an outlet through which the fluid is discharged, and an interior space connecting the inlet and the outlet. A plate-shaped member having a cross section of a predetermined shape is disposed in the interior space to form a flow path of the fluid. 
     Another aspect of the present invention provides a nozzle module including a hollow body to which a fluid is supplied, and a fluid discharge part for discharging the fluid to the outside, the fluid discharge part being connected to the body. One or a plurality of nozzles are formed in the fluid discharge part, and each of the one or the plurality of nozzles includes an inlet through which a fluid is supplied, an outlet through which the fluid is discharged, and an interior space connecting the inlet and the outlet. A plate-shaped member having a cross section of a predetermined shape is disposed in the interior space of the nozzle to form a flow path of the fluid. 
     According to many embodiments of the present invention, a plate-shaped member having a predetermined cross section is disposed in the interior space of the nozzle to form a flow path of a fluid such as coolant or a machining fluid, thereby increasing straightness of the fluid and capable of discharging the fluid at a target position or direction. Therefore, the fluid such as the coolant can be discharged to a target accurately and efficiently. Thus, diffusion (dispersion or turbulence) out of the target position can be prevented. The plate-shaped member causes a flow of the fluid in the interior space of the nozzle to be laminar or rectified. In addition, according to many embodiments of the present invention, the plate-shaped member having a plurality of folds parallel to the flow of the fluid is disposed in the interior space of the nozzle. Since the plate-shaped member is press-fitted to the wall surface of the interior space of the nozzle by its own elastic force, disposition and assembly of the plate-shaped member can be easily performed. 
     According to some embodiments of the present invention, the plate-shaped member forms an inner flow path surrounded by the plate-shaped member and outer flow paths formed in the outer side of the plate-shaped member and between the wall surface of the interior space of the nozzle and the plate-shaped member. Only the thickness of the plate-shaped member inhibits the flow of the fluid, and there is little loss of the flow rate. Further, it is possible to discharge the fluid at the target position or a predetermined angle in the form ensuring a sufficient flow rate of the fluid from the inner flow path. Since the fluid discharged from the outer flow paths also has straightness, it contributes to the cooling of the workpiece and helps to remove sludge (i.e. debris from the machining) and chips in the case that the nozzle of the present invention is applied to the machine tool. 
     In addition, according to some embodiments of the present invention, one or more nozzles are formed in a nozzle module and the plate-shaped member having a predetermined cross section is disposed in the interior space of one or more nozzles to form one or more flow paths of the fluid. This increases straightness of the fluid and the fluid such as the coolant can be discharged from the outlet of each nozzle at a target position or angle accurately and efficiently. Since the plate-shaped member is press-fitted to the wall surface of the interior space of the nozzle by its own elastic force, disposition and assembly of the plate-shaped member can be easily performed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in conjunction with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended to limit the scope of the invention. 
       Here: 
         FIG. 1  shows an example of a machine tool including a nozzle according to an embodiment of the present invention. 
         FIG. 2  shows a nozzle connected to a coolant hose according to a first embodiment of the present invention. 
         FIG. 3  shows a nozzle provided with a plate-shaped member having a cross section in the form of a four-petaled flower. 
         FIG. 4  shows an operation of installing the plate-shaped member having the cross section in the form of the four-petaled flower in the nozzle. 
         FIG. 5  is a cross-sectional view of the nozzle with the plate-shaped member having the cross section in the form of the four-petaled flower disposed in the interior space of the nozzle. 
         FIG. 6A  is a perspective view of a plate-shaped member having a cross section in the form of a four-petaled flower which is not tapered. 
         FIG. 6B  is a perspective view of a plate-shaped member having a cross section in the form of a four-petaled flower which is tapered. 
         FIG. 7  is an exterior view of a nozzle provided with a plate-shaped member having a cross section in the form of a four-pointed star, according to a second embodiment of the present invention. 
         FIG. 8  shows an operation of installing the plate-shaped member having the cross section in the form of the four-pointed star in the nozzle. 
         FIG. 9  is a cross-sectional view of the nozzle with the plate-shaped member having the cross section in the form of the four-pointed star disposed in the interior space of the nozzle. 
         FIG. 10  is a perspective view of the plate-shaped member having the cross section in the form of the four-pointed star. 
         FIG. 11  shows various types of the cross section of the plate-shaped member ((A) to (L)), and a slit and plate-shaped members with the slit ((a) to (c)). The drawings (a) to (c) of  FIG. 11  are a cross-sectional view for showing the slit, a perspective view of a plate-shaped member with the slit having a uniform cross section, and a perspective view of a plate-shaped member with the slit which is tapered, respectively. 
         FIG. 12  shows a different example of a machine tool including a nozzle of an embodiment of the present invention. 
         FIG. 13  shows another example of a machine tool including a nozzle of an embodiment of the present invention. 
         FIG. 14  shows a nozzle module connected to the coolant hose according to a third embodiment of the present invention. 
         FIG. 15  shows a nozzle module provided with a plate-shaped member having a cross section in the form of a four-petaled flower. 
         FIG. 16  shows an operation of installing the plate-shaped member having the cross section in the form of the four-petaled flower in the nozzle module. 
         FIG. 17  is a cross-sectional view of the nozzle module with the plate-shaped member having the cross section in the form of the four-petaled flower disposed in the interior space of the nozzle module. 
         FIG. 18  shows a nozzle module provided with a plate-shaped member having a cross section in the form of a four-pointed star according to a fourth embodiment of the present invention. 
         FIG. 19  shows an operation of installing the plate-shaped member having the cross section in the form of the four-pointed star in the nozzle module. 
         FIG. 20  is a cross-sectional view of the nozzle module with the plate-shaped member having the cross section in the form of the four-pointed star disposed in the interior space of the nozzle module. 
         FIG. 21  shows a nozzle module including a cylindrical fluid discharge part in which a plurality of nozzles are arranged in a row according to a fifth embodiment of the present invention. 
