Patent Description:
It is known that a front face of a workpiece is machined by a headstock and a tool post and then a back face of the workpiece chucked by a collet of a sub spindle is machined by a backworking unit. In such a lathe, oil or air is supplied to the sub spindle to block cut chips from entering the sub spindle through a slit of the collet. <CIT>, especially the paragraph <NUM> discloses a backworking unit provided with a blow air supplying mechanism and a cutting oil supplying mechanism.

<CIT> discloses a machine tool comprising a spindle, a stationary nozzle and a draw bar, which enables the nozzle to supply high-pressure coolant to a drill in a noncontact way.

<CIT> teaches a machine tool having a main spindle apparatus including a multispindle head and a cutting oil supply pipe.

<CIT> describes a machine tool having a spindle which comprises a stationary feeder in order to minimize the leakage during the transporting of coolant and lubricant.

It is an object of the invention to provide a machine tool having improved means for fluid leakage prevention. The object is satisfied by the subject matter of claim <NUM>.

Switching product ejecting apparatuses needs replacement of parts according to product ejecting methods. When a fluid supplying unit which supplies blow oil or blow air is removably mounted on a supporting unit of a sub spindle, a fluid seal needs be considered. When fluid is supplied from the stationary fluid supplying unit to a rotatable spindle, a clearance is necessarily provided between them. A wider clearance leaks more fluid, resulting in less oil or less air supplied to the collet and deficient removal of cut chips. A narrower clearance causes an interference of the spindle with the fluid supplying unit due to thermal expansion of the spindle. It is difficult for an operator to adjust the clearance to a constant value in replacing the parts. Parts replacement would take time and a wider clearance unintentionally adjusted would leak more fluid. The problem is not limited to a lathe provided with a backworking unit, but applied to various kinds of machine tools.

The present invention discloses a machine tool capable of facilitating a process of mounting the fluid supplying unit to the supporting unit which rotatably supports the spindle.

The machine tool of the invention comprises, i. a rotating unit including a spindle provided with a chucking unit which releasably chucks a workpiece, a supporting unit which rotatably supports the spindle around an axis of the spindle; and a fluid supplying unit removably mounted on the supporting unit to supply fluid to the chucking unit via the spindle. The fluid supplying unit has an insert to be received in the rotating unit in the direction of the axis of the spindle. The rotating unit has an inner circumferential surface opposite an outer circumferential surface of the insert received in the rotating unit. A labyrinth clearance is formed between the outer circumferential surface of the insert and the inner circumferential surface of the rotating unit when the fluid supplying unit is mounted on the supporting unit. The labyrinth clearance allows rotation of the rotating unit and restricts leak of fluid from the spindle when the rotating unit is rotated.

The present invention provides a machine tool capable of facilitating a process of mounting the fluid supplying unit to the supporting unit which rotatably supports the spindle.

Hereinafter, an embodiment of the present invention will be described. The invention is not limited to the exemplary embodiment and the features disclosed herein are necessarily not essential to the invention.

A machine tool <NUM> comprises a rotating unit U1, a supporting unit U2, and a fluid supplying unit U3. The rotating unit U1 includes a spindle (a sub spindle <NUM>, for example) provided with a chucking unit <NUM> for releasably chucking a workpiece W1. The supporting unit U2 rotatably supports the sub spindle <NUM> around a spindle axis AX1. The fluid supplying unit U3 is removably mounted on the supporting unit U2 to supply fluid to the chucking unit <NUM> via the sub spindle <NUM>. The fluid supplying unit U3 has an insert P1 to be received in the rotating unit U1 in the direction of the spindle axis (the Z-axis direction). The rotating unit U1 has an inner circumferential surface U1i opposite an outer circumferential surface P1o of the insert P1. When the fluid supplying unit U3 is mounted on the supporting unit U2, a labyrinth clearance C1 is formed between the outer circumferential surface P1o of the insert P1 and the inner circumferential surface U1i of the rotating unit U1. The labyrinth clearance C1 allows rotation of the rotating unit U1 and restricts leak of fluid from the sub spindle <NUM> when the rotating unit U1 is rotated.

