Tool positioning device and machining tool

A tool positioning device and a machining element have simple structures which can reduce running cost. In addition to a hole that engages with a shank of an end mill, a channel is provided so that it penetrates through the device such that one end thereof communicates with an upper face of the device and the other end communicates with a lower end of the device. In this case, it is more effective to provide a concave portion that is opened to the upper face and communicates with the hole. The same effect may be obtained by making a cylindrical hole, for example, instead of the channel.

FIELD OF THE INVENTION

The present invention relates to a cylindrical and hollow tool positioning device having a hole that fits with a tool to position an edge of the tool when attached with the tool and to a machining element using the same.

BACKGROUND TECHNOLOGY

FIG. 4is a front view of a main part of a conventional printed board machining apparatus,FIGS. 5A and 5Bare drawings showing a collet chuck section of the printed board machining apparatus, whereinFIG. 5Ais a front section view thereof andFIG. 5Bis a view taken in the direction of an arrow A inFIG. 5A.FIG. 6is a front section view of a tool holding unit.

InFIG. 4, an X table1is movable in an X direction perpendicular to the face of the sheet. A tool holding unit20and a printed board15are placed on the X table1. A Y table2is movable horizontally in a Y direction in the figure. The Y table2holds a Z table3so as to be movable vertically in the Z direction in the figure by a motor4having an encoder and a ball screw5. The Z table3holds a spindle6that rotatably holds a tool (here an end mill)8through the intermediary of a collet chuck7. An NC unit9controls rotation of the motor4to accurately position an edge7aof the collet chuck7.

As shown inFIGS. 5A and 5B, the collet chuck7has a hole7bformed at the center thereof and slits7shaving a width of around 0.5 mm and provided at the edge portion thereof. The portion where the slits7sare provided will be referred to as a claw portion7dhereinafter (note that only the claw portion7dis shown inFIG. 5A). The claw portion7dis provided with a channel7min a middle part thereof. A pad10made of an elastic member is disposed in the channel7m. A thickness of the pad10itself is thicker than a width of the slit7s, so that the pad10urges the claw portion7din a direction of widening the slit7s.

An outer periphery of the claw portion7dis formed so as to have a tapered plane7fhaving the same angle as a tapered plane6fof the spindle6. When the tapered plane7fis separated from the tapered plane6fby moving the collet chuck7downward in the figure by means not shown, the claw portion7dis opened due to the resilience of the collet chuck7itself and the pad10, and a diameter of the hole7bbecomes larger than that of a shank8aof the end mill8. When the collet chuck7is moved upward in the figure by the means not shown, and when it is urged further upward in a state when the tapered plane7fabuts against the tapered plane6f, the claw portion7dis urged in a direction of narrowing the slit7s, thus holding the shank8arigidly with frictional force.

The Z table3supports a pressure foot11by means of a pair of cylinders12that urges the pressure foot11downward in the figure. A ringed brush13is disposed at a bottom face of the pressure foot11. It is noted that the pressure foot11is located at its rising end in the figure.

As shown inFIG. 6, a base21of a tool holding unit20supports a holder22so as to be movable in the vertical direction. A spring23urges the holder22upward. The holder22is provided with, at the center part thereof, a hole22awhose diameter is larger than an outer diameter of the shank8aof the end mill8, i.e., the tool, or larger than a blade portion8twhen an outer diameter of the blade portion8tis larger than the outer diameter of the shank8a. Still more, the holder22is configured so that its upper face22ureaches a preset height from the surface of the X table1.

A ring30is made of hard synthetic resin, for example, and has a hole30awhich is provided at the center thereof and whose diameter is slightly smaller than the outer diameter of the shank8a. As a result, when the shank8ais inserted into the hole30a, the ring30is combined in a body with the end mill8due to its resilience. That is, the ring30is a tool positioning device of the end mill8. The holder22supports the end mill (machining tool)8attached with the ring30. It is noted that the ring30has an outer diameter of around 7 to 8 mm and a height h of around 4 to 8 mm, and the shank8ahas the outer diameter of around 3 mm.

Next, an operation of the conventional printed board machining apparatus will be explained.

At first, a procedure for holding the end mill8with the spindle6will be explained. It is noted that the holder22supports the end mill8in a state in which it is inserted into the ring30. Still more, the ring30is fixed with the end mill8so that a distance from a bottom face30dthereof to a point8pof the end mill8becomes a distance k. Accordingly, because a height h of the ring30in the vertical direction is preset, a distance from an upper face30uof the ring30to the point8pof the end mill8is determined.