         FIG. 22  shows an operation of installing a plate-shaped member in each nozzle of the nozzle module. 
         FIG. 23  is a cross-sectional view of the nozzle module with the plate-shaped member disposed in the interior space of the nozzle module. 
         FIG. 24  shows arrangements of nozzles formed in the fluid discharge part. 
         FIG. 25  shows a nozzle module connected to the coolant hose according to a sixth embodiment of the present invention. 
         FIG. 26  shows a nozzle module including a panel-shaped fluid discharge part in which a plurality of nozzles are arranged in a row. 
         FIG. 27  shows an operation of installing a plate-shaped member in each nozzle of the nozzle module. 
         FIG. 28  is a cross-sectional view of the nozzle module with the plate-shaped member disposed in the interior space of the nozzle module. 
         FIG. 29  shows an example of a machine tool including a nozzle module according to an embodiment of the present embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiments in which a nozzle or a nozzle module of the present invention is applied to machine tools such as a grinding machine or a machining center will be mainly described herein. However, the field of application of the present invention is not intended to be limited to the illustrated examples. The nozzle or the nozzle module of the present invention is applicable to various situations requiring supply of a fluid. 
     Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. 
       FIG. 1  shows an example of a machine tool including a nozzle according to one of some embodiments of the present invention. The machine tool of the present example is a surface grinding machine. A surface grinding machine  100  includes a grinding blade (a grindstone)  2 , a protection cover  4 , a height adjusting unit  6 , a coolant pipe  8 , a coolant hose  9 , and a nozzle  10 . Although not shown in the drawing, the surface grinding machine  100  includes a table for moving a workpiece W 1  in a plane, and a column for vertically moving the workpiece W 1  or the grinding blade  2 . 
     The grinding blade  2  is rotationally driven in the clockwise direction in the plane of  FIG. 1  by a driving source (not shown in the drawing). A surface of the workpiece W 1  is ground by friction between the outer circumferential surface of the grinding blade  2  and the workpiece W 1  at a grinding spot G. The protection cover  4  surrounds the grinding blade  2  rotating at a high speed and protects workers around the grinding machine by preventing chips of the workpiece W 1  from scattering during grinding. 
     The height adjusting unit  6  is provided on the protection cover  4 , and fixes the coolant pipe  8  movable up and down at a desired height. By this, it is possible to position the nozzle  10  connected to the coolant pipe  8  at a suitable height with respect to the grinding blade  2  and the workpiece W 1 . The nozzle  10  is connected to one end of the coolant pipe  8  via a coolant hose  9  and a tank in which the coolant (for example, water, oil, or the like) is stored (not shown in the drawing) is connected to the other end of the coolant pipe  8 . The nozzle  10  can be fixed at the optimum position or in the optimum direction by manipulating the height adjusting unit  6  or adjusting the angle of the coolant hose such that the coolant is discharged from the nozzle  10  toward the grinding spot G. 
     First Embodiment 
       FIG. 2  shows connection between the nozzle  10  and the coolant hose  9  according to a first embodiment of the present invention. It is possible to obtain a desired length of the coolant hose  9  by connecting a plurality of pairs of female and male units in spherical contraposition to each other. The material of the coolant hose  9  may include resin (plastic). Further, an angle at which two pairs of the units can be appropriately adjusted by the connection mechanism, and, as a result, the direction of the nozzle  10  can be determined. The nozzle  10  may be made of resin (plastic), but the present invention is not limited thereto. 
       FIG. 3  is an enlarged view of the nozzle  10 ,  FIG. 4  shows a state in which a plate-shaped member  11  is being inserted into the nozzle  10 , and  FIG. 5  is a cross-sectional view showing a state in which the the plate-shaped member  11  is fixed in the nozzle  10 . As clearly understood from these drawings, the nozzle  10  is connected to the coolant hose  9  and includes an inlet  10 - a  through which the coolant (or a fluid) flows in, an outlet  10 - b  through which the coolant is discharged, and a wall surface  10   c  forming an interior space connecting the inlet  10 - a  and the outlet  10 - b . The inlet  10 - a  has a spherical surface and is connected to the male unit at the end of the coolant hose  9 . The wall surface  10   c  is cylindrical, and a plate-shaped member  11  of uniform cross section is inserted into the interior space of the nozzle  10  from the inlet  10 - a  or the outlet  10 - b  and fixed to the wall surface  10 - c . In the case that the wall surface  10   c  is tapered to form a truncated cone shaped interior space of the nozzle such that its cross section gradually decreases from the inlet toward the outlet, the plate-shaped member  11  to be inserted into the nozzle  10  may have a cross section gradually decreasing from the inlet toward the outlet in accordance with the shape of the wall surface  10 - c . The former plate-shaped member  11  is shown in  FIG. 6A , and the latter one is shown in  FIG. 6B . 
     The plate-shaped member  11  shown in each of  FIGS. 3 to 5 ,  FIG. 6A  and  FIG. 6B  has a cross section in the form of a four-petaled flower and includes three folds  11 - t  and one slit  11 - s  to form the flower shape. The plate-shaped member  11  is formed by, for example, cutting a thin flat plate made of metal such as stainless steel into a predetermined size, and then bending it into the four-petaled flower. It is also possible to cut a thin flat plate after bending it into the flower shape. The plate-shaped member  11  has elasticity due to the three folds  11 - t  and the slit  11 - s . In the case that the inner diameter of the wall surface  10   c  of the nozzle  10  and the outer diameter of the plate-shaped member  11  are equal, or the outer diameter of the plate-shaped member  11  is slightly larger than the inner diameter of the wall surface  10   c  of the nozzle  10  but the plate-shaped member  11  is compressed by the slit so that they become equal, an elastic force is generated as a result of repulsion against the compression and the plate-shaped member  11  is press-fitted (i.e. pressed and fixed) to the wall surface  10   c  forming the interior space of the nozzle  10 . Since the plate-shaped member  11  is press-fitted to the wall surface  10   c  of the interior space of the nozzle  10  by its own elastic force, arrangement and assembly of the plate-shaped member  11  can be easily performed. 
