JPH06143005A - Tailstock - Google Patents

Abstract

PURPOSE:To maintain the thrust of a center even when the pressure of a pressure medium of a fluid pressure cylinder is reduced, in a tailstock of a grinder and the like, in which the fluid pressure cylinder is used. CONSTITUTION:A piston rod 14 of a hydraulic cylinder 13 is connected to the rear part of a feeding screw of a tailstock sleeve 2 through an axis connection tool 12, while the piston rod 14 is protruded to the rear part of the hydraulic cylinder 13 to fix a front part spring seat member 28 to the rear end of the piston rod 14. A feeding screw 33 for rear part spring seat member is fixed to a tailstock main body 1 through a bracket and the like, and a feeding nut 34 for rear part spring seat is inserted into the feeding screw 33. A rear part spring seat member 29 is rotatively mounted on the nut 34 in a correlated manner, while compression springs 31a, 31b are provided between the front part spring seat member 28 and the rear part spring seat member 29 in a contracted form, and a movable device that moves in the axial direction of the rear part spring seat member, is provided to adjust the position of the rear part spring seat member 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tailstock used for machine tools such as cylindrical grinders and reciprocating surface grinders.

[0002]

2. Description of the Related Art Conventionally, in a cylindrical grinder, the spindle and tailstock of a workpiece headstock are provided with a center, both ends of the workpiece are supported by both centers, and the workpiece is rotated by a workpiece rotating device provided on the workpiece headstock. The workpiece is rotated by rotating the wrench fixed to the. In the tailstock, the tailstock center is supported by, for example, a cylindrical sleeve in a cylindrical grinding machine so that the tailstock center can be moved back and forth, and is supported by a slide when a surface grinder grinds a spline shaft, for example. The advance / retreat of the center carrier such as the cylindrical sleeve or the slide is usually performed by a screw feeder and a fluid pressure cylinder.
It is said that the spindle of the work headstock can be moved back and forth while it is fixed, but this movement is for position adjustment, and the automatic or manual drive device that moves the workhead headstock back and forth from the spindle side. A threaded pair or a worm gear is used so as to be immobile.

[0003]

A cetane carrier is pushed forward by a screw feed device and a work piece is mounted on a spindle center attached to the spindle of the work headstock and on a tailstock center attached to the center carrier of the tailstock. It is necessary to propel it with an appropriate pressing force to the extent that it can be supported by the grinding force. When grinding is performed, the work piece expands due to grinding heat and thermal stress is generated, and a large pressing force is applied to the center, but since the center carrier is moved forward and backward by the screw feeder, the distance between centers does not move. , A heavy load is applied to the center. For this reason, there is a possibility that machining defects may occur due to bending of the workpiece, machining accuracy may deteriorate due to uneven wear of the center hole, and seizure of the center may occur.

When a fluid pressure cylinder is used for advancing and retracting the center carrier on the tailstock side, the fluid pressure cylinder pushes the work piece with a constant thrust, and even if the work piece expands due to grinding heat, the center support of the tailstock is carried. The body recedes and there is no problem because a constant thrust is applied to the work piece, but it requires pressure oil, compressed air as a pressure medium to drive the fluid pressure cylinder,
Various control valves are used because they require a pressure fluid generation source, pressure fluid transportation piping, a constant pressure circuit for control, a direction control circuit, and the like. If the pressure of the pressure fluid decreases for some reason on the pressure fluid device side, the center of the tailstock side is pushed and the pressure is reduced or no pressure is applied because the grinding force is applied to the workpiece. The pressure cylinder is retracted, and in an extreme case, the workpiece drops from between the centers. Even if it does not fall off, the workpiece cannot be sufficiently supported by both centers against the grinding force, so that the workpiece may not rotate accurately and the machining accuracy may be deteriorated. When such a situation occurs, a processed product made of a high-priced material such as various rolls and axles will be processed poorly, resulting in a significant loss.

According to the present invention, in a tailstock using a fluid pressure cylinder for advancing and retracting a center carrier, the tailstock can maintain the thrust of the center when the pressure of the pressure fluid decreases and can be used even when the pressure of the pressure fluid disappears. Is intended to provide.

Further, when it is necessary to reduce the pressing force applied in the axial direction when supporting a work piece with a light and slender work piece, the work force is smoothly pressed at a sufficiently low pressure when hydraulic pressure is used because of the throttle performance. If this is not possible, the hydraulic pressure is simply used to automatically retract the tailstock center, and the purpose is to provide a tailstock that can generate a small pressing force by the spring during forward movement.

