Tap holder

It is an object of the invention to provide a tap holder in which even when an error is brought about in synchronizing spindle feeding and rotation of a tapper body and a tap collet of a tap holder in correspondence with a machine tool spindle, the synchronization can be established by absorbing the error by a simple constitution. As means therefor, the tap holder is characterized in that a tapper body and a tap collet are inserted by a locking member at portions of the tapper body and the tap collet overlapping each other, and the tap collet is fixed to the tapper body by engaging the locking member with at least one of the tap collet and the tapper body in a state of being interposed with an elastic member on both sides thereof in an axial direction X.

BACKGROUND OF THE INVENTION

The present invention relates to a tap holder for holding a tap for tapping and for equipping with a machine tool spindle.

When tapping is carried out by a machine tool by utilizing synchronization with feeding and rotation of a machine tool spindle, rotation and feeding of the machine tool spindle are controlled to synchronize in accordance with a pitch of a tap. However, in actual tapping, owing to a phenomenon referred to as servo delay, an amount of running a tap while machining by rotating becomes larger, or conversely smaller than a tap pitch per rotating the machine tool spindle, tapping is progressed fast or slow by an incoincidence of spindle feeding and rotation, and therefore, a deviation is brought about among an amount of spindle feeding per rotation and a tap pitch. Although in a background art, the incoincidence is prevented by providing floats on both sides in an axial direction of a tap holder, in recent years, the floats are eliminated and the tap holder are an integral structure is constituted by a promotion in an accuracy of synchronizing (synchronizing) spindle rotation and feeding by a development of a mechanism or a control technology.

Further, a tap holder deals therewith by being separated into a tapper body and a tap collet to allow a size of a tap by the tap collet. Also a synchronized tap holder constituting an object of complete synchronization is separated into a tapper body and a tap collet and when the tapper body and the tap collet are connected, the tap collet is attached thereto as gapless as possible.

However, although a synchronization accuracy of the machine tool is promoted, for example, when a spindle feeding direction and a spindle rotating direction are switched in order to draw a tap from a subject work, rotation of a machine tool spindle does not synchronize with spindle feeding and a small sift of the tap in an axial direction cannot completely be excluded from being brought about, and therefore, there is a drawback of enlarging or leaning a screw thread.

As a constitution of absorbing such a synchronization error, there is proposed a constitution in which a tap mounting portion is made to be movable (able to sift) in a rotating axis direction of a spindle by connecting a spindle mounting portion and the tap mounting portion by way of a leaf spring (refer to Patent Reference 1, paragraph No. [0011] shown below), or a constitution in which as in a background art, a tension spring and a compression spring are urged in directions reverse to each other in an axial direction between a spindle and a tap collet and the tap collet is stopped at a position for balancing urge forces, when an error of feeding the spindle is brought about in tapping and a feed amount and a pitch of a tap are incoincident, the spindle is slid slightly in a direction of making the feed amount and the pitch coincident by reacting with an external force from the tap at a front end thereof (refer to Patent Reference 2, paragraph number [0030], FIG. 2 shown below), or a constitution in which a tap driver is provided with a spiral coil having a compressing performance and an extending performance, an attachment body is moved by a small amount in an axis line direction in accordance with a predetermined force exerted to a tap to be able to synchronize (refer to Patent Reference 3, paragraph number [0018], FIG. 2).

However, the constitutions described in Patent References 1 through 3 pose a problem that structures are complicated in any of the cases and cost becomes expensive.

Further, although Patent Reference 4 shown below describes a tap holding apparatus in which in order to lock a tap to a tap holding shaft, a lock bolt is used, at a position opposed to the lock bolt, an elastically deformable bush is filled between a fixing pin brought into contact with an outer peripheral face of a handle portion and an inner wall of a long hole provided at the tap holding shaft, the fixing pin and a lock ring is made to be pivotable in a circumferential direction relative to the tap holding shaft, and the bush is filled also at a gap between the fixing pin in an axial direction and the inner wall of the long hole (page 8, line 14 through page 9, line 10), such a tap holding apparatus prevents the lock bolt from being loosened by restraining a rotational force and a force in a direction of pressing the tap from being operated to the lock bolt and is not for restraining a synchronization error of spindle feeding and rotation of a spindle.

