EP1928625A1

EP1928625A1 - Synchronized clamping chuck for machine tool

Info

Publication number: EP1928625A1
Application number: EP06798817A
Authority: EP
Inventors: Hong Suk Seo
Original assignee: Samchully Machinery Co Ltd
Current assignee: Samchully Machinery Co Ltd
Priority date: 2005-09-23
Filing date: 2006-09-20
Publication date: 2008-06-11
Also published as: WO2007035037A1; JP2009508705A; CN101272878A; CN101272878B; KR100639412B1

Abstract

The present invention is to provide a synchronized clamping chuck for a machine tool, in which a plurality of jaws (30, 40, 50) move at the same time to clamp a work piece with hydraulic pressure increased by hydraulic oil pressurizing (20) in a state that a center of the work piece is positioned at a center of the chuck, and then other jaw clamps the work piece, so that the machining can be done in a state the work piece is clamped rigidly when the centers of the work piece and the chuck are coincident.

Description

SYNCHRONIZED CLAMPING CHUCK FOR MACHINE TOOL

Technical Field

[1] The present invention relates to a clamping chuck for a machine tool, and more particularly, to a synchronized clamping chuck for a machine tool for chucking a work piece such that a center of the work piece coincident with a center of a chuck housing exactly with jaws moving by means of a hydraulic pressure of hydraulic oil filled in the chuck housing.

[2]

Background Art

[3] In general, as a chuck for a machine tool, a scroll chuck is used, whereby jaws move in a direction for clamping/releasing the work piece following rotation of a scroll rotated by a lever.

[4] Though not shown, the scroll chuck is provided with the scroll and the jaws in the chuck housing and a chuck cover such that, if a gear lever is rotated, a bevel gear rotates to rotate a crown gear on the scroll together with the scroll, to move a plurality of the jaws engaged with the scroll toward a center of the chuck housing or opposite thereto depending on a rotation direction of the scroll.

[5] When the jaws move toward the center of the chuck housing to hold the work piece, the work piece is machined with a bite while the work piece is rotated together with the chuck, or the work piece is machined with a rotating bite while the work piece is kept stationary together with the chuck.

[6] However, the scroll chuck has problems in that the manual rotation of the gear lever every time the worker clamps/releases the clamp the work piece with jaws is not convenient and impairs work efficiency, and the low clamping power of the manual rotation can not sustain an accurate machining, and causes cases when the work piece falls off the jaws in the middle of machining.

[7] In order to solve the problems, recently, a hydraulic chuck is applied, in which the jaws move with hydraulic cylinders working with a hydraulic pressure.

[8] The hydraulic chuck is provided with wedge plungers therein having guide holes sloped at predetermined angles each with a jaw engaged therein, for moving the wedge plungers back and forth with the hydraulic cylinders to move the jaws along the guide holes so that the jaws clamp or release the clamping of the work piece.

[9] In the application of multi-hydraulic chuck for a machine tool of the applicant filed at the same date with this application, the applicant suggests storing hydraulic oil in the chuck housing, applying a pressure to the hydraulic oil with the hydraulic oil pressurizing means to increase a hydraulic pressure, to move a plurality of jaws toward the chuck housing, to hold the work piece.

[10] However, the related art hydraulic chuck has problems in that a high cost is required due to a hydraulic unit having a direction change valve, a hydraulic pump, and a holding tank which requires supply of a hydraulic pressure for moving the hydraulic cylinder which moves the wedge plungers back and forth, and accurate machining of circular work piece is difficult due to difficulty in clamping the circular work piece with centers of the work piece and the chuck coincident, accurately.

[11] Moreover, the multi-hydraulic chuck for a machine tool filed by the applicant, having a structure in which the hydraulic oil pressurizing means applies a pressure to the hydraulic oil held in the chuck housing to increase a hydraulic pressure, has a problem in that the hydraulic pressure increased by the hydraulic oil pressurizing means is transmitted to a jaw closest to the hydraulic oil pressurizing means at first, and then is transmitted to jaws gradually proportional to distances from the means.