As fully described later, in a comparative example as shown in <FIG>, it is difficult and time consuming for an inexperienced operator to invisibly provide a clearance C9 in the direction of the spindle axis between a rear end of a flange F1 of the rotating unit U1 and a front end of an outer pipe of a fluid supplying unit U9. In the embodiment of the invention, in a state that the fluid supplying unit U3 is mounted on the supporting unit U2, the rotating unit U1 is rotatable with respect to the fluid supplying unit U3 and the labyrinth clearance C1 formed between the outer circumferential surface P1o of the insert P1 and the inner circumferential surface U1i of the rotating unit U1 to restrict leak of fluid from the sub spindle <NUM> when the rotating unit U1 is rotated. Accordingly, the embodiment provides a machine tool capable of facilitating a process of mounting the fluid supplying unit to the supporting unit which rotatably supports the spindle.

The spindle is not limited to the sub spindle and may be a main spindle. The chucking unit comprises various chucking means for holding the workpiece such as a collet and claw. The fluid comprises liquid and gas such as blow oil and blow air. The workpiece comprises a product. The labyrinth clearance comprises a clearance where a labyrinth phenomenon is observed due to rotation of the rotating unit and a clearance where a seal effect is generated. The labyrinth clearance may be a clearance fit in accordance with ISO (International Organization for Standardization) <NUM>-<NUM>:<NUM> and JIS (Japanese Industrial Standard) B0401-<NUM>:<NUM>; "Geometrical product specifications (GPS) -- ISO code system for tolerances on linear sizes -- Part <NUM>: Tables of standard tolerance classes and limit deviations for holes and shafts".

<FIG> schematically shows an example of configuration of the machine tool. The machine tool <NUM> comprises an NC apparatus <NUM>, a headstock <NUM> mounted on a stationary base <NUM>, a backworking unit <NUM> mounted on a stationary base <NUM>, and a tool post <NUM> mounted on a stationary base <NUM>. The NC apparatus <NUM> controls the headstock <NUM>, the backworking unit <NUM>, and the tool post <NUM>.

The headstock <NUM> is movable in the Z-axis direction along a main spindle axis AX0. The NC apparatus <NUM> controls the Z-axis position of the headstock <NUM> via a not-shown driving unit thereof. The headstock <NUM> is provided with a main spindle <NUM>. The main spindle <NUM> releasably chucks a cylindrical or bar workpiece WO by a not-shown collet to rotate the workpiece WO on the main spindle axis AX0 along the longitudinal direction of the workpiece WO. The Z-axis direction may be the horizontal direction in the embodiment but not limited thereto.

The backworking unit <NUM> is movable in the Z-axis direction along the spindle axis AX1 and in a Y-axis direction perpendicular to the Z-axis direction. The NC apparatus <NUM> controls the Z-axis position and the Y-axis position of the backworking unit <NUM> via a not-shown driving unit thereof. The backworking unit <NUM> is provided with the sub spindle <NUM>. The sub spindle <NUM> releasably chucks the workpiece W1 whose front face has been machined. The workpiece W1 is rotated by the sub spindle <NUM> on the spindle axis AX1. The sub spindle <NUM> is called an opposite spindle since it is opposite the main spindle <NUM>. The Y-axis direction may be the horizontal direction in the embodiment but not limited thereto.

The tool post <NUM> has a plurality of tools T1 for machining the workpiece WO, W1 attached thereto. The tool post <NUM> is movable in an X-axis direction perpendicular to the Z-axis direction and the Y-axis direction. The NC apparatus <NUM> controls the X-axis position of the tool post <NUM> via a not-shown driving unit thereof. The X-axis direction may be the vertical direction in the embodiment but not limited thereto. The tool post may be a turret tool post or a gang tool post. Various types of tool posts are available. The moving direction of the headstock <NUM>, the backworking unit <NUM>, and the tool post <NUM> is not limited to the direction as shown in <FIG>.

<FIG> is a longitudinal section view along the spindle axis of the backworking unit provided with the sub spindle as an example of a spindle of an embodiment of the invention. <FIG> is an expanded longitudinal section view of an insert and the neighborhood of the fluid supplying unit. The backworking unit <NUM> comprises the rotating unit U1 having the sub spindle <NUM> provided with the chucking unit <NUM>, the supporting unit U2 which rotatably supports the sub spindle <NUM>, the product ejector <NUM>, and the fluid supplying unit U3. The combination of the product ejector <NUM> and the fluid supplying unit U3 is replacable by another part such as a product passage pipe U4.