That is, the fixing pin arranged with the bush is brought into contact with an outer peripheral face of the tap operated with a force in an axial direction to lock when the synchronization error of feeding and rotation of the spindle of the machine tool is brought about, and therefore, the force in the axial direction operated to the tap is not sufficiently transmitted to the fixing pin, and even when the elastically deformable bush is arranged on a front side in the direction of pressing the fixing pin, a difference between an amount of moving the top holding shaft and an amount of spontaneously running the tap cannot be absorbed.

Further, Patent Reference 5 shown below discloses a tapper mechanism in which a first member and a second member are connected by a connecting pin and an elastic member in a ring-like shape, further, a clutch for reverse rotation and a connecting member (key member) are connected by the connecting pin and the elastic member (refer to paragraph numbers [0009], [0018] FIGS. 3, 7). However, even the elastic member arranged at either of the connecting pins is for alleviating an impact when a clutch for regular rotation is engaged, or for absorbing attachment error of the connecting member and the clutch for reverse rotation, and not for restraining a synchronization error between spindle feeding and rotation of the spindle.Patent Reference 1: JP-A-7-60544Patent Reference 2: JP-A-2004-142033Patent Reference 3: JP-A-2002-46020Patent Reference 4: JP-UM-A-59-8725Patent Reference 5: JP-A-2000-61729

SUMMARY OF THE INVENTION

The invention has been carried out in consideration of the above-described point and it is an object thereof to provide a tap holder in which in a constitution of separating a tap holder in correspondence with a machine tool spindle to a tapper body and a tap collet, even when an error is brought about in synchronizing feeding and rotation of the machine tool spindle, an error between the tapper body and the tap collet can be absorbed by a simple constitution to synchronize the feeding and the rotation.

A tap holder according to the invention is including a tap collet for chucking a tap at one end thereof, and a tapper body for receiving an outer face side of other end of the tap collet in an axial direction to fix unrotatably, and attached to a machine tool having a tap synchronizingly feeding mechanism, and characterized by in which the tap collet and the tapper body are inserted with a locking member at portions of the tap collet and the tapper body overlapping each other, and in which the locking member engages the tap collet and the tapper body in a state of interposing an elastic member on both sides in an axial direction between the locking member and at least one of the tap collet and the tapper body.

According to the invention, an error of synchronizing spindle feeding and rotation of a machine tool spindle can be absorbed by a simple constitution by producing a small amount of movement in an axial direction between a tapper body and a tap collet.

Further, the tapper body and the tap collet as well as the locking member and the elastic member can be fabricated with high productivity and inexpensively by a simple structure by reducing basic constituent elements.

Further, by interchanging the elastic member, a difference in a tap size or a difference in a machined material, wear or an aging change can easily be dealt with.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

A first embodiment of the invention will be explained in reference to the drawings as follows.

FIG. 1is a sectional view of a tap holder10according to a first embodiment of the invention,FIG. 2is a sectional view enlarging an essential portion of the tap holder10,FIG. 3is a sectional view taken along a line A-A ofFIG. 1, andFIG. 4is a disassembled view of the tap holder10.

The tap holder10according to the embodiment is a tap holder for mounting a tap40to a machine tool having a tap synchronizingly feeding mechanism, having a tapper body20including a shank portion22attachably and detachably mounted to a spindle1of the machine tool, a tap collet50having a tap holding member42for holding the tap40at a front end thereof, and attachably and detachably attached to the tapper body20, and a locking member70for connecting the tap collet50to the tapper body20.