[12] Consequently, the differences in transmission of the hydraulic pressure increased by the hydraulic oil pressurizing means to the jaws in the chuck housing cause sequential movements of the jaws with slight differences between the movements until the jaws clamp the work piece, resulting in the work piece clamped not coincident with a center of the chuck slightly, which causes failure in accurate machining of the work piece and causes a big error in a case the work piece is machined with a cutting tool.

[13]

Disclosure of Invention Technical Problem

[14] An object of the present invention devised to solve the problem lies on providing a synchronized clamping chuck for a machine tool, in which a plurality of jaw move at the same time to clamp a work piece with a hydraulic pressure increased by hydraulic oil pressurizing means so that a center of the work piece is positioned at a center of the chuck, and then other jaw clamp the work piece, so that accurate machining can be made in a state the work piece is clamped rigidly in a state the centers of the work piece and the chuck are coincident, the error can be minimized. Technical Solution

[15] To achieve the above object and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the synchronized clamping chuck for a machine tool including a chuck housing having a body with a work piece hole, a main hydraulic chamber filled with hydraulic oil, and a first working hydraulic oil chamber and a plurality of second hydraulic oil chambers, both of which are formed in a radial direction toward the work piece hole and in com- munication with the main hydraulic oil chamber, hydraulic oil pressurizing means mounted to the main hydraulic oil chamber for applying a pressure to the hydraulic oil in the main hydraulic oil chamber to increase a hydraulic oil pressure of the working hydraulic oil chambers, a main jaw mounted to the chuck housing and coupled to the first working hydraulic oil chamber in the chuck housing for moving toward a center of the work piece hole, synchronized jaws mounted to the chuck housing and coupled to the second working hydraulic oil chambers for moving toward a center of the work piece hole in synchronization with the main jaw, a plurality of working jaws mounted to the chuck housing and coupled to the second working hydraulic oil chambers for moving toward a center of the work piece hole, main jaw moving means mounted to the first working hydraulic oil chamber in the chuck housing for moving the main jaw coupled to the first working hydraulic oil pressure chamber toward the center of the work piece hole or an outside of the chuck housing with a hydraulic oil pressure increased by the hydraulic oil pressurizing means, synchronized jaw moving means mounted to the second working hydraulic oil chambers in the chuck housing and connected to, and synchronized with the main jaw moving means for moving the synchronized jaws toward the center of the work piece hole or the outside of the chuck housing in synchronization with the main jaw, working jaw moving means mounted to each of the second working hydraulic oil chambers in the chuck housing for moving jaws coupled to the second working hydraulic oil pressure chambers toward the center of the work piece hole or the outside of the chuck housing with the hydraulic oil pressure increased by the hydraulic oil pressurizing means, and synchronized moving connection means for connecting the main jaw moving means to the synchronized jaw moving means for synchronization.

[16] That is, if the worker places the work piece in the work piece hole in the chuck housing for clamping the work piece, and operating the hydraulic oil pressurizing means to increase a hydraulic pressure of the main hydraulic chamber, the hydraulic oil pressure is transmitted to the first working hydraulic oil chamber to operate the main jaw moving means.

[17] If the main j aw moving means is operated, the synchronized j aw moving means connected to the main jaw moving means with the synchronized moving connection means is operated, such that the hydraulic oil pressure increased at the main hydraulic chamber is transmitted to the second working hydraulic chambers 14 to move the main jaw and the synchronized jaws in synchronization without any slight differences, to clamp the work piece at the center of the work piece hole, coincidently.

[18]

Brief Description of the Drawings [19] The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention.