The X and Y tables1and2are moved so that the axial center of the collet chuck7, i.e., the spindle6, coincides with an axial line of the hole22a. Then, the Z table3is moved downward while opening the collet chuck7to position the edge7aof the collet chuck7at position N indicated by a two-dot-chain line inFIG. 6. When the collet chuck7is closed in this state, the end mill8is held in a state in which the edge7aof the chuck7contacts with the upper face30uof the ring30.

Next, a procedure for machining a channel on the printed board15will be explained.

After positioning the axial center of the end mill8to the center of the channel to be machined, the Z table3is moved downward while supplying air to the center part of the spindle6so that the point8pof the end mill8cuts to a predetermined depth of the printed board15. Then, the X and Y tables1and2are moved in accordance to a machining program. The air supplied to the center of the spindle flows out of the slits7sof the collet chuck7and prevents chips from entering the slits7s.

Because the use of the ring30enables one to accurately control the position of the point8pof the end mill as described above, the cutting depth can be set at a required minimum value in machining the printed board, thus improving the machining efficiency. It also causes no insufficient cutting of the end mill8. Still more, it becomes unnecessary to confirm the position of the point8pduring machining.

By the way, the life of the tool may be prolonged by suppressing an increase of temperature of the tool during machining. The prolongation of life of the tool not only improves the machining efficiency but also reduces running cost.

A linear and concave coolant supplying section in parallel with an axial line, from the rear end of the shank portion to a cutting face of the blade portion, to directly apply the coolant to the cutting face of the blade portion of the end mill is disclosed in Japanese Publication Patent No. 2894924. A plurality of independent cutting blades disposed in spiral in the axial direction on a rectangle whose width can be defined in the axial direction, so that an interval in the axial direction is wider than the cutting blade, is disclosed in Japanese Patent Laid-Open No. 2002-337016. A blow outlet of compressed air is disposed in the vicinity of the tool as disclosed in Japanese Patent Laid-Open No. 1997-117815.

However, because the channel is provided on the shank portion in both the conventional technologies disclosed in Japanese Publication Patent No. 2894924 and Japanese Patent Laid-Open No. 2002-337016, the unit cost of their tools becomes expensive as compared to a standard tool. Still more, because the structure of the tool disclosed in Japanese Patent Laid-Open No. 1997-117815 is complicated, its maintenance and inspection are cumbersome.

Accordingly, it is an object of the invention to provide a tool positioning device and a machining element which are capable of solving the above-mentioned problem, whose structures are simple, and which allow a running cost to be reduced.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problem, according to a first aspect of the invention, there is provided a hollow and cylindrical tool positioning device for positioning an edge of a tool. A hole penetrates through a center part of the device in an axial direction to attach the tool. An upper face is a plane orthogonal to the axial direction, a lower face is a plane orthogonal to the axial direction, and an outside face connects an outer edge of the upper face with an outer edge of the lower face. A hollow portion in the axial direction communicates with the upper and lower faces.

In this case, there may be provided a concave portion that communicates with the hole and is opened to the upper face and one end of the hollow portion may communicate with the upper face via the concave portion.

The hollow portion may communicate with the hole across the whole range thereof in the axial direction.

The hollow portion may be a channel provided on an outside face of the device or may be a cylindrical hole.

According to another aspect of the invention, there is provided a machining element wherein the tool positioning device described above is removably attached with a shank portion of the tool having the shank portion and a blade portion.

The invention described above allows a standard tool to be used and the life of the tool to be prolonged, so that the running cost may be reduced. Still more, the invention requires no change in the structure of a printed board machining apparatus, so that it is applicable to the conventional printed board machining apparatus.

Still more, because the inventive device is provided with the concave portion, it requires no positioning of a channel in the collet chuck with the hollow portion, thus facilitating the work of attaching the tool to the collet chuck and holding the tool in the tool holding unit.

Further, because air flows along the surface of the tool in using the apparatus, the tool cooling effect may be enhanced.

According to the invention, the hollow portion may be readily formed, so that the tool positioning device and the machining element may be formed at low cost.

It is noted that the summary of the invention described above does not necessarily describe all necessary features of the invention. The invention may also be a sub-combination of the features described above.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on preferred embodiments, which are not intended to limit the scope of the invention, but exemplify the invention. All of the features and the combinations thereof described in the embodiments are not necessarily essential to the invention.

FIGS. 1A and 1Bshow an inventive ring, whereinFIG. 1Ais a plan view thereof andFIG. 1Bis a front section view. It is noted that parts therein which are the same or have the same function with those shown inFIGS. 4 through 6will be denoted by the same reference numerals and overlapping explanation thereof will be omitted here.