     In the case that the plate-shaped member  11  having the cross section in the form of the four-petaled flower is inserted and fixed in the nozzle  10 , the plate-shaped member  11  forms an inner flow path  12 - c  surrounded by it and outer flow paths  12 - d   1  to  12 - d   4  in the outer side of the plate-shaped member  11  and between the wall surface  10   c  of the interior space of the nozzle  10  and the plate-shaped member  11 . Since the plate-shaped member  11  is in the form of a thin plate, only its thickness inhibits the flow of the fluid and there is little loss of the overall flow rate. The fluid flowing in the interior space is guided by the plate-shaped member  11  having the cross section in the form of the four-petaled flower such that turbulence is prevented and the flow becomes laminar or rectified. In other words, the plurality of folds  11 - t  and the slit  11 - s  are parallel to the flow of the fluid, and a curved surface between two adjacent folds  11 - t  and a curved surface between the fold  11 - t  and the slit  11 - s , as well as the plurality of folds  11 - t  and the slit  11 - s , guide the fluid to increase straightness of the fluid. Therefore, the inner flow path  12 - c  enables the fluid to be discharged at the target position or a predetermined angle. Thus, diffusion (dispersion or turbulence) of the fluid out of the target position can be prevented. Since the fluid discharged from the outer flow paths  12 - d   1  to  12 - d   4  also has straightness, it contributes to the cooling of the workpiece W 1  and helps to remove sludge and chips in the case that the nozzle  10  is applied to the machine tool. 
     According to the present embodiment, the slit  11 - s  is formed in the plate-shaped member  11  and the plate-shaped member  11  is press-fitted to the wall surface  10   c  of the interior space of the nozzle due to the elastic force generated from the repulsion against the compression by the slit  11 - s . However, the slit  11 - s  is not necessarily required. In other embodiments, the plate-shaped member  11  can be press-fitted to the wall surface  10   c  by adjusting the outer diameter of the plate-shaped member  11  and the inner diameter of the wall surface  10 - c . The plate-shaped member  11  may be fixed in the interior space by a method other than the press fit, such as adhesion. This also applies to other embodiments than the first embodiment. The shape of the four-petaled flower caused by inserting the plate-shaped member  11  into the interior space can be appropriately changed by adjusting each of the intervals of the three folds  11 - t  and the slit  11 - s . By this, flow rates of the fluid flowing through the inner flow path  12 - c  and the outer flow paths  12 - d   1  to  12 - d   4  can be varied. While the plate-shaped member  11  has the cross section in the form of the flower having four petals according to the present embodiment, the number of the petals may be two or more and an example having eight petals is shown in (A) of  FIG. 11  which will described later. In addition, the bulge of the petal can also be properly changed, for example, to (E) or (I) of  FIG. 11 . Thus, the ratio of the flow rate of the fluid flowing through the inner flow path  12 - c  to the flow rate of the fluid flowing through the outer flow paths  12 - d   1  to  12 - d   4  can be determined. Generally, as the number of the petals increases, the flow rate of the fluid flowing through the inner flow path  12 - c  increases. Similarly, as the bulge of each petal is rounder (for example, the bulge of (I) of  FIG. 11  is rounder than (E) of  FIG. 11 ), the flow rate of the fluid flowing through the inner flow path  12 - c  increases. 
     Second Embodiment 
       FIGS. 7 to 10  show a nozzle according to a second embodiment of the present invention. The same reference numerals are used for the same features as those of the first embodiment and descriptions of the same features will be omitted.  FIG. 7  is an enlarged view of the nozzle  10 ,  FIG. 8  shows a state in which a plate-shaped member having a cross section in the form of a four-pointed star  111  is being inserted into the nozzle  10 , and  FIG. 9  is a cross-sectional view showing a state in which the the plate-shaped member  111  is fixed in the nozzle  10 . The wall surface  10   c  is cylindrical, and the plate-shaped member  111  having the uniform cross section shown in  FIG. 10  is inserted into the interior space of the nozzle  10  from the inlet  10 - a  or the outlet  10 - b  and fixed to the wall surface  10 - c . In the case that the wall surface  10   c  is tapered to form a truncated cone shaped interior space of the nozzle such that its cross section gradually decreases from the inlet toward the outlet, the plate-shaped member  111  to be inserted into the nozzle  10  may have a cross section gradually decreasing from the inlet toward the outlet in accordance with the shape of the wall surface  10 - c.    