[20] In the drawings:

[21] FlG. 1 illustrates a front view of a synchronized clamping chuck in accordance with a preferred embodiment of the present invention;

[22] FlG. 2 illustrates a section across a line A-A'in FlG. 1 ;

[23] FlG. 3 illustrates a section across a line B-B'in FlG. 2;

[24] FlG. 4 illustrates a back view of a synchronized clamping chuck in accordance with a preferred embodiment of the present invention.

[25]

Best Mode for Carrying Out the Invention

[26] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[27] FlG. 1 illustrates a front view of a synchronized clamping chuck in accordance with a preferred embodiment of the present invention.

[28] Referring to FlG. 1, the synchronized clamping chuck includes a chuck housing having jaw guide grooves formed in a front surface in a radial direction toward a work piece hole, and a main jaw, synchronized jaws, and working jaws movably mounted in the jaw guide grooves, respectively.

[29] FlG. 2 illustrates a section across a line A-A' in FlG. 1, showing hydraulic oil pressurizing means, main jaw moving means, and working jaw moving means.

[30] FlG. 3 illustrates a section across a line B-B' in FlG. 2, comparing synchronized jaw moving means connected to main moving means with synchronized moving connection means to working jaw moving means which is not connected to the main moving means.

[31] FlG. 4 illustrates a back view of a synchronized clamping chuck in accordance with a preferred embodiment of the present invention, showing a state the synchronized jaw moving means is connected to the main jaw moving means with the synchronized moving connection means at a back side of the synchronized clamping chuck.

[32] Referring to FlG. 1, the chuck housing 10 of the present invention has a circular body with a work piece hole 11 at a center for placing the work piece therein, and jaw guide grooves 15 in a front surface formed in a radial direction toward the work piece hole 11 in each of which the main jaw 30 or the working jaw 50 is movably mounted as described later.

[33] The jaw guide groove 15 having the main jaw 30 or the working jaw 50 placed therein serves to guide movement of the main jaw 30 or the working jaw 50 toward the center of the work piece hole 11.

[34] Referring to FlG. 2, the chuck housing 10 has a main hydraulic oil chamber 12 therein opened to an outside of the chuck housing 10 filled with hydraulic oil.

[35] The chuck housing 10 also has a first working hydraulic oil chamber 13 formed toward the center of the work piece hole 11 in communication with the main hydraulic oil chamber 12, and second working hydraulic oil chambers 14 formed in a radial direction toward the center of the work piece hole 11 at regular intervals in communication with the first working hydraulic oil chamber 13.

[36] The first and second working hydraulic oil chambers 13 and 14 are formed in the chuck housing 10 with a number and positions corresponding to the jaw guide grooves 15 in the chuck housing 10. There are main jaw moving means 60, synchronized jaw moving means 70, and working jaw moving means 80 formed from a rear side to a front side passed through the chuck housing 10 for moving the main jaw 30 and the working jaws 50.

[37] The main hydraulic oil chamber 12 has hydraulic oil pressurizing means 20 mounted thereto for applying a pressure to the hydraulic oil in the main hydraulic oil chamber 12, wherein the hydraulic oil pressurizing means 20 includes a moving up/ down bolt 21 having a continuous thread on an outside circumference engaged to the chuck housing 10 to turn with a tool and an end positioned in the main hydraulic oil chamber 12, and a master piston 22 at the end of the moving up/down bolt 21 having an outside circumferential surface in close contact with an inside wall of the main hydraulic oil chamber 12 for applying a pressure thereto with the hydraulic oil.

[38] The moving up/down bolt 21 has a hexagonal hole 21a in a top for rotating with a hexagonal wrench.

[39] On an outside circumference of the master piston 22, there is an O-ring 22a for sealing between the master piston 22 and the hydraulic oil chamber.

[40] That is, when the worker places the wrench in the hole 21a, and turns the moving up/down bolt 21 in a direction the master piston 22 moves down, the master piston 22 moves down to apply a pressure to the hydraulic oil in the main hydraulic oil chamber 12, to increase a pressure of the hydraulic oil.

