JPS60177804A - Balance chuck - Google Patents

Abstract

PURPOSE:To remarkably improve rigidity of a chuck body for precise heavy cutting by compensating centrifugal force applied to a pawl for gripping a work with a balance weight. CONSTITUTION:When a chuck body 1 is rotated, moment of rotation in the clockwise direction around the center of a connecting portion 14 acts on a balance weight 11. This causes radially outward resilent deformation of the weight 11 around the connecting portion 14, and an engaging portion 11a pushes forward the rear surface 3e of a master jaw 3. This prevents lifting phenomenon of a pawl 5, and therewith reduction of gripping force caused by rotation of the chuck can be compensated and initial gripping force is maintained even at high speed rotation to allow heavy cutting.

Description

[Detailed Description of the Invention] Technical Field This invention relates to a balance chuck in which the centrifugal force applied to the jaws gripping a workpiece is compensated by a balance weight, and is particularly effective when used as a high-speed rotating chuck. It is.

Conventional technology and its problems Conventionally, this type of balance chuck is
No. 2-1195.81, U.S. Patent No. 2,729,459,
As disclosed in the same No. 2657068 and the same No. 4047723, a balanced weight is slidably mounted in the radial direction in the weight mounting groove on the rear side of the chuck body facing the jaw, and the balanced weight is and the pawl are connected by a lever lever to cancel out the centrifugal force acting on the pawl, Utility Model No. 51-4517
6, U.S. Patent No. 2828134, U.S. Patent No. 298255
As disclosed in No. 8, a balance weight is provided on one or both sides of the claw, and the balance weight and the claw are connected by a lever, JP-A-51-118181, U.S. Patent No. 337.
A known example is disclosed in No. 0859, in which a balance weight is attached to a crank lever that operates a pawl. However, in the above balance chucks, as shown in Fig. 5, the reaction force of the centrifugal force of the balance weight is absorbed by the claw 5.
E is applied toward the center of the chuck at a position rearward from the center 0 point of the groove fitting part of the jaw as shown by arrow A in Fig. 5, and the reaction force of the equilibrium weight is added to the initial grasping force of the jaw 5E. Since the centrifugal force applied to the jaws 5E is offset by tightening the jaws by the same amount, the gripping force of the jaws is significantly reduced by the centrifugal force applied to the jaws as shown by line a in Figure 6 while the chuck is rotating. This can prevent the gripping force of the claws from
As shown by b@ in the figure, the gripping force can be maintained close to the desired gripping force, but when the rotation of the chuck is stopped, the gripping force of the jaws is reduced by the centrifugal force of the balanced weight, as shown by line C in Figure 6. The amount of force compensated by the reaction force increases significantly compared to the initial gripping force, and as a result, the workpiece may be deformed after machining.
There was a big problem that caused some damage. Therefore, the conventional balance chuck as described above can be used not only for workpieces that require high machining accuracy and thin-walled workpieces that are easily deformed, but also for high-speed workpieces such as die casting and light alloy castings such as copper and aluminum. It is difficult to use it for grasping workpieces that require rotation and are easily deformed, but in reality, it is used for grasping workpieces that do not require deformation after machining, such as bar stock or rough machining. The scope of its use was severely limited. Therefore, in order to solve the problems of conventional balance chucks, the applicant of the present application has conducted various researches, and as a result, Japanese Patent Application Laid-Open No. 56-139809 (Patent Publication No. 58
As disclosed in Japanese Patent No. 58163), a balance chuck has been developed which can prevent the gripping force of the jaws from increasing significantly when the rotation of the chuck is stopped.