     The plate-shaped member  111  has the cross section in the form of the four-pointed star and includes seven folds  111 - t  and one slit  111 - s  to form the star shape. In the case that the plate-shaped member  111  having the cross section in the form of the four-pointed star is inserted and fixed in the nozzle  10 , the plate-shaped member  111  forms an inner flow path  112 - c  surrounded by it and outer flow paths  112 - d   1  to  112 - d   4  in the outer side of the plate-shaped member  111  and between the wall surface  10   c  of the interior space of the nozzle  10  and the plate-shaped member  111 . Since the plate-shaped member  111  is in the form of a thin plate, only its thickness inhibits the flow of the fluid and there is little loss of the overall flow rate. The flow of the fluid is guided by the plate-shaped member having the cross section in the form of the four-pointed star such that turbulence is prevented and the flow becomes laminar or rectified. In other words, the plurality of folds  111 - t  and the slit  111 - s  are parallel to the flow of the fluid, and a curved surface between two adjacent folds  111 - t  and a curved surface between the fold  111 - t  and the slit  111 - s , as well as the plurality of folds  111 - t  and the slit  111 - s , guide the fluid to increase straightness of the fluid. Therefore, the inner flow path  112 - c  enables the fluid to be discharged at the target position or a predetermined angle. Thus, diffusion (dispersion or turbulence) of the fluid out of the target position can be prevented. Since the fluid discharged from the outer flow paths  112 - d   1  to  112 - d   4  also has straightness, it contributes to the cooling of the workpiece W 1  and helps to remove sludge and chips in the case that the nozzle  10  is applied to the machine tool. While the plate-shaped member  111  has the cross section in the form of the four-pointed star according to the present embodiment, it may have different types of cross section. For example, an example of the four-pointed star is shown in (H) of  FIG. 11 , which will be described later, and an example of a eight-pointed star is shown in (L) of  FIG. 11 . The number of limbs (or arms) of the star is three or more. The sharpness of the limbs (arms) may also be properly changed. Thus, the ratio of the flow rate of the fluid flowing through the inner flow path  112 - c  to the flow rate of the fluid flowing through the outer flow paths  112 - d   1  to  112 - d   4  can be determined. Generally, as the number of the limbs increases, the flow rate of the fluid flowing through the inner flow path  112 - c  increases. Similarly, as each limb has a gentle slope, the flow rate of the fluid flowing through the inner flow path  112 - c  increases. According to the present embodiment, the slit  111 - s  is formed in the plate-shaped member  111  and the plate-shaped member  111  is press-fitted to the wall surface  10   c  of the interior space of the nozzle due to the elastic force generated from the repulsion against the compression by the slit  111 - s . However, the slit  111 - s  is not necessarily required. The plate-shaped member  111  can be press-fitted to the wall surface  10   c  by adjusting the outer diameter of the plate-shaped member  111  and the inner diameter of the wall surface  10 - c . The plate-shaped member  111  may be fixed in the interior space by a method other than the press fit, such as adhesion. This also applies to other embodiments than the second embodiment. 
     The drawings (A) to (L) of  FIG. 11 , which has been already referred to when describing the first and the second embodiments, show various modifications of the cross section of the plate-shaped member. Each of the drawings (A), (E) and (I) of  FIG. 11  shows a flowerlike cross-sectional shape. The drawing (B) of  FIG. 11  shows an elliptical cross sectional shape, and the drawings (C), (D), (F), (J) and (K) of  FIG. 11  show triangular and polygonal cross sectional shapes. The drawing (G) of  FIG. 11  shows a gourd-like cross-sectional shape, and each of the drawings of (H) and (L) shows a star like cross-sectional shape. The plate-shaped member may adopt any other suitable cross-sectional shape. While no slit is provided in any of (A) to (L) of  FIG. 11 , each of them may have a slit as shown in (a) of  FIG. 11 . Further, the plate-shaped member may be straight such that its cross section is uniform as shown in (b) of  FIG. 11 , or may be tapered such that its cross section gradually decreases toward the outlet as shown in (b) of  FIG. 11 . In the case of (c) of  FIG. 11 , the pressure of the fluid discharged from the outlet can be increased as compared with (b) of  FIG. 11 . In the above described first and second embodiments and other embodiments which will be described later, any of various plate-shaped members as shown in  FIG. 11  can be employed. 
     In the above description, the nozzle according to one of the embodiments of the present invention is employed in the surface grinding machine, but may be employed in other machine tools.  FIG. 12  shows another example of a machine tool including the nozzle. The machine tool of this example is a cylindrical grinding machine. A cylindrical grinding machine  200  includes a grinding blade  202 , a protection cover  204 , a position adjusting unit  206 , a coolant pipe  208 , a coolant hose  209 , and a nozzle  10 . As described above, the nozzle  10  includes the plate-shaped member according to the first embodiment shown in  FIGS. 3 to 6 , the second embodiment shown in  FIGS. 7 to 10 , or one of the examples shown in  FIG. 11 . Although not shown in  FIG. 12 , the cylindrical grinding machine  200  may include a transfer device which rotates a workpiece W 2  by supporting it at the center of its both end faces and move it along the central axis (i.e., in the Z axis direction). The grinding blade  202  is rotationally driven in the clockwise direction in the plane of  FIG. 12  by a driving source (not shown in the drawing). A surface of the workpiece W 2  is ground by friction between the outer circumferential surface of the grinding blade  202  and a contact surface of the workpiece W 2 . The protection cover  204  surrounds the grinding blade  202  rotating at a high speed and protects workers around the grinding machine by preventing chips of the workpiece W 2  from scattering during grinding. 
     The position adjusting unit  206  is provided on the protection cover  204 , and fixes the coolant pipe  208  movable in the X axis direction at a desired position. By this, the nozzle  10  connected to the coolant hose  9  coupled to the coolant pipe  208  is disposed at an optimum position to discharge the coolant around a grinding spot G of the workpiece W 2  and the grinding blade  202 . A tank in which the coolant is stored (not shown in the drawing) is connected to one end of the coolant pipe  8 . The nozzle  10  according to one of the embodiments of the present invention can also supply the coolant effectively toward the grinding spot G in such a cylindrical grinding machine. 
       FIG. 13  shows a machining center which is another machine tool employing a nozzle according to an embodiment of the present invention. A machining center  300  includes a spindle  304  and a number of different types of tools (blades)  302  can be replaceably provided on the spindle  304 . The spindle  304  can rotate the tool  302  by a spindle motor which is not shown in the drawing. The machining center  300  further includes a driving unit for moving the spindle  304  and/or the tool (blade)  302  up and down, which is not shown in the drawing. By exchanging the tool  302 , the machining center  300  enables various operations, such as milling, drilling, boring, and tapping, to be performed. A column  306  is provided with a plurality of nozzles for supplying the coolant as well as the spindle  304 . Two nozzles  10  discharge the coolant supplied via the coolant hose  9  around a machining spot G of a workpiece W 3  and one of them may be the nozzle of the first embodiment (see  FIGS. 3 to 6 ) or the nozzle of the second embodiment (see  FIGS. 7 to 10 ). The machining center  300  further includes three single small nozzles  303 . Each of the nozzles  303  is a tubular nozzle and has a structure capable of freely changing the angle at which the coolant is discharged. The coolant can be supplied more effectively by inserting and fixing the plate-shaped member in the tubular body of the nozzle, similarly to a single nozzle which will be described later. In the present embodiment, the column  306  is provided with the two nozzles  10  connected to the coolant hose  9  and the three single nozzles  303  in addition to the spindle  304  and the tool  302 . In a different embodiment, the column  306  is provided with a proper number and proper types of nozzles which are selected from a group including the nozzles  10  and/or single nozzles  303 . Each of the nozzles  10  and the single nozzles  303  is connected to a tank in which the coolant (for example, water or oil) is stored (not shown in the drawing). The workpiece W 3  can be moved two-dimensionally in a horizontal plane by a table (not shown in the drawing). 
