JPH0137847Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an improved power chuck for machine tools.

Prior Art A chuck attached to a spindle that grips a workpiece is subject to centrifugal force acting on the master yaw and top yaw that grip the workpiece as the spindle rotates. Centrifugal force is not much of a problem when the spindle rotates at a relatively low speed, but when the spindle rotates at a high speed, the centrifugal force increases, weakening the gripping force of the master yaw and drop yaw, and causing various safety problems in machining. do.
As a countermeasure for this, a counterbalance is installed so that the same force as the centrifugal force acts in the opposite direction to the centrifugal force acting on the jyo, and the increase in centrifugal force acts on the jyo and counterbalance in the same way, causing forces in opposite directions. They are designed to cancel each other out.

Problems that the invention aims to solve: However, since the size of the counterbalance is determined so that the magnitude of the centrifugal force acting on the counterbalance is balanced at a predetermined rotational speed of the spindle, it can be detected if the rotational speed of the spindle is low. When the force is too large and a cylindrical workpiece is being gripped, there is a problem in that it deforms the workpiece and leaves distortions after machining.

Means for Solving the Problem A tapered surface 8 that is inclined toward the center on the main shaft side is formed at each outer end of the master yaw 4, and a center axis is formed near the inner and outer periphery of the chuck body 2 at respective angular positions with respect to the master yaw 4. A wedge body 13 is provided which is supported so as to be slidable in a plane and has a taper whose leading end fits into the tapered surface, and a drive device for moving the wedge body 13 forward and backward in the direction of the central axis, and the top gear grips the workpiece. When this is done, the wedge body is inserted between the wall surface of the chuck body and the tapered surface of the master jaw.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings. A chuck main body 2 is fitted concentrically to the front end of a main shaft 1 of a machine tool, for example, a lathe, and T grooves 3 are cut in the radial direction at equal angular positions on the front end 3 from the center hole to the same circumference. The groove 3 is formed so as not to penetrate therethrough. This T-groove may be cut through and an outer cylinder may be fitted with a cap on the outside. A master jaw 4 having a T portion 5 on the lower surface is slidably inserted into each of the T grooves 3. A top jaw 6 for grasping the workpiece is attached to the front of the master jaw 4 in a replaceable manner, and a T-groove 7 is cut in the center end face on the opposite side to the main shaft 1 and inclined toward the center line. A tapered surface 8 that is inclined toward the center line on the main shaft 1 side is formed on the entire surface or a part thereof. A through hole is drilled in the center of the chuck body 2, and a wedge having a head having inclined T portions 9 formed at three equal angular positions so as to engage with the T grooves 7 of the respective master jaws is formed in this hole. A plunger 10 is slidably inserted in the axial direction, and this wedge plunger 10 is connected to a pull rod 11 inserted through the central hole of the main shaft 1. Square grooves 12 are cut in parallel to the central axis at angular positions corresponding to the three master jaws 4 of the chuck body 2 and at the outer end of the T-slot 3 on the main shaft side including the T-slot 3. Furthermore, a space 14 in which a disc 15 is housed is formed at the back of the chuck body 2. A wedge body 13 having a tapered surface whose tip engages with the tapered surface 8 of the master yaw 4 is slidably inserted into each of the square grooves 12, and the rear end of each wedge body 13 is housed in the space 14, and the wedge plunger 10 It is integrally attached to a disc 15 with a boss that can be slid on top.
The boss portion of the disc 15 is connected to a tension rod 16 inserted through the center hole of the main shaft 1. tension rod 1
Reference numerals 1 and 16 refer to a known double cylinder (not shown) which is integrally provided at the rear end of the main shaft 1 and to which pressure fluid is supplied by a known rotary joint (not shown). The tension rods 16 are connected to each other and moved back and forth in the axial direction. Note that the space 14 is used as a cylinder and the disk 14
When pressurized fluid is supplied to one side of the disk 15 and a spring is inserted to the opposite side to move the disc 15 forward and backward, the double cylinder becomes a single cylinder. It is also possible to operate the wedge bodies 13 with separate small cylinders.

Function: To grasp a workpiece, pressurized fluid is sent to the cylinder to advance the inner piston rod of the dual cylinders, and pressure fluid is sent to the cylinder to retract the outer piston rod to move the wedge plunger 10 forward. The top yaw 6 is opened, and the disc 14 and the wedge 13 are retracted so that the master yaw 4 is not engaged with the wedge 13.
When the workpiece is carried into the center of the three top yaws 6, the pressure fluid direction of the cylinder is changed to retract the inner piston rod that pulls the tension rod 11, the wedge plunger 10 is retracted, and the T section 9 moves to the master yaw. The T-groove 7 of No. 4 is pulled toward the center, and the top gear 6 moves toward the center to grip the workpiece. Next, when the pressure fluid direction of the cylinder is switched to advance the outer piston rod pushing the tension rod 16, the disk 15 and the wedge body 13 are advanced, and the tapered surface is aligned with the tapered surface 8 of the master jaw 4 and the outer circumferential wall of the chuck body 2. It fits in between and stops the outward movement of the master yo 4. When the workpiece is grasped in this way and the spindle 1 is rotated at high speed for machining, a large centrifugal force acts on the master yaw 4 and top yaw 6, causing them to try to escape outward, but the wedge body 13 has high rigidity. Since it is received by the chuck body and fitted into the tapered surface 8, escape to the outside is completely prevented.

Effects As detailed above, in the present invention, a tapered surface is formed on the outer end surface of the master jyo, and a wedge body that fits into the tapered surface is provided so that it can move forward and backward. The high chuck body allows for safe machining with no decrease in gripping force even during high-speed rotation. Further, by adjusting the fluid pressure to the cylinder, the working pressure of the wedge body can be adjusted, and it is possible to obtain an appropriate pressing force that does not cause deformation of the tubular workpiece or the like.

[Brief explanation of drawings]

The drawing is a cross-sectional view of a part of the chuck of the present invention. 1...Main shaft, 2...Chuck body, 4...Master yaw, 6...Top yaw, 10...Wedge plunger, 13...Wedge body, 11, 16...Tension rod.

Claims (1)

[Scope of utility model registration request] The master yaw has a top yaw in front and is moved in the radial direction by a wedge plunger that is moved forward and backward by power.The outer end of each master yaw is formed with a tapered surface that slopes toward the center on the main shaft side, near the inner and outer periphery of the chuck body. a drive device for moving the wedge body forward and backward in the direction of the central axis, the wedge body being slidably supported parallel to the central axis at each angular position with respect to the master yaw and having a taper whose leading end fits into the tapered surface; A power chuck characterized in that when the top jaw grips a workpiece, a wedge body is inserted between the wall surface of the chuck body and the tapered surface of the master jaw.