As an example of this balance chuck is shown in FIG. 7, a balance weight 11F is rotatably supported in a cavity 100 formed in the chuck body IF to compensate for the centrifugal force applied to the jaws 5F. A claw 5 in which the contact portion 11aF of the balance weight 11F is attached to the chuck body IF so as to be slidable in the radial direction.
It is configured so that it can come into contact with the back surface 3eF near the outer periphery of the claw 5F, and when the chuck rotates, the centrifugal force of the balance weight 11F acts on the back surface 3eF near the outer periphery of the claw 5F to push the claw 5F forward. There is. In such a balance chuck,
The moment M (fifth
When the tip of the claw is about to rise due to the movement of the claw (see figure), the centrifugal force of the balance weight ILF acts in the direction of canceling the moment M acting on the claw 5F, as shown by arrow B in Fig. 5. This prevents the lifting of the jaws 5F while the chuck is rotating, and prevents a significant drop in gripping force as the chuck rotates, as shown by line d in Figure 8. Furthermore, when the chuck stops rotating, the jaws 5F Both the moment due to the applied centrifugal force and the moment due to the centrifugal force of the balance weight 11F become zero, and the gripping force of the claw 5F becomes as shown in Fig. 8e.
As shown by the line, the gripping force returned to approximately the same level as the initial gripping force, which had a great effect in preventing accidents that would deform the workpiece after machining. However, in the balance chuck developed above, a balance weight 11F is installed inside the chuck body IF, similar to the conventional balance chuck mentioned at the beginning.
Since the cavity 100 is formed to accommodate the
A balanced weight 11F is pivotally supported in the 00, and the balanced weight 11F is
The contact portion 11aF is brought into contact with the back surface portion 38F of the claw 5F, so that the contact portion 11aF and the back surface portion 3aF are in contact with each other.
It is difficult to bring the point of contact with the outer peripheral surface of the chuck body IF very close to the outer peripheral surface of the chuck body IF, and it is also difficult to increase the lever ratio around the pivot of the balance weight 11F, so that the centrifugal force of the balance weight 11F can be compensated for by the centrifugal force of the claw 5F. Therefore, there is a problem that it cannot be used sufficiently, and therefore, it is necessary to increase the size of the cavity 100 and the balance weight 11F, and it is difficult to implement it in a small balance chuck with a small diameter.

Purpose and Summary The present invention aims to solve the above problems of the conventional balance chuck, and is capable of maintaining the gripping force of the claws at approximately the same level as the initial gripping force when the chuck rotates, and also stops the rotation of the chuck. The rigidity of the chuck body can be significantly increased without impairing the function of preventing the gripping force of the jaws from increasing significantly when the gripping force is removed. In addition, the present invention aims to provide a balance chuck in which the size of the balance weight can be made relatively small and can be easily applied to a small balance chuck with a small diameter.The balance weight is formed by a part of the chuck body. However, this balance weight is characterized in that it pushes the back surface near the outer periphery of the claw forward by elastically deforming using a thin continuous section connected to other parts of the chuck body as a fulcrum.