[41] At first, the increased hydraulic pressure is transmitted to the first working hydraulic oil chamber 13 directly in communication with the main hydraulic oil chamber 12, and therethrough to the second working hydraulic oil chamber 14.

[42] In the meantime, the main jaw 30 in the jaw guide groove 15 of the chuck housing

10 is coupled to the first working hydraulic oil chamber 13.

[43] The working jaws 50 in the jaw guide grooves 15 of the chuck housing 10 are coupled to the second working hydraulic oil chambers 14 respectively and synchronizing jaws 40 are coupled to at least one of the second working hydraulic oil chamber 14. In the embodiment, the synchronizing jaws 40 are coupled to the two second working hydraulic oil chambers 14 spaced 120 degrees away from the main jaw moving means 60.

[44] Each of the main jaw 30, the synchronizing jaws 40, and the working jaws 50 has a movable guide hole 100 having an inwardly sloped surface in a back surface thereof. The sloped surface of the movable guide hole 100 has an angle opposite to each of movable projections 110 from main jaw moving bar 63 and working jaw moving bars 83 respectively to be described later placed therein such that the movable projections 110 move along the sloped surfaces of the movable guide holes 100 of the main jaw 30, the synchronizing jaws 40, and the working jaws 50, respectively.

[45] Each of the main jaw 30, the synchronizing jaws 40, and the working jaws 50 includes a master jaw 30a having the movable guide hole 100 in a back surface sloped inwardly from an outside surface, and a soft jaw 30b fixedly secured to a front surface of the master jaw 30a having one end projected toward the work piece hole 11 in the chuck housing 10 for clamping the work piece.

[46] The main jaw moving means 60 provided to the first working hydraulic oil chamber

13 for moving the main jaw 30 and includes a cover plate 61 on a back side of the chuck housing 10 for closing the first working hydraulic oil chamber 13, a main piston 62 having a body in close contact to an inside surface of the first working hydraulic oil chamber 13 for moving along an inside wall of the first working hydraulic oil chamber 13 with a first projection 62a projected to the back side of the chuck housing 10 through the cover plate 61 and connected to connection means, and the hydraulic oil of the working hydraulic oil chamber 13 filled in front, a main jaw moving bar 63 in front of the main piston 62 passed through the first working hydraulic oil chamber 13 and projected to a front surface of the chuck housing 10, having an end provided with the movable projection 110 sloped toward the center of the work piece hole 11, and a main piston return spring 64 between the main piston 62 and the cover plate 61 for supporting the main piston 62, elastically.

[47] Moreover, on an outside circumference of each of the main piston 62 and the main jaw moving bars 63, there are first, and second sealing rings 62b, and 63a for preventing the hydraulic oil from leaking from the first working hydraulic oil chamber 13, respectively.

[48] The synchronized jaw moving means 70 connected to the main jaw moving means

60 with synchronized moving connection means 90 for synchronizing with the main jaw moving means 60 is mounted to each of the second working hydraulic oil chambers 14 spaced at 120 degrees from the main jaw moving means 60, respectively.

[49] The synchronized jaw moving means 70 includes the cover plate 61 on the back side of the chuck housing 10 for closing the second working hydraulic oil chamber 14, a synchronized piston 72 having a body in close contact to an inside surface of the second working hydraulic oil chamber 14 for moving along an inside wall of the second working hydraulic oil chamber 14 with a second projection 72a projected to the back side of the chuck housing 10 through the cover plate 61 and connected to the connection means, and the hydraulic oil of the working hydraulic oil chamber 14 filled in front, a synchronized jaw moving bar 73 in front of the synchronized piston 72 passed through the second working hydraulic oil chamber 14 and projected to the front surface of the chuck housing 10, having an end provided with the movable projection 110 sloped toward the center of the work piece hole 11, and a synchronized piston return spring 74 between the synchronized piston 72 and the cover plate 61 for supporting the synchronized piston 72, elastically.