     Third Embodiment 
     A nozzle module including a single nozzle having one fluid discharge outlet according to a third embodiment of the present invention is described referring to  FIGS. 14 to 17 . The same reference numerals are used for the same features as those of the first and second embodiments and descriptions of the same features will be omitted.  FIG. 14  shows a nozzle module  400  connected to the coolant hose  9  according to the third embodiment of the present invention. The nozzle module  400  may be made of resin (plastic) or metal such as stainless steel, but the present invention is not limited thereto. 
       FIG. 15  is an enlarged view of the nozzle module  400 . The nozzle module  400  includes a body  401  and a fluid discharge part  410  (which is a cylindrical single nozzle). A female screw is formed on the inner surface of a protrusion  403  of the body  401 , and a male screw  410 - 1  is formed on a corresponding portion (i.e. an inlet) of the fluid discharge part  410  and engaged with the female screw. The connection between the body  401  and the fluid discharge part  410  is not limited to the screw-joining, but may be achieved by any method for connecting them detachably, such as inserting or press fitting. As will be described later, the body  401  is hollow inside and sends the fluid supplied from the coolant hose  9  to the fluid discharge part  410 . 
       FIG. 16  shows a state in which the plate-shaped member  11  is being inserted into the fluid discharge part  410  of the nozzle module  400 , and  FIG. 17  is a cross-sectional view showing a state in which the the plate-shaped member  11  is fixed in the nozzle module  400 . As clearly understood from these drawings, the nozzle module  400  is connected with the coolant hose  9  by screw-joining. More specifically, a female screw  401 - 1  is formed at the inlet side of the body  401  and engaged with a male screw formed at one end of the coolant hose  9 . Similarly, a female screw  401 - 2  is formed at the outlet side of the body  401  and engaged with the male screw  410 - 1  of the fluid discharge part  410 . As shown in  FIG. 17 , the interior space of the hollow body  401  is extended in the width direction. Thus, a flow path of the coolant in the fluid discharge part  410  is narrower than that in the body  401  and the coolant is discharged from the outlet of the fluid discharge part  410  at a high pressure. As shown in the drawings, the flow path is formed in an interior space of the fluid discharge part  410 . More specifically, the fluid discharge part  410  includes an inlet  410 - a  through which the coolant (or a fluid) flows in, an outlet  410 - b  through which the coolant is discharged, and a wall surface  410   c  forming the interior space connecting the inlet  410 - a  and the outlet  410 - b . A cylinder having the same diameter from the inlet  410 - a  to the outlet  410 - b  is formed by the wall surface  410 - c . In other words, the wall surface  410   c  is cylindrical and the plate-shaped member  11  of uniform cross section is inserted in the cylinder formed by the wall surface  410   c  from the inlet  410 - a  or the outlet  410 - b  and fixed therein. In the case that the wall surface  410   c  is tapered to form a truncated cone shaped interior space of the fluid discharge part such that its cross section gradually decreases from the inlet toward the outlet, the plate-shaped member  11  to be inserted may have a cross section gradually decreasing from the inlet toward the outlet in accordance with the shape of the wall surface  410 - c . The former and latter plate-shaped members  11  are shown in  FIGS. 6A and 6B  described with respect to the first embodiment, respectively. 
     The plate-shaped member  11  shown in each of  FIGS. 15 to 17  has a cross section in the form of the four-petaled flower and includes the three folds  11 - t  and the one slit  11 - s  to form the flower shape. The plate-shaped member  11  is formed by, for example, cutting a thin flat plate made of metal such as stainless steel into a predetermined size, and then bending it into the four-petaled flower. It is also possible to cut a thin flat plate after bending it into the flower shape. The plate-shaped member  11  has elasticity due to the three folds  11 - t  and the slit  11 - s . In the case that the inner diameter of the wall surface  410   c  of the fluid discharge part  410  and the outer diameter of the plate-shaped member  11  are equal, or the outer diameter of the plate-shaped member  11  is slightly larger than the inner diameter of the wall surface  410   c  of the fluid discharge part  410  but the plate-shaped member  11  is compressed by the slit so that they become equal, an elastic force is generated as a result of repulsion against the compression and the plate-shaped member  11  is press-fitted to the wall surface  410   c  forming the interior space of the fluid discharge part  410 . Since the plate-shaped member  11  is press-fitted to the wall surface  410   c  of the interior space of the fluid discharge part  410  by its own elastic force, arrangement and assembly of the plate-shaped member  11  can be easily performed. 
     In the case that the plate-shaped member  11  having the cross section in the form of the four-petaled flower is inserted and fixed in the fluid discharge part  410 , the plate-shaped member  11  forms an inner flow path  412 - c  surrounded by it and outer flow paths  412 - d   1  to  412 - d   4  in the outer side of the plate-shaped member  11  and between the wall surface  410 - c  of the interior space of the fluid discharge part  410  and the plate-shaped member  11 . Since the plate-shaped member  11  is in the form of the thin plate, only its thickness inhibits the flow of the fluid and there is little loss of the overall flow rate. The fluid flowing in the interior space is guided by the plate-shaped member  11  having the cross section in the form of the four-petaled flower such that turbulence is prevented and the flow becomes laminar or rectified. In other words, the plurality of folds  11 - t  and the slit  11 - s  are parallel to the flow of the fluid, and the curved surface between two adjacent folds  11 - t  and the curved surface between the fold  11 - t  and the slit  11 - s , as well as the plurality of folds  11 - t  and the slit  11 - s , guide the fluid to increase the straightness of the fluid. Therefore, the inner flow path  412 - c  enables the fluid to be discharged at a target position or a predetermined angle. Thus, diffusion (dispersion or turbulence) of the fluid out of the target position can be prevented. Since the fluid discharged from the outer flow paths  412 - d   1  to  412 - d   4  also has straightness, contributes to cooling of a workpiece and helps to remove sludge and chips in the case that the nozzle module  400  is applied to the machine tool. 