[0007]

A first invention of the present invention is to provide a center carrier for supporting a center for supporting a workpiece, which is supported by a tailstock main body so as to be movable in an axial direction, and a means for lowering the center carrier. In a tailstock including a center carrier driving device and a tailstock main body, the center carrier driving device has a fluid pressure cylinder fixed to a rear part of the tailstock body. The front part of the piston rod of is connected to the center carrier, the rear part is fixed to the front spring seat member, and the rear spring seat member having a spring seat facing the spring seat of the front spring seat member is attached so that it can move back and forth. A tail spring is characterized in that a compression spring is contracted between both spring seats, and a rear spring seat member axial movement device for adjusting the position of the rear spring seat member is provided.

A second invention of the present invention is the tailstock according to the first invention, wherein the piston rod of the fluid pressure cylinder and the center carrier are directly connected to each other.

According to a third aspect of the present invention, the piston rod and the center carrier of the fluid pressure cylinder are a feed screw screwed into a feed nut fixed to the center carrier and a pair of the piston rod which are rotatable relative to each other. Driven rotary member which is connected by a shaft connecting tool which is constrained from moving relative to each other, is fitted to the rear portion of the feed screw so as to be axially movable and does not rotate, and is rotatably supported by the tailstock body. The tailstock according to the first invention, characterized in that

According to a fourth aspect of the present invention, in the tailstock according to the third aspect, the driven rotary member is connected to a manual or automatic drive source via a power transmission member. is there.

A fifth aspect of the present invention is characterized in that the fluid pressure cylinder is a fluid pressure cylinder that generates thrust only in the backward direction against the compression spring and does not always generate thrust in the forward direction. It is the tailstock according to any one of the first to fourth inventions.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a vertical sectional view showing a main portion, FIG. 2 is a vertical sectional view showing an outline of the whole, and FIG.
-A sectional view, FIG. 4 is a BB sectional view of FIG. 2, and FIG. 5 is a CC sectional view of FIG.

As shown in FIG. 2, a cylindrical sleeve 2 as a center carrier is fitted in the cylindrical hole 1a of the tailstock main body 1 so as to be movable in the axial direction. A tapered hole (not shown) is provided at the tip of the sleeve 2, and the tailstock side center 3 is fitted in the tapered hole. An axial key groove 2a is provided on the outer periphery of the sleeve 2, and the tip of the key 4 fitted and fixed to the tailstock main body 1 is slid into the key groove 2a, so that the sleeve 2
It is a detent. As shown in FIG. 5, a center carrier fixing means is provided. The fixing means is fixed to the tailstock main body 1 and is fixed to the tip of the piston 7a of the hydraulic cylinder 7 for clamping which is arranged in the radial direction of the sleeve 2 and which is fixed to the metal plate 8.
By pressing the outer periphery of the sleeve 2 in this way, the sleeve 2 is biased in the range of the gap between the tailstock hole 1a and the sleeve 2 to keep the tailstock side center 3 at a fixed position. It is desirable that the pushing direction be the same as the direction in which the grinding force is applied. The fixing of the sleeve 2 by the hydraulic cylinder 7 for clamping is such that when the axial thrust applied to the sleeve 2 is large, the sleeve 2 moves against the frictional force at the position of the abutment 8. That is, the fixing means using the hydraulic cylinder 7 as a drive source carries a part of the thrust applied to the tailstock sleeve 2, and the rest is carried by the drive device of the sleeve 2. The clamp hydraulic cylinder 7 retracts the dowel 8 when advancing and retracting the tailstock sleeve 2, and advances the dowel 8 when the sleeve 2 is stopped. A drive device for the sleeve 2 is arranged at the rear of the tailstock body 1. A feed nut 9 is fixed to the center hole of the sleeve 2, and a feed screw 11 is screwed into the feed nut 9. The feed screw 11 is the shaft connecting tool 1.
It is fixed to one of the two.