The sub spindle <NUM> has a through-hole along the spindle axis AX1. The sub spindle <NUM> is rotatably attached to a body <NUM> of the supporting unit U2 via a bearing B1. The sub spindle <NUM> is provided with a chuck sleeve <NUM> and a push sleeve <NUM> inserted in the Z-axis direction (the direction of the spindle axis). A sleeve nut N1 for the product ejector <NUM> is removably attached to the chuck sleeve <NUM>. The sleeve nut N1, the chuck sleeve <NUM>, and the push sleeve <NUM> each has a through-hole along the spindle axis AX1 through which the product ejector <NUM> is inserted in the Z-axis direction. The sub spindle <NUM> along with the chuck sleeve <NUM> and the push sleeve <NUM> is rotated on the spindle axis AX1 around the product ejector <NUM>. A built-in motor <NUM> is mounted around the sub spindle <NUM>, comprising a stator <NUM> on the side of the supporting unit body <NUM> and a rotor <NUM> on the side of the sub spindle <NUM>. The sub spindle <NUM> is driven by the motor <NUM> under control of the NC apparatus <NUM>.

The chucking unit <NUM> comprises a collet <NUM>, a cap <NUM>, and a collet open/close mechanism <NUM> to <NUM>. The chucking unit <NUM> chucks the workpiece W1 inserted in the sub spindle <NUM> and releases it after the back face of the workpiece W1 is machined. The collet <NUM> is attached to the front end of the sub spindle <NUM> to releasably chuck the workpiece W1 supplied from the headstock <NUM>. The collet <NUM> is rotated along with the sub spindle <NUM>. The collet <NUM> is provided with a taper part 61a made gradually thinner toward the rear. The taper part 61a has a slit at a plurality of spots (three spots, for example). The cap <NUM> is attached to the front end of the sub spindle <NUM> to hold the collet <NUM>.

The collet open/close mechanism comprises the chuck sleeve <NUM>, a coil spring <NUM> for opening the collet, the push sleeve <NUM>, a claw <NUM>, a shifter <NUM>, a shifter lever <NUM>, and an actuator <NUM> for opening/closing the collet. The chuck sleeve <NUM> is in contact with the taper part 61a of the collet <NUM> and slidabe in the Z-axis direction. The spring <NUM> is suspended on the collet <NUM> at the side of an advancing direction D2 thereof while on the inner circumferential surface of the chuck sleeve <NUM> at the side of a retracting direction D3 thereof. The spring <NUM> thereby urges the chuck sleeve <NUM> toward the retracting direction D3. The advancing direction D2 is a direction in which the workpiece W1 is pushed out toward the front side of the sub spindle <NUM> along the Z-axis direction. The retracting direction D3 is opposite the advancing direction D2. The push sleeve <NUM> is in contact with the rear end of the chuck sleeve <NUM> and slidabe in the Z-axis direction. The claw <NUM> has a distal end 66a, a base 66b, and a shaft 66c. The distal end 66a is in contact with a taper part 67a of the shifter <NUM>. The base 66b is in contact with the rear end of the push sleeve <NUM>. The claw <NUM> is tilted around the shaft 66c. The claw <NUM> is rotated along with the sub spindle <NUM>. The taper part 67a of the shifter <NUM> is made gradually thinner toward the rear. The shifter <NUM> is slidable in the Z-axis direction. The shifter <NUM> is driven by the shifter lever <NUM>. The shifter lever <NUM> is driven by the actuator <NUM> under control of the NC apparatus <NUM>.

When the shifter <NUM> slides in the retracting direction D3 via the shifter lever <NUM> by the actuator <NUM>, the claw <NUM> is rotated so that the distal end 66a thereof is moved away from the spindle axis AX1. The chuck sleeve <NUM> then slides in the advancing direction D2 via the push sleeve <NUM> by the base 66b of the claw <NUM>. The collet <NUM> is then closed to chuck the workpiece W1. When the shifter <NUM> slides in the advancing direction D2 via the shifter lever <NUM> by the actuator <NUM>, the chuck sleeve <NUM> and the push sleeve <NUM> are retracted by urging force of the spring <NUM>. Accordingly the claw <NUM> is rotated so that the distal end 66a thereof is moved toward the spindle axis AX1. The collet <NUM> is then opened to release the back-machined workpiece W1.