The tapper body20is provided with an outer cylinder portion24integrally with the shank portion22at a front end side thereof, the outer cylinder portion24is formed with an attaching hollow portion26for inserting a shaft portion52of the tap collet50, and formed with through holes28,28penetrated from an outer face of the outer cylinder portion24to the attaching hollow portion26in a diameter direction of the outer cylinder portion24.

Further, an inner portion of the tapper body20is formed with a flow path30for pressurizing a cutting fluid, and the flow path30is opened to the attaching hollow portion26.

The tap collet50includes the shaft portion52slidingly inserted into an inner peripheral face of the attaching hollow portion26of the tapper body20in a state of being brought into tight contact therewith, and a flange portion54provided at a front end side of the shaft portion52.

The shaft portion52is provided with a through hole56penetrated in a diameter direction at a position in correspondence with the through hole28provided at the tapper body20, the through hole28of the tapper body20and the through hole56of the tap collet50are communicated by inserting the shaft portion52into the attaching hollow portion26, thereby, the locking member70is made to be able to be inserted to the outer cylinder portion24and the shaft portion52at which the tap collet50and the tapper body20are overlapped.

The locking member70includes a male screw portion72, and a locking shaft portion74formed on a front end side of the male screw portion72and inserted to the through holes28and56. A peripheral face of the locking shaft portion74is formed with a plurality of first recessed portions76in a groove-like shape continuous in a peripheral direction to be spaced apart from each other by predetermined intervals thereamong in an axial direction of the locking shaft portion74, and the respective first recessed portions76are arranged with elastic members78to project from the locking shaft portion74to an outer side. The elastic member78is a ring-like member formed by a synthetic resin having an elasticity of nylon or the like or rubber and is removably arranged to the locking member70.

The locking member70is fixed to the tapper body20by screwing the male screw portion72with a female screw portion32provided at an inner peripheral face of the through hole28in a state of inserting the locking shaft portion74to the through hole28,56, thereby, the tap collet50is engaged with the locking member70in a state of interposing the elastic members78on both sides in an axial direction of the tap collet50indicated by an arrow notation X, and is unrotatably fixed to the tapper body20.

Further, an end face52aof the shaft portion52opposed to a bottom face26aof the attaching hollow portion26is arranged with a plurality of resin balls60to project from the end face52a, and the bottom face26aof the attaching hollow portion26and the resin balls60are brought into contact with each other. Further, the plurality of resin balls may be constituted by one O ring.

As shown byFIG. 3, an inner portion of the tap collet50is formed with a flow path62for pressurizing a cutting fluid, and an outer peripheral face of the shaft portion52is provided with an opening portion communicated with the flow path62. The outer peripheral face of the shaft portion52is arranged with a pair of the O rings66by interposing the opening portion, in a state of connecting and fixing the tap collet50to the tapper body20, the flow path62formed at the inner portion of the tap collet50is communicated with the flow path30formed at the inner portion of the tapper body20, and the cutting fluid supplied from a side of the machine tool is pressurized to a blade tip portion of the tap40therethrough.

A side of the flange54of the tapper body20is formed with a projection68engaged with a key groove34formed at an opening edge of the hollow portion26, and a rotational shift of the tap collet50relative to the tapper body20is hampered.

As described above, according to the tap holder10for the embodiment, the locking shaft portion74inserted into the through hole56of the tap collet50is engaged with the tap collet50in the state of interposing the elastic members78on both sides in the axial direction of the tap collet50indicated by the arrow mark notation X, and therefore, even when a force in either direction of a pressing direction and a pulling direction is generated at the tap collet50by the synchronization error of feeding and rotating the spindle1of the machine tool, the force is operated to the locking member74by way of the elastic member78, a difference between an amount of moving the tapper body20and an amount of spontaneously running the tap40is absorbed by elastically deforming the elastic member78and highly accurate tapping can be carried out.