The inventive ring (tool positioning device)30has a hole30athat penetrates through a center part of the device in an axial direction (O-O) to attach the tool. An upper face30uis a plane orthogonal to the axial direction. A lower face30dis a plane orthogonal to the axial direction. An outside face30pconnects an outer edge of the upper face with an outer edge of the lower face. It is then provided with a concave portion31that opens to the upper face30uof the ring30and communicates with the hole30aand four channels (hollow portions)32that communicate with the hole30aacross the whole length of the hole30ain the axial direction and are formed in parallel with the axial line of the hole30a. The upper end of the channel32communicates with the upper face30uthrough the concave portion31and the lower end thereof communicates with a lower end30d, penetrating through the ring in the axial direction. Then, in using the inventive ring30, it is attached to an end mill (tool)8so that the concave portion31faces to the side of a collet chuck7.

Because the ring30is constructed as described above, a part of the air supplied to the axial center part of a spindle6, which flows out of the collet chuck7, enters the concave portion31and flows out of the lower face30dof the ring30after passing through the channels32. At this time, the air flows along the shank8a, so that the end mill8is cooled due to heat transmission. The part of the air flowing out of the ring30also cools down a blade portion8t.

As a result, even if the flow amount of air fed to the axial center part of the spindle, i.e., air flowing to the collet chuck7, is equalized with that of the conventional device, the end mill8is cooled down effectively.

FIG. 2is a graph showing machining results of the tool when the inventive ring is applied. The abscissa represents cutting speeds and the ordinate represents cutting lengths. Results of using the conventional ring are also shown for the purpose of comparison.

The test has been carried out under the following conditions:(1) Outer diameter of the blade portion of the end mill8: 1 mm;(2) Rotational speed of the spindle: 50,000 rpm, 60,000 rpm and 80,000 rpm;(3) A flow amount of air supplied to the center part of the spindle: 50 l/min.; and(4) Work: A pile of three glass epoxy resin boards (glass content: 20 wt. %) having a thickness of 1 mm.
It is noted that the number of channels32has been four, their width w has been 1.5 mm and a length l across the both ends of the channels32located on a diameter has been 5 mm. Still more, the diameter of the hole30ahas been 3.0 mm and the diameter of the shank8ahas been 3.175 mm.

As is apparent from the graph, the inventive ring can increase the cutting length by eight to ten times as compared to that of the conventional ring.

That is, because the invention allows the cutting speed to be increased, the machining efficiency may be improved. Still more, because the invention allows the cutting length to be prolonged, the number of times of replacement of the tool may be reduced when the cutting length is the same. Accordingly, the invention allows the machining efficiency to be improved further.

Still more, because the invention allows a standard tool to be used, the running cost may be reduced.

Further, because the invention allows the ring30to be used repeatedly, the running cost may be reduced.

The concave portion31is provided in the embodiment described above, so that it becomes unnecessary to adjust the position of the slit7sof the collet chuck7with the channel32, thus facilitating the work of attaching the end mill8with the collet chuck7and holding the end mill8with the holder22.

It is noted that although four channels have been provided in the embodiment, the number is not limited to be four and even one channel will do. Still more, the channel32may be formed into a spiral shape instead of a linear shape.

Further, it is not always necessary to provide the concave portion31.

FIGS. 3A and 3Bshow a structure of a ring30′ according to a modification of the invention, whereinFIG. 3Ais a plan view thereof andFIG. 3Bis a front section view.

The cutting length may be prolonged and the machining efficiency may be improved in the same manner as described above by providing holes (hollow portions)33, instead of the channels32, as shown in the figures.

It is noted that although the linear or spiral channel32may be provided on the outside face30pof the ring30, the cooling effect is apt to drop when the channel32is provided on the side face of the ring30as compared to the case described above.

Still more, in the invention, a large amount of air is supplied to the outer periphery of the blade portion as compared to the conventional case, so that chips caused by the machining are blown upward. As a result, dust collecting efficiency improves when the inside of the pressure foot is connected with a dust collector, reducing the chips remaining on the surface of the printed board and within the machined channels.

Although the case when the tool is an end mill has been explained above, the invention is also applicable to a case when the tool is a drill and to other tools as well.

Although the invention has been described by way of the exemplary embodiments, it should be understood that those skilled in the art might make many changes and substitutions without departing from the spirit and scope of the invention. It is obvious from the definition of the appended claims that the embodiments with such modifications also belong to the scope of the invention.