Embodiments Next, embodiments of the present application will be explained based on the drawings. In Figures 1 to 3, 1 is a cylindrical chuck body, on the front surface (right side in Figure 1) of which three mold mounting grooves 2 are cut radially at equal angular intervals. There is. As shown in FIG. 3, guide grooves 2a, 2a are formed on opposing sides of each of these mold mounting grooves 2. Each mold mounting groove 2 is provided with a claw 5 consisting of a master jaw 3 and a top jaw 4.
The master jaw 3 is slidably inserted in the radial direction. This master jaw 3 has the guide grooves 2a, 2a.
Protrusions 3a, 3a guided by are formed,
The claws 5 are slid in the radial direction by fitting the projections 3a, 3a into the guide grooves 2a, 2a. A T-shaped groove 3b is cut in the radial direction on the front surface of the master jaw 3, and a jaw nut 6 is movably fitted into this T-shaped groove 3b as is well known. A saw blade-like serration 3C is formed on the front surface of this master jaw 3, and this serration 3c
The serrations 4a of the top jaw 4 are engaged with the serrations 4a of the top jaw 4. This top jaw 4 is tightened and fixed to the master jaw 3 by screwing two bolts 7 into a jaw nut 6. A T-shaped taper portion 3d is formed at the radially inner end of the master jaw 3, as is well known. A wedge plunger 8 is fitted into the central hole la of the chuck body 1 so as to be slidable in the axial direction of the chuck body 1, and can be slidably engaged with the tapered portion 3d of the master jaw 3 on its outer periphery. Tapered grooves 8a each having a T-shaped cross section are formed, and the corresponding tapered portions 3d of the claws 5 are engaged with these tapered grooves 8a. Note that the sliding movement of the pawl 5 in the radial direction may be performed via a transmission means such as a crank. The wedge plunger 8 has a draw bolt 9 attached to the nut 1.
As is well known, this draw bolt 9 is connected to a drawper fitted into a central hole of a spindle (not shown), and is moved in the axial direction by the operation of a pneumatic or hydraulic fluid pressure operated cylinder. It is designed to move back and forth. Next, reference numeral 11 is a balance weight constituted by a part of the chuck body 1 corresponding to the winter melon 5, and a horizontal groove 12 cut from the back side of the chuck body 1 toward the front, and an outer circumference of the chuck body 1. It is separated from other parts of the chuck body 1 by a vertical groove 13 cut from the surface toward the center of the chuck body 1. This transverse groove 12 is formed from the back side near the outer periphery of the chuck body 1 toward the front in a direction perpendicular to the sliding direction of the claw 5 from the back side 3e of the master jaw 3, that is, from the rear inner surface 2b of the mold mounting groove 2. It is formed up to the front position. As shown in FIG. 2, the horizontal groove 12 is formed near the outer periphery, far away from the center of the chuck body 1, and the rigidity of the chuck body 1 closer to the center of the chuck than the horizontal groove 12 is greater. It is designed to be maintained. Further, the vertical groove I3 is formed at a position in front of the back surface 3e of the master jaw 3, that is, the claw mounting groove 2, and the rear inner surface 2b of the chuck body 1, from the outer circumferential surface of the main body 1 toward the center. The groove is formed to a depth that leaves a thin continuous portion 14 with a small thickness between it and the transversely divided groove 12 in the direction perpendicular to the groove. The wall thickness of the continuous portion 14 is set to a size that allows the balance weight 11 to elastically deform in a radial outward direction using the continuous portion 14 as a fulcrum due to the centrifugal force applied to the balance weight 11 when the chuck rotates.

The rear inner surface 2b of the claw attachment groove 2 in the balance weight 11 is configured as a contact portion 11a that comes into contact with the back surface 3e of the master jaw 3 when the balance weight 11 is elastically deformed in the radial outward direction due to centrifugal force. ing. Reference numeral 15 denotes a chamfered portion formed on the outer circumferential end of the contact portion 11a, and is used to adjust the distance between the fulcrum of the continuous portion 14 and the contact portion 11a, that is, the lever ratio. By enlarging this chamfered portion 15, the force amplification ratio when the centrifugal force of the balance weight 11 acts on the claw can be increased. Reference numeral 16 denotes a cylindrical cover fitted to the outer periphery of the chuck body 1 from the rear side, and a mounting piece 16a protruding toward the center is integrally bent and formed at the rear end of a portion corresponding to the balance weight 11. This mounting piece 16a is fitted into a fitting recess 17 formed by cutting off the rear end of the chuck body l,
This mounting piece 16 is fixed to the chuck body 1 by a mounting screw 18. An escape recess 19 is formed on the inner surface of the cover 16 so that the balance weight 11 can be elastically deformed radially outward by a required amount. Note that the cover 16
may be omitted. 20 is a fixing bolt for attaching the chuck body 1 to a spindle of a machine tool or a mounting member attached to the spindle; 21 is a cover plate attached to the chuck body 1 with a mounting screw 22;