Further, the elastic member78is arranged to be removably fitted to the first recessed portion76, and therefore, when the elastic member78is worn to deteriorate, the elastic member78can be interchanged by a new one thereof, a high tapping function can be maintained over a long period of time, an easiness of bending of the elastic member78can be adjusted by attaching the elastic member78having a different hardness to the first recessed portion76, and the tap holder10suitable for working various kinds of materials can be provided.

Further, although according to the embodiment, the elastic members78are arranged to all of the plurality of first recessed portions76provided at the locking shaft portion74, as exemplified inFIG. 5, by arranging the elastic members78at portions of the first recessed portions76and changing a number of the elastic members78interposed between the locking shaft portion74and the tap collet50, the easiness of bending the elastic members78can be adjusted, and the tap holder10suitable for working various kinds of materials can be provided.

Further, although according to the embodiment, the locking shaft portion74is provided with the plurality of first recessed portions76, and the respective first recessed portions76are respectively arranged with single pieces of the elastic members78, the invention is not limited thereto but, for example, as shown byFIG. 6andFIG. 7, a single one of the first recessed portion76may be arranged with a plurality of the elastic members78.

Furthermore, although according to the embodiment, the locking shaft portion74is engaged with the tap collet50by way of the elastic member78, the locking shaft portion74may be engaged with the tapper body20in a state of interposing the elastic members78on both sides in the axial direction indicated by the arrow notation X.

Second Embodiment

A second embodiment will be explained in reference toFIG. 8throughFIG. 10. Elements the same as or corresponding to those of the first embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 8throughFIG. 10are sectional views enlarging an essential portion of the tap holder10according to the embodiment.

Although according to the first embodiment, the elastic member78is arranged at the first recessed portion76provided at the locking member70, according to the tap holder10of the embodiment, an elastic member unit80including an elastic member82is interposed between the locking shaft portion74and the tap collet50.

Specifically, the elastic member unit80includes, for example, a cylinder member84in a circular cylindrical shape formed by a material having a rigidity larger than that of the elastic member82having a material the same as that of the tap collet50and the elastic member82arranged at the cylinder member84and removably fitted to the through hole56provided at the shaft portion52of the tap collet50, and a hollow portion88of the cylinder member84is inserted with the locking shaft portion74of the locking member70.

As shown byFIG. 8throughFIG. 10, the elastic member unit80may be provided with a plurality of second recessed portions86continuous in one peripheral face of the inner peripheral face and an outer peripheral face of the cylinder member84or in both of the peripheral faces in a peripheral direction and to be spaced apart from each other by predetermined intervals thereamong in an axial direction, and the second recessed portion86may be arranged with the elastic member82.

As described above, even in the tap holder10of the embodiment, by elastically deforming the elastic member82, the difference between the amount of moving the tapper body20and the amount of spontaneously running the tap40can be absorbed and the highly accurate tapping can be carried out.

Further, by providing the second recessed portion86arranged with the elastic member82only at the outer peripheral face of the cylinder member84, even when the locking member70is drawn or inserted in interchanging the tap collet50or the like, the locking shaft portion74and the elastic member are not rubbed directly by each other, and therefore, a durability of the elastic member82is promoted.

Third Embodiment

Next, a third embodiment will be explained in reference toFIG. 11. Elements the same as or corresponding to those of the first embodiment and the second embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 11is a sectional view enlarging an essential portion of the tap holder10according to the embodiment.

A characteristic of the embodiment resides in that the elastic member for absorbing the difference between the amount of moving the tapper body20and the amount of spontaneously running the tap40is arranged at the tap collet50.

That is, as shown byFIG. 11, the shaft portion52of the tap collet50is provided with a third recessed portion90penetrated in a diameter direction at a position in correspondence with the through hole28provided at the tapper body20, and by inserting the shaft portion52into the attaching hollow portion26, the through hole28at the tapper body20and the third recessed portion90at the tap collet50are communicated.