The product ejector <NUM> is inserted inside the chuck sleeve <NUM> and the push sleeve <NUM> to be movable in the Z-axis direction. The product ejector <NUM> comprises a nearly cylindrical product ejecting shaft <NUM> and an ejection pin <NUM> removably attached to the front end of the ejecting shaft <NUM>. The ejecting shaft <NUM> is provided with a through-hole 72c extended in the Z-axis direction. A coil spring <NUM> for ejecting a product (the workpiece W1) is suspended outside of the ejecting shaft <NUM>. The spring <NUM> is compressed in the Z-axis direction to be suspended on a larger diameter portion 72b of the ejecting shaft <NUM> at the front end thereof while on a flange F1 of the rotating unit U1 at the rear end thereof. The workpiece W1 whose front face has been machined is inserted in the loosened collet <NUM> and chucked thereby. The back face of the workpiece W1 is machined and the collet <NUM> is opened. The product (the workpiece W1) is ejected toward the advancing direction D2 by urging force of the spring <NUM>. The flange F1 is provided with a recess F1a for receiving the insert P1 of the fluid supplying unit U3. The flange F1 is inside the flange F2 of the supporting unit U2 and fastened to the rear end of the sub spindle <NUM> by a screw S1. The flange F2 of the supporting unit U2 is fastened to the rear end of the supporting unit body <NUM> by a screw S2.

The fluid supplying unit U3 removably attached to the rear end of the supporting unit U2 comprises a fluid pipe <NUM> for blow oil and blow air and an outer pipe <NUM> surrounding the fluid pipe <NUM>. The fluid pipe <NUM> and the outer pipe <NUM> are arranged along the spindle axis AX1. The front end 31a of the fluid pipe <NUM> is inserted in the rear end of the ejecting shaft <NUM>. The rear end 31b of the fluid pipe <NUM> is connected to an oil supplying unit <NUM> and a pressure air supplying unit <NUM> to selectively supply blow oil and blow air. Blow oil from the oil supplying unit <NUM> is supplied to the collet <NUM> via the fluid pipe <NUM> and the through-hole 72c of the ejecting shaft <NUM>. Cut chips are thereby removed. Blow air from the pressure air supplying unit <NUM> is supplied to the collet <NUM> via the fluid pipe <NUM> and the through-hole 72c of the ejecting shaft <NUM>. Cut chips are thereby removed. The outer periphery of the outer pipe <NUM> is held by a stop ring <NUM> in contact with the rear end of the flange F2. The outer pipe <NUM> is inserted in the flange F2 of the supporting unit U2 and fastened thereto by screws S3. The front end 32a of the fastened outer pipe <NUM> is inserted in the recess F1a of the flange F1 of the rotating unit U1. Accordingly, the front end 32a of the outer pipe <NUM> is an example of the insert P1 to be received in the rotating unit U1 in the Z-axis direction. Between the outer circumferential surface P1o of the front end 32a of the outer pipe <NUM> and the inner circumferential surface U1i of the recess F1a of the flange F1, the labyrinth clearance C1 is formed to allow rotation of the rotating unit U1 and to restrict fluid leak from the sub spindle <NUM> when the rotating unit U1 is rotated.

<FIG> is an expanded section view of the insert P1 of the fluid supplying unit U3 and the flange F1 of the rotating unit U1. The other portions are not shown. The outer circumferential surface P1o of the insert P1 is circular in section shape. The inner circumferential surface U1i of the flange F1 is circular in section shape. There is a clearance fit between the outer circumferential surface P1ο and the inner circumferential surface U1i in accordance with ISO <NUM>-<NUM>:<NUM> and JIS B0401-<NUM>:<NUM>. The labyrinth clearance C1 is thereby formed between them. For example, in view of fit tolerance of larger than <NUM> and less than <NUM> in diameter, the outer circumferential surface P1o can be set at a reference value of -<NUM> or more and a reference value of -<NUM> or less in diameter. The inner circumferential surface U1i can be set at a reference value of +<NUM> or more and a reference value of -<NUM> or less in diameter. This is only an example. The labyrinth clearance C1 may be variously set as far as rotation of the rotating unit U1 is allowed and fluid leak from the sub spindle <NUM> is restricted when the rotating unit U1 is rotated.