As shown in FIG. 1, the shaft connector 12 is connected to one of the feed screw 11 and the piston rod 14 of the hydraulic cylinder 13. A joint 15 to which the feed screw 11 is fixed is fitted and fixed to a bearing house 17 in which a bearing 16 is housed, and the shaft coupling 12 presses an outer ring of the bearing 16. Bearing 16
Is fitted in the bearing mount 18, and one surface of the inner ring of the bearing 16 is in contact with the brim of the bearing mount 18. The bearing mount 18 is fitted into the piston rod 14 so as to come into contact with the stepped portion of the piston rod 14 of the fluid pressure cylinder 13, and comes into contact with the collar 19 together with the inner ring of the bearing 16 so that the bearing mount 18 is screwed into the piston rod 14 by the bearing nut 18. A collar 19 is fixed to the piston rod 14. As a result, the shaft connecting tool 12 becomes the piston rod 14
It is also fixed to the feed screw 11. As a result, the feed screw 11 moves in the axial direction together with the piston rod 14, and the rotation of the feed screw 11 cannot be transmitted to the piston rod 14. The hydraulic cylinder 13 is fixed to the tailstock main body 1 via brackets of support members. That is, the tailstock body 1 is provided with a gearbox 2 as a bracket.
0, a tailstock rear casing 22 is continuously provided and fixed, and a hydraulic cylinder 13 is fixed to a relay plate 23 fixed to the casing 22. At both ends of the hydraulic cylinder 13, end covers 25 and 26 having a cylinder body 13a, a sealing member and a sealing member for the piston rod 14 are attached. The piston 27 is fitted through the inner circumference of the cylinder body 13a and the sealing ring 27a, and the piston 27 is hermetically fixed to the piston rod 14. The oil passage 13b of the hydraulic cylinder 13 extends from the oil inlet / outlet 13b-1 provided in the relay plate 23 to the end plate 2 through the relay plate 23 and the cylinder body 13a.
The oil passage 13c communicates with the rear cylinder chamber CR on the 6th side, and communicates with the front cylinder chamber CF on the end cover 25 side from the pressure oil inlet / outlet 13c-1 provided in the cylinder body 13a through the cylinder body 13a. A front spring seat member 28 is fixed to the rear end portion of the piston rod 14 protruding from the rear end cover 26, and the spring seat 28 of the front spring seat member 28 is fixed.
“A” faces the direction opposite to the tailstock side center 3. A rear spring seat member 29 having a spring seat 29a facing the spring seat 28a is attached so as to move back and forth so as to move in the same direction as the moving direction of the piston 27.
Two compression coil springs 31a and 31b having different coil center diameters are concentric with the hydraulic cylinder 13 between 9a and are inserted into the outer periphery of the front spring seat member 28 to be compressed.

The rear spring seat member axial movement device is as follows. In order to make the rear spring seat member 29 movable back and forth, in this example, the relay plate rear casing 32 also serving as a bracket is fixed to the relay plate 23. A spring seat feed screw 33 for guiding the rear spring seat member 29 is fixed to the relay plate rear casing 32. A male screw 33a is provided on the outer circumference of the spring seat feed screw 33 over the entire length. The rear spring seat member 29 is guided by the spring seat feed screw 33 by a rear spring seat member axial movement device that enables the position adjustment of the rear spring seat member 29 described later by power. The inner ring is fitted to a spring washer feed nut 34 having a screw to be screwed into the spring washer feed screw 33, and the outer ring of the bearing 36 fixed by a gear 35 fitted and fixed to the spring washer feed nut 34 is a bearing box. The bearing box 37 is fixed to the rear spring seat member 29 by fitting the spring seat feed screw 3 through the bearing 36 and the spring seat feed nut 34.
It is supported so that it can move in the axial direction. In order to prevent the position of the rear spring seat 29a from extending rearward and increasing the overall size, the front spring seat 28a is arranged as far forward as possible here. Therefore, the front spring seat member 28
Covers the hydraulic cylinder 13 as a hollow cylindrical portion 28b extending rearward from the front spring seat 28a. The spring seat feed screw 33 is hollow to cover the cylindrical portion 28b of the front spring seat member 28.

A spline shaft 41 for moving a spring seat member parallel to the spring seat feed screw 33 is axially formed by a relay plate 23 and bearings 42, 43 which are fitted and fixed in a relay plate rear casing 32 fixed to the relay plate 23, respectively. It has been fixed so that it does not move. A spline sleeve 44 is slidably fitted on the spline shaft 41. A gear 45 that meshes with a gear 35 fixed to the spring washer nut 34 is fitted and fixed to the spline sleeve 44. The inner ring of the spline sleeve 44 is fitted to the gear 45 and moves in the axial direction. The outer ring of the rolling ball bearing 46, which is fixed so as not to fit, is fitted into the rear spring seat member 29 and is fixed so as not to move in the axial direction. Spline shaft 41 for moving spring seat member
The driven gear 47 fixed to the relay plate 2 is, as shown in FIG.
Drive gear 5 fixed to the output shaft of a servomotor 49 with a reduction gear via an intermediate gear 48 rotatably attached to
It meshes with 0. The rear spring member moving spline shaft 41 is connected to an encoder 52 fixed to the relay plate 23. The encoder 52 detects the rotational position of the rear spring seat member moving spline shaft 41, and thus the position of the spring seat feed nut 34 via the spline sleeve 44 and the gears 45 and 35.