The third recessed portion90formed at the shaft portion52is removably fitted with an elastic member92in a cylindrical shape formed by a synthetic resin having an elasticity of nylon or the like or rubber, and the elastic member92is arranged at the third recessed portion90such that a hollow portion94of the elastic member92is communicated with the through hole28formed at the outer cylinder portion24. The elastic member92is pressed to be fixed by a bolt96penetrated from the end face52aof the shaft portion52to the third recessed portion90.

The through hole28formed at the outer cylinder portion24and the hollow portion94of the elastic member92are inserted with the locking shaft portion74of the locking member70in the state of being brought into tight contact therewith, and the locking member70is fixed to the tapper body20by screwing the male screw portion72of the locking member70with the female screw portion32formed at the inner peripheral face of the through hole28. Thereby, the tap collet50is engaged with the locking member70in the state of interposing the elastic member92on the both sides in the axial direction indicated by the arrow mark notation X to be fixed to the tapper body20unrotatably.

Modified Example 1 of Third Embodiment

Modified example 1 of the embodiment will be explained in reference toFIG. 12andFIG. 13. Elements the same as or corresponding to those of the embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 12is a sectional view enlarging an essential portion of the tap holder10according to the modified example andFIG. 13is a sectional view taken along a line B-B ofFIG. 12.

A point of a change from the embodiment resides in that the third recessed portion90formed at the shaft portion52of the tap collet50is not penetrated through the shaft portion52.

That is, as shown byFIG. 12andFIG. 13, a plurality (for example, three) of the third recessed portions90are arranged in the peripheral direction at equal intervals without penetrating the shaft portion52and each of the third recessed portions90is fitted with the elastic member92in the cylindrical shape. Also a plurality of the through holes28are formed at the outer cylinder potion24in correspondence with the third recessed portions90to be communicated with the hollow portions94of the elastic members92, and the tap collet50is fixed to the tapper body20by engaging the tap collet50and the locking member70by way of the elastic member92on the both sides in the axial direction indicated by the arrow mark notation X by inserting the locking shaft portion74of the locking member70to the through hole28and the hollow portion94of the elastic member92.

Modified Example 2 of Third Embodiment

Modified example 2 of the embodiment will be explained in reference toFIG. 14. Elements the same as or corresponding to those of the embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 14is a sectional view enlarging an essential portion of the tap holder10according to the modified example.

As shown byFIG. 14, according to a characteristic of the modified example, a side face92aof the elastic member92in the cylindrical shape inserted to the third recessed portion90formed at the shaft portion52, for example, a face thereof brought into contact with an inner wall90apartitioning the third recessed portion90is constituted by a recessed and projected face.

By providing the side face92aof the elastic member92by the recessed and projected face in this way, an easiness of bending the elastic member92can easily be adjusted by changing a contact area of the tap collet50and the elastic member92, and the tap holder10suitable for machining various kinds of materials can be provided by only changing the elastic member92. Although according to the modified example, the recessed and projected face is provided at the side face92aconstituting an outer periphery of the elastic member92, otherwise, the recessed and projected face may be provided only at an inner periphery thereof, or the recessed and projected faces may be provided at both side faces.

Further, the contact area of the tap collet50and the elastic member92may be changed by a front side and a rear side of a direction of pressing the tap collet50, in other words, by a case of operating a force in a pressing direction to the tap collet50and a case of operating a force in a direction of pulling thereto, thereby, the easiness of bending the elastic member92can respectively separately be adjusted for the force in the direction of pressing the tap collet50and the force in the direction of pulling the tap collet50.

Modified Example 3 of Third Embodiment

Modified example 3 of the embodiment will be explained in reference toFIG. 15. Elements the same as or corresponding to those of the embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 15is a sectional view of the tap holder10according to the modified example.

A characteristic of the modified example resides in that the elastic member92is arranged at the tapper body20.