As shown in <FIG> and <FIG>, the outer circumferential surface P1o of the insert P1 and the inner circumferential surface U1i of the flange F1 are parallel to the spindle axis AX1 in a longitudinal section view along the spindle axis AX1. The labyrinth clearance C1 is formed along the spindle axis AX1. Accordingly, when the fluid supplying unit U3 is attached to the supporting unit U2, the labyrinth clearance C1 is formed only by inserting the insert P1 into the recess F1a of the flange F1 in the Z-axis direction, thereby eliminating the need of clearance adjustment work.

When rotation of the rotating unit U1 is stopped, blow oil in the through-hole 72c of the ejecting shaft <NUM> gradually flows in the retracting direction D3 along the outer periphery of the fluid pipe <NUM>, flows in the advancing direction D2 between the outer periphery of the ejection shaft <NUM> and the inner periphery of the outer pipe <NUM>, and finally leaks through between the flange F1 and the front end 32a of the outer pipe (including the labyrinth clearance C1). Blow air similarly flows. When rotation of the rotating unit U1 is resumed, a labyrinth phenomenon is observed and a seal effect is generated at the labyrinth clearance C1. Leak of blow oil or blow air from the sub spindle <NUM> is thereby restricted.

Removing the product passage pipe U4 from the backworking unit <NUM> and mounting the project ejector <NUM> and the fluid supplying unit U3 is being described.

<FIG> shows a longitudinal section view of the backworking unit on which the product passage pipe U4 is mounted. The passage pipe U4 is fastened to the flange F2 via a slit pipe U40. The passage pipe U4 is provided with a through-hole U4c through which the back-machined product (the workpiece W1) passes in the Z-axis direction to be ejected from the not-shown rear end thereof. The slit pipe U40 having a slit is outside the passage pipe U4 around the spindle axis AX1. The slit pipe U40 is tightened by the screws S3 of the flange F2 to fasten the passage pipe U4. A sleeve nut N2 for the passage pipe U4 is removably attached to the chuck sleeve <NUM> mounted on the front end of the sub spindle <NUM>.

Removing the passage pipe U4 from the backworking unit <NUM> is being described. First, the screws S3 of the flange F2 are loosened at the rear end of the sub spindle <NUM> to release the passage pipe U4 from the slit pipe U40 toward the retracting direction D3. Then, the screw S2 is removed to release the flange F2 along with the slip pipe U40 from the supporting unit body <NUM>. The slit pipt U40 is removed from the flange F2 as shown in <FIG>.

The cap <NUM> is removed from the front end of the sub spindle <NUM>. The collet <NUM>, the spring <NUM> for opening the collet, and the chuck sleeve <NUM> along with the sleeve nut N2 are removed out of the through-hole along the spindle axis AX1. The sleeve nut N2 is removed from the chuck sleeve <NUM>. The sleeve nut N1 for the product ejector is mounted on the chuck sleeve <NUM>. Then, the flange f1 for the product ejector is fastened to the rear end of the sub spindle <NUM> by the screw S1. The spring <NUM> for ejecting a product and the push sleeve <NUM> are inserted in the through-hole of the sub spindle <NUM> and the flange F1 along the spindle axis AX1. The collet <NUM>, the spring <NUM>, and the chuck sleeve <NUM> along with the sleeve nut N1 are inserted in the through-hole of the sub spindle <NUM> along the spindle axis AX1. The cap <NUM> is attached to the front end of the sub spindle <NUM>. The flange F2 is fastened to the supporting unit body <NUM> of the supporting unit U2 by the screw S2 as shown in <FIG>.

Finally, as shown in <FIG> and <FIG>, the outer pipe <NUM> along with the fluid pipe <NUM> is inserted into the flange F2 in the advancing direction D2 until the stop ring <NUM> hits the flange F2. The outer pipe <NUM> is fastened to the flange F2 by the screws S3. The front end of the fluid pipe <NUM> is inserted into the through-hole 72c of the ejecting shaft <NUM> and the labyrinth clearance C1 is thereby formed between the outer circumferential surface P1o of the insert P1 and the inner circumferential surface U1i of the flange F1.