A rear portion of the sleeve moving feed screw 11 is a spline 11a, and a driven gear 51 as a driven rotating member is fitted to the spline 11a so as to be relatively movable in the axial direction. The driven gear 51 is supported by the gear box 20 via a bearing 52 so as not to move in the axial direction.

As shown in FIGS. 2 and 3, the gear 51 of the driven rotary member is connected to a manual drive source via a power transmission member. This power transmission member meshes with the driven gear 51 and the bearing 5 fitted into the support shaft 60 fixed to the gear box 20.
4, an intermediate gear 53 rotatably supported by the gear box 20, a gear 55 meshing with the intermediate gear 53, and a transmission shaft 57 fixed to one end of the tailstock main body 1 via a bearing 56. , The driven bevel gear 5 fixed to the other end of the transmission shaft 57
8. Drive bevel gear 59 and drive bevel gear 5 that mesh with the driven bevel gear
9 is fixed at one end, and the drive shaft 6 is supported by a bearing 62 mounted in a bearing housing 61 fixed to the tailstock main body 1.
3. A feed handle 64 fixed to the other end of the drive shaft 63 is provided. In the case of automation, the feed handle 64 is, for example, an electric motor.

As shown in FIG. 2, a dog plate 66 is provided on the rear spring seat member 29, and a plurality of dogs 67 whose positions are adjustable on the dog plate 66 push a switch (not shown) to press the rear spring seat member. The moving range of 29 is controlled.

The operation of the above configuration will be described.

In the state shown in FIG. 1, the piston 27 is at the retracted end, and the piston rod 14 pulls the feed screw 11 rearward through the shaft connector 12 and retracts the tailstock sleeve 2 through the feed nut 9. It is in the position. Further, the front spring seat member 28 fixed to the piston rod 14 is at the retracted end. In addition, the rear spring seat member 29 is at the retracted end, and the front spring seat member 28 of the front spring seat member 28 is in the piston retracted position.
The distance between a and the rear spring seat 29a is at the farthest position, and the compression amount of the compression coil springs 31a and 31b is small. In this state, pressure oil is supplied from one pressure oil inlet / outlet port 13b-1 to the oil passage 13b.
When the oil in the front cylinder chamber CF is allowed to be discharged from the other pressure oil inlet / outlet 13c-1 through the rear cylinder chamber CR through the piston 27, the piston 27 moves forward, and the piston rod 14 moves the shaft connecting member 12, the feed screw 11, The tailstock sleeve 2 is moved forward via the feed nut 9, and thereby the tailstock side center 3 is moved forward to move between the workpiece headstock side center fixed to the not-shown workpiece headstock side spindle. Hold the work piece by pinching. As the piston rod 14 advances, the front spring seat member 28 also advances, so that the compression coil springs 31a and 31b expand and the spring force weakens. The thrust applied to the workpiece is a value P1 obtained by multiplying the substantial sectional area of the rear cylinder chamber CR by the pressure of the pressure oil, and the compression coil springs 31a, 31.
It is the thrust obtained by adding the value P2 obtained by multiplying the compression amount from the free length of b by the spring multiplier. Here, the thrust applied to the tailstock side center 3 is adjusted by (1) changing the pressure of the pressure oil applied to the rear cylinder chamber CR. (2) When the servomotor 49 is driven to rotate the driving gear 50, the intermediate gear 48 rotates the driven gear 47, and the rear spring seat member moving spline shaft 41 rotates, the spline sleeve 44 rotates. By rotating the gear 45 fixed to the spline sleeve 44,
The gear 35 meshing with the gear 5 is rotated, the feed nut 34 fixing the gear 35 is rotated, and the feed nut 34 is moved in the axial direction. As a result, the rear spring seat member 29, which receives the propulsive force from the feed nut 34 via the bearing 36 and the bearing housing 37, moves forward and compresses the compression coil springs 31a and 31b, so the compressive force is the front spring seat member 28, Piston rod 14, shaft connector 12, feed screw 11, feed nut 9,
The thrust transmitted to the tailstock side center 3 through the sleeve 2 increases the thrust force for pushing the workpiece W. This compression coil spring 31
If the thrust by a and 31b is set appropriately, due to a failure of the hydraulic system or a partial power failure of the electric system that controls the hydraulic system,
Even if the hydraulic pressure is reduced or becomes no pressure, the thrust force of the piston 27 disappears and the tailstock side center 3 is pushed in the backward direction by the grinding force, the work force is generated by the spring force of the compression coil springs 31a and 31b. Is supported, and the distance between the headstock side center supporting the workpiece and the tailstock center 3 is long, so that the workpiece does not fall off, and defective machining due to defective grinding is prevented. In addition, the compression coil fields 31a and 31b have a wide range in which the rear spring seat member 29 can move in a wide range to change the spring force, so that it can be used for lightweight workpieces, light grinding, heavy grinding, elongated workpieces, etc. Therefore, it is possible to obtain an appropriate supporting thrust for the work piece.