In the structure described above, when the draw bolt 9 is moved in the axial direction (back and forth direction) by the operation of a fluid pressure cylinder (not shown) while the rotation of the chuck is stopped, the wedges that are fitted into each other The master jaw 3 moves in the radial direction due to the wedge action caused by relative sliding between the tapered groove 8a of the plunger 8 and the tapered portion 3d of the master jaw 3, and the top jaw 4 fixed to the master jaw 3 also moves in the radial direction. , grasp or release the workpiece. In this case, since the rotation of the chuck body 1 is stopped,
The balance weight 11 maintains the state shown in FIG. 1 without being subjected to centrifugal force. Therefore, the master jaw 3 is the balance weight 11
It is not pressed by the radial force and is smoothly moved in the radial direction. When the draw port 9 is pulled rearward and the workpiece is gripped by the top jaw 4, and the chuck is rotated in this state, the jaw 5 is attached to the jaw 5 as shown in FIG.
A rotational moment M acts on the claw 5 due to the centrifugal force applied thereto, causing a so-called lifting phenomenon in which the tip of the claw 5 rises, and the gripping force of the top jaw 4 on the workpiece tends to decrease significantly. However, due to the rotation of the chuck, a centrifugal force acts on the balance weight 11, and a clockwise rotational moment acts on the balance weight 11 in the clockwise direction in FIG. The weight 11 is elastically deformed radially outward using the continuous portion 14 as a fulcrum, and the contact portion 11a of the balanced weight 11 pushes the back surface 3e near the outer periphery of the master jaw 3 forward. The pressing force exerted on the master jaw 3 by this balanced weight 11 acts in the direction of canceling the rotational moment M of the claw 5 due to the centrifugal force acting on the claw 5.
This prevents the lifting of the claws 5, compensates for the large drop in gripping force caused by rotation of the chuck, and maintains the gripping force at approximately the same level as the initial gripping force even if the chuck rotates at high speed. When the chuck rotates while gripping the workpiece as described above, the jaws 5 are prevented from lifting up and are in the same state as the initial gripping when the workpiece is gripped with the chuck not rotating. This means that you understand it. Therefore, when the rotation of the chang and ri is subsequently stopped, the centrifugal force applied to the balance weight 11 becomes zero, and the balance type t@11
It returns to the original position shown in FIG. 1 due to the restoring force due to the elasticity of the claw 5, and the contact portion 11a no longer presses the back surface portion 3e of the claw 5. The centrifugal force applied to the claw 5 also becomes zero, and the top jaw 4 returns to approximately the same state as when it first gripped the workpiece, and the gripping force becomes approximately the same as the initial gripping force.

Therefore, even when a workpiece that is easily deformed is gripped and rotated at high speed, it is possible to prevent an accident in which the workpiece after machining is deformed by the gripping force when the rotation is stopped.

When the centrifugal force applied to the claws 5 during chuck rotation is compensated for by the centrifugal force applied to the balance weight 11 as described above, the balance weight 11 is constituted by a part of the outer circumferential portion of the chuck body 1. Since it is located near the outer periphery, the centrifugal force applied to the balance weight 11 becomes large, and the pressing force of the balance weight 11 to push the back surface 4e of the claw 5 forward can be increased. Further, the above-mentioned balance weight 11 has a horizontal cut groove 12 and a vertical cut groove 13, and a contact portion 11a of the balance weight 11 is formed.
A continuous portion 14 is located slightly forward and toward the center of the chuck.
As a result, the centrifugal force applied to the balance weight 11 can be increased by a large proportion, and thereby the pressing force that pushes the back surface 4e of the claw 5 forward by the balance weight 11 can be increased. .

Therefore, the size of the balance weight 11 can be made relatively small compared to the size of the claw 5, and moreover, the size of the balance weight 11 can be made relatively small compared to the size of the claw 5.
Since it is formed on the outer peripheral portion of the chuck body 1, the rigidity of the portion of the chuck body 1 other than the balance weight 11 can be significantly increased. Further, the above-mentioned balance weight 11 can be easily constructed by forming transverse grooves 12 and vertical grooves 13 in the chuck body 1.

FIG. 4 shows a different embodiment of the present application, in which the transverse groove 1
2h is formed in a direction perpendicular to the axis of the chuck body 1h, and a vertical groove 13h is cut to a position slightly above the front end of the horizontal groove 12h, thereby forming a balance weight 11h. It should be noted that parts that are considered to have the same or equivalent configuration as those of the above-mentioned embodiments are given the same reference numerals as the corresponding parts with the letter "h", and redundant explanation will be omitted.