     According to the present embodiment, the slit  11 - s  is formed in the plate-shaped member  11  and the plate-shaped member  11  is press-fitted to the wall surface  410   c  of the interior space of the nozzle due to the elastic force generated from the repulsion against the compression by the slit  11 - s . However, the slit  11 - s  is not necessarily required. In other embodiments, the plate-shaped member  11  can be press-fitted to the wall surface  410   c  by adjusting the outer diameter of the plate-shaped member  11  and the inner diameter of the wall surface  410 - c . The shape of the four-petaled flower caused by inserting the plate-shaped member  11  into the interior space can be appropriately changed by adjusting each of the intervals of the three folds  11 - t  and the slit  11 - s . By this, flow rates of the fluid flowing through the inner flow path  412 - c  and the outer flow paths  412 - d   1  to  412 - d   4  can be varied. While the plate-shaped member  11  has the cross section in the form of the flower having four petals according to the present embodiment, the number of the petals may be two or more and the drawing (A) of  FIG. 11  shows the example having eight petals as described above. In addition, the bulge of the petal can also be properly changed, for example, to (E) or (I) of  FIG. 11 . Thus, the ratio of the flow rate of the fluid flowing through the inner flow path  412 - c  to the flow rate of the fluid flowing through the outer flow paths  412 - d   1  to  412 - d   4  can be determined. Generally, as the number of the petals increases, the flow rate of the fluid flowing through the inner flow path  412 - c  increases. Similarly, as the bulge of each petal is rounder (for example, the bulge of (I) of  FIG. 11  is rounder than (E) of  FIG. 11 ), the flow rate of the fluid flowing through the inner flow path  412 - c  increases. 
     Fourth Embodiment 
       FIGS. 18 to 20  show a nozzle module including a single nozzle having one fluid discharge outlet according to a fourth embodiment of the present invention. The same reference numerals are used for the same features as those of the first to third embodiments and descriptions of the same features will be omitted.  FIG. 18  is an enlarged view showing a nozzle module  500  and the nozzle module  500  includes a body  401  and a fluid discharge part  410  which have similar structures as those of the third embodiment.  FIG. 19  shows a state in which the plate-shaped member having the cross section in the form of the four-pointed star  111  is being inserted into the fluid discharge part  410  connected to the body  401  of the nozzle module  500 , and  FIG. 20  is a cross-sectional view showing a state in which the the plate-shaped member  111  is fixed in the nozzle module  500 . The wall surface  410   c  is cylindrical, and the plate-shaped member  111  having the uniform cross section shown in  FIG. 10  is inserted into the interior space formed by the wall surface  410   c  from the inlet  410 - a  or the outlet  410 - b  and fixed therein. In the case that the wall surface  410 - c  is tapered to form a truncated cone shaped interior space of the fluid discharge part such that its cross section gradually decreases from the inlet toward the outlet, the plate-shaped member  111  to be inserted may have a cross section gradually decreasing from the inlet toward the outlet in accordance with the shape of the wall surface  410 - c.    
     In the present embodiment, the plate-shaped member  111  has the cross section in the form of the four-pointed star and includes the seven folds  111 - t  and the one slit  111 - s  to form the star shape. In the case that the plate-shaped member  111  having the cross section in the form of the four-pointed star is inserted and fixed in the fluid discharge part  410 , the plate-shaped member  111  forms an inner flow path  512 - c  surrounded by it and outer flow paths  512 - d   1  to  512 - d   4  in the outer side of the plate-shaped member  111  and between the wall surface  410   c  and the plate-shaped member  111 . Since the plate-shaped member  111  is in the form of the thin plate, only its thickness inhibits the flow of the fluid and there is little loss of the overall flow rate. The flow of the fluid is guided by the plate-shaped member having the cross section in the form of the four-pointed star such that turbulence is prevented and the flow becomes laminar or rectified. In other words, the plurality of folds  111 - t  and the slit  111 - s  are parallel to the flow of the fluid, and the curved surface between two adjacent folds  111 - t  and the curved surface between the fold  111 - t  and the slit  111 - s , as well as the plurality of folds  111 - t  and the slit  111 - s , guide the fluid to increase straightness of the fluid. Therefore, the inner flow path  512 - c  enables the fluid to be discharged at a target position or a predetermined angle. Thus, diffusion (dispersion or turbulence) of the fluid out of the target position can be prevented. Since the fluid discharged from the outer flow paths  512 - d   1  to  512 - d   4  also has straightness, it contributes to cooling of a workpiece and helps to remove sludge and chips in the case that the nozzle  500  is applied to the machine tool. While the plate-shaped member  111  has the cross section in the form of the four-pointed star according to the present embodiment, it may have different types of cross section. The cross section of the plate-shaped member may have an eight-pointed star shape as shown in (L) of  FIG. 11 . The number of limbs (or arms) of the star is three or more. The sharpness of the limbs (arms) may also be properly changed. Thus, the ratio of the flow rate of the fluid flowing through the inner flow path  512 - c  to the flow rate of the fluid flowing through the outer flow paths  512 - d   1  to  512 - d   4  can be determined. Generally, as the number of the limbs increases, the flow rate of the fluid flowing through the inner flow path  512 - c  increases. Similarly, as each limb has a gentle slope, the flow rate of the fluid flowing through the inner flow path  512 - c  increases. 
