Tool chuck for use with a rotating machine

Abstract

The central component of the chuck supports jaws that can be moved between a tool clamping position and a released position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Two possible embodiments of the invention will now be described by way of nonrestrictive examples with reference to the attached drawings:

FIG. 1 is an exploded perspective view of a chuck in accordance with the invention;

FIG. 2 is a side view of the chuck seen in FIG. 1, in the assembled position, and holding a tool;

FIGS. 3, 4 and 5 are perspective views of a jaw, a roller and a retaining member, respectively, for use with the chuck seen in FIG. 1;

FIG. 6 is a front view of the jaw of FIG. 3 containing the roller and retaining member;

FIG. 7 is a cross section through the jaw taken on the line marked AA in FIG. 6;

FIG. 8 is a cross section through the chuck taken on the line marked A′A′ in FIG. 2, before the chuck is spun;

FIG. 9 is an enlarged view of detail B marked in FIG. 8;

FIGS. 10 and 11 are similar views to FIGS. 8 and 9 when the chuck is turning to the right;

FIG. 12 is a view similar to FIG. 11 when the chuck is turning to the left; and

FIG. 13 is a diagrammatic view of the tool, the jaw and the roller with the normal and tangential forces acting on the roller.

Claims

1. A tool chuck for use with a rotating machine, comprising: a central component having an axis and comprising a rear part designed to be fixed to a drive shaft of the rotating machine and a front part to which are connected a number of jaws each having a central longitudinal plane; andmeans for moving the jaws between a tool clamping position and a release position;which chuck comprises a seat formed on the inward side of each jaw, said seat comprising an opening turned towards the axis of the central component, a back behind the opening, and, approximately parallel to the axis of the central component, first and second lateral faces; andat least one roller mounted in and approximately against the back of each seat with the aid of a rigid retaining member separated from the retaining member of each of the other jaws, the roller being rotatable about its axis which is approximately parallel to the axis of the central component, and movable translationally between the two lateral faces of the seat, the distance between which faces is greater than the diameter of the roller, and the roller being capable of acting on the jaw and on the tool;the back of which seat has two bearing portions, a first and a second, extending from the first lateral face and second lateral face, respectively, to the central longitudinal plane of the jaw, each bearing portion being curved or inclined transversely in such a way that the distance between the axis of the central component and said bearing portion increases with proximity to the central longitudinal plane, said bearing portions being adjacent and symmetrical about the central longitudinal plane and, where they meet, forming a roller positioning cavity so that when the tool is placed between the jaws the roller positions itself in contact with the back of the seat, essentially in the positioning cavity.

2. The chuck as claimed in claim 1, wherein, viewed in a transverse plane, at every point of the first bearing portion the angle (α) formed between the tangent to the first bearing portion at said point and the tangent to the roller passing through the point of contact between the roller and the tool when the roller is against the first lateral face of the seat is such that: tan α/2<Umin where Umin is the lesser of the following values: the coefficients of friction u between the roller and a tool selected from a predetermined set of tools that may be held in the chuck;and the coefficient of friction u′ between the roller and the jaw.

3. The chuck as claimed in claim 1, wherein the first bearing portion is essentially planar and parallel to the axis of the central component and wherein, viewed in a transverse plane, the angle (α) formed between the first bearing portion and the tangent to the roller passing through the point of contact between the roller and the tool when the roller is against the first lateral face of the seat is such that: tan α/2<Umin where Umin is the lesser of the following values: the coefficients of friction u between the roller and a tool selected from a predetermined set of tools that may be held in the chuck;and the coefficient of friction u′ between the roller and the jaw.

4. The chuck as claimed in claim 2, wherein the angle (α) is between 0.5 and 2°.

5. The chuck as claimed in claim 1, wherein the first and second bearing portions basically form, where they meet, an obtuse angle of between 165° and 175°.

6. The chuck as claimed in claim 1, wherein the seat is formed longitudinally in the jaw and in that the retaining member is fitted in the opening of the seat of said jaw to retain the roller in said seat while allowing it to move rotationally and translationally, a slot being provided in said retaining member to allow the roller to partially project out of the seat and contact the tool.

7. The chuck as claimed in claim 6, wherein the roller is essentially cylindrical and at each end has an axial rod able to engage in a part of the retaining member that borders the slot.

8. The chuck as claimed in claim 1, wherein the jaws are guided in translation in seats formed in the central body component, said jaws converging towards the front and having a thread on their outward face, and in that the chuck comprises a nut placed around the central component and having an internal thread engaging with the thread of the jaws so that the jaws can be moved in order to clamp or release the tool.

9. The chuck as claimed in claim 1, wherein the jaws are guided in translation in seats formed in a body rotating about the central component so as to move the jaws in order to clamp or release the tool, the jaws having a thread on their inward face engaging with a thread on the forward part of the central component.