That is, as shown byFIG. 15, the outer cylinder portion24of the tapper body20is arranged with a plurality (three in the embodiment) of the third recessed portions90in the peripheral direction without penetrating the outer cylinder potion24. Each of the third recessed portions90is fitted with the elastic member92in the cylindrical shape, and the hollow portion94of the elastic member92is communicated with a stop hole66provided at a position in correspondence with each of the third recessed portions90at the shaft portion52of the tap collet50. The tap collet50is fixed to the tapper body20by engaging the tap collet50and the locking member70by way of the elastic member92on the both sides in the axial direction indicated by the arrow mark notation X by inserting the locking shaft portion74of the locking member70into the stop hole66formed at the shaft portion52and the hollow portion94of the elastic member92.

Modified Example 4 of Third Embodiment

Modified example 4 of the embodiment will be explained in reference toFIG. 16throughFIG. 20. Elements the same as or corresponding to those of the embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 16is a sectional view enlarging an essential portion of the tap holder10according to the modified example,FIG. 17is a sectional view taken along a line C-C ofFIG. 16, andFIG. 18throughFIG. 20are partial sectional views of the tap collet50in the state of being inserted with the locking member70.

A characteristic of the modified example resides in that a clearance98constituting a margin of escaping the deformed elastic member92is provided between the elastic member92and the locking member70.

Specifically, as exemplified inFIG. 16andFIG. 17, the clearance98is formed by forming an inner diameter of the hollow portion94of the elastic member92to be larger than an outer diameter of the locking shaft portion74and bending the elastic member92by pressing a bolt96to an outer peripheral face of the elastic member92.

The clearance98constitutes the margin of escaping the elastic member92elastically deformed by the synchronization error of feeding and rotation of the spindle1of the machine tool. Therefore, for example, the easiness of bending the elastic member92can be adjusted by changing a size of the clearance98by changing a size of the hollow portion94or the like, and the tap holder10suitable for machining various kinds of materials can be provided.

Further, the contact area of the locking shaft portion74and the elastic member92can be made to differ from each other by the case of operating the force in the pressing direction to the tap collet50and the case of operating the force in the pulling direction thereto, and the easinesses of bending the elastic member92in the respective cases can individually be adjusted.

Further, other than the modified example, for example, the clearance98may be formed between the locking shaft portion74and the elastic member92by inserting the elastic member92substantially in a shape of a concentric cylinder into the third recessed portion90sectional shapes of which are provided in an elliptical shape, a shape of a triangle having rounded corners and the like as shown byFIG. 18throughFIG. 20. In this way, also the sectional shape of the hollow portion94can be changed by changing the sectional shape of the third recessed portion90, and therefore, the contact area of the locking shaft portion74and the elastic member92can be changed by the case of operating the force in the pressing direction to the tap collet50and the case of operating the force in the pulling direction thereto, and the easinesses of bending the elastic member92can separately be adjusted in the respective cases.

Modified Example 5 of Third Embodiment

Modified example 5 of the embodiment will be explained in reference toFIG. 21throughFIG. 23. Elements the same as or corresponding to those of the embodiment are attached with the same notations and a duplicated explanation thereof will be omitted.FIG. 21throughFIG. 23are partial sectional views of the tap collet50in the state of being inserted with the locking member70.

According to the modified example, as exemplified inFIG. 21throughFIG. 23, the elastic member92interposed between the locking shaft portion74and the shaft portion52of the tap collet50on one side in the axial direction indicated by the arrow mark notation X (front side in a direction of pressing the tap collet50according to the modified example) is formed to be more thick-walled than the elastic member92interposed between the locking shaft portion74and the shaft portion52of the tap collet50on other side (rear side in the direction of pressing the tap collet50according to the modified example). Thereby, the easinesses of bending the elastic member92can respectively separately be adjusted in the case of operating the force in the pressing direction to the tap collet50and the case of operating the force in the pulling direction thereto.

Further, although according to the modified example, the elastic member92on the front side in the pressing direction of the tap collet50is provided to be more thick-walled, the elastic member92on the rear side in the pressing direction of the tap collet50may be provided to be more thick-walled.