Effects As described above, in the present invention, when the chuck is rotated, the balanced weight is elastically deformed toward the outer circumference by centrifugal force, and the centrifugal force of the balanced weight is applied to the back surface near the outer periphery of the claw. Since the outer periphery of the jaw is pushed forward, it is possible to prevent the jaw from floating while the chuck is rotating and compensate for the decrease in gripping force of the jaw due to the rotation of the chuck. The gripping force can be returned to the initial gripping force, and an increase in the gripping force when rotation is stopped can be prevented. Therefore,
It is possible to increase the rotational speed of the chuck, improving machining ability and machining accuracy, and also enables high-speed rotation of thin-walled workpieces and light alloy castings that are easily deformed by gripping. In addition, since the above-mentioned balance weight is constructed from a part of the chuck body that is integrally connected to the other part of the chuck body through a thin continuous part, the position of the balance weight can be brought close to the outer peripheral surface of the chuck body. The centrifugal force applied to the balance weight can be increased, and the balance weight required to compensate for the centrifugal force on the jaws can be made smaller, making it possible to downsize the chuck as a whole and making it easy to implement on small-diameter chucks. There are benefits to be gained. Furthermore, since the balance weight is formed in a portion near the outer periphery of the chuck body as described above, there is no need to provide a cavity for storing the balance weight inside the chuck body, and the rigidity of the chuck body can be significantly increased. Moreover,
As mentioned above, since the balance weight is integrally connected to other parts of the chuck body via the continuous part, it is possible to eliminate parts for attaching the balance weight, which significantly reduces manufacturing costs. be able to.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and FIG. 1 is a longitudinal cross-sectional view;
Fig. 2 is a front view with some parts omitted, Fig. 3 is a plan view with the cover omitted, Fig. 4 is a sectional view of main parts showing a different embodiment, and Fig. 5 is a centrifugal view due to rotation of the claw. An explanatory diagram showing the state when force is applied, FIG. 6 is a graph showing the relationship between chuck rotation speed and gripping force in a conventional balance chuck,
FIG. 7 is a longitudinal sectional view of a conventionally developed balance chuck, and FIG. 8 is a graph showing the relationship between chuck rotation speed and gripping force in the developed balance chuck. 1... Chuck body, 3e... Back part, 5...
・Claw, 11... Balance weight, 12... Lateral groove,
13... Vertical groove, 14... Continuous part Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Δ Fig. 6 Fig. 8 Fig. 7

Claims (1)

[Claims] 1. A plurality of claws that can slide in the radial direction are attached to the chuck body, and a balance weight that compensates for the centrifugal force of the claws is provided on the chuck body, and the centrifugation of the balance weight when the chuck rotates. In a balance chuck configured such that force acts on the back surface near the outer periphery of the claw to push the claw forward, the balance weight is provided with a cut groove near the outer periphery of the chuck body so that the balance The centrifugal force of the balanced weight when the balanced weight is elastically deformed using the continuous part as a fulcrum. A balance chuck characterized in that the chuck is configured such that it acts on the back surface of the jaw. 2. The chuck body at the rear part of the winter melon constitutes a balanced weight, and when the balanced weight elastically deforms toward the outer periphery using the continuous part as a fulcrum, the balanced weight pushes the back side near the outer periphery of the direct mold. A balance chuck opening 3 according to claim 1, characterized in that a cut groove is formed in a direction substantially perpendicular to the sliding direction of the jaw from the back side of the chuck body toward the front from the back side of the jaw. In addition, a thin cut groove is provided in a direction approximately perpendicular to the axis of the chuck body at a position forward of the back surface of the jaw from the outer peripheral surface of the chuck body toward the center of the chuck body. 3. The balance chuck according to claim 1, wherein a part of the chuck main body separated by both of the cut grooves is provided as a balance weight. 4. Claims 1, 2, or 4, characterized in that a chamfered portion for adjusting the boosting ratio is provided at the outer peripheral end of the abutting portion of the balance weight that abuts the back surface of the claw. Balance chuck as described in item 3.