[50] Moreover, on an outside circumference of each of the synchronized piston 72 and the synchronized jaw moving bars 73, there are third, and fourth sealing rings 72b, and 73a for preventing the hydraulic oil from leaking from the second working hydraulic oil chamber 14, respectively.

[51] In each of the working hydraulic oil chambers, there is working jaw moving means

80 for moving the working jaw 50, wherein the working jaw moving means 80 includes the cover plate 61 at the back side of the chuck housing 10 for closing the working hydraulic oil chamber, a working piston 82 having a body in close contact to an inside surface of the second working hydraulic oil chamber 14 for moving along an inside wall of the second working hydraulic oil chamber 14, and the hydraulic oil filled from the main hydraulic oil chamber 12 in a front, a working jaw moving bar 83 in front of the working piston 82 passed through the working hydraulic oil chamber and projected to the front surface of the chuck housing 10, having an end provided with the movable projection 110 sloped toward the center of the work piece hole 11, and a working piston return spring 84 between the working piston 82 and the cover plate 61 for supporting the working piston 82, elastically.

[52] Moreover, on an outside circumference of each of the working piston 82 and the working jaw moving bars 83, there are fifth, and sixth sealing rings 82a, and 83a for preventing the hydraulic oil from leaking from the second working hydraulic oil chamber 14, respectively.

[53] The synchronized moving connection means 90 includes a connection plate 91 at the back side of the chuck housing 10 fastened to the synchronized jaw moving means 70 which is connected to the main jaw moving means 60 with bolts 92.

[54] That is, referring to FlG. 4, the main piston 62 is fixedly secured to the connection plate 91 with the bolt 92 through the first connection projection 62a, and the working piston 82 of the synchronized jaw moving means 70 is connected to the connection plate 91 with the bolt 92 through the second connection projection 72a, thereby connecting the main jaw moving means 60 to the synchronized jaw moving means 70.

[55] The operation of the synchronized clamping chuck of the present invention will be described.

[56] The hydraulic oil is filled in the main hydraulic oil chamber 12 in the chuck housing

10, the first working hydraulic oil chamber 13 in front of the main piston 62, and the second working hydraulic oil chambers 14 in front of the synchronized pistons 72 and the working pistons 82 at a fixed pressure.

[57] In this state, in order to clamp the work piece in the work piece hole 11, if the worker places the tool in the hole 21a, and turns the moving up/down bolt 21 in a direction the moving up/down bolt 21 moves down, the master piston 22 moves down as the moving up/down bolt 21 moves down, to apply a pressure to the hydraulic oil in the main hydraulic oil chamber 12 to increase the hydraulic pressure.

[58] Then, the increased hydraulic pressure is transmitted from the main hydraulic oil chamber 12 to the first working hydraulic oil chamber 13 at first, and pushes the main piston 62 backward toward the back side of the chuck housing 10.

[59] If the main piston 62 moves backward, the synchronized pistons 72 connected thereto through the connection plate 91 also move backward synchronized thereto.

[60] If the main piston 62 and the synchronized pistons 72 move backward, the movable projection 110 of the main jaw moving bar 63 moves out of the movable guide hole 100 of the main jaw 30 and the working jaws 50, so that the main jaw 30 and the working jaws 50 move toward the center of the work piece sliding on the sloped surface of the movable guide hole 100 to clamp the work piece.

[61] The increased hydraulic pressure of the main hydraulic chamber 12 is transmitted to the second working hydraulic oil chamber 14 near to the first working hydraulic oil chamber 13 with a slight difference, to push the working piston backward which is not connected to the main piston 62.

[62] As the working piston 82 is pushed backward, the working jaws 50 clamp the work piece in succession with slight differences.