     Fifth Embodiment 
       FIGS. 21 to 23  show a nozzle module including a multi-nozzle mechanism according to a fifth embodiment of the present invention. The same reference numerals are used for the same features as those of the first to fourth embodiments and descriptions of the same features will be omitted.  FIG. 21  is an enlarged view showing a nozzle module  600  and the nozzle module  600  includes a body  401  similar to that of the third (or fourth) embodiment. A fluid discharge part  610  is connected to the body  401 , for example, by screw-joining, and provided with a plurality of through holes (for example, seven (7) through holes) formed therein which form nozzles  620 - 1  to  620 - 7  arranged in a row. The cross section of the fluid discharge part  610  has a plurality of (i.e. seven) holes arranged in a row.  FIG. 22  shows a state in which small plate-shaped members  611  are being inserted into the fluid discharge part  610  connected to the body  401  of the nozzle module  600  and each of the small plate-shaped members  611  has a cross section of a predetermined shape (for example, one of (A) to (L) of  FIG. 11 ).  FIG. 23  is a cross-sectional view showing a state in which the the plate-shaped members  611  are fixed in the nozzle module  600 . As clearly understood from the drawings, the female screw  401 - 2  is formed at the fluid outlet side of the body  401  and engaged with a male screw  610 - 1  of the fluid discharge part  610 . The interior space of the hollow body  401  is extended in the width direction. Thus, a flow path of the coolant in the fluid discharge part  610  is narrower than that in the body  401  and the coolant is discharged from the outlet of the fluid discharge part  610  at a high pressure. An end surface  615  on the inlet side of the fluid discharge part  610  is, for example, conical or spherical in shape, so that the fluid easily flows into each of the narrow tubular nozzles  620 - 1  to  620 - 7 . 
     A wall surface  610   c  of each of the nozzles  620 - 1  to  620 - 7  is cylindrical, and the plate-shaped member  611  of uniform cross section as shown in  FIG. 11  is inserted into the interior space of each nozzle from an inlet  610 - a  or an outlet  610 - b  and fixed to the wall surface  610 - c . In the case that the wall surface  610   c  is tapered to form a truncated cone shaped interior space of the nozzle such that its cross section gradually decreases from the inlet toward the outlet, the plate-shaped member  611  to be inserted may have a cross section gradually decreasing from the inlet toward the outlet in accordance with the shape of the wall surface  610 - c.    
     The plate-shaped members  611  of the present embodiment has the cross section of the predetermined shape such as one of (A) to (L) of  FIG. 11  and includes a plurality of folds and one slit to form the shape. In the case that the plate-shaped member  611  is inserted and fixed in each of the nozzles  620 - 1  to  620 - 7 , an inner flow path surrounded by the plate-shaped member  611  is formed and outer flow paths are formed in the outer side of the plate-shaped member  611  and between the wall surface of the interior space of each nozzle and the plate-shaped member  611 . Since the plate-shaped member  611  is in the form of a thin plate, only its thickness inhibits the flow of the fluid and there is little loss of the overall flow rate. The fluid flow is guided by the plate-shaped member of a predetermined shape such that turbulence is prevented and the flow becomes laminar or rectified. In other words, the plurality of folds and the slit are parallel to the flow of the fluid, and a curved surface between two adjacent folds and a curved surface between the fold and the slit, as well as the plurality of folds and the slit, guide the fluid to increase the straightness of the fluid. Therefore, the inner flow path of each of the nozzles  620 - 1  to  620 - 7  enables the fluid to be discharged at a target position or a predetermined angle. Thus, diffusion (dispersion or turbulence) of the fluid out of the target position can be prevented. Since the fluid discharged from the outer flow paths of each of the nozzles  620 - 1  to  620 - 7  also has straightness, it contributes to cooling of a workpiece and helps to remove sludge and chips in the case that the nozzle module  600  is applied to the machine tool. 
     According to the fifth embodiment, the nozzles  620 - 1  to  620 - 7  are disposed horizontally in a row in the cylindrical fluid discharge part  610  as shown in  FIGS. 21 to 23 , and a plurality of small holes of the nozzles are arranged in a row as shown in (A) of  FIG. 24 . In other embodiments, the small holes may be formed over the entire surface as shown in (B) of  FIG. 24 , or may be arranged in multiple stages as shown in (C) of  FIG. 24 . In another embodiment, the upper part of the fluid discharge part  610  may be cut and flattened and the small holes may be arranged in a V-shape in accordance with the shape of the blade (or the grindstone), as shown in (D) of  FIG. 24 . The small holes may be arranged in a different form from those described above. 
     Sixth Embodiment 
     In the following, a nozzle module including a multi-nozzle mechanism which has a plurality of fluid discharge outlets according to a sixth embodiment of the present invention is described with reference to  FIGS. 25 to 28 . The same reference numerals are used for the same features as those of the first to fifth embodiments and descriptions of the same features will be omitted.  FIG. 25  shows a nozzle module  700  according to the sixth embodiment connected with the coolant hose  9 . The nozzle module  700  may be made of resin (plastic) or metal such as stainless steel, but the present invention is not limited thereto. 