A comparative example of mounting the fluid supplying unit to the supporting unit is being described referring to <FIG> is a longitudinal section view of a comparative example of a backworking unit where a fluid supplying unit is mounted. First, an outer pipe <NUM> along with a fluid pipe <NUM> is inserted in the flange F2 in the advancing direction D2 until comes to the flange F1 of the rotating unit U1. The front end of the fluid pipe <NUM> is inserted in the through-hole 72c of the ejecting shaft <NUM> and the fluid supplying unit U9 comprising the fluid pipe <NUM> and the outer pipe <NUM> is mounted on the stationary flange F2. The clearance C9 is necessarily provided between the front end of the outer pipe <NUM> and the rear end of the flange F1. A wider clearance would leak more fluid, resulting in less oil or less air supplied to the collet and deficient removal of cut chips. A narrower clearance would cause an interference of the flange F1 of the rotating unit U1 with the stationary outer pipe <NUM> due to thermal expansion of the spindle. The clearance C9 is formed inside the backworking unit <NUM> and therefore not visually checked by using a measuring tool. Clearance is therefore provided in the following manner.

First, a nut N9 engaged with the outer periphery of the outer pipe <NUM> is turned until comes to the flange F2. With the nut N9 pressed against the flange F2, the outer pipe <NUM> is turned counterclockwise by for example <NUM>/<NUM> round corresponding to a clearance of <NUM>. The nut N9 is fastened. Then the outer pipe <NUM> is fastened to the flange F2 by a screw S9. In this manner, the clearance C9 (<NUM> for example) is formed between the stationary outer pipe <NUM> and the flange F1 of the rotating unit U1.

The clearance C9 is not visually checked by using a measuring tool. It is difficult for an inexperienced operator to adjust the clearance C9 to a constant value. It causes an increase in parts replacement man-hours and work time. A wider clearance unintentionally adjusted would leak more blow oil and more blow air. Leak amount is varied according to operators.

The embodiment of the invention eliminates such clearance adjustment process. The labyrinth clearance C1 is formed only by bringing the insert P1 into the recess F1a of the flange F1 in the Z-axis direction when the fluid supplying unit U3 is mounted on the supporting unit U2. Accordingly, the embodiment facilitates a process of mounting the fluid supplying unit to the supporting unit which rotatably supports the spindle. Further, parts replacement man-hours is reduced. Variation in leak amount due to different operators is prevented.

(<NUM>) Modified embodiment: The invention may be embodied in various ways. For example, the invention is applied to the headstock where the fluid supplying unit is removably mounted.

Claim 1:
A machine tool (<NUM>) comprising:
a tool post (<NUM>) provided with a tool (T1) for machining a workpiece (W1);
a rotating unit (U1) including a spindle (<NUM>) provided with a chucking unit (<NUM>) for releasably chucking the workpiece (W1) which is subjectable to machining by the tool (T1) mounted on the tool post (<NUM>);
a supporting unit (U2) which rotatably supports the spindle (<NUM>) around an axis (AX1) of the spindle (<NUM>); and
a fluid supplying unit (U3) removably mounted on the supporting unit (U2) to supply fluid to the chucking unit (<NUM>) via the spindle (<NUM>);
wherein, the fluid supplying unit (U3) has an insert (P1) to be received in the rotating unit (U1) in the direction of the axis of the spindle (<NUM>), and
wherein the rotating unit (U1) has an inner circumferential surface (U1i) opposite an outer circumferential surface (P1o) of the insert (P1) received in the rotating unit (V1);
wherein a labyrinth clearance (C1) is formed between the outer circumferential surface (P1o) of the insert (P1) and the inner circumferential surface (U1i) of the rotating unit (U1) in a state that the fluid supplying unit (U3) is mounted on the supporting unit (U2), the labyrinth clearance (C1) allowing rotation of the rotating unit (U1) and restricting leakage of the supplied fluid from inside the spindle (<NUM>) when the rotating unit (U1) is rotated, and
at a time that the fluid supplying unit (U3) is mounted on the supporting unit (U2) from a state that the fluid supplying unit (U3) is separated from the supporting unit (U2), the labyrinth clearance (C1) is formed by bringing a stop member (<NUM>) provided on the outer circumference of the fluid supplying unit (U3) into contacting the supporting unit (U2).