[63] Accordingly, because the working jaws 50 clamp the work piece with slight differences after the main jaw 30 and the synchronized jaw 40 clamp the work piece at a time to position at the center of the work piece hole 11 such that the centers of the work piece and the work piece hole 11 are coincident owing to the main piston 62 and the synchronized pistons 72 connected to, and moving with the main piston 62 by the increased hydraulic pressure from the main hydraulic oil chamber 12, the synchronized clamping chuck of the present invention can clamp the work piece rigidly such that the centers of the work piece and the work piece hole 11 are coincident.

[64] Therefore, if cutting of the work piece is made in a state the work piece is rotated clamped by the chuck housing 10, since the work piece rotates with the centers coincide, an accurate cutting can be made, permitting machining of a true round.

[65] When it is intended to release clamping of the work piece machined thus, if the worker places the tool in the hole 21a and turns the moving up/down bolt 21 in a moving up direction, the hydraulic pressure in the main hydraulic oil chamber 12 decreases, and the main piston 62, the synchronized pistons 72, and the working pistons 82 move toward a front side of the chuck housing 10 by elastic force of the main piston return spring 64, the synchronized piston return springs 74, and the working piston return springs 84 which support the main piston 62, the synchronized pistons 72, and the working pistons 82, elastically.

[66] If the main piston 62 and the working pistons 82 move toward the front side, the movable projection 110 of the main jaw moving bars 63 are placed in the movable guide hole 100 in the main jaw and the working jaws 50, so that the main jaw 30 and the working jaws 50 move toward an outside of the chuck housing 10 sliding on the sloped surface of the movable guide holes 100, to release the clamping of the work piece.

[67] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[68]

Industrial Applicability

[69] The synchronized movements of the main jaw and the synchronized jaws by an increased hydraulic pressure from hydraulic oil pressurizing means permit to clamp the work piece at a time without any slight time difference with the centers of the work piece and the work piece hole coincident, accurately.

[70] The clamping of the work piece with the plurality of working jaws after the clamping of the work piece with the main jaw and the synchronized jaws permits a rigid clamping of the work piece.

[71] The clamping of the work piece with the centers of the work piece and the work piece hole coincident accurately enables true round machining, and significant reduction of an error in turning, to allow accurate machining. Thus the present invention is very useful invention.

Claims

[1] A synchronized clamping chuck for a machine tool comprising: a chuck housing 10 having a body with a work piece hole 11, a main hydraulic chamber 12 filled with hydraulic oil, and a first working hydraulic oil chamber 13 and a plurality of second hydraulic oil chambers 14, both of which are formed in a radial direction toward the work piece hole 11 and in communication with the main hydraulic oil chamber 12; hydraulic oil pressurizing means 20 mounted to the main hydraulic oil chamber 12 for applying a pressure to the hydraulic oil in the main hydraulic oil chamber

12 to increase a hydraulic oil pressure of the working hydraulic oil chambers; a main jaw 30 mounted to the chuck housing 10 and coupled to the first working hydraulic oil chamber 13 in the chuck housing 10 for moving toward a center of the work piece hole 11 ; synchronized jaws 40 mounted to the chuck housing 10 and coupled to the second working hydraulic oil chambers 14 for moving toward a center of the work piece hole 11 in synchronization with the main jaw 30; a plurality of working jaws 50 mounted to the chuck housing 10 and coupled to the second working hydraulic oil chambers 14 for moving toward a center of the work piece hole 11 ; main jaw moving means 60 mounted to the first working hydraulic oil chamber