       FIG. 26  is an enlarged view showing the nozzle module  700  and the nozzle module  700  includes a body  701  and a fluid discharge part  710  which is a flat plate-like flat nozzle. In the present embodiment, the body  701  is molded integrally with the fluid discharge part  710 . In other embodiments, they are manufactured individually and then combined.  FIG. 27  shows a state in which a plate-shaped member  711  is being inserted into each of a plurality of nozzles  720 - 1  to  720 - 23  formed in the fluid discharge part  710  of the nozzle module  700 . In the present example, the number of the nozzles is  23  and the nozzles  720 - 1  to  720 - 23  are  23  cylindrical small through holes formed in the fluid discharge part  710 .  FIG. 28  is a cross-sectional view showing a state in which the the plate-shaped member  711  is fixed in the nozzle. As clearly understood from these drawings, the nozzle module  700  is connected with the coolant hose  9  by screw-joining. More specifically, a female screw  701 - 1  is formed at the inlet side of the body  701  and engaged with a male screw formed at one end of the coolant hose  9 . At the outlet side of the body  701 , the fluid discharge part  710  is connected to the body  701 , for example, by the integral molding. As shown in  FIG. 28 , the interior space of the hollow body  701  is extended in the width direction. Thus, a flow path of the coolant in the fluid discharge part  710  is narrower than that in the body  701  and the coolant is discharged from the outlet of the fluid discharge part  710  at a high pressure. As shown in the drawings, a flow path is formed in an interior space of each of the nozzles  720 - 1  to  720 - 23  of the fluid discharge part  710 . More specifically, each of the nozzles  720 - 1  to  720 - 23  formed in the fluid discharge part  710  includes an inlet  710 - a  through which the coolant flows in, an outlet  710 - b  through which the coolant is discharged, and a wall surface  710 - c  forming the interior space connecting the inlet  710 - a  and the outlet  710 - b . A cylinder having the same diameter from the inlet  710 - a  to the outlet  710 - b  is formed by the wall surface  710 - c . In other words, the wall surface  710   c  is cylindrical and the plate-shaped member  711  of uniform cross section is inserted in the cylinder formed by the wall surface  710   c  from the inlet  710 - a  or the outlet  710 - b  and fixed therein. In the case that the wall surface  710   c  is tapered to form a truncated cone shaped interior space of the nozzle such that its cross section gradually decreases from the inlet toward the outlet, the plate-shaped member  711  to be inserted may have a cross section gradually decreasing from the inlet toward the outlet in accordance with the shape of the wall surface  710 - c . The former and latter plate-shaped members  711  are shown in  FIGS. 6A and 6B  described with respect to the first embodiment, respectively. 
     The plate-shaped member  711  of the present embodiment has the cross section of a predetermined shape such as one of (A) to (L) of  FIG. 11  and includes a plurality of folds and one slit to form the shape. In the case that the plate-shaped member  711  is inserted and fixed in each of the nozzles  720 - 1  to  720 - 23 , an inner flow path surrounded by the plate-shaped member  711  is formed and outer flow paths are formed in the outer side of the plate-shaped member  711  and between the wall surface of the interior space of each nozzle and the plate-shaped member  711 . Since the plate-shaped member  711  is in the form of a thin plate, only its thickness inhibits the flow of the fluid and there is little loss of the overall flow rate. The fluid flow is guided by the plate-shaped member of a predetermined shape such that turbulence is prevented and the flow becomes laminar or rectified. In other words, the plurality of folds and the slit are parallel to the flow of the fluid, and a curved surface between two adjacent folds and a curved surface between the fold and the slit, as well as the plurality of folds and the slit, guide the fluid to increase the straightness of the fluid. Therefore, the inner flow path of each of the nozzles  720 - 1  to  720 - 23  enables the fluid to be discharged at a target position or a predetermined angle. Thus, diffusion (dispersion or turbulence) of the fluid out of the target position can be prevented. Since the fluid discharged from the outer flow paths of each of the nozzles  720 - 1  to  720 - 23  also has straightness, it contributes to cooling of a workpiece and helps to remove sludge and chips in the case that the nozzle module  700  is applied to the machine tool. 
     Each of the nozzle modules  400 ,  500 ,  600 , and  700  according to the third to sixth embodiments can also be employed as a coolant supply means of various machine tools such as the surface grinding machine and the cylindrical grinding machine.  FIG. 29  shows a machining center  800  which employs the nozzle module  700  and the nozzle module  400  (or  500  or  600 ). The machining center  800  includes a spindle  804  and a number of different types of tools (blades)  802  can be replaceably provided on the spindle  804 . The spindle  804  can rotate the tool  802  by a spindle motor which is not shown in the drawing. The machining center  800  further includes a driving unit for moving the spindle  804  and/or the tool (blade)  802  up and down, which is not shown in the drawing. By exchanging the tool  802 , the machining center  800  enables various operations, such as milling, drilling, boring, and tapping, to be performed. A column  806  is provided with a plurality of nozzles for supplying the coolant as well as the spindle  804 . Two nozzle modules  700  and  400  (or  500  or  600 ) discharge the coolant supplied via the coolant hose  9  around a machining spot G of a workpiece W 4 . The machining center  800  further includes four single small nozzles  803 . Each of the nozzles  803  is a tubular nozzle and has a structure capable of freely changing the angle at which the coolant is discharged. The coolant can be supplied more effectively by inserting and fixing the plate-shaped member in the tubular body of the nozzle, similarly to the single nozzle described above. In the present embodiment, the column  806  is provided with the two nozzle modules  700  and  400  (or  500  or  600 ) connected to the coolant hose  9  and the three single nozzles  803  in addition to the spindle  804  and the tool  802 . In a different embodiment, the column  806  is provided with a proper number and proper types of nozzles which are selected from a group including the nozzle modules and/or the single nozzles. Each of the nozzle modules  700  and  400  (or  500  or  600 ) and the four single nozzles  803  is connected to a tank in which the coolant (for example, water or oil) is stored (not shown in the drawing). The workpiece W 4  can be moved two-dimensionally in a horizontal plane by a table (not shown in the drawing). 
     Although some embodiments of the present invention have been described above, the embodiments are for illustrative purposes only and not intended to limit the technical scope of the present invention. It will be apparent to those skilled in the art that many other possible embodiments and various modifications of the present invention may be made in light of the specification and drawings. Although a plurality of specific terms are used herein, they are used in a generic sense only for the purpose of explanation and are not used for the purpose of limiting the invention. The embodiments and modifications fall within the scope and the spirit of the invention described in this specification and within the scope of the invention as defined in the appended claims and equivalents thereof.