In the above description, the thrust applied to the tailstock side center 3 is the sum of the spring force of the compression coil springs 31a and 31b and the oil pressure for urging the piston 27 in the forward direction.
If the thrust is applied only to the tailstock center 3 by the spring force, the difficulty of adjusting the hydraulic pressure in the range of the small thrust is eliminated, and the thrust can be adjusted accurately. In this case, the rear cylinder chamber CR is always kept unpressurized, only the front cylinder chamber CF is used, and the cylinder chamber CF is kept unpressurized, so that the front spring seat is compressed by the spring force of the compression coil springs 31a and 31b. Member 28, piston rod 14, shaft connector 12, sleeve moving feed screw 11, feed nut 9,
Move the sleeve 2 forward, move the tailstock side center 3 forward,
To retreat the tailstock side center 3, pressure oil is inserted into the front cylinder chamber CF to move the piston 27 to the compression coil spring 31a,
It suffices to move backwards against 31b. In such a case, the rear cylinder chamber CR of the hydraulic cylinder 13 may always communicate with the tank of the hydraulic power source (not shown), or may communicate with the atmosphere.

In the above operation, since the encoder 52 is connected to the spline shaft 41 for moving the rear spring seat member, a signal of the encoder 52 is input to a numerical controller (not shown), and the servomotor 49 rotates the rotation angle of the spline shaft 41. Since it can be stopped by rotating a predetermined number of times, the compression amount of the compression coil springs 31a and 31b can be controlled.

When the handle 64 is rotated, the drive gear 59 fixed to the drive shaft 63 is rotated, and the driven bevel gear 58 meshing with this bevel gear is rotated, and this rotation is transmitted by the transmission shaft 57.
The rotation is transmitted to the intermediate gear 53 meshing with the gear 55 and the driven gear 51 meshing with the intermediate gear 53, and the driven gear 51 rotates on the bearing 52. The driven gear 51 includes the feed screw 11 and the spline 1.
The feed screw 11 is rotated because it is coupled to 1a. The rotation of the feed screw 11 is performed by rotating the joint 15 of the shaft connector 12 and the bearing house 1.
7, the outer ring of the bearing 16 is rotated, and this rotation is not transmitted to the piston rod 14. Here, in FIG. 1, when the pressure oil is supplied to the hydraulic cylinder 13 and the front cylinder chamber CF is filled with the pressure oil and the piston 27 hits the end cover 26, the feed nut of the sleeve 2 is kept in this state. 9 is moved to move the tailstock side center 3 back and forth. As a result, the operation reference position of the tailstock side center 3 or the amount of protrusion of the tailstock sleeve 2 from the tailstock body 1 can be adjusted. Further, when the pressure of the pressure oil is reduced or becomes no pressure, the compression coil springs 31a and 31b move to the rear spring seat 29.
The front spring seat 28a is pushed with reference to a, and the front spring seat member 28 moves forward together with the piston rod 14 to move the piston 2
The sleeve 2 can be moved forward and backward with the manual handle 64 based on the position where either the spring 7 or the front spring seat member 28 hits the other member at the forward end and stops. Since the position of the piston 27, that is, the front spring seat member 28 is a reference for the advance / retreat of the tailstock side center 3 by the feed handle 64, the thrust force applied to the tailstock side center 3 is the hydraulic pressure and the spring force or the spring force. Occurs.