13 in the chuck housing 10 for moving the main jaw 30 coupled to the first working hydraulic oil pressure chamber 13 toward the center of the work piece hole 11 or an outside of the chuck housing 10 with a hydraulic oil pressure increased by the hydraulic oil pressurizing means 20; synchronized jaw moving means 70 mounted to the second working hydraulic oil chambers 14 in the chuck housing 10 and connected to, and synchronized with the main jaw moving means 60 for moving the synchronized jaws 40 toward the center of the work piece hole 11 or the outside of the chuck housing 10 in synchronization with the main jaw 30; working jaw moving means 80 mounted to each of the second working hydraulic oil chambers 14 in the chuck housing 10 for moving jaws coupled to the second working hydraulic oil pressure chambers 14 toward the center of the work piece hole 11 or the outside of the chuck housing 10 with the hydraulic oil pressure increased by the hydraulic oil pressurizing means 20; and synchronized moving connection means 90 for connecting the main jaw moving means 60 to the synchronized jaw moving means 70 for synchronization. [2] The synchronized clamping chuck as claimed in claim 1, wherein the hydraulic oil pressurizing means 20 includes; a moving up/down bolt 21 having a continuous thread on an outside circumference engaged to the chuck housing 10 to turn with a tool and an end positioned in the main hydraulic oil chamber 12, and a master piston 22 at the end of the moving up/down bolt 21 having an outside circumferential surface in close contact with an inside wall of the main hydraulic oil chamber 12 for applying a pressure thereto with the hydraulic oil.

[3] The synchronized clamping chuck as claimed in claim 1, wherein the main jaw moving means 60 includes; a cover plate 61 on a back side of the chuck housing 10 for closing the first working hydraulic oil chamber 13, a main piston 62 having a body in close contact to an inside surface of the first working hydraulic oil chamber 13 for moving along an inside wall of the first working hydraulic oil chamber 13 with a first projection 62a projected to the back side of the chuck housing 10 through the cover plate 61 and connected to connection means, and the hydraulic oil of the working hydraulic oil chamber 13 filled in front, a main jaw moving bar 63 in front of the main piston 62 passed through the first working hydraulic oil chamber 13 and projected to a front surface of the chuck housing 10, having an end provided with the movable projection 110 sloped toward the center of the work piece hole 11, and a main piston return spring 64 between the main piston 62 and the cover plate 61 for supporting the main piston 62, elastically.

[4] The synchronized clamping chuck as claimed in claim 1, wherein the synchronized jaw moving means 70 includes; the cover plate 61 on the back side of the chuck housing 10 for closing the second working hydraulic oil chamber 14, a synchronized piston 72 having a body in close contact to an inside surface of the second working hydraulic oil chamber 14 for moving along an inside wall of the second working hydraulic oil chamber 14 with a second projection 72a projected to the back side of the chuck housing 10 through the cover plate 61 and connected to the connection means, and the hydraulic oil of the working hydraulic oil chamber 14 filled in front, a synchronized jaw moving bar 73 in front of the synchronized piston 72 passed through the second working hydraulic oil chamber 14 and projected to the front surface of the chuck housing 10, having an end provided with the movable projection 110 sloped toward the center of the work piece hole 11, and a synchronized piston return spring 74 between the synchronized piston 72 and the cover plate 61 for supporting the synchronized piston 72, elastically.

[5] The synchronized clamping chuck as claimed in claim 1, wherein the working jaw moving means 80 includes; the cover plate 61 at the back side of the chuck housing 10 for closing the working hydraulic oil chamber, a working piston 82 having a body in close contact to an inside surface of the second working hydraulic oil chamber 14 for moving along an inside wall of the second working hydraulic oil chamber 14, and the hydraulic oil filled from the main hydraulic oil chamber 12 in a front, a working jaw moving bar 83 in front of the working piston 82 passed through the working hydraulic oil chamber and projected to the front surface of the chuck housing 10, having an end provided with the movable projection 110 sloped toward the center of the work piece hole 11, and a working piston return spring 84 between the working piston 82 and the cover plate 61 for supporting the working piston 82, elastically.

[6] The synchronized clamping chuck as claimed in claim 1, wherein the synchronized moving connection means 90 includes a connection plate 91 at the back side of the chuck housing 10 fastened to the synchronized jaw moving means 70 which is connected to the main jaw moving means 60 with bolts 92.