[0026]

According to the first aspect of the present invention, the drive unit for the center carrier has a fluid pressure cylinder fixed to the rear portion of the tailstock body, and the front portion of the piston rod of this fluid pressure cylinder has a center portion. The rear portion is connected to the carrier, the rear portion is fixed to the spring seat of the front spring seat member, and the rear spring seat member having a spring seat facing the spring seat of the front spring seat member is attached so as to be movable back and forth. A compression spring is contracted in the rear spring seat member, and a rear spring seat member axial movement device for adjusting the position of the rear spring seat member is provided. Even if the fluid pressure decreases, the center of the tailstock side is not pressed by the spring force, and the work piece does not drop, or the pressing force is weak and grinding failure does not occur. This center pressing force can be adjusted to an optimum value because the position of the rear spring seat member can be adjusted.

According to the second invention of the present invention, the tailstock according to the first invention is characterized in that the piston rod of the fluid pressure cylinder and the center carrier are directly connected to each other, so that the structure is simple. Is.

In the present invention, the piston rod and the center carrier of the fluid pressure cylinder are a feed screw screwed into a feed nut fixed to the center carrier, and the piston rod is a pair of rotatable members which do not move relative to each other in the axial direction. And a driven rotating member which is connected to the rear portion of the feed screw so as to be axially movable and non-rotatable and rotatably supported by the tailstock body. With the tailstock described in the first invention (third invention), the center carrier can be screw-fed in addition to the driving of the center carrier by the fluid pressure cylinder. This allows the relative position of the fluid pressure cylinder and the center carrier to be adjusted.

A fourth invention of the present invention is the tailstock according to the third invention, wherein the driven member is connected to a manual or automatic driving source via a motion transmitting member. Therefore, the center carrier can be operated manually or automatically.

A fifth aspect of the present invention is characterized in that the fluid pressure cylinder is a fluid pressure cylinder that generates thrust only in the backward direction against the compression spring and does not always generate thrust in the forward direction. Since the tailstock according to any one of the first to fourth inventions is used, fine adjustment is possible even in a range where the thrust applied to the tailstock side center is extremely small. As a result, it is easy to adjust the optimum thrust force that does not bend the work piece when supporting the work piece that is lightweight and elongated.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a main part of an embodiment of the present invention.

FIG. 2 is a developed sectional view showing the whole of the present invention.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a sectional view taken along line BB of FIG.

5 is a sectional view taken along line CC of FIG.

[Explanation of symbols]

 2 Tailstock sleeve 9 Feed nut 11 Feed screw 12 Shaft coupling tool 13 Hydraulic cylinder 14 Piston rod 28 Front spring seat member 29 Rear spring seat member 31a, 31b Compression coil spring 33 Feed screw for rear spring seat member 34 Rear spring seat Member feed nut 41 Spline shaft for moving spring seat member 44 Spline sleeve

Claims (5)

[Claims] 1. A center carrier for supporting a center, which is supported by a tailstock main body so as to be axially movable, and supports a workpiece, a center carrier fixing means, and a center carrier drive device.
In a tailstock having a tailstock body, the drive device for the center carrier has a fluid pressure cylinder fixed to the rear portion of the tailstock body, and the front portion of the piston rod of the fluid pressure cylinder has a center bearing body. The rear spring seat member is connected to the body, the rear portion is fixed to the front spring seat member, and the rear spring seat member having a spring seat facing the spring seat of the front spring seat member is movably attached to and retracted from the front spring seat member.
A tailstock characterized in that a compression spring is contracted between both spring seats, and a rear spring seat member axial movement device for adjusting the position of the rear spring seat member is provided. 2. The tailstock according to claim 1, wherein the piston rod of the fluid pressure cylinder and the center carrier are directly connected to each other. 3. The piston rod and the center carrier of the fluid pressure cylinder are a feed screw screwed into a feed nut fixed to the center carrier, and the piston rod is a pair of rotatable members so as not to move relative to each other in the axial direction. A driven rotary member which is connected to the rear portion of the feed screw so as to be freely movable in the axial direction so as not to rotate and which is rotatably supported by the tailstock body. The tailstock according to claim 1. 4. The tailstock according to claim 3, wherein the driven rotary member is connected to a manual or automatic drive source via a power transmission member. 5. The fluid pressure cylinder according to claim 1, wherein the fluid pressure cylinder is a fluid pressure cylinder that generates a thrust force only in the backward direction against the compression spring and does not always generate a thrust force in the forward direction. Tailstock.